[Equest-users] Simple question...hopefully

[Kevin Kyte]

Increased glazing performance may result in less thermal transfer through the envelope.  This may result in increased or deceased energy savings.  Depending on climate, varying heat transfer through fenestration may result in more energy use in the winter and less in the summer or vice versa.  There is usually a happen middle point which will give the best returns.  The same applies to increasing and decreasing insulation.

________________________________
From: Nick Caton [mailto:ncaton at smithboucher.com]
Sent: Monday, November 16, 2009 12:21 PM
To: David Delasantos; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Simple question...hopefully

In a recent project,  our architect decided to "upgrade" to nicer (more expensive) glass.  These fenestrations had marginally better thermal properties, so I had the same surprise to find the annual energy figures going UP...

After some investigation, it turned into an important design lesson which may or may not apply to your case:   This project had a significant amount of daylighting, and the "improved" glass had a significantly lower Tvis figure.  Less light in means more energy spent on the lighting system!

In the role of lighting system designer, I used to ignore things like glass transmissivity, as I was taught to design around the worst case (i.e. nighttime where window contributions have little/no effect)... now I pay very close attention when daylight harvesting is a part of the project!

Hope this helps either your current situation, or otherwise in the future!

~Nick

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NICK CATON, E.I.T.
PROJECT ENGINEER
25501 west valley parkway
olathe ks 66061
direct 913 344.0036
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Check out our new web-site @ www.smithboucher.com

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of David Delasantos
Sent: Monday, November 16, 2009 11:02 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Simple question...hopefully


I ran a very quick and dirty EEM to compare the effects of using a different glass type when compared to the baseline model, which was created in the SD Wizard.  Contrary to my expectations, the higher performance glass resulted in higher annual energy usage!  The glazing is the only component I changed in the model.  If anyone can speak to this result, I would appreciate it.

Thank you...DD
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