ACHIEVING ENERGY EFFICIENCY AND IMPROVING INDOOR AIR QUALITY IN ARMY MAINTENANCE FACILITIES (TEMF)

Transcription

1 ACHIEVING ENERGY EFFICIENCY AND IMPROVING INDOOR AIR QUALITY IN ARMY MAINTENANCE FACILITIES (TEMF) Alexander Zhivov, Ph.D., Dale Herron and Richard Liesen, Ph.D. USACE Engineer Research and Development Center Michael Deru, Ph.D. National Renewable Energy Lab Introduction Section 109 of the Energy Policy Act of 2005 (EPAct 2005) states that for new federal facilities the buildings be designed to achieve energy consumption levels that are at least 30 percent below the levels established in the version of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard or the International Energy Conservation Code (IECC), as appropriate (U.S. Congress 2005). The energy efficient designs must be life cycle cost effective; however, cost effective is not defined in the law and left up to each federal agency to define. The U.S. Department of Energy (DOE) issued additional guidance in the Federal Register (NARA 2006), which states that savings calculations should not include the plug loads and implies that the savings shall be determined through energy cost savings. The U.S. Army decided it would use site energy for the HVAC, lighting, and hot water loads to determine the energy savings. The U.S. Army constructs buildings across the country and the Office of the Assistant Chief of Staff of the Installations Management and the U.S. Army Corps of Engineers (HQUSACE) decided to streamline the process of meeting the energy savings requirements. The U.S. Army Corps of Engineers (USACE) DOE worked in collaboration with the National Renewable Energy Laboratory (NREL), and the ASHRAE Military Technology Group (MTG) to develop baseline and target energy budgets and design guides with one prescriptive path for achieving 30% or more energy savings. The project covers eight building types over all U.S. climate zones: basic training barracks, unaccompanied enlisted personal housing, battalion headquarters, tactical equipment maintenance facilities, dining facilities, child development centers, Army reserve centers, and company operations. This paper focuses on TEMF; however, the process for developing all the design guides is similar. The concept for these design guides was adapted from the Advanced Energy Design Guides (AEDGs) from ASHRAE (2008). Each AEDG was developed for a specific building type and provides recommendation tables for each of the eight major climate zones and a how-to section on implementing the recommendations. The AEDGs do not provide baseline and target energy budgets, which are used by the Army in its requests for proposals. Approach Energy use baseline, target energy budgets were developed and energy savings using different sets of technologies were analyzed for the representative building. The model of the TEMF building used for this study is based on the information provided by the USACE Savannah District the TEMF Center of Standardization.. Energy conservation technology candidates were selected based on previous CERL studies of existing TEMF (Zhivov et al., 2007) which outlined energy and IAQ related issues in existing facilities, and used research data resulted from the IEA-ECBCS (International Energy Agency Energy Conservation in Buildings and Community Systems) Annex 46 Holistic Assessment Tool-kit on Energy Efficient Retrofit Measures for Government Buildings (EnERGo) (IEA ECBCS Annex 46).

2 All energy simulations for the UEPH were carried out with EnergyPlus version 2.0 (DOE 2008). NREL is part of the EnergyPlus development team and has developed additional programs that work with EnergyPlus. These programs work together to create input files, manage the numerous simulations, provide optimization, and post process the results. The optimization engine, called Opt-E-Plus, is used to help optimize building designs based on energy performance, energy cost performance, or life cycle cost performance. The first step in this whole building energy simulation project was to define the baseline building model, which meets the requirements of ASHRAE Standard following the Appendix G guidelines (ASHRAE 2004a). This project followed Appendix G with two exceptions, which were approved by DOE. In this project analysis we used site energy based on the Army decision, and developed baseline and target energy budgets without plug loads as our metric for savings following EPAct 2005 guidance from DOE. Finally, Standard does not contain requirements for building air leakage and infiltration levels. For the TEMF office area a baseline air leakage rate and an energy efficient leakage rate were defined and this factor was included in the energy efficiency analysis. Existing TEMF Facilities, Their Systems and Issues Tactical Equipment Maintenance Facilities (TEMF) are buildings used to provide shelter while maintaining Army vehicles. Figure 1 shows a typical Army maintenance facility. They are also equipped with lifts, utility services, and tools that enable service people to effectively perform the maintenance tasks. These tasks include periodic fluid and component changes, replacement of broken or damaged parts, and subassemblies, and the addition of some new components. The tasks are similar to those performed in an automotive repair garage. Tasks that require major rebuild of subassemblies are typically performed elsewhere. The TEMF come in a range of sizes. They generally are long buildings and consist of a number of bays that are 35 ft wide with a length in the range of 60 to 80 ft, which is long enough to drive in two vehicles end to end. At the short ends of the bay, there is an outside door large enough to allow a vehicle to enter. Also included in the TEMF are administrative offices, rest rooms, cribs for parts storage, and spaces for specialized maintenance operations. Vehicle bays may form wings off a central core area where non maintenance activities occur. The building may also be rectangular with administrative, storage, and specialized spaces occurring in bays similar to the maintenance bays. The common TEMF building is of masonry construction with a number of vehicle doors on opposite sides of the building. These doors often do not fit tightly and thereby provide easy access for outdoor air to enter the building. Windows are normally limited to a narrow band above the row of doors. 2

