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Question about Cross Ventilation

Posted by mimi72 (My Page) on
Sat, Aug 18, 12 at 12:02

Our bedroom is south facing, which is where our breeze comes out of. There is a bank of 3 double hung windows facing south, and two separated double hungs facing west. The room is connected by a standard size door (always open) to the master bath, which has two large 40 x 40" pictures windows at right angles to each other facing west and north which are inoperable.

I want to maximize north/south cross ventilation in the bed/bath by replacing the bath windows with ones that open. Given the size of the windows, my options are Marvin ultimate awnings (open 11.5") and Marvin Tilt and Turn Hopper widows, which will open up at the top and bottom and also I think hinge on the side as well (not quite sure how those work but it seems they open up a lot more).

The cost of the awnings is about $1200 less; for the purposes of creating cross ventilation do you think the opening is sufficient? My concern is that the principle of cross vent says the inlet (wind side) is supposed to be smaller than the outlet (leeward) window, and the awning opening would be smaller than the opening from the double hungs, so the inlet would be bigger than the outlet. Not sure how much it matters. Since there's a wall with only a door opening between the bedroom and bath anyway will I even get much cross vent?

Thanks for any direction here.


Follow-Up Postings:

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RE: Question about Cross Ventilation

Hi Mimi,

There's not too much science involving cross ventilation probably because of the site and design variability. Ive never heard of the smaller inlet size and would tend to think its the other way around but hopefully someone could correct me on this. Either way, I doubt it matters much.

I think the awning would make a bigger difference up high as opposed to down low. Casements offer the best cross ventilaton not only due to the entire window area being able to open but because the window opens out, it tends to "scoop" the air inside. For this reason, the tilt and turn may ventilate better. I would think it might make a bigger difference to change out the double hungs with casements.

While it may make a more comfortable living space, dont expect any cost returns from changing out windows to accomplish more ventilation.


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RE: Question about Cross Ventilation

mimi72 - If you want the inlet to be smaller than the outlet, then you just use the tilt option.

Casements offer the best cross ventilaton not only due to the entire window area being able to open but because the window opens out, it tends to "scoop" the air inside. For this reason, the tilt and turn may ventilate better.

SpringtimeHomes - Tilt and turn windows open in, not out.


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RE: Question about Cross Ventilation

I agree with Springtime....just opening those windows will help, and our casements are fab for capturing the breeze...it's like having fins on your house. I would also want to get those west windows open as much as possible as that's where so much heat comes from in the summer....north windows are nice to open as they capture the cooler breezes.


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