[Equest-users] U-Value unexpected impact

Omar Osama o_osama at live.com
Tue Oct 18 14:03:27 PDT 2011

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.
Omar AlRawiProject Engineer,EA Sustainable Building Consultants

From: o_osama at live.com
To: equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] U-Value unexpected impact
Date: Thu, 13 Oct 2011 21:37:04 +0200

Thanks so much,I do appreciate your reply ,, I shall re-check internal loads, guess I have excessive lighting loads. 

Omar AlRawiProject Engineer,EA Sustainable Building Consultants

From: akrickx at seriousenergy.com
To: chris at greenengineer.com; o_osama at live.com; equest-users at lists.onebuilding.org
Date: Thu, 13 Oct 2011 10:39:02 -0700
Subject: RE: [Equest-users] U-Value unexpected impact

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
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.

Alex Krickx, LEED AP
Building Energy Specialist
Serious Energy, Inc.
1250 Elko Dr, Sunnyvale, CA 94089
(t) 408.541.8124
akrickx at seriousenergy.com
The information contained in this e-mail and any attachments may be confidential, proprietary and/or privileged. If you are not the intended recipient then
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From: equest-users-bounces at lists.onebuilding.org [equest-users-bounces at lists.onebuilding.org] On Behalf Of Christopher Schaffner [chris at greenengineer.com]

Sent: Thursday, October 13, 2011 10:04 AM

To: Omar Osama; equest-users at lists.onebuilding.org

Subject: Re: [Equest-users] U-Value unexpected impact

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
LEED Fellow
Founder and Principal

The Green Engineer, LLP
Sustainable Design Consulting
50 Beharrell Street
Concord, MA 01742
T: 978.369.8978
chris at greenengineer.com

The Green Engineer, LLP is a Certified B Corporation

From: Omar Osama <o_osama at live.com>

Date: Thu, 13 Oct 2011 16:07:13 +0200

To: <equest-users at lists.onebuilding.org>

Subject: [Equest-users] U-Value unexpected impact

    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

Project Engineer ,  EA Sustainable Building Consultants


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