3 Figure 1. Typical Army maintenance facility. Energy Systems The energy systems required in a TEMF are those that provide power for tools, lighting, heating, and ventilation. Outlets providing electrical power are found in each bay. There is also a compressed air piping system with outlets in each bay. This allows for the use of both electrical and pneumatic tools. The lighting system consists of ceiling hung general lighting using a high wattage lamp and lower wattage task lighting for close-up work. The heating system is required to maintain reasonable space temperatures in the winter. This is typically difficult to accomplish in this type of facility due to the large number of vehicle doors and the need to occasionally open them. The maintenance areas typically use radiant heaters or unit heaters. The administration spaces normally have a forced air unit serving them. Heat is obtained by burning natural gas in the heating unit or using hot water from a building distribution system. Ventilation is accomplished by an air handling unit supplying outdoor air and/or by exhaust systems that remove vehicle exhaust from the maintenance areas. The restrooms have their own exhaust system. Space cooling is not provided except in the administrative areas. To power electrical equipment, an electrical transformer is used to reduce voltage from the site distribution system to voltages of 110, 220 or 460, which are those needed by the TEMF tools and systems. Some of the systems found in this facility are air compressors, hydraulic pumps for lifts, overhead cranes, and various test equipment. Other processes that use electricity are welders, grinders, sanders, and other machine shop tools. Building systems that use electricity are lights, ventilation and fans, water distribution and waste pumps, door openers, and local hot water heaters. Equipment and Processes The types of processes found inside a TEMF include normal maintenance operations where lubricating oils are changes, damaged body parts are replaced, brakes are changed and adjusted, engines are tuned, transmissions adjusted. Also, through the assistance of a crane the engine can be pulled and replaced with a new one. There a special maintenance bays for handling large transport trucks, armored troop carrying vehicles, and tanks. Typically these special bays are found in a few TEMP facilities on a Post. These facilities also have a location where welding is accomplished and another location where painting is done. Concerns with proper system operation There are a number of problem areas with the TEMF. The first is the lack of a good temperature control system. In the summer, these buildings can become quite hot in southern climates. The only relief is to open the doors to take advantage of whatever breeze is available. At some locations, large roll-around evaporative cooling units are used to provide a degree of temperature reduction, but they are only marginally effective. During the heating season, these buildings can be quite cold. Outside air enters the building through open doors and the cracks around the doors. Warm air heaters have a difficult time heating the lower occupied zone since the warm air rises. Radiant heaters can heat the floor, but they need to be placed where the people are located. Someone working under a vehicle does not gain any benefit from the overhead radiant heaters. At times the radiant heaters are placed near the roof along the perimeter of the building above the vehicle doors. This places the heaters in a location that does not interfere with the overhead crane operation, but away from the people in the space. 3

4 Another major area of concern is the ventilation system for the building. The tail pipe exhaust systems are hard to use (Figure 2); nozzles typically do not fit most of vehicles tail pipes or exhaust grills, and the hoses usually cannot withstand vehicle exhaust gas temperature and melt. Also, most of exhaust fumes are released by vehicles when they enter of exit the building. There are only few systems available to capture exhaust fumes from moving vehicles, but they are rarely specified for TEMFs operations. Thus, often no attempt is made to connect exhaust systems to the vehicles and take advantage from close capture. Figure 2. Tail pipe exhaust system (suspended above vehicle) is hard to use. Ventilation systems that consist of sidewall exhaust fans do not remove those fumes that are heavier than air. As the result general energy building ventilation should be provided to dilute these exhaust fumes to maintain a healthy environment. However, these systems require a lot of energy to move high volumes of air and to heat it during a cold season. There are many TEMF buildings where general ventilation is either inadequate or inefficient, or does not exist. Lighting is a concern in some of the buildings. The high level luminaries provide a good general walkaround light level, but the level is inadequate for any close work. Often the doors in the building are kept open, which increases the lighting level in the work areas significantly. A good task lighting system in the repair bays is a necessity. Dark internal surfaces result in increased electrical energy consumption for lighting and in increased heat radiation/discomfort to workers in summer Model Building Description The model of the TEMF is a two story structure (Figure 3) with a total area of 49,920 sq ft. Tables 1 to 3 list details of the building description, and Table 4 lists the building zones and internal loads. Figure 4 shows the building s floor plan and Figure 3 shows a rendered view of the energy simulation model. The building is nominally occupied from 8 a.m. to 5 p.m. Monday through Friday. 4

5 Figure 3. Schematic of the TEMF building used for energy simulation Table 1. Building description Building Component Baseline Building Model Efficient Building Model Area 49,920 sq ft (4,638 m 2 ) Same as baseline Floors 2 Same as baseline Aspect ratio 4.4 Same as baseline Fenestration type Standard See Table 2 See Table 3 Wall construction Steel frame Metal building Wall insulation Standard See Table 2 See Table 3 Roof construction Flat built up roof Metal building roof Roof insulation Standard equal to the insulation entirely above deck See Table 3 Roof albedo (CZ 1-5) 0.3 (CZ 6-8) Infiltration 0.5 ACH 0.5 ACH Temp set points 70 F heating; 75 F cooling set back when Same as baseline unoccupied to 55 F heating; 91 F cooling Repair bays, vehicle corridor, and storage 1: 55 F heating, no cooling HVAC PSZ with DX-AC (3.05 COP) and gas furnace (0.8 Et); See Table 4 packaged make-up air units for exhaust make-up air and gas fired unit heaters for the repair bays, vehicle corridor, and consolidated bench DHW Natural gas boiler (0.8 Et) Natural gas boiler (0.9 Et) 5

