The Building Envelope: Energy Efficiency and Economics

ISSUE 4/2009  V O L U M E 2 6  N U M B E R 4

Journal of architectural technology published by Hoffmann Architects, Inc., specialists in the rehabilitation of building exteriors. The Building Envelope: Energy Efficiency and Economics

Richard P. Kadlubowski, AIA and Dean W. Yates, AIA

According to the U.S. Environmen- As these structures age, we are tal Protection Agency (EPA), the con- faced with a choice: rehabilitate and struction and operation of buildings is upgrade the inefficient buildings, or responsible for nearly half of America’s replace them. greenhouse gas emissions. In com- With landmark and historic struc- parison, all forms of transportation tures, the importance of preserving combined—including airplanes, trucks, the existing building is clear. But what buses, and cars—account for just a about buildings that are neither ef- quarter of total emissions. Because so ficient nor architecturally significant? much of the country’s building stock Replacing an old building with a new was constructed when fuel was cheap one uses energy. That energy takes and plentiful, little regard was paid to many, many years to recover through designing energy-saving enclosures. improved performance—if at all. A better approach, then, is to improve the energy profile of the buildings we already have. To cut back on energy consumption, federal, state, and local authorities have adopted increasingly rigorous standards for building performance. These regulations, along with tax incentives for improved energy management, have led to an upsurge in energy efficiency retrofits for existing structures. Before investing in major capital improvements to heating and cooling systems, however, consider making simple, less costly upgrades to the building enclosure. A sound exterior envelope acts as a thermal shield, reducing demand on HVAC As the barrier between the indoor and outdoor environments, the building envelope is critical equipment, improving indoor comfort, to energy performance. and extending the lifespan of building components.

Richard P. Kadlubowski, AIA, vice president and senior architect, and Dean W. Yates, AIA, project architect, manage projects at Hoffmann Architects’ Washington DC office. They develop energy-saving strategies for the building envelope that are sensitive to system interdependence, performance objectives, and cost-effectiveness. JOURNAL

Roofs HEAT CONDUCTED THROUGH WET INSULATION More often than not, faulty roofs are behind performance-compromising conditions, from leaks to heat loss. As WARM AIR EXFILTRATION the portion of the building hit hardest AT OPEN by acid rain, UV light, snow, ice, foot JOINTS AND traffic, and chemical pollutants, the GAPS IN roof tends to degrade faster than do INSULATION other portions of the building exterior.

Leaks Are More than Dripping Water They’re also a source of heat loss. Wet roofing materials lose their insulating properties, causing the roof to act as a conductor, rather than an COLD insulator. Heat rises, so without a OUTSIDE thermal barrier at the roof level, heat AIR travels up and out of the building. Limit potential points of water entry by minimizing the number of pen- HEAT LOSS etrations through the waterproofing THROUGH POOR WINDOW SEALS membrane. Don’t neglect flashing details; the roof perimeter, along with any intersections between the roof membrane and parapet walls, pent- WARM RADIATION houses, or other roof levels, is an easy target for moisture if not correctly INSIDE AIR THROUGH WINDOWS sealed and protected by the flashings. Is Your Insulation Really Insulating? Insulation secured with fasteners may not have you covered as well as you thought. For steel decks, the metal acts as a thermal bridge, conducting HEAT LOSS heat through the insulation. A safe- THROUGH guard would be a multi-layer system, COLD AIR WET with chemically adhered insulation INFILTRATION INSULATION over mechanically fastened boards. Even with fully adhered insulation, if sections are not fully abutted, it is pos- sible for air to pass through the gaps between boards. Staggered joints cover any space between sections.

