Thanks, Brian. This is very helpful. I understand why this report won't show any heat loss but then how do I really find out what the heat loss through the roof is? I need to document the heat loss through walls, roof, windows, ground etc.

Thanks a lot,

Shalini

Date: Tue, 31 May 2011 15:24:58 -0400
From: bfountain at greensim.com
To: shalinimodi at msn.com
CC: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Roof conduction

Shalini,

I have not looked at the model but the issue will be that you have
defined a plenum. The LS-C report is showing only conditioned
spaces -- this is good because the area for plenums &
unconditioned spaces are not included in the area shown in LS-C --
but it does lead to the result you are seeing -- unconditioned &
plenum area conduction losses are not included.

The next logical question is why isn't is then shown in the LS-C as
an internal wall conduction loss through the ceiling to the plenum.
In the Loads portion of the program, it does not know what the space
temperatures are as those are based on the setpoints which are
defined as schedules in the system portion of the program. So, it
uses the space design temperature as an initial estimate.
Typically, this temperature is the same for the plenums and the
spaces -- so no internal heat transfer in the LS-C and other Loads
level reports.

In the system run, the plenum temperature does drop and the impact
of roof insulation is calculated. You can convince yourself of this
by changing the roof R-value and seeing the impact.

Hope this helps.

Brian

Dear all,

I need to check and document the heat loss and gain through
various components on the building envelope. Checking the report
LS-C for the same, my building reports to have zero heat loss or
gain due to roof conduction. If someone can have a look at my
model (attached herewith) and advice what the problem could be,
that will be greatly appreciated.

Thanks,

Shalini