6 Zone City Table envelope (baseline) Wall Ins. (ft 2 hf /Btu) Roof Ins. (ft 2 hf /Btu) 1A Miami, FL ci NR A Houston, TX ci NR B Phoenix, AZ ci NR A Memphis, TN ci NR B El Paso, TX ci NR C San Francisco, CA ci NR A Baltimore, MD ci NR B Albuquerque, NM ci NR C Seattle, WA ci NR A Chicago, IL ci 15 ci NR B Colorado Springs, CO ci 15 ci NR A Burlington, VT ci 15 ci NR B Helena, MT ci 15 ci NR A Duluth, MN ci 15 ci NR A Fairbanks, AK ci 20 ci NR Slab Ins. (ft 2 hf Window (U-Btu/ft 2 hf : SHGC) /Btu) N E S W NR NR NR 6

7 Table 3. Improved Envelope. Item Component Climate Zones Roof Assembly Max U-value U U U U U U U U Walls Floors Over Unconditioned Space Slab-on-Grade Insulation Entirely Above Deck Metal Building R-13 + R- 13 R-15ci R-15ci R-15ci R-20ci R-20ci R-20ci R-25ci R-30ci R-13 + R- 13 R-19 + R- 19 R-19 + R-11 LS R-19 + R-11 LS R-19 + R-11 LS R-19 + R-11 LS R-25 + R-11 LS Attic and Other R-19 R-19 R-19 R-38 R-38 R-38 R-49 R-49 Assembly Max U-value U U U U U U U U Mass R-11.4 R-11.4 R-11.4 R-11.4 R-15.0 R-15.0 R-15.0 R ci Steel Framed R-13 R-13 R-13 R-13 R ci Metal Building R-13 R-13 R-13 R-13 R ci R ci R ci R ci R ci R ci R ci Assembly Max U-value U U U U U U U U Mass R-6.3ci R-6.3ci R-6.3ci R-10.4ci. R-16.7ci. R-25.1ci. R-25.1ci. R-25.1ci. Steel Joists R-13 R-13 R-13 R-13 R-19 R-30 R-30 R-30 Wood Framed and R-13 R-13 R-13 R-13 R-19 R-30 R-30 R-30 Others Assembly Max F-value; F ; F ; F ; F ; F ; F ; F ; F ; Unheated NR NR NR R-15.0 for R-15.0 for R-20.0 for R-20.0 for R-20.0 for 24 in. 24 in. 24 in. 24 in. 48 in. Assembly Max F-value; NA F ; F ; F ; F-0.688; F-0.688; F-0.671; F-0.671; Heated R-10 for R-15.0 for R-20 for R-20.0 for R-20.0 for R-25.0 for R-25.0 for 24 in 24 in. 24 in. 48 in 48 in 48 in 48 in Doors Swinging U-0.70 U-0.70 U-0.70 U-0.50 U-0.50 U-0.50 U-0.50 U-0.50 Non-swinging U-0.50 U-0.50 U-0.50 U-0.50 U-0.50 U-0.50 U-0.50 U-0.50 Vertical Glazing Window to Wall Ratio < 10% < 10% < 10% < 10% < 10% < 10% < 10% < 10% (WWR) Thermal transmittance U-0.56 U-0.45 U-0.45 U-0.42 U-0.42 U-0.42 U-0.33 U-0.33 Solar heat gain NR NR coefficient (SHGC) Skylights Percent Roof Area 2% 2% 2% 2% 2% 2% 2% 2% Thermal transmittance U-1.36 U-1.36 U-0.69 U-0.69 U-0.69 U-0.69 U-0.69 U-0.58 Solar heat gain coefficient (SHGC) NR Table 4. Building zones and internal loads. Zone Area sq ft (m 2 ) Volume ft 3 (m 3 ) People Lights W/sq ft (W/m 2 ) Equipment W/sq ft (W/m 2 ) Infiltration cfm (m 3 /s) Repair Bay 22,272 (2,069) 757,248 (21,437) (7.5) 15,590 W 0.75 (8.1) 16,704 W 105 (2.98) 0.5 ACH Vehicle Corridor 6,144 (571) 122,880 (3,480) (7.5) 4,300 W 0.25 (2.7) 1,536 W 17.1 (0.483) 0.5 ACH Showers 2,048 (190) 40,960 (1,160) (6.5) 1,230 W 0.25 (2.7) 512 W 5.69 (0.161) 0.5 ACH Storage 1 4,096 (381) 81,920 (2,320) (9.7) 3,686 W 0.25 (2.7) 1,024 W 11.4 (0.322) 0.5 ACH 7

8 Zone Consolidated Bench Area sq ft (m 2 ) 3,072 (285) Storage 2 3,072 (285) Office 9,216 (856) Total 49,920 (4,638) Volume ft 3 (m 3 ) 61,440 (1,740) 61,440 (1,740) 129,024 (3,651) 1,254,912 (35,528) Lights People W/sq ft (W/m 2 ) (20.5) 5,836 W (9.7) 2,765 W (10.8) 9,216 W Equipment W/sq ft (W/m 2 ) 1.0 (10.8) 3,072 W 0.25 (2.7) 768 W 0.75 (8.1) 6,912 W ,624 W 30,528 W Infiltration cfm (m 3 /s) 8.53 (0.242) 0.5 ACH 8.53 (0.242) 0.5 ACH 17.9 (0.507) 0.5 ACH Figure 4. Thermal zoning for the TEMF. Locations Energy analysis was conducted for the locations selected as representative cities for the 15 DOE climate zones by the Pacific Northwest National Laboratory (Briggs et al. 2003). For the climate zone 5B Colorado Springs, CO was selected instead of Boise, ID to more closely align with the installations at Fort Carson. The 15 climate zones and the cities used to represent the climate zones (Table 5). 8

