[Equest-users] Really thick concrete walls, partitions, and floor

[Nick Caton]

Hi Dave,

From a LEED perspective, I think you have a lot of liberties here to model or not model specific elements.  The critical thing is for documentation to be clear & open regarding the decisions you make and be sure to  apply those decisions uniformly between the models.

Heat of curing is something you could opt to not model at all – reasonably choosing to model the eventual “steady state” as that should best represent the building’s long term annual internal load profile.  If you should choose to include this internal heat load for the model - intuitively I would expect to see this applied identically to both models as a uniform space equipment load (assigned to a “free” meter) for all affected spaces (perhaps with an annual fractional profile that reduces/eliminates the load over time, per your referenced calculations).

How to model that future “steady state” after heat of curing probably poses the more interesting conundrum – I would defer to your mechanical designers to take an approach to envelope loads to match their plans for sizing the heating equipment.  Some might consider the huge thermal lag of the earth/concrete masses to render heat transfer negligible over time (which would bend you towards modeling thermally massive but adiabatic partitions).  Others might consider the surrounding earth a constant heat drain and insulate or bump heating equipment capacities accordingly.  From a LEED modeling perspective, best advice is to not make assumptions that disagree with the rest of the design team – communicate and move forward with a consensus.
~Nick
[cid:489575314 at 22072009-0ABB]

NICK CATON, P.E.
SENIOR ENGINEER

Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
direct 913.344.0036
fax 913.345.0617
www.smithboucher.com

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Dave Weigel
Sent: Monday, July 16, 2012 12:41 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Really thick concrete walls, partitions, and floor

Hi group,

I have a building with 8-foot concrete floor slab (50 feet below grade), 3- to 6-foot below-grade exterior walls, and 3- to 8-foot interior partitions in the sub-grade shells.

I wondered if anyone had a quick hint they could give me, particularly in light of LEED 2009 review that will happen.  The calculus is done, and the transfer function time constant is so huge that the inner surface temperature of the walls just isn’t going to vary much.  Ground temperature is 60°F all year and doesn’t vary.  After they are poured, it’ll take 8 to 10 months for the 8-foot walls to cool down to indoor (conditioned) ambient temperature just from the heat of curing.

Any comments or experience will be most appreciated.

Thanks,

Dave

David R. Weigel, PE
Managing Member
1189 Golden Circle SW,  Lilburn GA 30047
678-353-6941 office       901-619-1716 cell
[wattdoxemailsiglogo]
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