[Equest-users] U-Values

[Nick Caton]

Peter,

 

This is the exact reason I've come to really enjoy energy modeling.
Anytime you get results that you don't expect, whether your
preconceptions are right or wrong, you're bound to learn something -
sometime profound!

 

You must make the call on whether this makes sense ultimately, but there
are probably reasonable explanations for what you're seeing.  It would
help us help you if you shared more, like what climate the building is
in, what systems you're using... etc.  You will want to come up with
explanations, then investigate the model results to see if that syncs
with the behavior modeled.

 

As a start: R-27 is a high wall value - Note that walls/roofs can be
both over- and under-insulated.  Likely, you're seeing gas savings from
losing less heat in the winter and thus having less heating load, while
simultaneously trapping heat inside your building during the cooling
months, increasing your cooling equipment loads.  Hard to make more
specific guesses without more information.

 

Sidenote - take care that you're not skewing results by wiping out the
effects of wall studs when comparing a new baseline insulation value
(Re: Table A9.2.B, 90.1-2004/2007).

 

~Nick

 

 

 

NICK CATON, E.I.T.

PROJECT ENGINEER

25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

Check out our new web-site @ www.smithboucher.com 

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Peter
Hillermann
Sent: Wednesday, June 09, 2010 10:48 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] U-Values

 

To All,

 

I seem to be having some issues with my baseline design and my first
parametric run. (I am working in detail mode with INP file) When I make
my baseline wall value R-13 and change it in my run to R-27 my heating
(MBTU) load goes down by 4% however my electric rate (kWh) goes up 1%. I
don't really understand because I thought both would have gone down. Am
I doing something wrong?

 

Thanks,

 

PETER HILLERMANN

 

peterh at westallarchitects.com

 

westall

architects

3404 pierce drive

chamblee, georgia 30341

 

o 770.458.4113

f  770.458.5352

c 678.898.2936

 

westallarchitects.com

  

 

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