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Summer sun control - Zone 6, Madison, WI

I'm advising the onwer of a 50 unit, 6 story multifamily building on how best to cost effectively control excessive heat gain in the summer. We started by looking into louvered overhang retrofits made from aluminum and attached to the 6th floor, south side units. ( The 1-5 floors have the balconies above them to shade some.) The price? $30,000 for 5 apartments. Not in anyone's price range. The existing glass is a tinted charcoal gray Insulated Glass Unit. For that reason, window film installers are saying that they can't guarantee the glass won't break if they install. I'm not even sure myself that insulated window quilts or a product like Comfortrack Plus by Comfortex would not cause breakage to a dark tinted glass IGU since tinted glass absorbs heat rather than reflect it. Any ideas on the best solution?

Duke.docx705.29 KB
Asked by Brian Driscoll
Posted Jan 21, 2013 5:42 PM ET
Edited Jan 21, 2013 5:45 PM ET


17 Answers

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Use the existing balcony structure to fill in between with some lightweight structures..maybe tensile textile on aluminum poles or something similar.
Some brands warranty their textile in the exterior sun for 10 years + now i believe.
Would have to check for wind loads in ur area though, but it can usually be designed to let wind through rear spacing.

I would aim to cover anything beyond 45-50 degree on as much height of the windows as possible.

30 000$ for 5 apartments is ridiculous, but architectural alumium custom parts are always high$$$$ .

Zone 6, doens't it require to get a good SHG during winter time through the same windows ?
Why consider a tint ?

Also if some fabric/textile, it could chosen to allow a certain % of light!!

made a very quick drawing on ur picture.

This is just 1 idea, in hope it sparks something for you.

Answered by Jin Kazama
Posted Jan 21, 2013 11:43 PM ET


These days, the best way to address excessive solar heat gain is by choosing the right kind of glazing. If you choose glazing with a very low solar heat gain coefficient (SHGC), your tenants will be comfortable.

Of course that isn't cheap -- but it is a good solution. You can either change the entire window, or just the glazing. Start with the apartment with the occupants who complain the most.

Answered by Martin Holladay
Posted Jan 22, 2013 5:31 AM ET


Martin : why not suggest a sunshade here ?? unless their winter heating is ridiculously low there ??
i also like sunshade because they remove the unpleasant glare that the summer sun brings in !

you could analyse both situation VS current winter heating loads.

Answered by Jin Kazama
Posted Jan 22, 2013 1:30 PM ET


Q. "Why not suggest a sunshade here?"

A. If an awning is made of fabric, it doesn't last long. If it is made of durable materials like aluminum, it costs a lot.

Answered by Martin Holladay
Posted Jan 22, 2013 1:34 PM ET


I should have been more specific when I described the property and the issue. It is only on the top floor. on the south face of the building ( the side shown in the photo) where the complaints are coming from. Current glass is the original tinted IGU. These residents don't have a balcony above to shade them or to use for fabric awning pole support structure. A good SHG during winter time through the same windows would be great but would have to be shaded in the summer. And that is the most preferable, except for price. Second best , in my opinion, would be glazing with a very low solar heat gain coefficient (SHGC), except for price.

Answered by Brian Driscoll
Posted Jan 22, 2013 2:02 PM ET


Martin and Mark.

A quick look over internet showed "~ 7500 HDD" for Madison WI
is that correct ??

In that case, why would he want to get low SHGC IGUs ??

My second try here!
Maybe some motorized awnings would do it ?
Would be pretty easy to fix on top of windows on the walls, could be controlled by yearly timer or individual owners .. i do'ntknow the height of the windows, but does not require much length to get near 45degree+ shade.

Replacing IGU would probably be easier, maybe also cheaper.
But i prefer sunshade whenever possible in any climate that require that many HDD .

Am i thinking wrong on that Martin ?

Also, yes aluminun costs alot ( i did a hole lot of custom aluminum motorized sunshades recently )
but some new fabrics are very sturdy, and most are easily replaced .

My parents house has pretty large/long fabric motorized awnings on the rear patio,
probably 10-11 years old. They use it all summer, and other than some loss of color
on the sun exposed face, ( wouldn't be a problem if all white ), they are still holding pretty good i'd say !

Answered by Jin Kazama
Posted Jan 23, 2013 12:04 AM ET


7500 HDD is correct.
Low SHGC glass replacement would be both an expensive and imperfect solution, the latter due to missing out on all the desirable solar gain in winter. I'm told that the windows on the top floor are 100" high so that changes a few things in terms of a summer awning depth and that the winter solar gain might very well make it too hot, or too bright at times. (could possibly use an awning for that too.) I'll have the customer price out custom cloth awnings and compare that to low SHGC glass and also to insulated window quilts or track cellular shades.

Answered by Brian Driscoll
Posted Jan 23, 2013 11:30 AM ET
Edited Jan 23, 2013 11:45 AM ET.


