[Equest-users] Slab on Grade Insulation

Nathan Miller nathanm at rushingco.com
Fri Sep 5 13:11:58 PDT 2014

In the past I've done a custom calculation for SOG assemblies. Essentially I look up the appropriate F-factor for the slab condition, multiply by the perimeter to get F*P heat loss in BTUH/Hr/° F . Then I back calculated appropriate U-values for each floor section so that the UA calculation comes out to the same heat loss. I concentrated the heat loss in the perimeter zones, since the SOG F factors are based on the principle that most of the heat loss occurs at the perimeter of the slab.

Attached is an example. In this case I had portions that were heated SOG, unheated SOG, and some exposed slab-edge (not at grade), so it was pretty complex to makes sure assigned U-values for each assembly worked out to match what the F- and U-factor parameters should be.  Hopefully the color coding helps you sort through it.

Nathan Miller, PE, LEED AP BD+C
Mechanical Engineer/Senior Energy Analyst

D 206-788-4577 | O 206-285-7100

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Campion Mark
Sent: Friday, September 05, 2014 3:52 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Slab on Grade Insulation

In eQUEST, when I select insulation under a slab for a basement, the Construction El1 UFLyrs(B.W1.U2) doesn't seem to recognize the default  horizontal R-10 insulation; for 2 or 4 foot selections.  In other words, the Construction layers do not change from an un-insulated slab in a basement......4 inch HW Concrete slab, 12 inch damp light soil, and a "dummy" value showing an R-Value of 100.   Any tips or explanations are appreciated.


Mark Campion
Policy Analyst
Policy & Technical Services
(503) 378-4530
mark.campion at state.or.us<mailto:mark.campion at state.or.us>

1535 Edgewater Street NW
PO Box 14470
Salem, Oregon 97309-0404

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