DISEÑO GREEN

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Internet: http://www.eren.doe.gov/femp/

IntroductionIncorporating energy efficiency, renewable energy,and sustainable green design features into allFederal buildings has become a top priority inrecent years for facilities managers, designers,contracting officers, and others in government buildings procurement. These progressive designstrategies have been formalized through ExecutiveOrder 13123 (known as Greening the Governmentthrough Efficient Energy Management), which wasissued on June 3, 1999. There are significant oppor-tunities to accomplish the goals set forth in the

executive order, whether in new building designor in the context of renovations. This guidebookaddresses the first categorythe design processfor new Federal facilities. Because energy-efficient buildings reduce both resource depletion and theadverse environmental impacts of pollution gener-ated by energy production, it is often consideredto be the cornerstone of sustainable design. In thispublication, we will be looking at what low-energydesign means, specific strategies to be considered,when and where to apply these strategies, and howto evaluate their cost effectiveness.

Low-energy building design is not just the result of applying one or more isolated technologies. Rather,it is an integrated whole-building process thatrequires advocacy and action on the part of thedesign team throughout the entire project devel-opment process. The whole-building approach iseasily worth the time and effort, as it can save 30%or more in energy costs over a conventional build-ing designed in accordance with Federal Standard10 CFR 435. Moreover, low-energy design does notnecessarily have to result in increased constructioncosts. Indeed, one of the key approaches to low-energy design is to invest in the buildings form and

enclosure (e.g., windows, walls) so that the heating,cooling, and lighting loads are reduced, and in turn,smaller, less costly heating, ventilating, and airconditioning systems are needed.

In designing low-energy buildings, it is important toappreciate that the underlying purpose of the build-ing is neither to savenor useenergy. Rather, the building is there to serve the occupants and their

activities. An understanding of building occu-pancy and activities can lead to buildingdesigns that not only save energy and reducecosts, but also improve occupant comfort andworkplace performance. As such, low-energy build-ing design is a vital component of sustainable, greendesign that also helps Federal property managersmeet the requirements of the Energy Policy Act of 1992, Executive Order 13123, and other climatechange goals.

The low-energy design process begins when theoccupants needs are assessed and a project budgetis established. The proposed building is carefullysited and its programmed spaces are carefullyarranged to reduce energy use for heating, cooling,and lighting. Its heating and cooling loads are mini-mized by designing standard building elementswindows, walls, and roofsso that they control,collect, and store the suns energy to optimumadvantage. These passive solar design strategiesalso require that particular attention be paid to building orientation and glazing. Taken together,they form the basis of integrated, whole-buildingdesign. Rounding out the whole-building pictureis the efficient use of mechanical systems, equip-ment, and controls. Finally, by incorporating build-ing-integrated photovoltaics into the facility, someconventional building envelope materials can bereplaced by energy-producing technologies. Forexample, photovoltaics can be integrated intowindow, wall, or roof assemblies, and spandrelglass, skylights, and roof become both part of the building skin and a source of power generation.

This guidebook has been prepared primarily forFederal energy managers to provide practical infor-mation for applying the principles of low-energy,whole-building design in new Federal buildings.An important objective of this guidebook is to teachenergy managers how to be advocates for renewableenergy and energy-efficient technologies, and howto apply specific strategies during each phase of agiven projects time line. These key action items are broken out by phase and appear in abbreviatedform in this guidebook.

Low-Energy Building Design GuidelinesEnergy-efficient design for new Federal facilities

F E D E R A L E N E R G Y M A N A G E M E N T P R O G R A M

A guidebook ofinformation oning energy-effiFederal buildin

Prepared by theNew TechnologDemonstrationProgram

No portion of thiscation may be alteany form without written consent frthe U.S. DepartmEnergy and the auing national labor

DOE/EE-0249


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DisclaimerThis report was sponsored by the United States Department of Energy, Office of Federal Energy ManagementPrograms. Neither the United States Government, nor any agency or contractor thereof, nor any of their employees,makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, complete-ness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use wouldnot infringe privately owned rights. Reference herein to any specific commercial product, process, or service by tradename, mark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommenda-tion, or favoring by the United States Government or any agency or contractor thereof. The views and opinions of theauthors expressed herein do not necessarily state or reflect those of the United States Government or any agency orcontractor thereof.


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ContentsIntroduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

About the Technology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

Application Domain. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

Energy-Saving Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

Advantages of Low-Energy Building Design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

Application. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7Applications Screening. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

Building Types: Characteristics and Profiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

Integrating Low-Energy Concepts into the Design Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

What to Avoid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29

Design Considerations and Computer Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29

Strategy Interactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29

The Benefits of Multiple Use. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

Costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

Design and Analysis Tools. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

Energy Savings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

Other Impacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

Case Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

The Technology in Perspective. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

Technology Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

Technology Outlook. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

Product Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

Who is Using the Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

For Further Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37

Appendix A: Climate and Utility Data Sources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42

Appendix B: Federal Life-Cycle Costing Procedures and the Building Life Cycle Cost (BLCC) Software. . . . . . . . . .42

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About the TechnologyBuildings consume roughly 37% of theprimary energy and 67% of the totalelectricity used each year in the UnitedStates. They also produce 35% of U.S.and 9% of global carbon dioxide (CO 2)emissions. Preliminary figures indicatethat in FY 1997, Federal governmentfacilities used nearly 350.3 trillionBritish thermal units (Btus) of energyin approximately 500,000 buildingsat a total cost of $3.6 billion.

By following a careful design process, itis possible to produce buildings that usesubstantially less energy without com-promising occupant comfort or the buildings functionality. Whole-buildingdesign considers the energy-relatedimpacts and interactions of all buildingcomponents, including the buildingsite; its envelope (walls, windows,doors, and roof); its heating, ventilation,and air-conditioning (HVAC) system;and its lighting, controls, and equip-ment. This stands in marked contrastto the traditional design process, wherethere is generally no goal to minimizeenergy use and costs beyond what isrequired by codes and regulations.

Executive Order 13123 calls for a 30%reduction in energy use per gross squarefoot by 2005. To achieve this goal, theagency and design team must establishminimized energy use as a high prioritygoal at the inceptionof the design process.A balanced and appropriately fundedteam must be assembled that will workclosely together, maintain open lines of communication, and remain responsiveto key action items throughout thedelivery of the project.

Continuing advocacy of low-energydesign strategies is essential to realizingthe goal. Therefore, it is important thatat least one technically astute memberof the design team be designated as theenergy advocate. This team memberperforms many useful functions, such as:

Introducing team members to designstrategies that are appropriate to build-ing type, size, and location.

Maintaining enthusiasm for the inte-gration of low-energy design strategiesas central components of the overalldesign solution.

Ensuring that these strategies are notabandoned or eliminated during thelater phases.

Overseeing construction to ensure thatthe strategies are not thwarted or com-promised by field changes.

For most projects, it is also highly advis-able to retain an experienced low-energydesign consultant. Because low-energydesign is not entirely intuitive, experi-ence gained from a range of projects isvital. Indeed, the energy use and energycost of a building depend on the com-plex interaction of many parametersand variables that require detailedanalysis on a project-by-project basis.Some of the attributes that an energyconsultant should bring to the projectinclude:

Sufficient background to identifypotential strategies based on experience.

Knowledge of Federal informationsources (e.g., Federal Energy Manage-ment Program, national laboratories),

Federal requirements (e.g., 10 CFR 435and 436 Energy Star buildings andequipment, energy-savings perform-ance contracting), the Energy PolicyAct of 1992 (EPAct), and other relevant

executive orders. Technical expertise that generatesenthusiasm, cooperation, and respectamong team members.

The capacity to efficiently use detailedcomputerized energy simulation pro-grams such as the latest version of Energy 10 or DOE 2.

The ability to make informed designrecommendations based on computerresults and life-cycle economic analyses.

A breadth of experience sufficient toconsider design options that not onlysave energy, but are also integrated withother project needs, including aestheticconsiderations.

