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32 This chapter will discuss practices for improving energy efficiency at airports as they relate to energy conservation. It focuses primarily on the building envelope and practices that limit unwanted heat gain or energy losses through the roof, walls, windows, and openings. BUILDING ENVELOPE A key aspect of energy efficiency for any building is pre- venting energy loss or gain through the exterior envelope. If improvements are made to operations procedures or mechan- ical systems without considering improvements to the building envelope, energy may continue to be lost through unnecessary cooling loads and air infiltration. The documentation of energy savings through building envelope improvements is difficult to quantify, especially in a retrofit scenario. Cost and payback for envelope improvements are discussed where respondent information was available. A poorly designed envelope will impact occupant comfort and heating, cooling, and ventilation costs. An envelope design that is specific to climate, site, building use, and occu- pancy patterns can provide savings in the form of reduced cooling and heating loads and reduced investment in mechan- ical equipment. The cost of high-performance envelopes can be offset by smaller mechanical systems and through reduced energy costs over the life of the building (DOE 2009a). REFLECTIVE MATERIALS TO REDUCE HEAT GAIN Building materials contribute indirectly to energy consumption at airport terminals by absorbing or reflecting the sunâs energy and increasing or decreasing cooling loads (CAP 2003a, p. 27). Reflectivity or albedo and âoverall environmental life-cycle impacts and energy costs associated with the production and transportation of different envelope materials vary greatlyâ (DOE 2009a). WEBLINKâCool Roofs U.S. Environmental Protection Agency http://www.epa.gov/heatisland/resources/pdf/ CoolRoofsCompendium.pdf Cool Roof Rating CouncilâCodes and Rebate Info Activities within the building, including occupants and systems, generate a significant amount of thermal loads that can often surpass energy entering the building from sunlight. These activities affect the rate at which the building gains or loses heat (DOE 2009a). When additional energy in the form of solar radiation heats the building, cooling loads increase. The primary materials strategy to reduce solar heat gain is to increase reflectance of the surface through installation of light colored or white roofing also called âcoolâ roofing. As noted by Seidenman and Spanovich (2008, p. 23), âthe roof, in fact, presents an excellent opportunity for maximiz- ing energy efficiency at an airport terminal, since it covers a tremendous amount of space.â âReflective, or âcool roofs,â can provide a building with up to 50 percent energy savings and reduce peak cooling demand by 10â15 percentâ (Commonwealth of Pennsylvania n.d., p. 30). GLAZING IMPROVEMENTS Window glazing can affect heating and cooling requirements by managing the amount of light and heat that enters the build- ing (DOE 2009a). Solar heat gain through windows and skylights can be a problem at airports built without modern, insulated glass with low emissivity coatings. Cooling loads can be dramatically increased by direct sun on south and west facing glass during summer months. Solar control window films are one strategy that provide a low-cost way to reduce heat gain. Films are typically attached to the interior surface of glazing. They utilize patterns of dots or stripes as well as reflective material to block sunlight. When films are applied, visibility is usually reduced but not impaired. Respondents noted a payback of 2 to 5 years and medium cost to install solar control window films. INSULATION IMPROVEMENTS Increasing insulation within the exterior envelope of a build- ing can reduce heating and cooling costs by reducing the energy loss to the exterior of the building. Because most terminals are only one to three story buildings with large CHAPTER SIX ENERGY EFFICIENCY PRACTICES: CONSERVATION AND BUILDING ENVELOPE
33 footprints, the primary surface that can benefit from added or improved insulation is the terminal roof (Seidenman and Spanovich 2008). Many airports use high-performance, low-slope roofs with long life spans. Building energy code requirements for roofing insulation have most likely changed since the last time a ter- minals roof was replaced and increasing insulation R-values may be required. Roofing Replacement Roofing replacement cost for buildings the size of airport terminals can be significant and varied owing to a wide range of factors; however, extra insulation can often be added with little difficulty (DOE 2009a). Survey respondents who have completed re-roofing projects with increased or high- performance insulation noted a payback of 2 to 5 years and medium cost. Super Insulation One insulation strategy for increased energy efficiency is to provide greater levels of insulation than required by build- ing codes. Called âsuper insulation,â R-values are often double typical specifications for a given region. This strategy serves to buffer the building from outside temperature swings and maintain interior temperatures for a longer period of time. Survey data show a limited response, with those using this strategy being located in southern or far northern climates, seeking to reduce heat gain or heat loss. Recent improve- ments at Juneau International Airport (JNU) include a âhigh- performanceâ envelope with an insulation R-value of 50 as part of a renovation and replacement of a 25-year-old roof (Martin 2009). Payback periods of 2 to 5 years with medium costs were noted for super insulation practices. AIR MOVEMENT At existing facilities, airport staff and consultants have a lim- ited ability to modify many of the envelope components with- out major renovations. Of all the envelope strategies noted in this chapter, âreducing outside air infiltration into the build- ing by improving building envelope tightnessâ may be the most feasible (DOE 2009a). Primary methods of reducing air infiltration include closure of envelope penetrations and controlling doors and openings. Reducing Infiltration and Loss One airport noted that a variety of security, communications, and data equipment attached to or located on the exterior of their building had led to multiple penetrations through the envelope that wasted energy. By sealing these openings, energy savings were expected. Payback periods of 2 to 5 years with medium costs were noted at Newark Liberty Inter- national Airport (EWR) for this improvement. Controlling Doors and Openings Multiple respondents noted the utilization of high-speed, roll- up doors at high traffic openings such as baggage handling areas to reduce heat loss and manage interior temperatures. Respondents noted a payback of 0 to 5 years and a medium cost to implement opening improvements. Chapter Summary The following practices were identified within the literature and survey data as building envelope improvements that reduce energy costs and improve energy efficiency within small air- port terminal buildings (see Table 3). â¢ Reduce solar heat gain and lower cooling loads by increasing reflectivity of exterior surfaces. â¢ Utilize window films or other retrofit shade devices to reduce solar heat gain and improve occupant comfort. â¢ Take advantage of infrequent roof replacement by increasing levels of insulation. â¢ Monitor and manage exterior openings to reduce air movement and heating or cooling energy losses.
34 *Notes: 1. Paybackâtime indicated refers to years required for improvement to return cost savings equivalent to project costs. 2. Cost information is based on energy rates for 2009 at respondent airport locations. 3. Cost can be defined as total project cost and not cost per square foot. 4. Percentageâvalue given represents a yearly reduction in energy or operations costs for that system or process. TABLE 3 ENERGY EFFICIENCY PRACTICESâCONSERVATION AND BUILDING ENVELOPE