[Bldg-sim] Impact of Overhangs

James V Dirkes II, PE jvd2pe at tds.net
Wed Feb 10 06:01:42 PST 2010


This article (or a version of it) appeared in the ASHRAE Journal a few months back and lit a firestorm of letters to the Editor.  I think the author is on target and also excellent at getting his readers to think in greater depth about some of the common design issues of our day. 

 

The Building Performance Team
James V. Dirkes II, P.E., LEED AP
1631 Acacia Drive NW
Grand Rapids, MI 49504
616 450 8653

 

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Nick Caton
Sent: Tuesday, February 09, 2010 6:13 PM
To: Maria Kordjamshidi; BldgSim Mailing List; equest-users at lists.onebuilding.org; trace-users at lists.onebuilding.org; Fareed Syed; John Aulbach
Subject: Re: [Bldg-sim] Impact of Overhangs

 

Maria, John, Fareed et al:

 

http://www.buildingscience.com/documents/insights/bsi-007-prioritizing-green2014it-s-the-energy-stupid

 

These guys have a good bit of interesting reading – recommend bookmarking this link if you also have the capacity to be entertained/chuckling with this kind of thing =).  As I read this call for reason/logic, I recalled this article they put out (linked above) that pretty well spells out the logic to a layman behind “less glass > better glass.”

 

That article above is probably worth your time and your architects’ to read over to get the point across.  If/when they want you to drive it home, I’d suggest simply building your site-specific 2/3 story building model and running it once with something like 30% glazing (with a picture so they can visually see that’s a lot of glass), and again with 100% storefront glass box and let their eyes bug at the energy cost differences.

 

Impact of overhangs for a “typical building” is something you’ll have trouble finding an answer to, as it’s obviously quite site and orientation specific.  Again I’d suggest running two models and observing the differences with/without the overhangs in question.   eQuest is one of many tools appropriate to the task-at-hand.

 

~Nick

 

 

 

cid:489575314 at 22072009-0ABB

 

NICK CATON, E.I.T.

PROJECT ENGINEER

25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

Check out our new web-site @ www.smithboucher.com 

 

 

cid:489575314 at 22072009-0ABB

 

NICK CATON, E.I.T.

PROJECT ENGINEER

25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

Check out our new web-site @ www.smithboucher.com 

 

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Maria Kordjamshidi
Sent: Sunday, February 07, 2010 6:03 AM
To: BldgSim Mailing List; equest-users at lists.onebuilding.org; trace-users at lists.onebuilding.org; Fareed Syed; John Aulbach
Subject: Re: [Bldg-sim] Impact of Overhangs

 


John

 

Free running: refers to the state of a building that is naturally ventilated and does not use any mechanical equipment to maintain or improve its indoor thermal condition.

 

Maria



--- On Sat, 2/6/10, John Aulbach <jra_sac at yahoo.com> wrote:


From: John Aulbach <jra_sac at yahoo.com>
Subject: Re: [Bldg-sim] Impact of Overhangs
To: "Maria Kordjamshidi" <m_kordjamshidi at yahoo.com>, "BldgSim Mailing List" <bldg-sim at onebuilding.org>, equest-users at lists.onebuilding.org, trace-users at lists.onebuilding.org, "Fareed Syed" <syedf at progressiveae.com>
Date: Saturday, February 6, 2010, 8:29 PM

Maria:

 

Excellent information.

 

Would you please describe what you mean by "free running mode"?

 

Thank you.

 


  _____  


From: Maria Kordjamshidi <m_kordjamshidi at yahoo.com>
To: BldgSim Mailing List <bldg-sim at onebuilding.org>; equest-users at lists.onebuilding.org; trace-users at lists.onebuilding.org; Fareed Syed <syedf at progressiveae.com>
Sent: Fri, February 5, 2010 9:47:04 PM
Subject: Re: [Bldg-sim] Impact of Overhangs


Fareed

 

I have examined the effect of many parameters on the thermal performance of 6 typical houses (single storey and double storey houses) for a moderate climate of Sydney. a part of my report comes in the following for your consideration.

 

"Adding an overhang above all windows improved annual thermal performance of the typical houses in conditioned mode. However, this was not the case for the houses in free running mode. The houses presented different patterns of annual thermal performance in the different modes, responding to increments in overhang width.

Increases in overhang width of 1m resulted in an average of 4.8% enhancement in the house’s annual thermal performance in conditioned mode. The same overhang generally caused 3.7% deterioration in annual free running performance, while a slight improvement was observed in thermal performance in some cases.  The reason for these different results is made clear when comparing the seasonal performances of each house in two different house modes. 

When all the overhang widths were increased to 1m, the summer performance improved by an average of 26.6% in conditioned mode. The improvement decreased to an average of 8% for all houses in free running mode. The winter performance of the typical houses in this situation deteriorated by an average of 8.2% in conditioned mode and 11.7% in the free running mode. Thus the deterioration that was observed in the annual free running performance of some of the houses in response to the setting of overhang with a width of 1m for all windows would appear to owe more to deterioration in their winter performance and less improvement in their summer performance in free running mode than in conditioned mode." 

  

 

Hope this help

 

Maria

 



--- On Sat, 2/6/10, Fareed Syed <syedf at progressiveae.com> wrote:


From: Fareed Syed <syedf at progressiveae.com>
Subject: [Bldg-sim] Impact of Overhangs
To: "BldgSim Mailing List" <bldg-sim at onebuilding.org>, equest-users at lists.onebuilding.org, trace-users at lists.onebuilding.org
Date: Saturday, February 6, 2010, 12:22 AM

Folks,

 

Does anyone have good research data using simulations on the impact of overhangs and shadings for a typical building? 

  

I am having hard time convincing architects to reduce the glazing. They will make it a glass building if they are given a chance. 

  

I want to show them that for a 2 or 3 storied building with ton of glazing and few feet of overhang will not help the cooling/heating loads at all. 

  

I would appreciate your input. 

  

Thanks much. 

  

  

Fareed Syed EIT, LEED® AP 

Mechanical Engineer 
cid:image001.png at 01C9B834.C9D7E7F0

1811 4 Mile Rd NE
Grand Rapids, MI  49525 

  

Phone: 616.361.2664 ext. 3247
Direct: 616.447.3447
Fax: 616.361.1493 

 <http://us.mc514.mail.yahoo.com/mc/compose?to=syedf@progressiveae.com> syedf at progressiveae.com
 <http://www.progressiveae.com/> www.progressiveae.com


  

 
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