[Bldg-sim] U Value

[Nick Caton]

Sambhav,

 

Don't have my copies of 90.1 handy.. but I think I can guide your questions - do ask again if I'm missing the mark.

 

1.       While your units look about right for a U-value (Btu/h·ft2·°F), baseline underground walls, in 90.1-2004, are defined with a C-factor, not a U-factor.  Appendix A section for underground walls explains how it's different from U-factor (I think C basically excludes air films), and has a table you can reference to find a C-value from chapter 5. Between that table and the relevant appendix A text section, you can build a custom construction to match the C-value specified.

2.       I don't think there's any specific guidance regarding wall/floor/partition construction absorptance values in 90.1.  It's one of those things that fall generally into "match the proposed."  90.1 does specify "solar reflectances" for roofs only, and we handle those (somewhat indirectly) through the absorptance inputs for roof constructions.

 

Hope this helps,

 

~Nick

 

 

 

NICK CATON, E.I.T.

PROJECT ENGINEER

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olathe ks 66061

direct 913 344.0036

fax 913 345.0617

Check out our new web-site @ www.smithboucher.com 

 

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of sambhav tiwari
Sent: Thursday, April 15, 2010 6:55 AM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] U Value

 

Hi All,
             What should be  U value for below grade walls for basline is it 1.14 btu/hrsqft2F. and how much should i consider absoptamce fro base line below grade walls.

I look forward for your response.

Thanks
Sambhav Tiwari.

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