HVAC Integration. Erin McConahey

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1 HVAC Integration Erin McConahey

2 Façade decisions are key to HVAC loads

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4 Effect of façade on interior 20 deep perimeter zone is affected by external environment Stable interior zone Always requires cooling

5 Climate impacts of glazing alone Single Glaze Double Glaze (No Low-E coating) High Performance Double Glaze (Low-E Coating) Triple Glaze (Low E-Coating) 5

6 San Francisco - Heating Capacity Heating Capacity (Mbh) 7,000 6,000 5,000 4,000 3,000 2,000 1, ,500 Type 1 2,300 3,100 Type 2 3,800 1,200 1,700 2,200 2,700 1,000 Type 3 1,300 1,700 1, Type 4 1,100 1,400 1,200 20% 40% 80% 60% Single Glaze Double Glaze (No Low-E coating) High Performance Double Glaze (Low-E Coating) Triple Glaze (Low E-Coating) 6

7 Perimeter heating systems Only three needs for heat: Outside air, perimeter heat loss, primary air boost 7

8 8 SFPUC Building SF Federal Building

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11 San Francisco - Cooling Capacity Cooling Capacity (Tons) % 60% 0 40% Type 1 Type 2 Type 3 Type 4 20% Single Glaze Double Glaze (No Low-E coating) High Performance Double Glaze (Low-E Coating) Triple Glaze (Low E-Coating) 11 Environmental Building News, April 2010

12 Why window wall ratio matters so much Conduction Heat Transfer = U * area * T (11F) 72 F 83 F = 72 F 83 F 4 sf of R-13 (U-0.075) = ONE sf of fully shaded insulated low e glass (U=0.3) 72 F 83 F = 72 F 83 F 65 sf of R-13 = ONE sf of unshaded insulated westfacing low-e glass (SHGC = 0.25) Solar heat gain = Btu/hr/sf solar x SHGC

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14 140 Comparison of External Heat Gain by glass type for one 500 sf wall (50' x 10' high) prorated onto a 1000 sf perimeter room zone Btu/hr/sf % single pane 50% single pane 25% single pane 100% clearclear 50% clearclear 25% clearclear 100% low-e 50% low-e 25% low-e 100% Non- North Hi-Perf Solar 50% Non- North Hi-Perf Solar 25% Non- North Hi-Perf Solar 100% North single pane

15 Concept Design: Zoning Natural ventilation potential Glazing/ operable windows Perimeter occupant comfort Heat loss/ gain versus HVAC loads Potential for shade

16 Key drivers for HVAC design in perimeter zones N N N N W E W E W E W E S S S S

17 Are we close to being Title 24 code compliant? SHGC 0.25 X 40% WWR + 0SHGC X (1-40%)= 0.1 prescriptive code compliance SHGC 0.37 x?% WWR + 0SHGC X (1-WWR) = 0.1 WWR = 0.27 match to prescriptive façade energy budget, but if pursuing performance method, base building would match any WWR lower than 40%. SHGC? X 100% WWR = 0.1 SHGC = 0.1

18 Façade effects on energy savings

19 Old paradigm vs new designs (update for new) Lights 1.3 W/sf, 4.44 Btu/hr/sf Small Power 2.2 W/sf, 7.5 Btu/hr/sf Sun 15 W/sf, 53 Btu/hr/sf 50%single pane or 100% low- e People 0.73 W/sf, 2.5 Btu/h/sf Conduction 1.4W/sf, 5 Btu/hr/sf Lights 0.9 W/sf, 3.07 Btu/hr/sf Small Power 1.0 W/sf, 3.41 Btu/hr/sf Sun 2.2 W/sf, 7.8 Btu/hr/sf 30% reduction in lighting 55% reduction in small power 52% reduction in solar (potentially) People 0.73 W/sf, 2.5 Btu/h/sf Conduction 1.6 W/sf, 0.46 Btu/hr/sf

20 Improvements in technology (and ASHRAE Measurement studies) 30% reduction in lighting 55% reduction in small power Btu/hr/sf Small Power Lights People Old office New office

21 140 Comparison of External Heat Gain by glass type for one 500 sf wall (50' x 10' high) prorated onto a 1000 sf perimeter room zone Btu/hr/sf % single pane 50% single pane 25% single pane 100% clearclear 50% clearclear 25% clearclear 100% low-e 50% low-e 25% low-e 100% Non- North Hi-Perf Solar 50% Non- North Hi-Perf Solar 25% Non- North Hi-Perf Solar 100% North single pane

22 Btu/hr/sf Solar Conduction Small Power Lights People Old office New office

23 Comparison of Internal Heat Gains by space type for 1000 sf room Btu/hr/sf Small Power Lights People 10 0

24 Heat absorption limitations of systems P A S S I V E Natural Ventilation w/ Thermal Mass Natural Ventilation New office internal loading Old office internal loading New office internal loading with 50% non- North, 0.24 SHGC Old office internal loading with facade M E C H A N I C A L 2 (6.8) 4 (13.6) 6 (20.4) 8 (27.4) 10 (34.1) 12 (41.0) Underfloor/Displacement Ventilation COOLING LOADS IN W/sf (Btu/hr/sf) Chilled Ceilings Chilled Beams Chilled Beams + DOAS cooling Fan Coil Units Variable Air Volume

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30 Drivers of Façade Optimization ASHRAE 50% AEDG for Small and Medium Office buildings 30

31 Questions? Erin McConahey 31