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telecomworx
Registered Users
Posts:2
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| 02/09/2008 11:38 AM |
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We have a brick rambler built around 1989. The roof was recently replaced with a standing seam system from Englert. The three roof areas all now- have ridge vents, previously no ridge vents and only openings in the gables and soffits all around.
We have an unfinished basement. We discovered that the return air duct is near the middle of the basement but- there's a huge gap (rectangle) about 7" x 14" all the way to the attic, unobstructed. Standing near this area- all windows, doors shut- you can feel the breeze of air going upward. Before the roof was replaced we never noticed it- and only use the basement for storage until now.
This is, I think is a chimney effect for cooling or ventilating the basement? The downside, I believe is that this is also a fire trap- (ie) a great way for fire to spread fast and furiously?
I'm not a builder and want to know should I have it (the penetration 7" x 14" penetration around the air return) closed in or not?
thank you |
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blackdogarch
Registered Users
Posts:31
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| 02/20/2008 10:48 AM |
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I think you should definitely close it in.
The roof redesign did the venting properly, as opposed to gable end vents which typically do not work as well with soffit vents. It will lead to a greater venting. THis may also affect your attic temperature and need for insulation.
I assume the AC equipment is in the attic?
You are right in assuming the shaft is a chimney and a great route for fire. Talk to your local building officials, but at a minimum, safe off the area with sheet metal tightily attached to the floor and duct, and the basement framing and ducts. There is also fire-rated foam that works well for plugging openings (similar to the window insulation foam, but with a fire-retarder in it) that you could use.
The other issue is the duct itself. All this safeing is to give you time to get out of the house. Sooner or later the duct itself will be penetrated by the fire. One further level of control (though not typically used in residential construction) would be a fire damper in the duct that would close it immediately on senseng smoke or fire. However, this may not be useful, since a house typically has multiple openings such as stairs and open doors that allow free air passage throughout, as opposed to an office with contained areas.
Another idea gaining wider use is to insulate the roof well (foam) and do not vent it at all. This becomes part of the homes living/conditioned space which can eliminate the temperature swings the equipment adn ducting is subjected to. It also reduces or eliminates the pull of air from lower levels due to the venting.
At a minimum, close off the hole. |
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