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90.1-2013 Major Corrections

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  • ASHRAE Press Release
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  • ASHRAE Journal (Feb. 2010)
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  • Thermal Design News Release
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Newly Published ASHRAE Standard 90.1-2013
Effects Metal Buildings.

ASHRAE publishes new 2013 energy standard incorporating major revisions:

Pre-engineered metal buildings represent at least 50% of the low rise non-residential US market and the changes to insulating metal buildings will make a huge impact. Previously industry has published performance values of 20% to 40% greater than the typical installed performance which are technically unsupported.

Corrections in default u-factor roof
and wall tables (Tables A2.3.3 & A3.2.3)

Acknowledges dramatic performance reduction from all of ASHRAE's previously published U-factors of traditional compressed laminated insulation in roof and walls. Revised U-factors reflect installed performance expectations for roof assemblies which were found to be overstated up to 35% and wall assemblies up to 42% when comparing to all previous versions of ASHRAE Standard 90.1 dating back to their 1999 Standard.

ASHRAE published their news release regarding the revised U-factors for compressed metal building roof and wall insulation assemblies in January 2010 and are now finally implemented in their 2013 Standard. For a more complete analysis of 90.1-2013 specifically relating to metal buildings visit our CodeAnalysis. The chart below summarizes a hand full of metal building roof and wall R-value assemblies that make up the vast majority of the prescriptive requirements going as far back as ASHRAE 90.1-2004 Standard.

 

Metal Building Roof
Insulation
Assembly
Pre-Installed
R-value
Overall U-factor for Roof Assembly Overstated
Perforance1
Minimum r-value assembly listed in Prescriptive tables
ASHRAE: non-residential
IECC: All Other
90.1-2013 90.1-2010
Standing Seam Roof with Thermal Block Spacers
SINGLE LAYER R-19 U-0.082 U-0.065 20.7% 90.1-2004 & 2007
climate zones 1-7
–––––––––––––––––-----
90.1-2010
climate zone 1
2006 IECC
climate zones 2-6
–––––––––––––––––-----
2009 IECC
climate zone 1
DOUBLE LAYER R19+R13 U-0.075 U-0.055 26.7% 90.1-2010
climate zone 1
2009 IECC
climate zone 2-5
R19+R19 U-0.068 U-0.049 27.9% 90.1-2004 & 2007
climate zones 8
–––––––––––––––––-----
90.1-2010
climate zone 6-7
2009 IECC
climate zone 6-7
Screw Down Roof
SINGLE LAYER R-19 U-0.151 U-0.098 35.1%    
1 Percent based upon comparing differences in U-factors from 2013 and 2010 versions of Standard of the same R-value assembly.

 
Metal Building WALL
Insulation
Assembly
Pre-Installed
R-value
Overall U-factor for Roof Assembly Overstated
Perforance1
Minimum r-value assembly listed in Prescriptive tables
ASHRAE: non-residential
IECC: All Other
90.1-2013 90.1-2010
SINGLE LAYER R-13 U-0.162 U-0.113 30.3% 90.1-2004 & 2007
climate zones 1-6
2006 IECC
climate zones 1-4
R-16 U-0.156 U-0.093 40.4% 90.1-2010
climate zone 1-2
2009 IECC
climate zone 1-2
R-19 U-0.147 U-0.084 42.9% 90.1-2010
climate zone 3-4
2009 IECC
climate zone 3-4
DOUBLE LAYER2 R13+R13 NA2 U-0.057 NA2 90.1-2010
climate zone 7-8
2006 IECC
climate zone 5-8
"HYBRID"3 R13+R5.6ci U-0.079
(R13+R6.5ci)
U-0.069
(R13+R5.6ci)
NA3 90.1-2010
climate zone 5-6
2009 IECC
climate zone 5-6
R19+R5.6ci U-0.075
(R19+R6.5ci)
U-0.057
(R19+R5.6ci)
NA3 90.1-2010
climate zone 7-8
2009 IECC
climate zone 7-8
1 Percent based upon comparing differences in U-factors from 2013 and 2010 versions of Standard of the same R-value assembly.

2 The double layer fiberglass wall assembly was eliminated in the 90.1-2013 Standard because of constructability issues and in which how the installed performance was calculated and published in previous Standards. The previous published installed performance used the installed R-value (1 / U-factor = installed R-value) for each layer, then added the two installed R-values together, then finally converting the total installed R-value back to the U-factor (1 / total installed R-value = U-factor).

3 The 'hybrid" insulation assemblies combine metal building fiberglass insulation in addition to continuous insulation ('ci'), in this case intended to be rigid insulation board. The R-value increments were adjusted when comparing the 90.1-2013 Standard to the 90.1-2010 Standard. As an example, the first increment of rigid board value starts at 6.5ci (90.1-2013) vs. 5.6ci (90.1-2010). A full list of each Standards 'ci' increments are listed within the columns of the default metal building roof and wall default tables in Appendix A respectively. The published installed performance uses the installed R-value (1 / U-factor = installed R-value) of the fiberglass insulation, then adds the full R-value of continuous insulation, then finally converts it back to the U-factor (1 / total installed R-value = U-factor).
 
DOE Climate Zone map

Modifications to roof and wall assembly descriptions
(Normative Appendix A)

Provides additional insulation assembly configuration details, components and descriptions for roof and walls which are directly linked to default U-factor tables A2.3.3 and A3.2.3.

Increases thermal envelope stringency (Tables 5.5-1 through 5.5-8)

Prescriptive criteria increases the minimum insulation levels for roof and walls in all eight climate zones and throughout all three categories: non-residential, residential and semi-heated compared to previous 90.1 Standards. The roof and wall charts below provide a sample of the increases of stringency in the codes and standards specifically for metal buildings (ASHRAE 90.1: Non-residential criteria, IECC: All Other criteria).

Metal Building Roofs Chart

Metal Building Roofs Chart

The default U-factor corrections in 90.1-2013 provides code officials, designers, installers, suppliers and building owners a more accurate account of installed thermal performance of traditionally installed insulation assemblies. The previously published R-values / U-factors did not reflect the thermal performance from such installation methods, which typically yield lower R-values and higher U-factors. At this time, the inflated thermal performance (U-factors) for metal building insulation assemblies are still directly embedded and referenced within COMcheck™, 2006 & 2009 IECC, 90.1-1999, 2001, 2004, 2007 & 90.1-2010, along with multiple ASHRAE Advanced Energy Design Guides.

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