In sum, the energy consultant shouldserve as a catalyst for eliciting innova-tive energy-conserving design ideasfrom the entire design team. In somecases, other members of the projectteam (such as the design architect andengineer) may, themselves, be quite pro-

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Estimated Costs for Low-Energy Design Consulting Services

Investment ($/ft2)

Small buildings Medium buildings Large buildingsEnergy Use Type (0 to 20,000 ft2) (20,000 to 100,000 ft2) (100,000 ft2 and above)

Moderate Energy UsersIncluding single familyresidences, housing,and warehouses $0.35 to $0.25 $0.25 to $0.15 $0.15 to $0.05

High Energy UsersIncluding offices,factories, and servicecenters $0.40 to $0.30 $0.30 to $0.20 $0.20 to $0.10

Very High Energy UsersIncluding laboratoriesand hospitals $0.45 to $0.35 $0.35 to $0.25 $0.25 to $0.15

Note:This table adjusts the rule of thumb for building size and energy use characteristics andprovides a more precise guideline.Note that as buildings get larger, there is an economy ofscale, so it is not necessary to expend as much on a square-foot basis.

U.S. Department of Energy (DOE) Federal Energy Management Program (FEMP), March 1999.Procuring Low-Energy Design and Consulting Services: A Guide for Federal Managers, Architects, andEngineers, available at www.nrel.gov or www.eren.doe.gov/femp.


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ficient in low-energy building designand will respond well to the challenge.

The only thing that may hold them backfromadvocating low-energy design onany particular project is the lack of a com-mitment and appropriate funding by theowner or agency. Estimated costs for thisconsulting service can be obtained fromthe table on the previous page.

Application DomainThe application domain for low-energydesign is not so much a case of wherethe technology should be installed, butwhere it is integrated with the otherelements of the project to produce anenergy-efficient building that serves both the environmental and functionalneeds of its users. When thinking aboutwhole buildings, it is important to con-sider not only the discrete componentsand materials but how the various partscan best work together to achieve thedesired results. That is what is meant bythe phrase integrated, whole-buildingdesign. Low-energy design strategiesand renewable energy concepts can beapplied to almost any type of newFederal building.

Energy-Saving MechanismsIn Federal buildings, low-energy designmechanisms range from a few high-pro-file architectural features that are solarresponsive to the application of moreconventional, and often less conspicu-ous, energy conservation technologies.Many applications are reconfigurationsof typical building components, such asa change from flat faades and roofs tothose that are articulated and have sur-faces designed to bounce or block directsolar rays.

The low-energy design process describedin this guidebook combines a broad rangeof practical systems, devices, materials,and design concepts that should be con-sidered simultaneously whenever possible to achieve significant reductions inenergy use. For most non-residential buildings, an energy-use reduction of 30% below what is required by codesand standards can usually be achievedwith little, if any, increase in construc-

tion cost. The figure is closer to a 50%reduction in residences. Savings of 70%or more are possible for exemplary build-ings, although achieving such significantreductions can be challenging in light of

the demands occasioned by budgetingconstraints and cost-effectiveness crite-ria. For example, daylighting, coupledwith dimmable lighting and light-levelcontrols, is increasingly commonplace.An effective and highly recommendedenergy conservation strategy, this tech-nology cluster is an important compo-nent of low-energy building design.(See Applications Screening and Howto Apply)

Because energy-efficiency concepts andtechnologies must dovetail with all other

building elements, one of the mostimportant energy-saving tools is theuse of computer modeling and designsoftware. This strategy should be usedearly in the design process to analyzethe efficiency and cost effectiveness of candidate strategies. Detailed computersimulation results are then referred tothroughout the design process, andoften through the value engineering(VE) phase, to ensure that the buildingwill efficiently perform as intended, and

that subsequent changes to the designin the interest of cost-cutting do notadversely affect performance. By usingappropriate energy simulation tools inthe context of a whole-buildingapproach that emphasizes solar tech-nologies and energy efficiency, designteams can achieve significant operatingcost savings while still staying on bud-get. Alist of design and analysis tools isprovided later.

Advantages of Low-Energy BuildingDesignWhile basic techniques and concepts areimportant, of greater relevance to a given

building project are the specific low-energy building design techniquesthemselves. One key element of low-energy building design is the inventiveuse of the basic form and enclosure of a

building to save energy while enhancingoccupant comfort. The section titled Howto Apply describes a wide range of low-energy building design strategies thatcan be commonly applied to new Federal

buildings. Low-energy building designcombines energy-conservation strategiesand energy-efficient technologies. Someof these are described in FEMP FederalTechnology Alerts (FTAs), includinghigh-efficiency lighting and lightingcontrols, spectrally selective glazing,and geothermal heat pumps.

Low-energy design represents both aload-reduction strategy and the incor-poration of renewable energy sources.Many low-energy building design strat-egies result in an absolute reduction inthe use of power produced from fossilfuels. Together these innovations cansave energy, reduce costs, and preservenatural resources while reducing envi-ronmental pollution. Low-energy build-ing design strategies (including variousdaylighting techniques) can also providea renewed sense of connection with theoutdoors for occupants of Federal facili-ties. Low-energy design can also inspireplanning concepts, such as interior pri-vate offices that borrow light from openoffice spaces at the buildings perimeter.

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Basic energy-saving techniques should be used to reduce building energy use.

Siting and organizing the building configuration and massing to reduce loads. Reducing cooling loads by eliminating undesirable solar heat gain.

Reducing heating loads by using desirable solar heat gain.

Using natural light as a substitute for (or complement to) electrical lighting.

Using natural ventilation whenever possible.

Using more efficient heating and cooling equipment to satisfy reduced loads.

Using computerized building control systems.


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More difficult to measure are the increasesin workplace performance and produc-tivity that are often achieved throughwhole-building design and its resultingeconomic value. Nonetheless, organiza-

tions housed in low-energy buildingshave reported that their indoor environ-ments help retain employees, reducetension, promote health, encouragecommunication, reduce absenteeism,and, in general, improve the work envi-ronment. Another potentially significant benefit is the public perception that, byits own example, the Federal govern-ment is helping to lead the constructionindustry toward a more responsible andsustainable future. Similarly, by usingpublic funds for cost-effective measures

that reduce operating costs, Federalagencies are performing these tasks ina responsible and frugal manner.

ApplicationLow-energy building design techniquesare application specific. This sectionprovides a practical method of deter-mining the potential use of design tech-niques in different types of Federal buildings, in different climatic locations,and under various local energy cost

scenarios. It also details the processand level of advocacy required to assuresuch strategies are considered and incor-porated into the design process, begin-ning with the earliest project phases(see Needs Assessment and Site Selec-tion) and continue through Construc-tion and Building Occupancy. Refer tothe time line on pages 2223 for anillustration of the various phases andkey action items to be addressedthroughout the process.

For a particular project, the specific ener-gy-saving techniques, strategies, andmechanisms to be deployed will varygreatly, depending on building andspace type. Their selection and configu-ration will also be influenced by:

Climate

Internal heat gains from occupants andtheir activities, lights, and electricalequipment

Building size and massing

Illumination (lighting) requirements

Hours of operation

Costs for electricity and other energysources.

In reviewing this list, one can quicklygrasp that strategies specific to a partic-ular building or space may not worknearly as well (or at all) in another appli-cation. Therefore, some general guid-ance about building and space types(provided in Applications Screening)will prove useful in understanding thefactors that lead to significant energy usein buildings and in identifying the strat-egies that can yield optimum savings.

It is essential that the team appreciate that

a successful design solution under oneset of circumstances may not be appro-priate or cost effective for a different

building type, size, or configuration; thesame building type constructed in a dif-ferent climate; or where variable energycosts apply.

Applications ScreeningThe use characteristics discussed beloware representative of the majority of Federal building projects. The first steptoward assuring low-energy buildingdesign for a particular project is tounderstand the energy implications of the structures basic form, organization,and internal operations. These criteriawill dictate the relative importance of strategies to be deployed for heating,heat rejection, lighting, and, in somecases, hot water. The term heat rejectionis used (as opposed to cooling) based onthe idea that a fundamental goal of low-energy building design is to greatly mini-mize the need for, and dependence on,

mechanical cooling.It is important for those involved in Fed-eral design projects to know how andwhy office buildings, courthouses, labo-ratories, hospitals, visitor centers, borderstations, warehouses, and various resi-dential building types use energy. Eachof these will be summarized later, butfirst, some background informationshould prove useful in forming a basisof understanding.