Not Every System Is Right for Every Building Cool roofs, green roofs, solar roofs… Heat Loss In Winter overwhelmed with all the options? You’re not alone. But the kind of

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A design professional can assess your Cool roofs reflect heat, cutting energy costs and normalizing urban temperatures. Pictured roof’s insulating properties. here is a modified bitumen roof (MBR) with a reflective capsheet. building you have—as well as the roof absorbing concrete and asphalt, cool Facades that’s already in place—might make roofs help to cut down on mass heat A facility manager replaces outdated choosing an energy-efficient roofing retention known as the “heat island cooling equipment to improve energy system easier than you thought. effect.” When selecting a product, performance, then adds a solar film Green roofs, also known as vegetated consider material shortcomings, such to the windows as an inexpensive ef- roofs or verdant roofs, incorporate as potential for split seams or non-uni- ficiency upgrade. Smart thinking, right? plants into the roof assembly. They form coverage; for some systems, the Well, almost. These are both good add insulating value, reduce storm risk of premature failure may outweigh ideas—just in the wrong order. the benefit of increased reflectance. water runoff, cool the building interior The facility manager bought the chiller and the surrounding area, provide Solar roofs use photovoltaic cells to system to accommodate existing cool- habitat for birds and insects, and look convert sunlight into usable energy. ing demands, and then reduced those great. But they can also be heavy. Solar panels are not a roofing material, demands by adding the window coat- While this might be an excellent however; like any rooftop equipment, ing. Not only did the facility manager sustainable retrofit for some buildings, they can cause leaks if installed incor- overspend, the now-outsized chiller it could be structurally disastrous for rectly. Unless your roof is in good wastes energy, costs more to operate, others. Before you commit, a design shape, the expense of repairing water and decreases indoor comfort. professional should evaluate the load- damage could cancel out any cost sav- bearing capacity of the building and The lesson: before making big-ticket ings from the solar power. determine if structural modifications improvements to mechanical systems, would be necessary to support plant- The Energy Star program, created by ensure that your facade provides a ings, growing and drainage media, and the U.S. Environmental Protection good thermal barrier. related components. Agency and the U.S. Department of Seal It Up… Cool roofs sound appealing. But what Energy, can help you and your de- Cracked, loose, or missing mortar is a cool roof, anyway? In its simplest signer evaluate the options, with tools joints and deteriorated sealant joints form, a cool roof is just a roof that’s to measure performance, compare allow moisture to enter the wall. Be- light-colored. So what’s the hype? products, and track savings. All of the cause water conducts heat, wet walls Darker colors absorb heat. A white above systems can earn Leadership lose their insulating value and make or reflective roof can cut cooling costs in Energy and Environmental Design mechanical equipment work harder to by reflecting heat away from the (LEED) points for a retrofit project. keep up with heat transfer. The same building. In urban areas, where there The important thing is finding which holds true for glass curtain walls and one is right for your building. is little greenery and lots of heat- windows, where deteriorated gaskets