9 Climate Zone Table 5. Climate zones and cities used for simulations. City HDD (Base 65ºF) CDD (base 50ºF) 1A Miami, FL A Houston, TX B Phoenix, AZ A Memphis, TN B El Paso, TX C San Francisco, CA A Baltimore, MD B Albuquerque, NM C Seattle, WA A Chicago, IL B Colorado Springs, CO A Burlington, VT B Helena, MT A Duluth, MN A Fairbanks, AK Energy Modeling The energy simulations were completed using EnergyPlus version 2.0 (DOE 2008). All simulations were completed with the NREL analysis platform that manages EnergyPlus simulations. The approach to modeling the energy efficiency improvements was to add one improvement at a time starting with the envelope then infiltration and HVAC. The approach to modeling each of these areas is presented in the following sections. Baseline Envelope The baseline building envelope features are modeled as steel frame wall construction, roof insulation entirely above deck, and door and fenestration types from ASHRAE Standard The door, window, and skylight sizes and distribution are exactly the same in all building models. Skylights are included at 2% of the roof area in the repair bays, vehicle corridor, and office for daylighting. Table 2 lists the building envelope parameters. The TEMF buildings are constructed as metal buildings, which have slightly different insulation requirements in Standard Infiltration The infiltration for the baseline and energy efficient building models was assumed to be 0.5 air changes per hour (ACH). The infiltration in all zones except the repair bays was assumed to be 0.05 ACH when the building was pressurized by the HVAC system. The infiltration in the repair bays is strongly affected by the operation of the overhead doors, and it was assumed that the average infiltration over the day remains at about 0.5 ACH. No improvements to the infiltration were modeled to show energy savings in this study. Ventilation The outdoor air requirements from ASHRAE Standard (ASHRAE 2007) are calculated by V oz = R p P z + R a A z (1) 9

10 Where V oz is the zone outdoor air requirement assuming a air distribution effectiveness of 1, P z is the number of occupants, A z is the area of the zone, and R p and R a are the outdoor air requirements per occupant and per area. Some areas have an exhaust requirement instead of an outdoor air requirement. The exhaust makeup air may be any combination of outdoor air and transfer air (ASHRAE 2007). All simulations completed for this study used only outdoor air for the makeup air. Table 6 lists the exhaust and outdoor air requirements for different building areas from ASHRAE Standard Table 6. Baseline building outdoor air requirements from ASHRAE Standard Zone Rp (cfm/person) Ra (cfm/sq ft) Total (cfm) Total (ACH) Notes Repair Bay , Exhaust for auto repair room Vehicle Corridor 1.5 9, Exhaust for auto repair room Showers Exhaust for locker/dressing room Storage Ventilation for storage room Consolidated Bench 1.5 4, Exhaust for auto repair room Storage Ventilation for storage room Office Ventilation for office space Fans The TEMF models have several fans, which use a large portion of the total energy. Table 7 lists the assumptions for modeling the fans in EnergyPlus. The fan flows for the repair bays, vehicle corridor, and consolidated bench make-up air units (MAUs) are determined by the exhaust air requirements. The other fans are autosized by EnergyPlus to meet the outdoor air requirements and satisfy the zone loads, which change slightly with each climate and model variation. The baseline fan efficiencies were set from the allowable fan efficiency equations in ASHRAE Standard (Appendix G). Table 7. Baseline fan model assumptions. Flow Pressure Rise Baseline Efficiency System (m 3 /s) (Pa) Fan Motor Total Fan Repair Bay Vehicle Corridor Showers Storage Consolidated Bench Storage Office Results - Target Energy Budgets The annual energy use intensity for each climate as simulated by EnergyPlus forms the baseline energy budget. The target energy budget is 70 percent of these baseline values. Table 8 lists the site energy use intensities (EUI) with and without plug loads for the baseline and target energy budgets for each climate zone. Figure 5 shows breakouts of the energy consumption by end use. 10

11 Climate Zone City Table 8. Energy budgets by climate zone. Baseline Energy Budget (kbtu/sq ft) With Plug Loads Target Energy Budget (kbtu/sq ft) Baseline Energy Budget (kbtu/sq ft) Without Plug Loads Target Energy Budget (kbtu/sq ft) 1A Miami, FL A Houston, TX B Phoenix, AZ A Memphis, TN B El Paso, TX C San Francisco, CA A Baltimore, MD B Albuquerque, NM C Seattle, WA A Chicago, IL B Colorado Springs, CO A Burlington, VT B Helena, MT A Duluth, MN A Fairbanks, AK Annual Total Site Energy (MWh) 3,500 3,000 2,500 2,000 1,500 1, Heating Cooling SWH Pumps Fans Interior Equipment Interior Lighting 0 1A 2A 2B 3A 3B 3C 4A 4B 4C 5A 5B 6A 6B 7A 8A Climate Figure 5. Energy use by end use for the baseline building. Energy Conservation Measures Several energy conservation measures (ECMs) were considered in the analysis to reach energy targets listed in Table 8. Some of them, included in a final set of technologies, allow to achieve building energy use that is better than energy targets. Other, are presented as optional and can be used to further reduce building energy consumption, improve working environment, and increase productivity. Table 9 lists these ECMs. Table 3 lists the envelope ECM parameters. The baseline HVAC system was assumed to be a packaged single zone system with air conditioning (PTAC) according to ASHRAE Appendix G requirements. The baseline system uses direct expansion (DX) coil for cooling and natural gas coil for heating. 11