Perhaps the most basic division is that of houses and larger, non-residential build-ings. Houses are the most commonexample of skin-load-dominated build-ings, because their energy use is predi-

cated by heat gain and loss through the building enclosure or skin (also knownas the envelope, e.g., walls, windows,roof, floor). Houses and other skin-load-dominated buildings primarily requireheat in cold climates, cooling in hot cli-mates, and very little energy of any type(except hot water) in benign climateslike San Diego. For low-energy perform-ance, it is common for houses and otherskin-load-dominated buildings to bewell-insulated and to invite the low win-ter sun in while keeping it out (through

shading and proper building orienta-tion) during the summer.

Simplistically, larger non-residential orcommercial buildings are often referredto as internal-load-dominated buildings

because a large portion of their energyuse is in response to the heat gains from

building occupants, lights, and electricalequipment (e.g., plug loads for computers,copiers). As a result of these internal heatsources, internal-load-dominated build-ings are often designed to turn their

backs on the sun, and further reducesolar gain through the use of tinted andreflective glass. There is some logic tothis, but such an approach is too univer-sal and precludes some of the most ben-eficial low-energy design strategies.Moreover, it often is too simplistic tothink of a building with offices as simplyan office building. The structure is alsolikely to have a lobby and circulationspaces, a cafeteria, a computer room,meeting rooms, and other spaces thathave environmental needs and thermal

characteristics that are very differentfrom those of offices. Ideally, designstrategies should first satisfy the needsof each individual space or zone. Thisrequires careful attention during theprogramming phase of the project.

Evaluating a specific project for selectingand integrating low-energy designstrategies starts with an understandingof the following factors:

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Climate

Not just is it hot or cold, but how humidis it? Is it predominantly clear or cloudy,and during what times of the year? Clearwinter climates are well matched withspaces that incorporate passive solarheating strategies. In contrast, spaces(and buildings) in clear summer climatesgenerally require a high degree of suncontrol. Clear climates also make the best use of light shelveshorizontalsurfaces that bounce daylight deeperinto buildings. Even the site-specificand seasonal nature of the wind needsto be understood if natural ventilationstrategies are to be incorporated into a building design.

Internal Heat Gains The heat gains from building occupants,lights, and electrical equipment can bethought of as the interior climate andshould not be generalized. Instead, dur-ing the early programming of the proj-ect, the heat gains anticipated from thesesources should be quantified for the var-ious spaces where they apply. In somecases, such as in storage buildings andother areas with relatively few occu-pants and limited electrical equipment,

these heat gains will be minor. In otherinstances, the presence of intensive andenduring internal heat gains may be adetermining factor in HVAC systemdesign. Examples of intensive andenduring influences include activity- based gains, such as those produced bycafeterias and laundry facilities (whereincreased humidity is also a factor), andtechnological or industrial gains, suchas the heat produced by mainframecomputers or heavy machinery. Thesefactors should be identified early on,

and appropriate design strategies inves-tigated (such as heat recovery or usinga closed-loop heat pump system).

Building Size and Massing

In a low-energy building, both theindoor and outdoor climates exert apowerful influence on all aspects of building design. Sometimes, they com-plement one another, such as the caseof a building with a lot of internal heatgains sited in a very cold climate. At

other times, however, the two climatesare antagonistic, such as when there area lot of internal heat gains in a very hotclimate. Understanding the implicationsof these factors is fundamental to deter-

mining appropriate low-energy designstrategies for a particular building proj-ect. Under hot/hot conditions, buildingswith large footprints and a large amountof floor space far from the exterior of the

building will require heat removal in theinterior zones (generally by mechanicalcooling) all or much of year.

The other basic planning approach is toposition all spaces that can benefit fromconnection to the outdoors in proximityto exterior walls. To achieve this, build-ings become much narrower, with amaximum width of about 70 feet. Suchan approach to building massing must,

by necessity, be introduced very earlyin the design process. Also, recognizethat not all spaces need or want to beexposed to the exterior, including manyareas of complex building types likehospitals and courthouses. These spacesoften function better as interior place-ments within a wider and more compact

building form.

Lighting Requirements

The lighting needs of a buildings variousspaces need to be identified, both quan-titatively and qualitatively, as part of theenvironmental programming conductedearly in the project. Many spaces, includ-ing lobbies and circulation areas, requiregeneral ambient lighting at relativelylow foot-candle levels (10 foot-candlesor less). Such spaces are ideal candidatesfor daylighting. In contrast, some spacesare used for demanding tasks that requirehigh light levels (50 foot-candles or more)and a glare-free environment. Here thedesign teams attention may shift fromdaylighting to a very efficient electricallighting system with integrated occu-pancy sensors and other controls.

Hours of Operation

Typically, on a per-square-foot basis, themost energy-intensive Federal buildingtypes are those in continuous use, suchas hospitals and border stations. In these

buildings, the balance of heating and

heat removal (cooling) may be altereddramatically from that of an office build-ing with typical work hours. For exam-ple, the around-the-clock generation of heat by lights, people, and equipment

will greatly reduce the amount of heat-ing energy used and may even warranta change in the heating system. Intensive

building use also increases the need forwell-controlled, high-efficiency lightingsystems. Hours of use can also enhancethe cost effectiveness of low-energydesign strategies, such as daylightingin a border station or weather station.In contrast, buildings scheduled foroperations during abbreviated hours(including seasonal occupancy facilities,like some visitor centers), should be

designed with limited use clearly inmind.

Energy Costs

The cost for energy, particularly electricalenergy, for most non-residential build-ings is a critical factor in determiningwhich design strategies will not onlyconserve energy, but will also be costeffective. In most locations in the UnitedStates, electricity is three to four timesmore expensive than natural gas perBtu. This disparity can, at times, be capi-talized upon by introducing designstrategies that effect a trade-off in energyuse. For example, increasing the glassarea and the commensurate daylightentry can save expensive electrical use

but, at the same time, occasion the pur-chase of additional (but relatively low-cost) heating energy. However, such anexample should not be misconstrued asindicating that daylighting requires anexcessive amount of glass, as that is justnot the case. Daylighting primarily

requires placing the glass carefullyand selecting the appropriate glazing.

In many locations, utility deregulationimposes an uncertainty on future electri-cal and other energy prices. To the great-est extent possible, the life-cycle benefitsof various design strategies should beinvestigated for the range of energy-costscenarios deemed plausible. For somestrategiesparticularly those that affectthe amount of heating energy used

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deregulation may be of lesser importance.In other cases, however, rate structures,particularly those based on peak electri-

cal demand, may significantly affect theeconomic impact of strategies such asdaylighting.

As part of a whole-building design strat-egy, purchasing bulk green powerresources complements many building-specific design measures. Through aholistic approach to building design andoperation, incorporating green powerresources can further decrease the envi-ronmental impacts already minimizedthrough the specification of energy effi-

ciency and renewable energy measuresin the design process. Minimizing elec-trical load requirements, and then meet-ing these requirements with clean elec-tricity resources, is at the core of awhole-building design strategy.

Green powerrefers to utility-scale elec-tricity resources that are in some wayenvironmentally preferable to conven-tional system power. The terms greenand clean are often used interchangeablyto describe this type of electricity. Green

power supplied from the utility gridmay be comprised of electricity fromone or more types of renewable sources.

The term renewable powerrefers to elec-tricity generated from one or more of the following types of resources:

Windgenerated from wind-poweredturbines, often grouped together intowind farms

Solartypically generated from pho-tovoltaic (solar cell) arrays, often placedon rooftops

Geothermalgenerated from steamcaptured from below the earths surfacewhen water contacts hot, undergroundrock

Biomassburning of agricultural,forestry, and other byproducts (includ-ing landfill gas, digester gas, and munic-ipal solid waste)

Small hydroelectricgenerated fromdams with a peak capacity of less than30 megawatts (MW).

Building Types: Characteristics andProfilesThe following brief descriptions give

broad categories of building types andsome likely successful strategies forconsideration.

