[Equest-users] Floor Slab F-factor

[Nick Caton]

Rick,

 

If you'll flip your copy of 90.1 to Appendix A, you'll find there's a
section for "slab on grade floors" (not just "floors"), and
corresponding table that will describe the exact construction layers to
achieve a target F-Factor.  Matching these slab-on-grade construction
layers/insulation will mean you're achieving the target F-factor for
your perimeter zone(s).

 

>From memory, I believe F-0.73 is a commonly looked up value that
corresponds to an un-insulated 6" slab, but you should review that
section/table in its entirety  (it's small) to confirm.  

 

There are resources outside 90.1 that will lead you to similar F-factor
information, including a paper that explains how DOE2 handles perimeter
insulation that pops up every so often on this list (sorry not sure
where it's found online), but your Appendix A bullets out what you need
pretty well for this case.  I'd suggest verifying what construction
layers Appendix A is suggesting you use, make any construction
modifications that may be necessary in your baseline model, and respond
to your reviewer with your findings and any changes made in response,
with updated results if changes were necessary.  Be sure to cite
appropriate 90.1 sections where applicable in your written response.


If the reviewer (not you) is bringing up perimeter/core slab heat loss
under discussion, take care!  She/he may be either testing you or
otherwise may not fully understand what F-factors are supposed to
represent: a perimeter heat loss factor.  Carefully word your response
in a way that demonstrates you understand this distinction, but don't
turn it into a lecture as an uninformed reviewer may take offense and
unfairly turn the reviewing process against you and your project.

 

Best of luck!

 

~Nick

 

 

 

 

NICK CATON, E.I.T.

PROJECT ENGINEER

25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

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

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Routh
Consulting Engineers
Sent: Monday, May 17, 2010 10:24 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Floor Slab F-factor

 

Could someone please help me with how to input or figure out what the
F-factor is for slab-on-grade floors? I've just input floor areas
through the wizard and selected the type of foundation insulation I have
from the drop-down lists. I have received a comment back from the LEED
reviewers to explain what I have and how my baseline case uses the
unheated floor slab F-factor of 0.73. Several of my thermal zones are
interior spaces which have a concrete floor with Earth contact but no
exposed perimeter, but I do have Earth contact floors in all of my zones
so there is supposedly heat loss from all of them. Any help with this
would be appreciated.

 

Thanks,

 

Rick Routh

Routh Consulting Engineers, Inc., P.S.

P.O. Box 3187

Pasco, WA  99302

(509) 547-8262

(509) 542-0650 FAX

routhconsultingengineers at charter.net

 

 

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