[Equest-users] F-Factor to U-Value

[Kelsey VanTassel]

Hmm, now that I am looking at it again, I am not sure I am doing it right either. I thought the F-factor presented in the tables was already correcting for the R-value of the slab and soil, but now I'm not sure. I may be double-counting.


I ran into this problem too because in wizard mode, the menu of insulation configurations for slab-on-grade floors did not have the particular combination I needed. Here's what you can do in detailed edit mode instead:


1.       On a space-by-space basis (or for the whole floor if it is all heated or unheated slab) calculate the R-value of the fictitious layer of insulation covering the slab:

Equivalent R-value = ((F-factor * Exposed Perimeter length)/Area of space or floor)^-1

(hint for determining exposed perimeter length: just add up all the widths of the exterior walls for that space. Double-click on the first exterior wall in the component tree and then press the down arrow in the menu to page through the list of just exterior walls)


2.       Create a custom material of type Resistance with this R-value.


3.       Create (or modify) the underground floor construction using the following layers (outside to inside):


·         Material you just made

·         Light soil damp 12 in

·         6 in HW (140lb) concrete

Kelsey Van Tassel
Mechanical Engineer | kvantassel at sustaineng.com<mailto:kvantassel at sustaineng.com>
608.836.4488 ext. 20 | Fax: 608.836.4477

Sustainable Engineering Group
901 Deming Way, Suite 201
Madison, WI 53717
www.sustaineng.com<http://www.sustaineng.com/>


From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Will Mak
Sent: Thursday, October 14, 2010 10:47 AM
To: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] F-Factor to U-Value

eQuest requires an input of a U-Value when modeling a slab on grab layer. Typically, you enter a F-Factor to account for the loss per perimeter length. I did some research but could not find any solid conclusions on what is suppose to be done to convert the F-Factor to a U-value or configure eQuest to correctly model this. Any suggestions?

Thanks!

William Mak, LEED Green Associate
Mechanical Design Engineer

EPSTEIN
Architecture
Interiors
Engineering
Construction

600 West Fulton Street
Chicago, Illinois 60661-1259

D (312) 429-8116
F (312) 559-1217
wmak at epsteinglobal.com<mailto:hmoats at epsteinglobal.com>
www.epsteinglobal.com<http://www.epsteinglobal.com/>

þ Epstein is a firm believer in sustainability. We ask that you please consider the environment before printing this e-mail.