Residential Buildings

In cold climates, the classic, skin-load-dominated building type really benefitsfrom using high-performance, low emis-sivity (low-e) windows and high levelsof insulation. In many cold climates,residential buildings can also signifi-cantly benefit from passive solar heat-ing, so long as a reasonable amount of heat-absorbing thermal mass is incorpo-rated into the design. In hot climates,solar control is paramount, based on theneed to keep cooling loads and costsunder control. It is also important totake advantage of the opportunity forpassive or active solar water preheating.For remote structures that do not haveeasy access to the utility grid, photo-voltaic systems should be considered asthe primary, or sole, source of electricity.

Small Non-Residential Buildings

This profile describes buildings in whichlighting and internal gains play a rela-tively small role in the buildings energy

balance. Such buildings are the heartand soul of low-energy building design,as a multitude of low-energy buildingdesign strategies can be successfullyapplied to their construction. One com-

mon Federal building type that fallsinto this category is the visitor center.

Visitor centers are among the mostadvanced energy-conserving structures.They generally have a robust budget,allowing the purchase of durable mate-rials. They are normally located in severe

9

Natural Gas:Typical Cost for One Million Btu

1,000,000 Btu

100,000 Btu/Therm* x 0.75 (Heating System Eff.)

Electricity:Typical Cost for One Million Btu

1,000,000 Btu

3413 Btu/kWh x 1.00 (Site Eff.)kWh = kilowatt-hour

X $0.60/Therm = $8 per million Btu

X $0.08/kWh = $23 per million Btu

An example of an energy-efficient home in a cold climate using direct-gain passive solarheating.


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(either hot or cold) climates inaccessibleto utilities; they have a natural connec-tion with the outdoors; and the struc-tures present an opportunity to interpretthe resource-conservation mission of the agency to the visiting public. Thesestructures typically combine a need forwindow area, massive construction, anda tolerance for temperature swingsallof which are highly compatible withlow-energy building design. Daylight-ing is another key strategy for deploy-ment in these building types.

Urban Office Buildings

This building type evinces characteristicscommonly found in major urban centers,where Federal office buildings are oftenlocated. Land is often expensive andmust be used at a high density. The building is typically dominated by onerepetitive useoffice spacealthoughit may also contain a number of otheruses, such as support facilities. These buildings are often landmarks or show-pieces. In highly controlled areas likeWashington, D.C., this translates intoheight limits and tight controls overfaade treatment. In most cities, how-ever, there are few controls on the styleor height of downtown office buildings.

As a result, many of these buildingsinclude or consist of towers that shadeand are shaded by neighboring build-ings, a factor that may significantly

affect the design and sizing of themechanical cooling system.

Curtain walls are, by far, the most com-mon enclosures for downtown office

buildings, but most curtain walls areclassic examples of a building as afortress against the environmentphilosophy. The low-energy buildingdesign strategy for flat curtain walls istypically defensive in nature, limitingthe boring and often unattractive resultfrom the overuse of glass and by a lackof orientation-specific faades. Fortu-nately, there has been somewhat of astylistic revolt against all-glass build-ings, which has led to more articulatedfaades, variation in building faadetreatments, and a resurgence in the useof masonry. All of these factors greatlyenhance low-energy building designpossibilities by creating opportunitiesto tune faades to suit their orientationand the activities taking place behindthem. In most cases, thoughtful strate-gies will be needed to reduce solar gain.Exterior sunscreens or new glazingtypes (fritted, shaded) can both enliventhe faade and provide substantial cool-ing load reduction.

An excellent way to take advantage of low-energy building design is to moveas many private offices away from thefaade as possible. In this way, morelight can be directed further into the

building, and more of the buildingsusers can enjoy access to views andnatural lighting. This scenario oftenyields increases in productivity andenables the adoption of more energy-efficient HVAC strategies.

If an atrium serves the programs needs,it should be located and designed to

substitute natural lighting for artificiallighting, to minimize cooling loads, andto take advantage of solar heating, if itis needed. The location and shape of theatrium will be highly building-specific.In general, taking full advantage of theunique opportunities of each urban siterequires considerable expertise, particu-larly because of shading from surround-ing buildings and the complex inter-actions among lighting, HVAC, faadedesign, orientation, and climate.

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The Zion Visitor Center is designed to use 70% less energy than a typical building withoutcosting more to build.

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Boston Edison joined Northwestern Univer-sity to use solar electricity to power the EllStudent Center on the Universitys Bostoncampus. The rooftop PV system incorpo-rates 90 285-W p modules installed on inno-vative ballasted mounting trays that requireno roof penetration.

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Courthouses

This building type typically entails high-

ly complex and interrelated space pro-gramming. Many diverse functions must be accommodated, sites are often con-stricted, and the professional occupantsare demanding. In addition, courthousesoften serve a ceremonial function. Inmany cities, they are the most presti-gious and conspicuous of Federal build-ings. Their typically urban location oftenrequires a sensitivity to surrounding buildings with historical styles and valueand most certainly will require carefulintegration into the existing urban plan.Oftentimes, the functional needs of courthouses (i.e., security requirements)must be fully satisfied before energy- based programming concerns can beaddressed, and solar design strategiesmay not always apply to this buildingtype. Still, low-energy design opportuni-ties abound, especially in terms of effi-cient lighting, HVAC systems, equip-ment, and controls. It is also worthwhileto note that many of the design issuesdescribed for urban office buildings

will also apply to courthouses.Hospitals

These facilities tend to have a lot of smallspaces, many of which need to be win-dowless. Offices and patient rooms can be thought of as small, mixed-use areasthat incorporate both residential andcommercial features. Cafeterias and pub-lic lobbies present special opportunitiesfor daylighting. Overall, this buildingtype has many spaces that require large

quantities of outside ventilation air. There-fore, ventilation-air heat-recovery systemsthat are not prone to cross-contaminationare particularly useful in these applica-tions especially in very cold climates.The around-the-clock nature of hospitalsis a perfect opportunity to incorporatevery efficient and well-controlled light-ing and power systems.

Laboratories

Laboratories are an energy-intensive building type that often consumes morethan 200,000 Btu per square foot, due tolarge ventilation requirements and in

part to the long operating hours (two orthree shifts) that are typical. The labora-tory working environment normallyrequires enormous amounts of ventila-tion air to ensure good indoor-air qual-ity, often making heat recovery systemscost effective.

If there is a considerable demand for hotwater, preheating the water using solarenergy is recommended, particularly for

facilities located in clear climates. This building type can often benefit from day-lighting, but because the walls tend to beoccupied with equipment, it is appropri-ate to consider either high windows or

toplighting by roof monitors on theupper floor. Either way, avoiding glareis crucial. Circulation corridors alongsouthern faades can function as solar-heated sunspaces. Sunlight on southfaades can be bounced through highglazing by way of light shelves. Depend-ing on the regional climates, thermalmass walls for heat storage between labsand corridors may also make sense. Thecorridors can double as pleasant meetingand lounge spaces, while serving as a buffer to the south sun, thus permitting

wider temperature swings than would be permissible in the main labs. Onnorth-facing walls, small, well-spacedview windows can double as a sourceof diffuse daylight.

Incorporating atriums into laboratory buildings also makes sense, both as ameans of bringing natural light intothe labs and providing casual meetingspaces adjacent to the labs. West faadesmay serve as good locations for window-less lecture halls. Cafeterias can usedirect gain, or in some temperate cli-mates, might even have a fabric roof.

Warehousing/Shipping/Repairing

These activities are typically carried outin one-story buildings with high ceilings.Offices, supervisory booths, employeeservices, restrooms, and loading docksoften complement a main unpartitionedspace. For roof and wall assemblies,steps must be taken to counteract heat

A courthouse in St. Paul, Minnesota.

The National Renewable Energy Laboratorys Solar Energy Research Facility.

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loss due to continuous metal contactsthroughout the construction. Thoughnot limited to metal components, thisprocess is known as thermal bridging,which can significantly compromisethe resistance value of insulation. Inclimates with hot summers, a whiteor reflective roof is advisable.

If lighting can be controlled electronicallythrough light sensors and other devices,natural lighting strategies can be veryuseful. If the budget does not allow forproper roof monitors with vertical glassfacing south or north, consider usinghigh windows along the south and northwalls with south-facing glass shaded byproperly designed overhangs. Exercisecare in using scattered skylights, as theycan create glare and let in excessiveamounts of solar heat.