12 Table 9. Energy conservation measures (succeeding ECMs are cumulative). No ECM Description 1 Envelope Wall and roof insulation for metal buildings and fenestration from the ASHRAE Small Office AEDG (ASHRAE 2004b); insulated overhead doors (R-4), high roof reflectivity for climate zones 1-5 (0.65) 2 Lower lighting power density (LPD) and daylighting Lower LPD in office (0.9 W sq ft) and consolidated bench (1.3 W/sq ft), daylighting in repair bays, office, and vehicle corridor 3 High efficiency HVAC equipment Increased efficiency of the baseline HVAC system to 3.52 COP, 0.9 Et, and efficient fans (see Table 7). 4 Radiant floor heating Radiant floor heating for the first floor. Requires R-10 (R-15 for climate zone 8) insulation under slab. 5 Transpired Solar Collector Ventilation air heating in transpired solar collector on repair bays 6 Energy recovery Energy recovery from exhausted air to preheat air supplied into repair bay, vehicle corridor, and consolidated bench exhaust systems. Assumed on sensible heat recovery at 70% to 75% effectiveness. 7 Close capture exhausts for moving and stationary vehicles with a reduced make-up air supply into repair bays, vehicle corridor, and consolidated bench Reduced exhaust and make-up air requirements to 0.75 cfm/sq ft Building Envelope Improvement Table 3 lists the envelope insulation levels for metal buildings and the window types taken from the ASHRAE Small Office AEDG. The overhead door insulation levels were increased to R-4 sq ft h ºF/Btu. Cool Roofs In TEMF, which are conditioned in warm season only by ventilation, cool roofs do not save energy. However they can improve comfort conditions (and hence productivity) in the space (Figure 6). In cold climates, a cool roof can increase the heating load, since the solar radiation reflected by the cool roof would otherwise be absorbed, resulting in a warmer roof. Cool roof materials are available as white coatings single-ply white membrane or painted metal (white, cool colored). The EPA and DOE established the ENERGY STAR Roof Products Program to distinguish those products that are energy efficient. The criteria for an ENERGY STAR labeled roof product are based on the initial and aged total solar reflectance (TSR) the initial and aged total solar reflectance (TSR). The ENERGY STAR criteria vary for low and steep slope applications. Table 10 lists the Total Solar Reflectance (TSR) required. Table 10. Total Solar Reflectance (TSR) required. Minimum initial TSR 3-year Aged TSR Low slope roofing ( 2:12) Steep slope roofing (>2:12) Based on the analysis conducted by CERL and NAVFAC, the first cost of most of Energy Star Roof Products that can be used for TEMF does not exceed the cost of regular (not cool roofing materials). For TEMF roofs with high reflectivity (0.65) are recommended for climate zones

13 25 % Available Work Hours Lost Base Model Cool Roof 0 ZN 1: FL ZN 2-Hum: TX ZN 2-Dry: AZ ZN 3-Hum: TN ZN 3-Dry: TX ZN 4-Hum: MD ZN 4: Dry: NM ZN 5: Hum: IL ZN 6: Dry: ID ZN 7: Hum: VT ZN 7: Dry MN ZN 8: AK Figure 6. Percent of work hours lost in the base industrial building and in the building with a cool roof (based on the analysis under the Annex 46 study. Daylighting Repair bays and warehouses are good candidates for hybrid lighting systems, which include a combination of electrical lighting and daylighting (Figure 7a). Installing skylights to reducing lighting costs is not a new concept. Skylight technology, however, has advanced significantly in recent years (Figure 7b). a Figure 7. Maintenance facility with a daylighting system (a); Schematic of modern skylight installation details (b) b To automatically dim the lights, a photoelectric sensor measures the amount of light in a zone. If the specified amount of light has been reached, the controller turns off a bank of lights. Systems can be obtained to control only lights near windows or an entire building. Small controllers can control the banks of lights near windows and larger systems can control an entire building that is illuminated by natural lighting. The controls can be set to dim the lights once a certain level of light has been achieved. Proper lighting levels can be found in the IESNA Lighting Ready Reference. Controls systems can typically either perform step dimming, which simply turns off certain banks of lights or linear dimming, and which linearly dims the lights until a minimum power level has been reached. Linear dimming, however, requires special dimming ballasts that are quite expensive and less efficient than standards ballasts above 50 percent. Based on the simulation results from the 13

14 Annex 46 study, for the ventilated industrial building with no air conditioning, average pay-back ranges from 4 9 years. Close Capture Evacuation System for Vehicle Exhaust Fumes Vehicle exhaust ventilation system can mitigate and reduce exposure to Diesel and gasoline fumes generated by moving vehicles. Vehicle exhaust ventilation systems can be adopted to specific conditions of the maintenance facility (e.g., maintenance bay, drive-through corridor) and allow a range of exhausted air volume and withstand temperature ranges specific to variety of vehicles/tactical equipment serviced or repaired in these facilities. For the biggest vehicles the military needs to service, exhaust flow varies from 1700 to 3300cfm at temperatures of 650 up to 1200 F. Vehicle exhaust capture systems trap and remove by-products of the engine combustion process (gas or Diesel) without contaminating the building air. Vehicle exhaust fumes contain hydrocarbons (HC), nitrogen oxides (NOx), carbon monoxide (CO), sulfur dioxides (SOx), carbon dioxide (CO2) and approximately 100 other volatile organic and acidic compounds. Traditional ventilation systems for maintenance facilities include a general dilution system sized for approximately 1.5 cfm of outdoor air per sq ft of floor area. This flow rate is based on ASHRAE Std. 62 and assumes that running vehicles are entering the building prior to attachment of the stationary close capture exhaust system. If the close capture system is attached before the vehicle enters the building, the general dilution rate can be assumed to be similar to mechanical or assembly shops (~0.75 cfm/sq ft) (HPAC Engineering, 2000). The reduction could be achieved through demand controlled exhaust and make-up air systems and using the exhaust air from the office space as part of the makeup air. Conditioning the make-up air is the largest single energy use in the TEMF. This ECM results in the most significant energy savings in all climate zones. Figure 8 shows a stationary hose reel type system requiring ~1.5 cfm/sq ft of outdoor air. Figure 8. Stationary hose reel type system. Reduction in the general dilution rate can be achieved by means of well designed suction rail or pivoting boom systems (Figure 9). Vehicles are connected to these systems prior to entering the facility and remain attached while moving in and out of the facility. 14

