Section III- Case Studies: • • •
Homeland Security Education Center Center for Science and Math Police Department
o Homeland Security Education Center
Implemented Strategies: • • • • • • •
Roof insulation R-25 continuous insulation (vs. R-20 code minimum) Wall insulation U-0.057 total wall (vs. U-0.064 code maximum) Solar Heat Gain Coefficient 0-24-0.39 (vs. 0.40 code maximum) Heating efficiency 88% (vs. 82% code minimum) Sensible and latent heat recovery Condenser heat recovery 23% Energy Cost Savings (vs. ASHRAE 90.1-2007)
1.) Roof insulation R-25 continuous insulation (vs. R-20 code minimum) Per ASHRAE 90.1 2007, insulation located entirely above the roof decking were required to have a total assembly maximum U-Factor of U-0.048 (minimum R-20.0 continuous insulation). The table below provides a summary of the assembly calculations for the roof assemblies with and without tapered insulation. The components and material thermal resistance values (R-Values) used are from supplemental information (shop drawings) provided by the architect. U-Factor
R-Value
Assembly Component
Roof Assemblies with Tapered Insulation 0.17 Exterior air film 12.10 2" polyisocyanurate insulation base layer
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U-Factor
U-0.0393
R-Value 9.00 3.00 0.56 0.61 R-25.44
Assembly Component 1 1/2" polyisocyanurate insulation intermediate layer 1/2" polyisocyanurate insulation minimum starter edge on tapered insulation 1/2" densdeck high density wood fiberboard insulation Interior horizontal surfaces air film (heat flow up) Total Assembly
Roof Assemblies with Sloped Structure 0.17 Exterior air film 12.10 2" polyisocyanurate insulation base layer 12.10 2" polyisocyanurate insulation intermediate layer 0.56 1/2" densdeck high density wood fiberboard insulation 0.61 Interior horizontal surfaces air film (heat flow up) U-0.0392 R-25.54 Total Assembly
The overall roof insulation value (“Overall U-Factor”) of U-0.048 Btu/(h-ft2-°F) is equal to the code allowed maximum U-Factor for insulation entirely above deck. Roof Assembly—Conclusion: The installed roof assemblies with U-Factor 0.0392 are better than required for minimum prescriptive energy code compliance.
2.) Wall insulation U-0.057 total wall (vs. U-0.064 code maximum) Above-Grade Wall Assemblies—Prescriptive Minimum Code Compliance: Per ASHRAE 90.1 2007, Table 5.5-5, steel framed walls must meet an assembly maximum U-Factor of U-0.064 (R-13.0 + R-7.5 continuous insulation). The table below summarizes the calculations used to determine the wall assembly performance. Above Grade Wall Assembly Effective Performance U-Factor
R-Value
Metal Composite Wall 0.17 10.10 0.93 5.00 0.56 0.68 U-0.057 R-17.44
Assembly Component Assemblies Exterior air film 1.55" Thermax™ ci exterior insulation 1.5" air space - ASHRAE 90.2 Table A9.4A Values for Cavity Air Spaces 1.5" Spray Foam Insulation between metal studs @ 16" o.c. 5/8” cement board with plaster finish on the interior Interior vertical surfaces air film Total
Face Brick Wall Assemblies 0.17 Exterior air film 0.80 Brick, 4" common 10.10 1.55" Thermax™ ci exterior insulation Case Studies
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U-0.055
0.93 5.00 0.56 0.68 R-18.24
1.5" air space - ASHRAE 90.2 Table A9.4A Values for Cavity Air Spaces 1.5" Spray Foam Insulation between metal studs @ 16" o.c. 5/8” cement board with plaster finish on the interior Interior vertical surfaces air film Total
The overall wall insulation value (“Overall U-Factor”) used is U-0.064 Btu/(h-ft2-°F). Above-Grade Wall Assemblies—Conclusion: The specified wall assemblies with a U-Factor of 0.055 are better than required for minimum prescriptive code compliance.