If the building is subject to around-the-clock use, large high-intensity discharge(HID) lamps are appropriate whenarranged in such a way as to light between inventory stacks when daylightis unavailable. Interior surfaces should

be light-colored to reflect light. If the building is used intermittently, moreand smaller HID or fluorescent lampsthat easily switch on and off should beused. HVAC should be localized towork areas, with the overall buildingmaintained at the maximum tempera-ture range needed for its contents andthe proper operation of machinery.

Campus Layout

This profile describes a wide variety of building types where space adjacencyrequirements are not crucial, and thereis ample site area availability. Possible

building types include rural or suburbanoffice buildings, training and classroomfacilities, some laboratories, barracks,and other multi-family housing.

If the buildings can be spread out, moreof the interior space will be close to anoutside wall. A campus plan makes themost sense in designing buildings for

housing and classroom use, wheredeep interior spaces are inappropriate.Compared to a compact building form,the campus plan generally costs moreat the outset, based on the need for alarger site, the cost of added buildingenclosures, and added lengths for serviceconnections. When life-cycle economicsare taken into account, these additionalcosts can be justified if the additionalexposure is used to optimum advantageand daylighting and natural ventilationare brought into play.

For spaces that can benefit from passivesolar heating, it is essential that south-facing solar glazing be clear of anyshade during the heating season, evendeciduous trees. The bare branches of trees can change a sunspace from onethat provides useful heat into one thatdoes not. In very cold climates, it isworth considering a partially earth-sheltered building, especially in thecontext of a sloping site.

Renovations

Renovating and reusing a building makesit low energy and sustainable in anothervery important way. Much less energy isneeded to produce construction materi-als and deliver them to the site when the

buildings basic shell is being reused.Older buildings, in particular, oftenmake excellent candidates for low-energydesign that utilizes their mass, higherceilings, and narrower building form.Many aspects of low-energy buildingdesign are applicable to many large-scale renovation projects. The onlystrategies that are clearly precluded arethose based on siting, building form, ororientation. While these established fea-tures can limit a buildings low-energyperformance potential, renovations canstill reduce energy costs by 20% to 30%.

Integrating Low-Energy Conceptsinto the Design Process

Feasibility Phase

The feasibility phase is normally whenFederal building managers or other deci-sion makers in the Federal sector deter-mine that a project will be built to addressa particular need. At this stage, the

enabling premises of low-energy designand construction need to be defined andestablished. Think of this as the timewhen the seeds of the overall sustainabledesign and construction strategies aresown, and the framework is establishedfor decisions to be made and actions to

be taken throughout the design andconstruction process. Defining param-eters; establishing general goals; andidentifying policies, directives, andenabling legislation will guide andpropel the process.

During the feasibility phase, architectsand engineers develop a capital projectscope and planning document that pro-vides a design program, an implementa-tion strategy, and a budget assessment.Identifying these elements early is essen-tial to establish project feasibility, sup-port project selection, and coordinateproject execution. Community plans formajor cities and surrounding areas iden-tify long-term space needs for Federal

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An example of a multi-use building.

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agencies and propose appropriate actionsto address those needs. Major projectsinvolving renovation or construction of Federal buildings must be developed inaccordance with applicable community

plans. Agencies often conduct studies tosupport project planning or assess build-ing conditions, some of which may takeinto account coordination with state andlocal authorities, community groups,and others who may have a stake in thedevelopment process.

Because Federal policy calls for coopera-tion with state and local authoritieswhen planning Federal facilities, localgovernment officials must be contactedto ensure that all documents impactingthe project are discussed. These docu-ments may include master plans, currentand future land-use plans, zoning maps,traffic studies, and other documents thataddress the availability of essential sup-port services (e.g., fire, police, utilities,telecommunications). Helpful informa-tion can also be obtained from youragencys local office, including docu-mentation of current building condi-tions, maintenance concerns, site access,communication with other agencies, andother potential impacts on project scope

and implementation.Action Items

Conduct all required feasibility analy-ses (including, but not limited, to thosedescribed above).

Review all existing directives and poli-cies to be sure of what your agency cur-rently requires in the way of energyperformance, materials usage (i.e., quality,durability, recycled content, energy sav-ing features, impact on indoor environ-mental quality [IEQ]), daylighting, useof renewable energy sources, contractingissues, and other relevant concerns.

Select an energy champion and givethem the authority to make decisionsrelating to low-energy design and con-struction practices.

Establish explicit energy-use targetsthat surpass those described in 10 CFR435; specifically, reference ExecutiveOrder 13123. Factor in any additional

criteria that may be specific to youragency or organization, facility location,or end use.

Identify and list your agencys goalsfor other sustainable issues, such as siteplanning, materials use, water use, orIEQ.

Budgeting Phase

Some projects may be constructed usingstandard designs (those completed forsimilar projects or off-the-shelf, prefabri-cated structures). Be certain that yourspecific low-energy goals have beenaccounted for.

Action Items

Program any special requirements intoyour budget submission.

Submit a budget that allows for anenergy champion (as well as the meet-ings and other resources required toaccommodate a team process), the addi-tional studies, analyses, and verifica-tions that will be needed, and slightlyhigher design fees (generally 2%4%).

Include the requirement for an energyexpert in your Request for Proposal/Architectural & Engineering (RFP/A&E)

solicitation. Conduct a design charrette prior toconcept development to ensure thatlow-energy building components andstrategies will be adopted early in theplanning and design stages, when theseelements can be incorporated at the low-est possible cost.

Identify the certification and testingmeasures required to ensure compliancewith energy targets and sustainabilitygoals.

Project Pre-Planning Phase

At inception, and during the early phasesof a low-energy projects time line, a needsassessment is conducted (often with theassistance of a consultant). This processconsiders the long-term requirements of the building occupants and yields a pro-gram for the project that includes:

User group needs and square footagerequirements

Location and site options

Estimated costs and schedule.

For many Federal agencies, it is essentialthat the budget established at this time

be based on all factors that will influencecosts, including the incorporation of low-energy design strategies.

Action Items

Select appropriate candidate low-energydesign strategies.

Associate these strategies with the par-ticular project phase during which theymust be considered and evaluated.

Identify the team members who will be responsible for evaluating and incor-

porating the strategies at each phase. Identify the appropriate evaluationtools to use at each phase and who willuse them.

Identify the actions to be taken by var-ious team members at each phase andcarry them out.

Establish low-energy design as a coreproject goal.

Use case studies and passive solar per-formance maps to help determineappropriate strategies for the specificproject type at hand.

Establish energy-use targets that sur-pass applicable codes and standards. Ingeneral, energy-use reductions in non-residential buildings should be targetedat 30% or better in comparison to a stan-dard, code-compliant building.

Ensure that the planned building con-figuration takes maximum advantageof the site and climate.

In selecting consultants, consider theirlevel of experience and expertise in low-energy design.

Strategies to Consider During ThisPhase

User Energy Needs Assessment

Description:This is a direct assessmentof the energy-related needs of facilityusers. Whether it is in the form of anEnvironmental Programming Matrix

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or other, less formal, documentation, it isa fairly rigorous and thorough evaluationthat considers occupancy, operatinghours, and all aspects of the interiorand exterior climates.

Goal:The needs assessment yields moreprecise energy use requirements, which,in turn, helps determine the applicabilityof low-energy building strategies.

Best Applied:The needs assessment isappropriate for use on all projects.

How to Do It: Classify users on the basisof specific needs that directly relate tospecific low-energy building strategies.In addition to temperature, humidity,and general lighting standards, focuson other user needs such as the desirefor exterior views and natural daylight;tolerance to moving air and temperatureswings; and the type of automatic light-ing control that is most appropriate fora given user.

Related Strategies:The needs assessmentis considered a prerequisite to almost allother strategies.

Comments:This document may be seenas an expansion of the typical needsassessment procedure, and as such, may

entail revision(s) to standard agencyassessment protocols. Coming up withuseful questions to ask in the needsassessment requires an understandingof the effects of various low-energydesign strategies on user comfort.

Building-Appropriate Site Selection

Description:This process involves choos-ing a site that fully supports the energyreduction strategies contemplated forthe project.

