[Equest-users] Roof Conduction - Where are you?

[Gary.Schrader at tac.com]

I've definitely noticed the anomaly, and I have definitely had a
difficult time running loads because of it.
 
The way I have compensated for this is by assigning a temperature set
point to the plenum. eQuest seems to not consider any load going across
the roof and into space because it seems that the entire roof load is
assigned to the return air stream for the "Loads" portion of DOE2. If
the plenum is the same temperature as the space, no heat transfer can
occur, obviously.
 
By assigning the plenum a temperature, however, eQuest does calculate
heat gain/loss and such gain/loss is shown on the loads report as an
adjacent surface but NOT roof load. I've actually setup parametric runs
where a different plenum temperature is used each month based upon a
calculation that I run outside of eQuest calculating my plenum temp
considering the roofing materials and amount of return air passing
through the plenum. I've also included in my estimate how much heat
comes off the lights. It seems to me to be the only work-around to this
rather mysterious problem, and makes running loads in eQuest very
convoluted, IMHO.
 
In short, with roof load being assigned to the return air, the only way
you can account for a roof load in a space load calc is to tell eQuest
what temperature the plenum is. You have to do that outside of eQuest,
unless somebody has figured out a way to do it another way.
 
Thanks,

Gary Schrader 
Engineer I

TAC 
16011 College Boulevard, Suite 212
Lenexa, KS  66219

 

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From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Craig
Simmons
Sent: Thursday, August 27, 2009 12:20 PM
To: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Roof Conduction - Where are you?



I recently noticed this as well and decided to revive this thread to see
if anyone has insight. How do the roof conduction loads translate to
HVAC loads?

 

Based on the models I've run it's obvious that roof conduction is being
accounted for on the HVAC side and it appears to be about the right
magnitude. However, added roof conduction loads to the plenum do not
translate to any added space loads or  building loads in the LS-x
reports. Does anyone have insight on how eQuest is handling them and why
they do not show up in space or building loads reports?

 

Thank you in advance.

 

Craig Simmons, LEED AP

The Green Engineer, LLP

 

 

From: Eckwahl, Tom [mailto:TEckwahl at karpinskieng.com] 
Sent: Thursday, July 23, 2009 9:29 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Roof Conduction - Where are you?

 

My baseline building energy usage is much lower than expected and in
trying to track down the cause I've found that the "Building Peak Load
Components" lists no roof heat gain or heat loss.  I did find that there
is a gain/loss located in the upper floor plenum and it's shown in the
"Space Peak Load Components".  

 

Is the plenum not considered part of the building?  I'm concerned that
the plenum walls and roof are not being included in the energy modeling
run.

Thomas N. Eckwahl
Project Engineer, Mechanical

karpinski
ENGINEERING

 

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