3.) Solar Heat Gain Coefficient 0-24-0.39 (vs. 0.40 code maximum) Vertical Glazing Assemblies—Prescriptive Minimum Code Compliance: The energy code prescribes maximum whole assembly U-Factors for windows— including frames, glazing, spacers, etc. Per ASHRAE 90.1 2007, the maximum allowable assembly U-Factor for metal framed curtainwall and storefront windows in the climate zone is U-0.45. The maximum allowable solar heat gain coefficient (SHGC) is 0.40. In the absence of whole assembly performance criteria in the specification, and/or tested performance data from the window manufacturer, we must estimate U-Factor for these assemblies based on current research. The estimated overall thermal performance is U 0.45. Larger windows may perform better (due to high glazing to frame ratios). Vertical Glazing Assemblies—Construction Document Performance: There is no performance criteria specified for whole assembly U-Factor in either the section for Aluminum-Framed Storefronts (§08 4313) or the section for Glazed Aluminum Curtain Walls (§08 4413). Framing members are to be thermally broken. The specified maximum U-Factor for all insulating glass units (§08 8000 2.02) is U 0.29 (center of glass), with SHGC as noted below. Glazing Type Designation
Description
Type E-1
Insulated Green Glass Units Insulated Sandblasted Green Glass Units Insulated Blue Glass Units Insulated Sandblasted Blue Glass Units Insulated Clear Glass Units
Type E-2 Type E-3 Type E-4 Type E-5
4.) Heating efficiency 88% (vs. 82% code minimum) Case Studies
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Solar Heat Gain Coefficient (SHGC) .24 .24 .33 .33 .39
Condenser heat recovery is provided by a heat reclaim condenser integrated with one of the two chillers (CH-2) installed in the building. The heat recovery (and associated energy savings) this equipment provides is not reflected in the energy models (or estimated natural-gas savings)—because the design engineer indicated that “there was no way to model it” in the HAP software. In actual performance, condenser recovered heat is used to offset a portion of the energy requirements of the heating hot water system for VAV reheat during the shoulder seasons and summer months. According to the design engineer the building gets “full reheat from April through October” from the condenser recovery system. This accounts for a significant portion of the reduced natural gas consumption for the boilers in actuality and (we believe) easily offsets the minor inconsistencies in the modeled boiler efficiencies. 5.) Sensible and latent heat recovery: The modeled heating energy savings is primarily a result of the inclusion of continuous sensible and latent heat recovery in the proposed energy model (and installed in the building)—not included in the baseline model (not required). 6.) Condenser heat recovery: Condenser heat recovery is provided by a heat reclaim condenser integrated with one of the two chillers (CH-2) installed in the building. The heat recovery (and associated energy savings) this equipment provides is not reflected in the energy models (or estimated natural-gas savings)—because the design engineer indicated that “there was no way to model it” in the HAP software. In actual performance, condenser recovered heat is used to offset a portion of the energy requirements of the heating hot water system for VAV reheat during the shoulder seasons and summer months. According to the design engineer the building gets “full reheat from April through October” from the condenser recovery system. This accounts for a significant portion of the reduced natural gas consumption for the boilers in actuality and (we believe) easily offsets the minor inconsistencies in the modeled boiler efficiencies.
Energy Cost Savings:
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2.) Center for Science and Math
https://www.rockvalleycollege.edu/News/Article.cfm?customel_datapageid_9035=106190
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Implemented Strategies: • • • •
Roof insulation: R-30 continuous insulation (vs. R-20 code minimum) Solar Heat Gain Coefficient: 0.32 (vs. .40 code maximum) Lighting Power Density (0.71 W/sf (vs. 1.2 W/sf code maximum) VAV with reheat and Active Chilled Beam with GSHP, ERC, and economizer 42.1% Energy Cost Savings (vs. ASHRAE 90.1-2007)
•
This building operates at levels far beyond the current Code. o Roof insulation: R-30 continuous insulation (vs. R-20 code minimum) Prescriptive Minimum Code Compliance: Per ASHRAE 90.1 2007, insulation located entirely above the roof decking must have a total assembly maximum U-Factor of U-0.048 (min. R-20.0 continuous insulation). Construction Document Performance: There are two roof types in this project. Per the construction documents, the total roof assembly equivalent thermal resistance (R-Value) for the roofs is R-31.5 (U-0.03). The two roof types are detailed in the table below. U-Value R-Value Flat Roof 0.17 0.24 n/a 30.00 0.00 1.10 0.032 31.51
Area of roof
31,056.00
Assembly Component Outside Air Film Fully Adhered Membrane Tapered Rigid Insulation - Polyisocyanurate 5" Rigid Board - Polyisocyanurate Steel Structure Interior Air film heat flow up Total
Gable Roof 0.17 0.00 0.00 22.30
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Outside Air Film Copper Siding Ice and Water Shield 4" Nail Base Insulation
0.00 4.80
0.032
3.60 0.61 31.48
0.032
31.51
2,625.00
Metal Roof Deck Icynene spray foam insulation assume over 4" metal decking. Effective R-value = ~3.6 1" additional Icynene spray foam insulation continuous Interior Air film heat flow up Total Average Values
Conclusion: The specified roof assembly for the overall roof matches the model inputs within 1% and exceeds what is required for minimum prescriptive code compliance. The baseline and proposed energy models both use acceptable thermal performance values.