15 Suction Rail Systems Boom Systems Figure 9. Well designed suction rail or pivoting boom systems. Selection of the hose for a particular application depends on exhaust temperature and flow rate. Selection of the nozzle depends on the size and configuration of the tail-pipe or exhaust grill. In most small vehicle maintenance and repair facilities, it is uncommon for several vehicles to drive in or out of the facility simultaneously. Likewise, it is uncommon to run all the engines in the facility at the same time. Typically a demand controlled local exhaust system is sized for a maximum duty cycle of 50 percent of the total available capacity thereby reducing the size of the exhaust duct, fan as well as its operating airflow rate. The exhaust airflow rate is controlled using a variable frequency drive (VFD) and a pressure sensor installed in the main duct. Demand based control of the local exhaust system is initiated by a mechanical damper that opens when the hose is pulled down from the reel. Each of these mechanical dampers initiates the activation of air flow from a specific hose reel during maintenance operations. The system fan ramps up or down to accommodate the number of hose reels activated without affecting the airflow through other reels. Figures 10 and 11 show the simple payback for both the rail and boom systems based on the simulation results conducted under the Annex 46 study. For both systems in all climates, the payback is less than 4.5 years. The significant reduction in outdoor air flow rate is responsible for the savings. 15

16 Payback in Years Min Max Avg ZN 1: FL ZN 2-Hum: TX ZN 2-Dry: AZ ZN 3-Hum: TN ZN 3-Dry: TX ZN 4-Hum: MD ZN 4: Dry: NM ZN 5: Hum: IL ZN 6: Dry: ID ZN 7: Hum: VT ZN 7: Dry MN ZN 8: AK Figure 10. Estimated simple payback for rail system. 3.5 Payback in Years Min Max Avg ZN 1: FL ZN 2-Hum: TX ZN 2-Dry: AZ ZN 3-Hum: TN ZN 3-Dry: TX ZN 4-Hum: MD ZN 4: Dry: NM ZN 5: Hum: IL ZN 6: Dry: ID ZN 7: Hum: VT ZN 7: Dry MN ZN 8: AK Figure 11. Estimated simple payback for boom system. General Ventilation General supply and exhaust ventilation shall be designed to respond maintain indoor air quality and provide a make-up air for local exhaust systems. Demand controlled ventilation with variable frequency drives (VFD) and CO and NOx sensors to control residual fumes from gasoline, can be implemented following the indoor air quality (IAQ) procedure in ASHRAE Standard Cascading air from offices to maintenance bays and vehicle corridor pressurizes office areas and prevents odors/contaminants from more polluted zones to office spaces. It also provides heated or cooled air for the repair bays area and results in energy conservation. Since vehicle exhaust fume are 16

17 heavier that the air and tend to stay close to the floor, two-thirds of air shall be exhausted by general exhaust system from within 1 ft from the floor level, and the rest from the upper zone. If TEMF has a pit, it shall be ventilated by supplying air directly into the pit and have an exhaust from its bottom. HVAC equipment efficiency improvement Compared to the ASHRAE Standard 90.1 minimum requirement, the cooling equipment efficiencies were increased by 20 percent, the gas burner efficiencies were increased to 0.9, and the fan efficiencies were improved (Table 11). The improved efficiency fan performance numbers are based on available high efficiency fans. The last column shows the pressure increase in the fan system for the inclusion of the energy recovery ventilator (ERV). The fan pressure was increased by 50 Pa when the transpired solar collector was included. For the cases with reduced ventilation, the pressures were reduced by 15 percent for the repair bays, vehicle corridor, and the consolidated bench. Table 11. Improved fan model assumptions. Pressure Baseline Efficiency Improved Efficiency ERV System Flow (m3/s) Rise (Pa) Fan Motor Total Fan Fan Motor Total Fan Pressure Drop (Pa) Repair bay Vehicle corridor Showers Storage Consolidated bench Storage Office Fan coil units Varies The fan improvements had the largest affect in the climate zones 1 to 3. Ventilation air preheating in transpired solar collector A transpired solar collector or a solar wall preheats ventilation air by drawing make-up air through a perforated steel or aluminum plate that is warmed by solar radiation. The solar wall consists of perforated steel or aluminum cladding attached to the south façade of a building with an air gap between the existing wall and the cladding. The solar wall is dark-colored to absorb the maximum amount of solar radiation. Air is drawn through the small holes in the wall and heated at the same time (Figure 12). The warm air rises to the top of the wall and is drawn into the building s ventilation system as shown in the figure below. Figure 13 shows a solar wall installed on the maintenance facility at Fort Drum, NY. 17

18 a. b. Figure 12. Schematic of air flows through (a) a solar wall and (b) typical installation. a. b. Figure 13. Solar wall installed on (a) the maintenance facility at Fort Drum, detail showing (b) perforated panel element The performance of a solar wall depends primarily on four parameters: the solar reflectance of the wall, the orientation of the wall, the size and spacing of the perforations in the wall, and the pressure drop maintained by the ventilation system across the wall. The solar reflectance is primarily affected by the coating applied to the solar wall. In general, darker colors have a lower reflectance, and thus absorb a greater fraction of incident solar radiation. The orientation of the wall also greatly affects its performance The intensity of the incident solar radiation is dependent on the cosine of the angle of incidence, the angle between the outward facing normal of the surface and the line of sight to the sun. Walls that more directly face the sun will receive more solar radiation. In winter months in the northern hemisphere, south facing walls perform best. The cost effectiveness of applying solar collectors to East and West facing walls (to catch morning and afternoon sun) must be analyzed on a case by case basis. Simulation of solar wall energy performance conducted under the IEA Annex 46 study shows, that a simple pay back is under 6 years for all heating dominated climates. 18