Goal:Proper siting increases the likeli-hood that many other low-energy build-ing strategies can be implemented.

Best Applied:This strategy is appropriatefor all new building projects.

How to Do It: During site selection, locate buildings that do not require extensiveexterior exposure on shaded or confinedurban sites. Buildings that will benefitfrom a greater degree of exterior expo-sure should be located on open sites.

Related Strategies:See Extended Plan.

Comments:For many projects, the sitemay have been selected before the man-agers involvement.

Complementary Building UsesDescription:This process involves defin-ing the nature of the facility and thenmatching the end use with complementa-ry energy needs and minimizing theresulting wastes.

Goal:The design team takes advantageof the natural symbioses and commonal-ties that exist between building uses thatmight otherwise be overlooked.

Best Applied:When compatible projectsare at similar points in their development;ideally, from the planning stages forward.

How to Do It: At the earliest stages of project conception and site selection,consider co-locating any types of facili-ties where the waste products of onecan be used to provide needed energyfor another, or where construction- based support services can be shared.

Related Strategies:Building-AppropriateSite Selection; User Energy NeedsAssessment

Comments:Currently used in designingco-generation facilities, ecological indus-trial parks, district heating, and commu-nity-scale energy storage facilities; otherapplications may be identified on a case- by-case basis. Opportunities may alsoexist for co-locating non-pollutingindustrial and residential facilities. Inall circumstances, action is required atthe earliest stages of the project, beforedetailed plans for the various uses arefully developed.

Project Planning Phase In close consultation with agency projectpersonnel, the design consultants (e.g.,architects and engineers) prepare initialand schematic design options. At thistime, options for placing the proposed building(s) on the site and massing alter-natives are evaluated. Fundamentallow-energy design strategies (as detailed below) are also assessed for applicabilityto a specific project. Design consultants

generally present their design options andanalyses to agency project personnel forreview and evaluation; this process isoften repeated several times until the

basic design is decided upon and

approved. At the conclusion of thisphase, the design should clearly indi-cate which low-energy design strategieshave been incorporated in sufficientdetail so that heating and cooling loadscan be estimated and so HVAC systemoptions can be examined.

Action Items

Establish an interdisciplinary designteam, including an energy professional,as early in the process as possible.

Develop a preliminary layout thatmaximizes or minimizes solar gain.Consider atrium spaces, direct or indi-rect passive solar heating, earth-protected spaces, and natural andconstructed shading.

Develop landscape plans that con-tribute to the facilitys energy perform-ance. Consider shading options, wind

breaks, and using existing site features.

Develop a basic layout that maximizesthe use of daylighting. Consider building

orientation, the size and placement of windows, and toplighting.

Investigate using renewable powersources as part of the facilitys overallpower supply. Consider using solar(domestic) hot water on building typeswith high hot water usage (such as labo-ratories) and building-integrated photo-voltaics (BIPV) to reduce reliance onnon-renewable power.

Conduct a preliminary energy analysis(analysis tools depend on scale of proj-

ect). Use ENERGY-10 and other user-friendly tools for smaller, simpler projects(those with two or fewer zones, androughly 50,000 square feet or less). UseDOE 2.2 and other applicable tools forlarger and more complex projects.

Strategies to Consider During ThisPhase

The following strategies need to beassessed during the project planningphase of the time line. Their incorpora-

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15

tion will influence the overall siting andmassing of the building, as well as the basic organization of spaces.

Perimeter Circulation Space

Description:This passive solar strategyuses circulation (corridors) and casualmeeting spaces as buffers between thefaade and the interior conditionedspaces.

Goal:To support several low-energy building strategies that are not compatible with certain uses (e.g., direct-gainsunspaces and office space).

Best Applied:The strategy is appropriatein buildings needing large areas for cir-culation, waiting, and casual meetings,

such as a visitors corridor in a hospitalor casual meeting sunspaces outsidelaboratories or offices.

How to Do It: Because perimeter circula-tion plans generally require slightlymore total floor area, it is necessary toexamine user needs and evaluate thestrategy in light of the overall budget.If the strategy is acceptable, look for buffer spaces that can be located alongthe buildings exterior, particularlyalong the south faade.

Related Strategies:Atrium Spaces; OpenOffice Space at Perimeter; Direct-GainPassive Solar Heating; Daylightingthrough Windows; Light Shelves;Selective Glazing; Shading Devices;Window Geometry; Natural Ventilationthrough Windows.

Comments:An accurate energy needsassessment is key to the effective inte-gration of this strategy.

Extended Plan

Description:By extending the plan to pro-duce a longer, narrower footprint, youcan create more exterior wall surface. Inmost climates, elongating the buildingin an east-west direction makes the mostsense from the standpoint of daylightingand passive solar heating.

Goal:To increase the amount of usablespace that is close to an outside wall.

Best Applied:Building types that benefitmost from exterior exposure include

good candidates for daylighting anddirect-gain passive solar heating.

How to Do It: This is best accomplishedearly in the design process, as modifyingthe basic building form may occasion aslight increase in the construction budget.

Related Strategies:Atrium Spaces; OpenOffice Space at Perimeter; PerimeterCirculation Space; Daylighting throughWindows; all forms of Passive SolarHeating; Building-Appropriate SiteSelection; Landscape Shading; LightShelves; Shading Devices; NaturalVentilation through Windows.

Direct-Gain Passive Solar Heating

Description: Installing south-facing glaz-

ing in an occupied space enables the col-lection of solar energy, which is partiallystored in the walls, floors, and/or ceilingof the space, and later released.

Goals:With direct-gain passive solarheating, the savings achieved in heatingenergy is augmented by the aestheticand productivity-enhancing benefitsof daylighting, a valuable amenity foroccupants. The functioning of the spaceshould not be compromised by directglare from glazed openings or by local

overheating.

Best Applied:This strategy works well incold, clear climates.

How to Do It: Glazing must face within15 degrees of true (solar) south, and theaffected areas must be compatible withdaily temperature swings.

Examples:Some appropriate contexts fordirect-gain heating include corridorspaces, eating spaces, meeting spacesthat can be scheduled for use duringtimes when the temperature is mostcomfortable, sleeping spaces, and recre-ational sunspaces. Working with theenergy consultant, the designer can finetune the amount and type of glazingwith glare and temperature controls,materials in the affected space, auxiliary

heating, and cooling to address localclimatic changes.

Related Strategies:Atrium Spaces; Differ-entiated Faades; Extended Plan; Perim-eter Circulation Space; Daylightingthrough Windows; Building-Appropri-ate Site Selection; Landscape Shading;Selective Glazing; Shading Devices;Window Geometry.

Comments:Because true north and mag-netic north are different, the design teamwill need to account for magnetic decli-

An example of direct-gain passive solar used in a residential building.


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nation. For optimum effect, floor andwall finish materials with high heat-storage capacity must be exposed todirect illumination by the low wintersun. Overall, this strategy is considered

central to low-energy building design. Atrium Spaces

Description:Atrium spaces are multi-floor open areas appropriate for circula-tion, lobbies, dining, or other sharedspace. Atriums are typically covered

by a glazed roof or one that incorpo-rates roof monitors.

Goal:Configure the atrium for minimumimpact on the buildings energy load.

Best Applied:Buildings with programmed

spaces that can be well-served by one ormore atrium spaces.

How to Do It: Avoid configurations thatproduce heat losses or gains with nocompensatory benefits. The atriumshould bring daylight to the interior of the building while providing a chim-ney for natural ventilation during mildweather. In some cases, atriums can col-lect useful solar heat in cold climatesserving as a kind of transition zone, withlarger temperature swings than would

otherwise be appropriate in the rest of

the building. The atriums configurationshould be defined at the earliest possiblestages of the design process, before anundesirable or arbitrary configurationis locked in.

Related Strategies:Building-AppropriateSite Selection; Extended Plan; PerimeterCirculation Space; Roof Monitors; GlazedRoofs; Fabric Roofs; Direct-Gain PassiveSolar Heating; Selective Glazing; ShadingDevices; Induced (Stack-Effect)Ventilation.

Comments:There is no hard and fast dis-tinction between atriums and glazedroofs over large open spaces (such asgallerias).

