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Old 07-02-2010, 04:35 PM  
Kelly M Bray
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Default Attic ventilation and furnace

I have a customer who had a remodel where all of the attic vents around the perimeter were covered by stucco, and the dormers vents were removed when the roofing was done. The windows and doors are all new and tight. What effect does this have on the AC and the heating units? She has stated that the attic air feels moist and the house is stale. The bathroom fans have nowhere to easily vent, so at the moment they vent into the attic. Thoughts please!



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Old 07-02-2010, 08:20 PM  
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A functional vent system is part of a roof installation and should be a part of the contact with a roofing company. Failure to install proper ventilation will void most shingle MFG material warranties, some allow roof application over a insulated under deck spray foam. Even metal, hard surfaces such as slate, tile want the deck to be ventilated because of potential damage to the wood framing and structure that results from high heat exposure. Wood will become brittle and plywood can delaminate after prolonged exposure to high attic heat.

I would recommend for your customer to get the attic properly ventilated to dissipate heat and humidity that is trapped in the attic. Moisture will allow for mold growth.



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Old 07-05-2010, 12:57 PM  
Kelly M Bray
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What about the effects on the Heating and AC systems? Does this create problems with combustion air?

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Old 07-05-2010, 01:24 PM  
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What about the effects on the Heating and AC systems? Does this create problems with combustion air?
If the house is sealed no combustion air will be stolen regardless of the fans. Then whatever infiltration the HO's house has supplies combustion air.

I recommend 3 ea. CO detectors, the sensitive kind.
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Old 07-05-2010, 02:25 PM  
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What about the effects on the Heating and AC systems? Does this create problems with combustion air?
Yes, and also to the units thmselves.
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Old 07-05-2010, 05:18 PM  
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If your evaporator coils are in the attic, then you have some serious issues.
If not, then the absence of ventilation in the attic should not have a direct impact to the performance of your HVAC system. Ideally, the system should have it's own source of combustion and make-up air.
As Olddog has mentioned, your concerns should be with the roofing and materials. HVAC should be the least of your concerns. Get a ridge vent installed, make sure there is not blockage of the soffit vents and vent the bathroom to the outside.

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Old 07-05-2010, 09:29 PM  
Kelly M Bray
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The problem is that it is a tile roof making any modifications difficult. The contractor who did it is out of business I believe. Another covered all the soffit vents with Styrofoam molding and stucco. I get to find them from inside the attic as they are not visible from outside. The customers have a limited budget. I think first steps would be to open the soffits, then vent the bathrooms, then check with a roofing contractor about venting higher up.

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Old 07-06-2010, 05:47 AM  
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The problem is that it is a tile roof making any modifications difficult. The contractor who did it is out of business I believe. Another covered all the soffit vents with Styrofoam molding and stucco. I get to find them from inside the attic as they are not visible from outside. The customers have a limited budget. I think first steps would be to open the soffits, then vent the bathrooms, then check with a roofing contractor about venting higher up.
It may make it difficult but its not impossible. Tile Mfg make venting ridge tiles. If you don't open both intake and exhaust you will not gain any air movement, you have trapped air.

I think you are correct to first vent the bath exhaust because of the introduction of additional moisture to the trapped air space, but properly venting the attic should not go without out addressing that issue. Make sure if you vent to the soffit that you vent through and not just to the sofit area, you want the moisture sent outside the house envelope.

Now, even if your customer has a limited budget, they need to find a way to correct this, because the potential for long term problems created by this will be a LOT more expensive to correct than making the resources available now to resolve these issues.


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