19 Energy recovery ventilators Heating energy recovery from the stream of air exhausted from repair bays, vehicle corridor, and consolidated bench can be used to preheat supply air. Use of ERV results in the increased pressure drop in the supply air system. There is also a need for better duct insulation to reduce heat losses in the return duct. Given these additional costs and losses, according to (Malmstrom et al., DATE) ERVs are not cost efficient in mild climates (with HDD < 2500). Considering that exhaust air may contain sticky particulates, ERVs were selected with a plate heat exchangers, which are 75 to 70 percent effective.. Hydronic radiant floor heating Low intensity hydronic radiant floor heating systems are commonly used in industrial facilities, hangars, warehouses, garages, gymnasiums, hospitals, kindergartens, apartments, and in different other types of buildings. Heat to the space is provided by hot water supplied through pipes embedded in floors. Thermal energy is exchanged by at least 50% by radiation between the room and people present in the space and the heated floor surface. Transfer from the hot water pipes to the surface of the floor is the important consideration. The uniform temperature distribution from floor heating increases comfort and reduces room air temperature stratification especially in high ceiling buildings. Low intensity radiant heating provides greater comfort for mechanics working near or on the floor. Radiant energy transmitted to the cold (sometimes snow-covered) vehicles results in rapid conditioning of the vehicles for service, which improves workers productivity and adds to their comfort. Radiant floor systems are more energy efficient. Compared to warm air heating systems traditionally used in TEMF, a radiant floor system provides the same comfort level in the working zone at a lower room air temperature during the heating season. This results in reduced ventilation and infiltration losses. In hydronic radiant floor systems, energy is transported by water instead of air. Auxiliary energy for circulation pumps is less than for fans. The system uses lower water temperature for heating, than the warm air heating systems. This allows for using HVAC heating coil return water for radiant floor system, which increases energy performance of boilers (condensing boilers) and heat pumps. Reduced air temperature stratification along the room height results in heating energy saving, typically at least by 25 to 30 percent. With the introduction of polybutelene tubing and new design techniques, as well as reduced energy losses due elimination of room air temperature stratification, the first cost of radiant floor system became comparable or even lower than the warm air system. Application of radiant floor systems requires under the slab insulation with 2 in. of EPS insulation (R-10) for climate zones 1 to 7 and 3 in. (R-15) for climate zone 8. Vestibules with airlocks Vestibule with an airlock (Figure 14) prevents cold air drafts into the building and allows to heat the vehicle prior to bringing it in. The building is protected from outdoor air by two sequentially installed doors with an enclosed space (airlock). There is only one door open at a time to let a vehicle in or out the building. After the vehicle enters the airlock the first door closes and the second one opens. Simulation of vehicle vestibules conducted under the IEA Annex 46 study shows that the simple pay 19

20 back is under 4 years for all heating dominated climates. Figure 14. Example vestibule at auto manufacturing plant. Results Energy Savings with Recommended Technology Sets Table 9 lists specific sets of energy conservation technologies that allow reduction of energy consumption in TEMF to the levels that meet or exceed EPACT 2005 requirements. Tables 12 and 13 list energy savings resulted from application of these technology sets with and without the plug loads. Table 14 lists climate specific sets of energy conservation technologies that allow reduction of energy consumption in TEMF to the levels that meet or exceed EPACT 2005 requirements. Table 12. Final energy efficient design solutions without plug loads. Final Energy Efficient CZ City Baseline (kbtu/sq ft) Solution (kbtu/sq ft) Energy Savings 1A Miami, FL % 2A Houston, TX % 2B Phoenix, AZ % 3A Memphis, TN % 3B El Paso, TX % 3C San Francisco, CA % 4A Baltimore, MD % 4B Albuquerque, NM % 4C Seattle, WA % 5A Chicago, IL % 5B Colorado Springs, CO % 6A Burlington, VT % 6B Helena, MT % 7A Duluth, MN % 8A Fairbanks, AK % 20

21 CZ Table 13. Final energy efficient design solutions with plug loads. City Baseline (kbtu/sq ft) Final Energy Efficient Solution (kbtu/sq ft) 1A Miami, FL % 2A Houston, TX % 2B Phoenix, AZ % 3A Memphis, TN % 3B El Paso, TX % 3C San Francisco, CA % 4A Baltimore, MD % 4B Albuquerque, NM % 4C Seattle, WA % 5A Chicago, IL % 5B Colorado Springs, CO % 6A Burlington, VT % 6B Helena, MT % 7A Duluth, MN % 8A Fairbanks, AK % Energy Savings Table 14. Summary of Climate Specific Sets of Energy Conservation Measures Zone City Improved Envelope Lighting & Daylighting High Efficient HVAC Radiant Floor Heating Transpired Solar Collector Energy Recovery 1A Miami, FL 2A Houston, TX 2B Phoenix, AZ 3A Memphis, TN VC & CB 3B El Paso, TX VC & CB 3C San Francisco, CA VC & CB 4A Baltimore, MD VC & CB 4B Albuquerque, NM VC & CB 4C Seattle, WA VC & CB 5A Chicago, IL VC & CB 5B Colorado Springs, CO VC & CB 6A Burlington, VT VC & CB 6B Helena, MT VC & CB 7A Duluth, MN RP, VC, CB 8A Fairbanks, AK RP, VC, CB Legend Include Include, but with savings less than 5% Not included Energy Recovery Zones RB = Repair Bay, CB = Consolidated Bench, VH = Vehicle Corridor 21

