Technical Information
Technical Information / Codes and Standards
90.1-2013 Major Corrections
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Effects Metal Buildings.
ASHRAE publishes new 2013 energy standard incorporating major revisions:
- Corrections in Default U-factor Roof and Wall Tables
- Modifications to Roof and Wall Assembly Descriptions
- Increases Thermal Envelope Stringency
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). |
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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).
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.