Induced (Stack-Effect) Ventilation

Description:Heated air rises within amid- or high-rise building to the top(often below a glazed roof in an atrium),where it exits through roof openings.This process induces ventilation of theadjoining spaces below.

Goals:This strategy removes heat andreduces mechanical cooling and fanenergy use requirements.

Best Applied:Spaces that are not adverselyaffected by increased air motion areappropriate targets for natural whole- building ventilation, which effectivelyconditions the space during fair weatherwithout using air conditioning.

How to Do It: Incorporate air inlets, gen-erally in the form of operable windows,at the building perimeter. For best results,use open-office space planning andavoid partitions that inhibit air move-ment. Consider complementing naturalventilation with controllable passiveventilators located in the upper portions

of the building. Carefully coordinate theimplementation of this strategy with building HVAC system and controls.

Related Strategies:Atrium Spaces; GlazedRoofs; Roof Monitors; Natural Ventila-tion through Windows; Night-timeCooling Ventilation.

Comments:Natural ventilation works best in low-humidity climates. An atri-um often serves as an ideal chimney toexhaust hot air.

Open Office Space at Perimeter

Description:Locating private offices atinterior positions leaves the perimeteropen to general office space.

Goal:Program open spaces at the peri-meter to allow for more extensive use of daylighting deeper into interior sections.

Best Applied:Use this strategy in build-ings with large areas of office space.

How to Do It: Private, interior-locatedoffices need compensating amenities. Atminimum, install glazing that lets ontothe open office space or overlooks anatrium space. This strategy is especiallyappropriate for buildings with limitedfaade glazing, such as earth-protected

buildings.

Related Strategies:Atrium Spaces; Earth-Protected Space; Perimeter CirculationSpace; Daylighting through Windows;Light Shelves; Selective Glazing; ShadingDevices; Window Geometry; NaturalVentilation through Windows.

Comments:This is an effective strategythat requires a strong commitment bythe agency or organization to keepperimeter spaces open and not reservethem for high-ranking executives. (Thisis perhaps not as significant an issue inFederal buildings as compared to theprivate sector.)

Landscape Shading

Description:The use of existing orplanned trees and major landscapingelements to provide beneficial shading.

Goal:Locate trees and major landscapeelements to provide useful shading andreduce cooling loads.

Best Applied:Landscape shading works

best when shading west and southfaades.

How to Do It: Study planting plans of existing site landscaping to determinewhether existing trees can be retainedand incorporated into the planningprocess. Perform shading analyses of plants in both immature and matureforms to estimate energy savings duringplants anticipated life span. Wheneverpossible, avoid or remove plantings thatwould compromise useful solar gain.

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An example of an atrium space.

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Related Strategies:Atrium Spaces; Day-lighting through Windows; all forms of Passive Solar Heating; Building-Appro-priate Site Selection; Selective Glazing;Shading Devices; Natural Ventilationthrough Windows.

Comments:Trees and landscaping canreduce peak cooling loads through shad-ing and can cool the ventilation airentering a building. Even during thewinter, most deciduous trees and plantscast substantial shade on solar collectors(e.g., south-facing windows).

Earth-Protected Space

Description:Bermed, or partially buried,construction can moderate buildingtemperature, save energy, and preserveopen space and views above the building.

Goals:To minimize heating and coolingenergy use by protecting more of the

building from fluctuating outdoor airtemperatures.

Best Applied:Sites with a large naturalslope in cold climates are ideal candi-dates for incorporating earth-protectedspaces.

How to Do It: Berm against walls or earth-cover roofs (in severely hot or cold cli-mates) or combine high horizontal win-dows with light shelves located aboveearth-sheltered walls. In some cases,

using "invisible" earth-protected build-ings can help counter community resist-ance to bulky new construction.

Related Strategies:Open Office Space atPerimeter; Roof Monitors; Building-Appropriate Site Selection; LandscapeShading; Insulation.

Comments:Similar low-energy perform-ance can also be achieved by using addi-tional insulation.

Solar Water Heating

Description:Solar water heating usesflat-plate solar collectors to preheatdomestic hot water.

Goal:To be considered effective, thisstrategy should yield a significant por-tion (50% or more) of the domestic hotwater needed for day-to-day operations.

Best Applied:Look to building typeswhere hot water use is high year-round,such as hospitals and laboratories. Bestperformance will be achieved in hot cli-mates with high solar radiation levels.

How to Do It: Design an array of flat-platesolar collectors that include an absorberplate (usually metal), which heats whenexposed to solar radiation. Most common

among these are indirect systems thatcirculate a freeze-protected fluid througha closed loop and then transfer heat topotable water through a heat exchanger.Typically roof-mounted, solar collectorsshould face south and tilt at an angleabove horizontal, approximately equal

to the latitude of the project location. Thisconfiguration will provide optimumyear-round performance. Provide a pipechase to a mechanical room. The roomneeds to be large enough for storage

tanks.Related Strategies:Roof Monitors; Non-Absorbing Roofing.

Comments:Collectors should be mountedin a location that is unshaded by sur-rounding buildings or trees during thehours of 8 a.m. to 4 p.m. (at minimum)throughout the year. As is the case withmany of the strategies described herein,an effective conservation program willhelp to minimize hot water demandand, in turn, reduce material and sys-

temic requirements.Building-Integrated PhotovoltaicSystems

Description:Photovoltaic (PV) arrays arenow available that take the place of ordi-nary building elements (such as shinglesand other roofing components), convert-ing sunlight into electrical energy with-out moving parts, noise, or harmfulemissions.

Goal:Reduce the first cost of the PV

array by using it in place of high-cost building elements and take into accountthe energy cost reductions over time.

Best Applied:Consider deployment insunny climates with high electrical utilitycharges.

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Landscaping and trees help minimize heat gain to the building and surroundingconcrete.

An example of an earth-sheltered building in Tempe, Arizona.

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How to Do It: Commercially availablesystems include thick, crystal, circularcells assembled in panels and thin-filmproducts deposited on glass or metalsubstrates. At todays prices, BIPV often

provides a good payback if it replaceshigh-cost glazing, such as fritted glass(the arrays can even resemble frittedglass). To be cost effective, BIPV mustintercept nearly a full days sun, so it isoften most effective as a replacement forroof or atrium glazing. BIPV also workswell as spandrels that are fully exposedto the sun.

Related Strategies:Atrium Spaces;Differentiated Faades; Glazed Roofs;Roof Monitors; Building-AppropriateSite Selection; Shading Devices.

Comments:One of the benefits of grid-tied BIPV systems is that power produc-tion is typically greatest (on bright, sunnydays) at or near the time of the build-ings peak electrical and cooling loads.

Schematic Design (or Preliminary Design) Phase

During the previous phase of the timeline, Project Planning, basic decisionswere made regarding site placement,plan organization, and building mass-ing. Those determinations will nowinfluence the basic low-energy design

strategies (e.g., daylighting) that will be evaluated in detail during this phase,especially those relating to the buildingenclosure (or envelope).

Traditional building design has assigneda protective role to the walls, roofs, andfloors of buildingsprotection againstcold, sun, rain, and unwanted intrusion.In low-energy building design, the pro-tective role still exists, but the buildingenvelope is also thought of as a mem- brane that manages or mediates inter-actions between the interior spaces andthe outside environment. During sche-matic design, the Envelope-RelatedStrategies discussed below will beevaluated and integrated into theoverall building design.

Action Items

As the preliminary layout is refined,ensure that access to daylight continuesto be optimized. Consider perimeteraccess to light and views, roof monitors,skylights and clerestory windows, andlight shelves.

Develop material specifications and a building envelope configuration thatmaximizes energy performance. Considerwindow shape and placement, shadingdevices, differentiated faades, reflectiveroofing, fabric roofs, induced ventila-tion, nighttime cooling ventilation, andselective glazing.

Continue energy analyses, includingmultiple runs of similar products (e.g.,various glazings and insulation levels)to determine best project-specific options.In addition to first cost, consider durability and long-term energy performance.