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Problem areas to watch for: Solar films or tints keep rooms • Broken gaskets and seals. Without cooler in bright sunlight and cut down a proper seal, windows permit on glare. Shaded glass that responds water and air to pass through at the to an applied electrical current offers perimeter. Condensation between variable opacity control. panes usually points to a broken Thermal breaks, which are plastic or thermal seal, which means that the rubber separator materials, minimize insulating capacity of the window heat conduction across inner and has been compromised. outer window frames. Repair cracks, but leave weep holes open, • Failed thermal breaks. Cold / hot Technologies are constantly evolving. so water can make a quick exit. spots or condensation on window Work with your design professional to frames could point to damaged or assess your energy goals and building and seals not only let in water, they missing insulator material. condition to maximize window ef- create drafts and temperature fluctua- • Glare. Daylighting is important ficiency and minimize costs. tions at the building periphery. to minimizing energy consumption, but when it comes to sunlight, ...But Let It Out more isn’t necessarily better. Glare Not all holes in the building exterior diminishes visibility, particularly at are bad. Often, well-meaning mainte- computer workstations. nance personnel make the mistake of • Solar heat gain. Direct sunlight can sealing over weep holes, small voids in also cause overheating. Designers exterior walls that drain water from use the solar heat gain coefficient within the wall cavity. When dry, these (SHGC), a measure of transmitted cavities provide insulating value. But if solar energy, to optimize windows’ water becomes trapped, the thermal impact on indoor temperature. conductivity of the wall increases and Failed sealant provides a pathway for heat, air, and moisture transfer. heat escapes. The constant presence • Drafts. Heat fluctuations not only of moisture also leads to other prob- mean that HVAC systems have to work harder to stabilize tempera- lems, from mold growth to building ture, the variable conditions can Are Your Doors Leaving You Wide component degradation. make the building periphery uncom- Open? fortable. In terms of square footage, windows Strategies for improving window outrank doors as the facade element performance range from taking aim most critical to energy conservation. with a caulking gun to installing energy Acres of leaky single-pane windows efficient replacements. To maximize are much more of an energy concern natural lighting, reduce heating and than are a half dozen inefficient exte- cooling costs, and control the undesir- rior doors. Still, a building enclosure is able effects of overheating and glare, only as good as its weakest element. look for windows with some or all of If doors are drafty, an entrance lobby Condensation doesn’t just cloud the view, these properties: can feel unpleasantly hot or cold, and it points to poor thermal performance. Insulated glazing units (IGUs), also HVAC systems will run overtime. If called double-glazed or triple-glazed the insulating value of your doors is windows, improve thermal perfor- low, it might be worthwhile to replace Don’t Let Heating Dollars Fly Out them. As with windows, doors need the Window mance with the insertion of a gas or vacuum space between panes of glass. regular upkeep to maintain their rated To avoid overspending, have an archi- level of thermal protection, including Low-emissivity (low-E) glass reflects tect or engineer evaluate your existing periodic sealant replacement, hard- infrared radiation, and so reduces windows and recommend appropriate ware maintenance, and frame and heat transfer without affecting natural threshold repairs. options. lighting.

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What Is “Building Envelope Commissioning”? “Commissioning” is a term that’s being bandied about in the industry, but it’s really just a new way of expressing an old idea: make sure everything works together. A changing industry. Time was, buildings were made of a limited range of materials and built by master craftsmen. With the expanding array of building materials and shifting styles of contemporary construction, it’s difficult for an installer to have prolonged experience with any one type of system. Combine the daunting number of material options with decreased training Commissioning often includes performance testing, such as for construction teams, and you have a recipe for trouble. water intrusion tests, to see that assemblies react as designed. A demand for oversight. Building envelope commissioning addresses this problem by posting a building enclosure expert, usually an architect or engineer, at the job site. To assure the continuity of interdependent systems, he or she oversees the work of the diverse contractors, designers, and specialists responsible for the building envelope. An efficient building, built efficiently. From an energy conservation perspective, commissioning is important on a number of levels. First, it avoids wasted time and resources by managing installation sequencing and construction scheduling. Second, it protects against premature component failure due to incompatible materials or differential movement. Finally, it optimizes building envelope performance by identifying and correcting energy leaks at building intersections. A holistic approach to energy upgrades enables the building enclosure to function as an integrated system, rather than as a collection of disjointed parts.

