[Equest-users] Window shade

[Bruce Easterbrook]

The ideal overhang depends on your latitude.  It is an easy and standard 
passive solar calculation.  You can google calculators based on your 
zip.  Your window shade can be designed to exclude the summer sun and 
allow the winter sun to enter.  Depending on your results you might want 
to adjust your window sill height.  If your building has fans on 24 
hours a day you may not see a big winter benefit due to the heat loss at 
night without insulating curtains.  If your fans only run during 
occupied times you might think you have a benefit but is is only because 
eQuest is not calculating the heat loss when the fans are off.  At the 
end of the day, you have a chunk of wall at R-2.  It is actually a 
little worse than this, the glass is radiating heat outside at a higher 
rate than an insulated wall would as well.  This is also why there is 
such a game being played with the low E coatings, you can adjust the 
selectivity of incoming and out going radiation depending on where you 
are and what you are trying to accomplish.  One of the glass 
manufacturers has what is called "Canadian low E", it maximizes incoming 
radiation and minimizes out going, no good in Miami though, you want to 
minimize incoming and maximize outgoing(maybe).  I don't think eQuest is 
totally "tuned" in this area from some of the observations others have 
made concerning glass and shading.
Bruce Easterbrook P.Eng.
Abode Engineering

On 08/07/2010 05:18 PM, Sami, Vikram wrote:
>
> I'm not sure thats a surprising result. Depending on your window 
> height, you might be over shading your window and reducing some of the 
> passive solar heat gain in winter. I don't see how the shades will 
> help in winter - they will reduce the heat gain.
>
> The trick is always to balance out when your summer benefits outweigh 
> your winter penalty. This is why we model - to optimize these aspects.
>
> *Vikram Sami*, LEED AP
>
> Sustainable Design Analyst
>
> 1382 Peachtree St. NE, Atlanta, GA 30309
>
> t: 404-443-7462    f: 404.892.5823     e: vikram.sami at perkinswill.com 
> www.perkinswill.com <http://www.perkinswill.com/>
>
> *Perkins+Will.* Ideas + buildings that honor the broader goals of society
>
> *From:* equest-users-bounces at lists.onebuilding.org 
> [mailto:equest-users-bounces at lists.onebuilding.org] *On Behalf Of 
> *Bosch, Crina
> *Sent:* Thursday, July 08, 2010 4:44 PM
> *To:* equest-users at lists.onebuilding.org
> *Subject:* [Equest-users] Window shade
>
> I have a residential building that needs to be modeled with window 
> shading on the south side. When I input the shading 24" to each window 
> on the south side of the building my heating during winter and the 
> pumps results every month are increased and the shading doesn't help 
> at all. This doesn't make any sense to me. In the winter time on the 
> south side during summer the shading should help after theory. In the 
> winter should help too because the sun will heat the windows and heat 
> up the spaces.
>
> Any help would be appreciated.
>
> Thank you.
>
> Crina Bosch
>
>
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