<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
</head>
<body bgcolor="#ffffff" text="#000000">
i just received a clarification about the f-factor for 4" slab on grade
vs 6" slab on grade for the purposes of leed review. the usgbc
response (through the website/contact section) is:<br>
<br>
"Thank you for your technical customer service inquiry regarding
LEED-NC
v2009: EAc1. It is assumed that you are following the Performance
option (Option 1) of EAp2 & EAc1, using Appendix G of ASHRAE 90.1.
<br>
<div class="moz-text-html" lang="x-western"><br>
Yes, the 4" slab (modeled & specified) should meet the requirements
for LEED purposes. Please note that there is no F-factor requirement
listed as part of the Mandatory provisions of Section 5.4; it is only
listed for the Prescriptive approach requirements of section 5.5, which
is not necessary for LEED EAp2/EAc1 compliance. <br>
<br>
If you model the slab as a 4” slab with 12” of earth (0.75 soil
conductivity) underneath it in the Proposed Case model, the energy
model should indicate the U-value of this slab. You could simply state
in your submittal (4” slab modeled with 12” of earth with 0.75
Btu/h-ft-° soil conductivity, U-value calculated within energy model as
x.xx). Please be careful to avoid the common mistakes of modeling the
slab without any earth beneath it, or modeling the Baseline slab
"U-value" using the "F-factor" values from Tables 5.5-1 - 5.5-8.
F-factors and U-values are not interchangeable, of course. Also, if
the energy model cannot reflect an F-factor, please model the Baseline
slab-on-grade floor as a 6 inch concrete slab over earth with a soil
conductivity of 0.75 Btu/h-ft-degree F, in accordance with A6.1. <br>
<br>
We trust that this will help you with your process and we thank you for
your interest in LEED Rating Systems. <br>
<br>
If you have any further questions, please feel free to contact us via
the GBCI contact page: <a moz-do-not-send="true"
href="http://www.gbci.org/contactus" target="_BLANK">http://www.gbci.org/contactus</a>.
<br>
<br>
Regards,
<br>
<br>
<name redacted><br>
GBCI Technical Customer Service
<br>
Green Building Certification Institute <br>
2101 L St. NW • Suite 500 <br>
Washington DC 20037
<br>
800.795.1746 • fax 202.828.5110 <br>
<a class="moz-txt-link-abbreviated" href="http://WWW.GBCI.ORG">WWW.GBCI.ORG</a>
<br>
<br style="font-style: italic;">
<span style="font-style: italic;">The text above represents a staff
opinion on a particular issue, and does NOT set any precedent to be
upheld during a LEED Certification Review. For official rulings in
advance of a LEED Certification review, customers should utilize the
formal inquiry process available in LEED Online. Applications for LEED
Certification will be thoroughly reviewed based upon the LEED Rating
Systems balloted & approved by USGBC Members, applicable Addenda,
USGBC-approved LEED Interpretations, and Project Credit Interpretation
Rulings (CIRs) administered by GBCI, as applicable. Please note that
certain inquiries submitted to USGBC are forwarded to GBCI for reply,
as appropriate."</span></div>
<br>
</body>
</html>