Venting through the rafters?


  #1  
Old 05-25-09, 09:22 PM
Yukon Youngun's Avatar
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Venting through the rafters?

I just bought a house with a "bonus" room above the garage. Now, this room is obviously going to be too hot for any comfort during the season, so I am looking for some suggestions on improving it.

From what I can see, everything is "sufficiently" insulated, 6" in the knee walls, between the joists in the attic side spaces and apparently between the rafters above the room. No access to the peak to see what's there. I say "sufficiently" only as in the inspectors verified that it all met code when it was built four years ago.

I see, though, that there is NO venting of any kind in the peak above the room and it looks like the insulation in the rafters does not allow any air flow from the side spaces to the peak. I have noticed only one soffit vent in the immediate area, but the side spaces are open to the greater attic area.

I was thinking to install a ridge vent, some soffit vents and slide those foam vent channels up some, or all, of the rafters. Would that cool things down a bit, at least enough for the a/c to keep up?
 
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Old 05-26-09, 06:06 AM
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Hi Yukon, before you start, you need to determine the intent of the builder. And we need to know where you are, Yukon doesn't sound like a location where a room would be too hot, maybe.

The builder may have chosen to NOT vent, although I rarely like the option, but it can be an option. Trying to change that to a vented attic could be challenging. Getting air in, getting it to flow up through each rafter bay, then getting it to a large enough vent, and then getting it to work well enough to solve your problem without causing more issues, like condensation from the AC in the rafters.

Tell us what your climate is so we can judge what you need.
Also, is there any space where the top attic would normally be or does everything just come to a peak?

Bud
 
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Old 05-26-09, 04:03 PM
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Well, it's interesting what one can see when one is awake. I stopped by the house on my way home from work to check things a bit closer.

First off, I am in mid-Missouri, plenty hot enough, especially with dark, full-on south facing roof directly over the room. Not nearly cold enough for me, but for two days of the year. Wonder why I stay around...

What I found was 3-1/2" insulation in the knee walls, at least 6" in the sloped ceilings, and guessing same in the top. There is attic space above the room, in the peak, but I failed to look whether it is open from the "back" end toward the main attic area. I'm guessing yes, with enough room to crawl, if necessary.

Also, I noticed that they doubled the rafters edge-to-edge, so I assume they meant to vent, although most of the batts are stuffed too close for air flow.

Finally, there is plenty of soffit vent, the perforated panels. I just didn't see any daylight through it because they weren't so careful with the blown-in in the garage ceiling/attic floor.

So basically, with all this, I'm thinking: 1) clear the soffits, with foam panels if necesary; 2) add ridge vent; 3) reposition the rafter batts with an inch or two of clear gap; and 4) add horizontal batts along both knee walls for a little extra. If I can get to the peak area, maybe a bit more there too.

Thanks for your comments.
 
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Old 05-26-09, 04:48 PM
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Sounds like things are better in the daylight. Here is some reading for you.
Welcome To Home Energy Magazine Online

More insulation where ever you can as energy costs will go up.

Bud
 
 

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