Strategies to Consider During this Phase

Selective Glazing for Walls

Description:Glass products are nowavailable with a wide range of perform-ance attributes that allow designers tocarefully select the amount of solar gain,visible light, and heat that they allow topass through. Solar heat is measured bythe properties of shading coefficient(SC) and solar heat gain factor (SHGF).An SC of 1.0 applies to clear 1/8-inch-thick glass with other glasses that admit

a lesser amount of solar heat having alower SC (e.g., 0.50 for a tinted glass thatadmits 50% as much solar heat as 1/8-inch clear glass). The term SHGF, whichis now widely used by the glazing (fen-

estration) industry because it takes intoaccount a range of angles of solar inci-dence, is considered to be equal to avalue of 0.86 times the SC. The degreeof daylight, or visible light transmission,is expressed by the term Tvis, and theamount of heat loss is measured by theU-factor, which, expressed numerically,is the inverse of the total resistance of the glazing assembly.

Single-glazing is about R-1 or 1/1 for aU-factor of about 1.0. Double-glazing isabout R-2 for a U-factor of about 0.50.Commercially available low-e glasstypically ranges in U-factor from about0.35 down to 0.10, depending on thetype and number of coatings and thefills (e.g., argon) used in the spaces

between glazing layers.

Goal:Specify glazings with the best com- bination of performance characteristicsfor the specific application at hand.

Best Applied:The choice of glazing(s) isan essential consideration for all build-

ing types. How to Do It: Begin by incorporatingglass performance characteristics (e.g.,U-factor, shading coefficient) as required

by the applicable codes or standards.Then, use computer analysis to investi-gate alternate glazings and narrow thefield to those most beneficial to admit-ting daylight and saving energy, whilestill remaining within the project budg-et. Glazing technology has nowadvanced to the point that alternativeglazings with very different perform-ance characteristics can physically lookvery much alike. This increases thepotential to use different glass typeson different faades, although such anapproach may be considered a mainte-nance headache. The best glazing selec-tions are not merely those with thehighest numerical performance levelsin a given area. For example, daylightinga space with a large expanse of glass,using glazing with the highest daylight

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An example of Building-Integrated PV is 4 Times Square in New York City.

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transmission may result in excessiveglare. Fritted glass should be consideredwhen glare reduction through othermeans is difficult to achieve.

Related Strategies:Atrium Spaces; GlazedRoofs; Roof Monitors; Scattered Sky-lights; Daylighting through Windows;Direct-Gain Passive Solar Heating;Landscape Shading; Light Shelves;Shading Devices; Window Geometry.

Comments:Of the various building enve-lope components, glazing almost alwayshas the most significant effect on heat-ing, cooling, and lighting energy use. Inthe last 20 years, glazing technology hasprogressed more dramatically than per-haps any other building product or sys-

tem. By using high R-factor glazing(indicating substantial resistance to heatinflow), it is often possible to eliminateperimeter baseboard heaters.

Shading Devices

Description:Fixed or movable (manualor motorized) devices located inside oroutside the glazing are used to controldirect or indirect solar gain.

Goal:Shading should be used to providecost-effective, aesthetically acceptable,

functionally effective solar control.Best Applied:This strategy works well onsouth faades where overhangs provideeffective shading for work space and canalso serve as light shelves. Shading westfaades is critical to reduce peak coolingloads.

How to Do It: A wide range of shadingdevices are available, including over-hangs (on south faades), fins (on eastand west faades), interior blinds andshades, louvers, and special glazing

(such as fritted glass). Reflective shadingdevices can further control solar heatgain and glare.

Related Strategies:Atrium Spaces; BIPV;Differentiated Faades; Open OfficeSpace at Perimeter; Perimeter CirculationSpace; Glazed Roofs; Roof Monitors;Scattered Skylights; Daylightingthrough Windows; Direct-Gain PassiveSolar Heating; Light Shelves; SelectiveGlazing; Window Geometry.

Comments:Devices without moving partsare generally preferable. Movable deviceson the exterior are typically difficult tomaintain in corrosive environments orin climates with freezing temperatures.

Other building elements, such as over-hanging roofs, can also serve as shadingdevices.

Daylighting through Windows

Description:Using daylighting through building windows can displace artificiallighting, reduce energy costs, and isassociated with improved occupanthealth, comfort, and productivity.

Goal:Reduce lighting and cooling energymore than the increase in heating energyoccasioned by reduced lighting loads.(In summer, cooling energy demandis less because the heat from artificiallighting sources is reduced. In winter,the heat that is not being produced byartificial lighting may need to be com-pensated for by the buildings heatingsystem).

Best Applied:Daylighting through win-dows is best accomplished on faades

that have a generally clear view of thesky, particularly the sky at angles of 30degrees or more above the horizon.

How to Do It: Place much of the faadeglazing high on the wall, so that day-light penetration is deeper. Considerthe enhanced use of daylighting byinstalling light shelves on southfaades. Recognize the interdependen-cies in glazing, light fixtures and con-trols, and HVAC systems. Wheneverpossible, electrical lighting should beconsidered a supplement to natural light.When the sun goes down on buildingswith long hours of operation, however,efficient electrical lighting design takeson added importance.

Related Strategies:Differentiated Faades;Extended Plan; Open Office Space atPerimeter; Perimeter Circulation Space;Direct-Gain Passive Solar Heating;Building-Appropriate Site Selection;Landscape Shading; Light Shelves;Selective Glazing; Shading Devices;Window Geometry.

Comments:Daylighting is a central com-ponent of the vast majority of low-energy

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Shade from trees is a simple but effective strategy to reduce costly cooling requirements.


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buildings and, as such, merits significanttime and attention.

Extended Daylighting throughWindowsLight Shelves

Description: A horizontal device or shelfthat bounces direct sunlight off the ceil-ing and deeper into the interior spaces.Light shelves are also used to provideshading and suppress glare. Lightshelves are located above vision glazing(up to and slightly above eye level), but

below high glazing above. They may bepositioned inside or outside (where theyalso provide shading), or both (this istypical).

Goal:Save lighting energy, reduce glare,and provide useful shading.

Best Applied:In clear climates, lightshelves are appropriate for integrationon faades facing within about 30 degreesof true (solar) south.

How to Do It: Integrate the light shelveswith faade design, office layout, light-ing design, lighting controls, glazing,and shading devices. They tend to work

best with moderately high ceilings(about 10 feet, minimum) and openplanning.

Related Strategies:Differentiated Faades;Open Office Space at Perimeter; Day-lighting through Windows; SelectiveGlazing; Window Geometry.

Comments:Transom windows can beused to allow light from the shelves toenter interior office spaces located farfrom exterior walls. Maintenance may

be an issue, and pigeons present a con-cern in some areas.

Natural Ventilation through Windows

Description:User-controlled operation of windows provides outdoor air for venti-lation and cooling, and should improveindoor air quality.

Goal:A balanced approach involves tak-ing advantage of users desire for envi-ronmental control without interferingwith efficient HVAC operation.

Best Applied:Particularly appropriate in building types and locations wheresecurity concerns and exterior noise or

air quality is not an issue. Users must be tolerant of increased horizontal airmotion.

How to Do It: Locate windows that willserve as air inlets to face prevailingwinds. During the cooling season, thisstrategy can be enhanced by landscap-ing features and projecting building fea-tures (such as fins). This strategy tendsto work best in residential-type occu-pancies, where the user already hascontrol over HVAC.

Related Strategies:Atrium Spaces; Differ-entiated Faade; Perimeter CirculationSpace; Window Daylighting; LandscapeShading; Window Geometry; Econo-mizer Cycle Ventilation; Induced Venti-

lation; Nighttime Cooling Ventilation.Comments:A well-considered controlstrategy (either mechanical or social)is required to prevent air conditioningfrom operating in a space with openwindows. If such a control strategy can-not be devised or is not effective or real-istic because of the building occupants,operable windows can increase buildingenergy use.

Window Geometry

Description:Windows should be shapedand located in a manner that minimizesglare and unwanted solar gain and max-imizes useful daylight and desirablesolar heating.

Goal:The design team should applyfunctional criteria to the size, propor-tion, and location of windows. It isimportant to avoid incorporating morewindow area than is beneficial to the

building occupants or that is neededto enhance low-energy performance.

Best Applied:Shape, size, and location of windows are important considerationsin all projects.

How to Do It: Make window decisions based on occupant activities and low-energy performance rather than

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