[Equest-users] Slab on Grade Floor Heat Loss

Fri Feb 2 13:31:50 PST 2018

Some eQUEST models do have redundant roofs, exterior or underground floors
sandwiched between the Shells created in DD Wizard. These can be easily
identified by hiding some exterior and interior surfaces from 3D view,  to
look “inside” the building, like in the screenshots below. There is also a
nice summary of surface areas at the end of LV-D report, which can be used
to check that the modeled “UNDERGROUND” and “ROOF” areas are as expected
for the projects. That said, reviewers too make mistakes. We all know that
sometimes they are hands full J.

*Maria Karpman *LEED AP, BEMP, CEM

________________

Karpman Consulting

www.karpmanconsulting.net

Phone 860.430.1909

41C New London Turnpike

Glastonbury, CT 06033

*From:* Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] *On
Behalf Of *Paul Diglio via Equest-users
*Sent:* Friday, February 02, 2018 3:27 PM
*To:* Bishop, Bill <bbishop at pathfinder-ea.com>; Nathan Miller <
nathanm at rushingco.com>; equest-users at onebuilding.org
*Subject:* Re: [Equest-users] Slab on Grade Floor Heat Loss

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

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*

*Senior Energy Engineer*

134 South Fitzhugh Street                 Rochester, NY 14608

*T: (585) 698-1956*                        F: (585) 325-6005

bbishop at pathfinder-ea.com <wbishop at pathfinder-ea.com>
www.pathfinder-ea.com

[image: http://png-5.findicons.com/files/icons/977/rrze/720/globe.png]Carbon
Fee and Dividend - simple, effective, and market-based.

*From:* Equest-users [mailto:equest-users-bounces at lists.onebuilding.org
<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* | *O* 206-285-7100 | *C* 207-650-3942

*www.rushingco.com <http://www.rushingco.com/>*

*From:* Equest-users [mailto:equest-users-bounces at lists.onebuilding.org
<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* | *O* 206-285-7100 | *C* 207-650-3942

*www.rushingco.com
<https://url.emailprotection.link/?a6X-5ry0mOOudUi-eMfQ7K9LfplwNoMV9idJhgEyf85c~>*

*From:* Equest-users [mailto:equest-users-bounces at lists.onebuilding.org
<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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