I just finished building a new home and as part of the Energy Star rating transfer grilles were installed above each of the bedroom doors to allow air exchange when the doors are closed. The problem is that sound (and a small amount of light) pass freely through the vents negating all privacy of closing the door. I've read that I should install a baffle into the vents to allow air to pass through but deaden sound. I can't find any details for where I can buy this or what kind of materials I can use to construct it. Any advice would be greatly appreciated.
Transfer Grille Baffle
hvacsound-proofing
Related Solutions
Soundproofing and ventilation are not compatible. The louvers could be blocked/unblocked at will with a rectangular piece foam rubber that is several inches (10cm or so), for example from an old sofa cushion.
Insert it when you want privacy is desired. Take it down, or pull it back otherwise. You may find that you don't notice any difference in air quality inside the room, and end up leaving it in place all the time. Or you may find that the louvers allow heat into the room in the winter.
Cut it to size + a couple centimeters. If cut too big, it may bow away from the louvers. If too small, it may not have enough friction against the walls to keep it in place.
Larger cities have stores dedicated to selling foam rubber or different dimensions and densities.
Thick foam rubber is also available from repair shops that re-upholster furniture.
Looks like people are selling foam rubber on ebay:
http://www.ebay.com/sch/i.html?_nkw=foam+rubber
Per @longneck's comment, foam rubber can be purchased at craft and sewing stores.
A sufficiently thick pick can be built by laminating together thinner pieces, say 3 or 4 layers of 1", using double stick tape for example.
While such a thing as a wireless relay exists, it's mighty expensive compared to the simpler option, which'd be to run thermostat wire over to the transfer switch to carry the Y and switched-Y wires there, and use the existing relay contacts on the transfer switch control board.
Best Answer
You could experiment with making the baffle out of a piece of a furnace filter. Filters allow the air to pass but would block much of the light and some of the sound. The more expensive type filters with corrugated construction and a HEPA rating would probably offer better sound and light filtering than the cheaper thin flat filters.
You will gave to study on your side just what type of baffle you could fit behind your grilles.