All, I'am modelling a mid-rise, curtain wall, office building in Egypt (hot humid climate 2a). while I do decrease the glazing's U-value, below 0.5, the energy consumption tends to increase. does this issue have a reality related explanation, is it a problem in my file, or is it a software bug issue?
Thanks for consideration,
Omar AlRawi
In mild weather, with high internal heat gains, the losses through the
glazing reduce the cooling load. In this situation, increasing the
performance of the glass will cause increased energy consumption.
This counterintuitive result is often the result of an overestimation of
internal heat gains. You should perform a reality check on your internal
heat gains, before you determine if this result is correct.
--
Chris Schaffner, PE
From: Omar Osama Date: Thu, 13 Oct 2011 16:07:13 +0200 Subject: [Equest-users] U-Value unexpected impact
To:
All,
I'am modelling a mid-rise, curtain wall, office building in Egypt (hot
humid climate 2a). while I do decrease the glazing's U-value, below 0.5, the
energy consumption tends to increase. does this issue have a reality related
explanation, is it a problem in my file, or is it a software bug issue?
Thanks for consideration,
Omar AlRawi
Hi Omar,
Another thing to check is that you are modeling a glass with a low-Solar Heat Gain Coefficient (SHGC). Low SHGC glasses and glass-units are best for situations where there is no need for passive heating (hot climates and internal load-dominated buildings).
You can still maintain high VT (>0.5) with low SHGC (<0.3), so it doesn't need to sacrifice aesthetics and daylighting options.
Great point on the internal loads Chris.
Cheers,
Alex
Alex Krickx, LEED AP
Thanks so much,I do appreciate your reply ,, I shall re-check internal loads, guess I have excessive lighting loads.
Omar AlRawi
Now I decrease the U-value, and trace the components, what happens is that the maximum load (LS-D) tends to decrease, as well as the Building HVAC load (SS-D) tends to decrease as well, which is the normal thing. the abnormal thing is that the space cooling energy use, on the (PS-F) dramatically increase, by decreasing the U-value. I would be so grateful if anyone could help me with a reasonable explanation for that.
Thanks,
Omar AlRawi