No Roof Conduction Losses

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I am trying to model the impact of adding additional insulation to a 2-story
pitched roof office building using Equest. My baseline model shows the roof
U-value to be 0.026 and my parametric run to have a roof U-value of 0.019
(report LV-I). However, there was no change in heating and cooling energy
usage. I then looked at the building peak load components (report LS-C) and
noticed that there are no roof losses for either run.

So the main question I have is; why are there no roof conduction losses?
Have I incorrectly modeled something or is there an issue with pitched roofs
and conduction losses in Equest. I have attached the pd2 and inp files for
these runs for anyone's review.

Any help would be greatly appreciated.


Tony Kriel, LEED AP

Tony Kriel's picture
Joined: 2011-09-30
Reputation: 0

I havn't looked at your file yet, but I had this same problem before.
Since my project had plenem space above the top floor spaces, the roof
losses were counted into plenum spaces instead of the rooms. So if your
blg load didn't included the plenum load, you can't see the roof loss.
No sure if this is same case for you.

Lan Hu

Lan Hu's picture
Joined: 2011-09-30
Reputation: 0

As I can't check your project file but you may find the changes of the roof conduction by LS-E (Components) instead of LS-C(peaks of conditioned space). Also, if you remove the plenum at the top, the roof conduction should be affected to the conditioned spaces directly.
And I recommend the EEM Wizard to quickly describe the alternative cases to your baseline model.
Good luck!

Jaeyoon Koh


Jaeyoon Koh's picture
Joined: 2011-09-30
Reputation: 0

If you have a plenum above your conditioned space, the roof losses appear in
the load report for the plenum. In the load report for the space, you see
this loss through the ceiling, or internal partitions.

However, I have had many issues with the roof/attic simulation in eQUEST and
often find that it seems to under predict the impacts of roof/attic
insulation and reflective roof coatings. Even removing the plenum and having
the roof in direct contact with the conditioned zone still seems to under
predict the impacts you expect from hand calculations.

Kendra Tupper's picture
Joined: 2011-09-30
Reputation: 0