Below-grade Elements can be detected through infrared testing can be a useful diagnostic tool. thermographic testing. When incorporated into a compre- An un-insulated basement might be costing more than you’d expect, Infrared analysis can locate thermal hensive condition assessment, infrared especially if mechanical equipment is anomalies caused by, for example, analysis can save resources by priori- housed below grade. In winter, the missing insulation, air or moisture tizing renovation efforts and avoiding average temperature of earth, which is infiltration, or “hot spots” where unnecessary repairs. the same as that inside most un-in- mechanical or electrical equipment is Warranty Considerations sulated basements, is about 55°F. As malfunctioning. Thermography is non- heat moves through exposed ducts, it invasive and can be performed during Before putting an energy manage- raises the temperature of the sur- normal building operation. Using tem- ment plan into effect, check war- rounding air and escapes through the perature scanners, the test generates ranties. Some modifications, while walls. Adding insulation to ducts, base- pictorial representations of a building well-intentioned and, even, perfor- ment walls, and ceilings can therefore component’s thermal profile. Correct mance-enhancing, might void the reduce heat loss. As further incentive, analysis of this data can reveal prob- terms of the warranty. For example, protecting ductwork and mechanical lems not otherwise identifiable on an most roof membrane manufacturers systems helps to extend their service- existing, occupied structure. offer warranty protection but include able life by reducing on/off cycling stipulations about post-installation However, accurate interpretation of and heating loads through improved alterations. The same holds true for thermal images demands understand- efficiency. windows, doors, waterproofing mate- ing of building envelope composition. rials, and anything else with a written Quantifying Heat Loss Certain types of construction tend to guarantee. Be on the lookout, too, dissipate heat, leading to false negative Visual observation provides a general for how components interact; don’t readings, whereas others reflect heat attempt to reduce roof penetrations, picture of building envelope condition, and generate false positives. but there are many things you can’t for instance, by re-directing exhaust see. Deficiencies beneath the surface In the right hands, thermographic pipes without first checking with the

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an energy-efficient cool or green roof, and every window with a high-performance one. Wouldn’t it?

Not exactly. Tearing off existing components uses energy, and so does manufacturing and installing new ones. Before making the decision to replace an assembly, have a design professional evaluate your system’s condition, as well as your energy goals. A return- on-investment evaluation can tell you how quickly, if at all, you could recoup the cost of replacement through energy savings and net gain in value. Poorly performing doors make HVAC systems work overtime to stabilize temperature. LEED or Energy Star recognition for equipment manufacturer. You may find The idea behind these and other efficiency improvements can raise yourself out of luck if the equipment initiatives is to lead by example. By property values, improve tenant reten- fails due to your actions. championing energy efficiency at gov- tion, and generate a positive public ernment-owned properties, legislators image. If roofs or windows are at the Municipal, State, and Federal hope to encourage broader adoption end of their lifespan, it makes sense to Regulations of similar carbon-reduction measures. install new, energy-efficient materials. But replacement of a serviceable com- Green Government Tax Incentives ponent for the sake of energy savings A number of state and federal agen- alone may not be worth it. For energy efficiency upgrades that cies have adopted “green” policies reduce heating and cooling loads for retrofits and rehabilitations. A All building types can benefit from by at least 50%, the IRS offers a tax sampling: better energy management. The deduction of up to $1.80/sf. Partial real dollar value of energy efficiency • In Washington DC, The Architect deductions can be taken for measures measures lies in knowing which im- of the Capitol (AOC), steward of that specifically target the building provements are appropriate—or, even, the U.S. Capitol complex, initiated envelope. In addition, some states and necessary—for your building. “Power to Save,” which encourages municipalities have their own pro- energy savings through operational grams to help offset the initial expense Realistic Goals for Existing improvements. “Green the Capitol” of performance upgrades. Buildings sets conservation goals that include While it’s important that new struc- building enclosure performance. Code Requirements tures be designed to minimize their • In New York City, the School Because energy codes are constantly carbon footprint, the real greening Construction Authority (SCA), which changing, you may not be able to sim- of America’s cities will come with manages the city’s 1,600 public ply call in a roofer to install the same improving the energy efficiency of the schools, launched the “NYC Green system you’re tearing off, nor replace buildings that have already been built. Schools Guide and Rating System” other building components in kind. As the building’s thermal barrier, the to quantify energy and resource A design professional should evalu- exterior envelope should be the first conservation. ate applicable requirements as part step in a multi-component energy of initial cost projections, and design • At the federal level, the General Ser- management strategy. An architect appropriately. vices Administration (GSA), responsi- or engineer experienced in building enclosure design can help you deter- ble for some 8,600 federally-owned Calculating Energy Savings facilities, applies mandated efficiency mine where best to focus your efforts, and sustainability guidelines to new It would be great to replace every phasing efficiency upgrades to build on construction and major renovations. roof in a large metropolitan area with one another over time. To realize the (continued on page 8)

