AC sizing for residences with large window surface

[mcoul098]

Looking for design help AC sizing for residence with a large window surface area. Can we include the window coverings (blinds, curtains etc.) shading when sizing the AC? The issue is for new homes, where the window coverings are not provided by the builder. The designer sizes the AC for the maximum solar load, which is considerable for some condo/apartments with floor to ceiling windows.

If the owner then installs window coverings, the AC then becomes grossly oversized which has its own issues. However if the owner does not install coverings, and the designer sizing considers shading, the AC could be 30-50% undersized. Does anyone have experience with this for Canadian regulation? Legally, is the owner expected to install window covering?

Thanks in advance for your help.

 

[bawhb]

I don't know about legally, but I would make sure you get something from the homeowner telling you that they are okay with window coverings if you are going that route. My concern would be that even if there is drapes, you cannot force people to draw them. People tend to have a short memory of what they tell you, when things don't go the way they thought later on. I had a guy insist on my designing a duct system parallel with the floor joists and using side take offs, then later asked me what I was thinking in designing it like that.
HRAI does allow you to design to as low as 80% of the cooling load.

 

[Drazen]

this what you asked us you should put in your own design documents and ask signature from the one who hired you.

that is the only way. it can be also helpful for client to be well informed about how much decision on shades affect things. he can, and must make decision than.

do not allow by any means to be bounced back by "do as you deem appropriate"; in cases like this one that's the way to ruin your career.

 

[GMcD]

Blinds and drapes on the inside of the window will help reduce the heat losses, but if the window faces south or west and doesn't have any exterior shading, the blinds/drapes on the inside will act like solar collectors and will become large radiant heating panels pretty quickly. Nearly all the solar heat gain will be emitted to the room anyway. I just came back from a south facing "too warm" problem classroom in a new school- they had light grey interior blinds that on a sunny day measured 37C surface temperature resulting in large radiant heating panels - the room air temperature was 24.5C at the time but it felt like over 30 (operative or resultant temperature). The exterior shades were "value engineered" out of the job.....