22 Conclusions EPAct 2005 sets energy performance requirements to reduce energy use in federal facilities. The OACSIM and USACE are determined to meet these requirements for the large number of new buildings to be constructed in the next few years by setting target energy budgets. USACE also wanted a prescriptive path to meet or exceed these energy saving requirements, and by using these technologies to improve soldiers and workers productivity and wellbeing and sustainability of buildings. With these objectives in mind, design guides for the most typical categories of Army buildings were developed. This paper presents the results of developing target energy budgets and energy design guide for Tactical Equipment Maintenance Facilities (TEMF). The approach for other seven building types is similar to that presented in this paper. Information on target energy budgets and design guidelines for Unaccompanied Enlisted Personal Housing (UEPH) barracks and for Dining Facilities are presented in two companion papers (Herron et al., 2009; Deru et al., 2009). For the model TEMF building energy savings against the baseline vary between 49% and 59%. Requirements to radiant floor heating, robust moving vehicle exhaust close capture, vehicle vestibule in colder climates and daylighting ensure soldiers/workers improved wellbeing and productivity. Results of this study were implemented through the Army s standard Bid-Build process in late 2007 by incorporation in RFP target energy budgets by climate zone and sets of technologies allowing to meet these budgets. Use of several technologies, e.g., radiant floor heating, solar wall air preheating, close capture vehicle exhaust, daylighting are listed as mandatory requirements. Designs and construction using RFP having new requirements began in They allow either a custom design following target energy budgets and using required set of technologies with a mandatory proof of compliance with energy targets, or contractors can use a complete set of technologies included in the prescriptive path, which doesn t require a proof of compliance. It is noteworthy to mention, that predicted energy savings strongly depend upon the climate, building orientation and for specific building design will vary. However implementation of developed energy budgets and a sets of technologies included in prescriptive path, allow to streamline and reduce the cost of facility design and construction process, ensures that newly constructed facilities comply with the intent of the EPACt 2005 without jeopardizing their functional quality. Acknowledgements This paper is based on the results of the project conducted for the Office of the Assistant Chief of Staff of the Installations Management and the Headquarters, U.S. Army Corps of Engineers (HQUSACE). Information on the energy conservation technologies analysis used in this project was based on research data resulted from the IEA-ECBCS (International Energy Agency Energy Conservation in Buildings and Community Systems) Annex 46 Holistic Assessment Tool-kit on Energy Efficient Retrofit Measures for Government Buildings (EnERGo) financially supported by the Office of the Assistant Chief of Staff, Installation Management (OACSIM) and Headquarters, Installation Management Agency (HQIMA). ASHRAE Technical Committee 7.6 Working Group members and the Annex 46 Subtask B members contributed to generation of the Energy Conservation Measures, their screening conditions and the industrial model building parameters. The authors express their gratitude to MTG group members.. 22

23 References 1. ASHRAE (2004a). ANSI/ASHRAE/IESNA Standard Energy Standard for Buildings except Low-Rise Residential Buildings. Atlanta, GA: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (ASHRAE, 2004a) 2. ASHRAE (2004b). Advanced Energy Design Guide for Small Office Buildings. Atlanta, GA: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (ASHRAE, 2004B) 3. ASHRAE (2007). ANSI/ASHRAE Standard Ventilation for Acceptable Indoor Air Quality. Atlanta, GA: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.(ASHRAE, 2007) 4. Briggs, R.S., Lucas, R.G., and Taylor, T.; Climate Classification for Building Energy Codes and Standards: Part 2 - Zone Definitions, Maps and Comparisons, Technical and Symposium Papers, ASHRAE Winter Meeting, Chicago, IL, January, (Briggs et al., 2003) 5. DOE (2006) Federal Register, Vol. 71. No CFR Part 433. December 4, Washington, D.C. U.S. Government. (DOE, 2006) 6. DOE (2007). EnergyPlus Energy Simulation Software. Washington, D.C. U.S. Department of Energy. (DOE, 2007) 7. Marion, W. and Wilcox, S. (1995). Solar Radiation Data Manual for Buildings. TP Golden, CO: National Renewable Energy Laboratory. (Marion and Wilcox, 1995) 8. Zhivov, A, D. Herron, and M. Deru. (2007) Tactical Equipment Maintenance Facilities. ERDC TR 08-XX (Zhivov et al., 2007) 9. IEA ECBCS Annex 46 Holistic Assessment Tool-Kit on Energy Efficient Retrofit Measures for Government Buildings Subtask B. (IEA ECBCS Annex 46) 10. Ventilation Guide for Automotive Industry. HPAC Engineering Penton Media, Inc. Cleveland, OH. (HPAC Engineering, 2000) 11. ASHRAE Applications Handbook. Atlanta, GA: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (ASHRAE 2005) 12. Malmstrom, T, J. Andrsson, F.R. Carrie, P. Watters and Ch. Delmotte. Source book for efficient air duct in Europe. European AIRWAYS project /Z DG TREN. (Malmstrom et al., DATE) 23

24 13. Herron, D, A. Zhivov and M. Deru Energy Design Guides for Army Barracks. ASHRAE Transactions. (Herron et al., 2009) 14. Deru, M, D. Herron, A. Zhivov, D. Fisher and V, Smith Energy Design Guidelines for Army Dining Facilities. ASHRAE Transactions. (Deru et al., 2009) 24