o Solar Heat Gain Coefficient: 0.32 (vs. .40 code maximum) Vertical Glazing Assemblies (Windows) Prescriptive Minimum Code Compliance: The energy code prescribes maximum whole assembly U-Factors for windows— including frames, glazing, spacers, etc. Construction Document Performance: The specification section for entrances and storefront glazing assemblies (§08911 Glazed Aluminum Curtain Walls) calls for an average system thermal conductance (Ufactor) of “not more than 0.45 Btu/sq. ft. x h x deg as determined according to NFRC 100.” Framing members are to be thermally broken. The specified insulating glass units (§08 8000 Glazing) have one clear uncoated pane and a second pane with “low emissivity coating.” No maximum U-factor is specified. The specifications call for a shading coefficient of 0.46 (SHGC = 0.40). The glazing specified has a Center of Glass value of U-0.25. The curtainwall system is a 7 ½” frame system designed to incorporate spandrel panels with a 5” insulated space behind the panel. The actual effective R-value of this system is not known but is expected to perform similar to an insulated steel frame wall with a cavity R-value of R-18 and an effective R-value of R-7.1 (U-0.14). Integrated photovoltaics are specified for glazing in a greenhouse on the upper floor. The glazed surface is approximately 600 sf, of which approximately 400 sf is vision glass. The SHGC is specified at 0.40 for clear vision glass. Much of this glazing is fritted glass which will further improve the ratings. Using interactive performance data tables from PPG, values ranging from U-0.29 to U-0.36 were obtained. Case Studies
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The overall vision glazing-to-wall ratio is approximately 30%. Approximately 75% of the curtainwall glazing system is vision glazing and 25% is spandrel glass. The table below gives a breakdown of exterior glazings used in the project and includes assumptions made for quantity of glazing to calculate effective values. Glazing Performance Characteristics and Quantities: Type
U-Value
SHGC
% of Type Glazing
Description (materials listed from outside to inside)
GL-2
0.25
0.39
11%
vision
1/4" Solarban 60 tempered; 1/2" Argon filled space; Low 'E'; 1/4" clear tempered
GL-3
0.25/0.14
0.29
42%
spandrel
1/4" Solarban 60 heat strengthened; 1/2" Argon filled space; 1/4" clear heat strengthened with solid white frit (#4)
GL-5A
PV @ greenhouse
1/8" low iron solar glass tempered - solar cells - 1/8" clear tempered & edged; 1/2" Argon filled space; Low 'E'; 1/4" clear tempered
GL-5B
PV @ greenhouse
1/8" low iron solar glass tempered - solar cells - 1/8" clear tempered and edged; 1/2" Argon filled space; 1/4" clear heat strengthened with solid white frit (#4)
GL-5C
PV @ greenhouse
1/8" low iron solar glass tempered - solar cells - 1/8" clear tempered & edged; purged air space; 1/4" clear heat strengthened
GL-6A
0.25
0.36
21%
Vision
1/4" Solarban 60 tempered; 1/2" Argon filled space; Low 'E'; 1/4" clear tempered with special frit -30% white vertical lines (#3)
GL-6B
0.25
0.30
26%
Vision
1/4" Solarban 60 tempered; 1/2" Argon filled space; Low 'E'; 1/4" clear tempered with special frit -50% white vertical lines (#3)
0.20
0.32
0.32
Effective Values Assuming 93% glazing/7% frame
Conclusion: It is very difficult to determine the precise effective U-value for the fenestration system due to the variety of glazing types on the building. However, the system clearly meets code.
o Lighting Power Density- 0.71 W/sf (vs. 1.2 W/sf code maximum) Prescriptive Minimum Code Compliance:
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Per ASHRAE 90.1 2007, Table 9.5.1 Lighting Power Densities Using the Building Area Method, school/university buildings are allowed a maximum lighting power density (LPD) in watts per square foot (W/sf) of 1.2 W/sf. The maximum allowable LPD would be different following the space-by-space method (ASHRAE 90.1 2007, Table 9.6.1) since the allowable LPD varies from 0.50 W/sf for corridors to 1.9 W/sf for workshops. The code allowances for exterior lighting are covered in ASHRAE 90.1 2007, Table 9.4.5. The maximum LPD varies by space type (parking, walkways, entries, etc). Following the prescribed maximum allowances for the types and areas of the spaces in the site design results in an allowance of approximately 18.8 kW total. Construction Document Performance: The interior LPD based on the construction documents provided is approximately 0.71 W/sf.Lighting control strategies implemented throughout the facility include occupancy sensors in most spaces, daylight sensor control at locations with adjacent exterior windows, as well as timer switches, and time clock control. Conclusion: These lighting values are considered acceptable.
o VAV with reheat and Active Chilled Beam with GSHP, ERV, and economizer Primary Heating and Cooling: Prescriptive Minimum Code Compliance: Per ASHRAE 90.1 2007, Table 6.8.1B, the minimum efficiency for ground source heat pumps with cooling capacity