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Energy Efficiency

Hoffmann Architects has spent over 30 years developing building enclosure solutions to optimize energy efficiency. From heat loss evaluation to rehabilitation design, the firm’s architects and engineers have the experience to restore building integrity and improve performance. Hoffmann Architects has enhanced the energy profile of a number of buildings, including: Yale-New Haven Hospital, 55 Park Street Laboratory in New Haven, CT. New construction Packer Memorial Church consultation and feasibility assessment for curtain wall, roofing, and foundation waterproofing. Lehigh University Defense Intelligence Agency Center Aramark Tower Bethlehem, Pennsylvania Bolling Air Force Base Philadelphia, Pennsylvania Master plan to restore and weatherproof Washington, District of Columbia Masonry and window repair design the historic structure Evaluation and design for waterproofing, Kings County Hospital Center Telcordia Technologies Headquarters insulation, and sealants Brooklyn, New York Piscataway, New Jersey Paramount Building Facade repairs and roof replacement to Window energy efficiency study, including New York, New York improve weather protection at the 175- building energy modeling, tax incentive Water infiltration investigation for below- year-old facility research, and return-on-cost analysis grade pedestrian tunnel Paul Rudolph Hall Arts and Industries Building (Formerly Art + Architecture Building) Smithsonian Institution Yale University Washington, District of Columbia New Haven, Connecticut Roof investigation and repairs to address Renovation, including new energy ef- recurrent leaks ficient windows, doors, and “cool” roofs. International Concrete Repair Institute Crowne Plaza Hotel Times Square Award, and AIA New York State and New York, New York AIA Connecticut Design Awards Facade and roof design consultation, addressing air and moisture leaks Capital Community College Mastercard Headquarters Hartford, Connecticut Schering-Plough Corporation in Summit, Window, roof, and facade retrofit for NJ. Facade reconstruction to improve energy Purchase, New York profile and aesthetics. New Jersey Golden Facade and entry plaza rehabilitation to historic retail building, now part of the Trowel Award, Special Recognition. arrest water penetration and deterioration downtown campus

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Hoffmann Architects, Inc. 2321 Whitney Avenue Hamden, CT 06518

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JOURNAL is a publication of Hoffmann Architects, Inc., specialists in the rehabilitation of building exteriors. The firm’s work includes investigative and rehabilitative architecture and engineering services for the analysis and resolution of problems within roofs, facades, glazing, and structural systems of existing buildings, plazas, terraces and parking garages.

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2321 Whitney Avenue Hamden, CT 06518 203-239-6660 A building envelope energy plan coordinates improvements, such as sealant replacement, stone panel repairs, and window upgrades, to optimize component integration and efficiency. 1040 Avenue of the Americas New York, NY 10018 212-789-9915 maximum benefit from your invest- tions, and system dynamics can make ment, opt for retrofits that integrate the difference between efforts that 2611 Jefferson Davis Highway, Suite 200 Arlington, VA 22202 multiple areas and work in concert to actually improve building performance, 703-253-9800 address energy leaks. and those that waste more energy www.hoffarch.com Building enclosure improvements need than they save. not break the bank. Many simple Lower heating and cooling costs, Editor: Alison Hoffmann actions to protect against heat loss, longer building component lifespan, Production: Cari Tate such as re-sealing joints or repairing improved building integrity, better oc- window frames, do a lot without cost- cupant comfort, and increased prop- ing a lot. Attention to details, junc- erty value are some of the advantages Printed on 50% recycled paper. of well-designed building envelope Related topics are covered in other upgrades. The trick is to set energy JOURNAL issues, which can be objectives that are attainable for the downloaded at www.hoffarch.com. building you have.