100" is pretty high... if you want 100% unobstructed view you will need near 10ft of awning ..
this requires probably special bracing at that height and heavy duty framing.

I've checkd the sun angles and you should be looking to block anything higher than 50degree
be it fixed or removable for winter will not make any difference in heating since you will get 100% sun until mid/end of april.

but at that height, i'd be quick to consider a tracked exterior motorized rooler sun shade/screen
with smoething in the 1-3% openness and white back color.

Phifer probably has the best quality fabric i've worked with, but some other brands exists in exterior approxed sun screens.

The problem with exterior roller shades in tracks is to get them to behave in wind, you'll have to search for a system that locks the fabric ( double tension or spring loaded ) .

this should be much cheaper than suitable awnings, and less "risky" at this height.
If you use Somfy motors, the occupants will be able to control the screens themselves
or it can be set on an auto sun sensor very cheaply.

Are the lower story complaning about the same proble ? cause it doens't look like the balcony cover much sun from the in between windows ... independant air systems ?

hope it helps !

Answered by Jin Kazama
Posted Jan 23, 2013 2:03 PM ET


Just additionally, if you are on a tight budget for this,
consider using interior sun shades also.

It might let in a little more heat, but a 1% open whi backed weave reflects something like 50% heat.
Might be enough, and it will be much much cheaper than exterior grade + system + installation.

I used this on a 96" patio door facing south with very short overhang, it was unbearably hot during summertime, and now is very confortable with AC on + removed completely the sun glare from the kitchen on this house.

Answered by Jin Kazama
Posted Jan 23, 2013 2:24 PM ET


Thanks Jin, We'll check out the roller shade and fabric shades with sensors. No complaints that I know of from apts below. Sounds like you're familiar with these systems; any idea on costs estimates?

Answered by Brian Driscoll
Posted Jan 23, 2013 2:36 PM ET


I am not really familiar with the costs, because it largely depends on the quantity ordered
and the type of system.

I purchased a pretty large interior roller shade quantity from a very respectable US reseller,
and was very pleased with the experience and pricing. I could look out the name of the contact and their company if you wish. They shipped it to me in Quebec , but i know they deliver for free or very low shipping price in all usa.

The somfy motors usually run for something in the 250-300$ each ( DC version ..ac is cheaper )
then aluminum tubbing per ft length ..
and fabric is sold by the sq ft if i recall..was less expensive than i thought it would be.

That is for interior, exterior grade is all much more expensive and systems with tracks and or cables if another thing completely.

Answered by Jin Kazama
Posted Jan 23, 2013 5:18 PM ET

Answered by Hein Bloed
Posted Jan 23, 2013 8:09 PM ET


Hein Bloed: guten tag!

Problem here is that we need to shade a 100" high window from 45-50deg +exposure
i don't know how u'd manage to install some 10ft wide solar panels this high on a building.

mark: you could also consider shading only partially the sun and only block it on a % of the windows ... don't know if occupants only complain during 1-2 months or if SHG needs to be blocks for a larger period.

I still believe that interior sun shades/sreens will be the less costly and most user friendly option.

Answered by Jin Kazama
Posted Jan 23, 2013 9:35 PM ET


Strange that the cooling load is not establised. And how much of it is actually caused by the passive solar gain via the windows - which is easy enough to be meassured.

There are civil engineers out there who are able to advise, including correct mechanical fixing methods if necessary.
As far as I can see the entire building is neither shaded or well insulated , by the description of the OP we learn that the windows are tinted already.
So how much of the cooling load is caused by the windows?

Are there air-conditioning units employed already, what is wrong with them, are they maintained by heating and cooling engineers, certified? How much electric energy do they use?
There are PV-driven air-conditioning units available for little money. ("Midea" or others)

Is aditional shading necessary to avoid light damage to floors, furnitures etc. ?

Answered by Hein Bloed
Posted Jan 24, 2013 8:24 AM ET


Hein: agreed that it could be caused by additive factors.
The heat from the lower apartment could be rising somehere and causing overheat also.

But i do not need an engineer to tell me that 100"High windows uncovered on south side
building in this city in summer = alot of SHG

I'd still start by considering shading first, probably interior refletive screens to be as cheap as possible, and then see how it goes ... if they still complain then maybe it will be required to determine the source of the exessive heat.

Shading is always easier than compensating ..and100" high south windows does not sound good at all !

Mark: do you have any other info on the current IGU tint ??

Answered by Jin Kazama
Posted Jan 24, 2013 10:43 AM ET


I believe the owner said the glass was 40% grey tint, which I took to mean a SHGC = .60

Answered by Brian Driscoll
Posted Jan 24, 2013 1:02 PM ET


I lack the knowledge on tints for this ..
but if it is near .6 , then he needs sunshades/screens ...

Answered by Jin Kazama
Posted Jan 24, 2013 1:09 PM ET

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