[Equest-users] Slab on Grade Floor Heat Loss

Fri Feb 2 12:26:32 PST 2018

Thanks Bill, you are always such a big help.  That is what I thought, but just wanted to run it by the forum.

Thanks to you too Nathan.
 Paul Diglio

      From: "Bishop, Bill" <bbishop at pathfinder-ea.com>
 To: Nathan Miller <nathanm at rushingco.com>; Paul Diglio <paul.diglio at sbcglobal.net>; "equest-users at onebuilding.org" <equest-users at onebuilding.org> 
 Sent: Friday, February 2, 2018 3:13 PM
 Subject: RE: [Equest-users] Slab on Grade Floor Heat Loss

#yiv9572653599 #yiv9572653599 -- _filtered #yiv9572653599 {panose-1:2 4 5 3 5 4 6 3 2 4;} _filtered #yiv9572653599 {font-family:Calibri;panose-1:2 15 5 2 2 2 4 3 2 4;} _filtered #yiv9572653599 {panose-1:2 11 6 3 2 1 2 2 2 4;} _filtered #yiv9572653599 {font-family:Verdana;panose-1:2 11 6 4 3 5 4 4 2 4;} _filtered #yiv9572653599 {}#yiv9572653599 #yiv9572653599 p.yiv9572653599MsoNormal, #yiv9572653599 li.yiv9572653599MsoNormal, #yiv9572653599 div.yiv9572653599MsoNormal {margin:0in;margin-bottom:.0001pt;font-size:11.0pt;}#yiv9572653599 a:link, #yiv9572653599 span.yiv9572653599MsoHyperlink {color:#0563C1;text-decoration:underline;}#yiv9572653599 a:visited, #yiv9572653599 span.yiv9572653599MsoHyperlinkFollowed {color:#954F72;text-decoration:underline;}#yiv9572653599 p.yiv9572653599msonormal0, #yiv9572653599 li.yiv9572653599msonormal0, #yiv9572653599 div.yiv9572653599msonormal0 {margin-right:0in;margin-left:0in;font-size:11.0pt;}#yiv9572653599 span.yiv9572653599EmailStyle18 {color:windowtext;}#yiv9572653599 span.yiv9572653599EmailStyle19 {color:windowtext;}#yiv9572653599 span.yiv9572653599EmailStyle20 {color:#1F497D;}#yiv9572653599 .yiv9572653599MsoChpDefault {font-size:10.0pt;} _filtered #yiv9572653599 {margin:1.0in 1.0in 1.0in 1.0in;}#yiv9572653599 div.yiv9572653599WordSection1 {}#yiv9572653599 Paul, Your reviewer may have thought that if the slab was showing up as an “exterior surface” (such as on the LV-D report) than the model was simulating heat transfer between the zones and the outside air through the slab. But eQUEST/DOE-2 simulates heat transfer across underground surfaces differently, as described in the UNDERGROUND-WALL and UNDERGROUND-FLOOR section of the DOE-2 help documentation. The main difference is that ground temperature is used instead of the OA temperature as the outside temperature. The monthly ground temperature is taken from the weather file, or can be entered as SITE-PARAMETERS:GROUND-T.    The eQUEST wizard creates custom constructions for each underground surface based on inputs for Exterior/Cavity Insulation and Perimeter Floor Insulation. Underground floors are given constructions with low U-factor (high R-value) consistent with the lower heat transfer that would be expected.    Regards, ~Bill    William Bishop, PE, BEMP, BEAP, CEM, LEED AP| Pathfinder Engineers & Architects LLP 
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   From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org]On Behalf Of Nathan Miller via Equest-users
Sent: Friday, February 02, 2018 2:35 PM
To: Nathan Miller <nathanm at rushingco.com>; Paul Diglio <paul.diglio at sbcglobal.net>; equest-users at onebuilding.org
Subject: Re: [Equest-users] Slab on Grade Floor Heat Loss    Fixed my typo in the F-factor heat loss calc (should have read 50 ft of perimeter)… See below.    Nathan Miller, PE, LEED AP BD+C –Mechanical Engineer/Senior Energy Analyst RUSHING|O206-285-7100 |C207-650-3942 www.rushingco.com    From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org]On Behalf Of Nathan Miller via Equest-users
Sent: Friday, February 2, 2018 2:33 PM
To: Paul Diglio <paul.diglio at sbcglobal.net>;equest-users at onebuilding.org
Subject: Re: [Equest-users] Slab on Grade Floor Heat Loss    In the past I’ve done a conversion of F-factor (perimeter based) slab-on-grade heat loss to U-factor (area) and input that in on a zone-by-zone basis if I really wanted to nail down SOG heat loss.    Example- Space is 20’ x 30’, but the exposed perimeter is only two of the faces (20’ + 30’). Lets say it is uninsulated SOG.    F-factor from 90.1: F = 0.73 Btu/(hr*ft*F)

Perimeter based heat loss: 0.73 Btu/(hr*ft*F) * 50 ft = 36.5 BTU/(hr *F)    Then we can back-calculate the U-factor to assume for the whole floor to equate to that heat loss: 36.5 BTU/(hr *F) = 600 SF * X BTU/(hr*SF*F) -> U = 0.0608 BTU/(hr*SF*F)    You can create a custom floor construction for each space to provide the U-factor to produce equivalent heat loss that the F-factor calcs are telling you lose. For purely core zones (no exposed perimeter), I guess the F-factor calcs are telling us were not really losing heat through that slab (doesn’t’ seem right, but it probably is relatively small)    Nathan Miller, PE, LEED AP BD+C –Mechanical Engineer/Senior Energy Analyst RUSHING|O206-285-7100 |C207-650-3942 www.rushingco.com    From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org]On Behalf Of Paul Diglio via Equest-users
Sent: Friday, February 2, 2018 2:19 PM
To: equest-users at onebuilding.org
Subject: [Equest-users] Slab on Grade Floor Heat Loss    I recently submitted a model to the local utility company for an incentive.  Part of the buildings' first floor is slab on grade.    One of the comments I received back is that this erroneously shows up as an exterior surface and I should delete all the slab on grade floors in the component tree.  Doesn't seem right to me.    I did a few and it does reduce the overall energy consumption.  In the 3D model, no floors show, just open to the interior of the zone.    So is eQuest assuming that without this floor, there is no heat loss out the bottom of the zone?  Is this reasonable?    Thank you,   Paul Diglio 

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