Insulating attic - no soffit vents


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Old 05-22-14, 05:00 AM
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Insulating attic - no soffit vents

Hello,
I just bought a 60 year old house and decided to put a new roof on it. I also added a ridge vent to the roof. There are two gables for ventilation, but no soffit ventilation in the roof (so 'high' ventilation only). My question is this...do I need to do anything special for ventilation when installing insulation? I do not want to cause any moisture issues. There is currently no insulation at all in the attic and I want to put batting on the floor and on the ceiling, and then place plywood on top of it. But I am not 100% sure on insulation without soffits. Will the ridge vent and the gables be enough? I could easily install a fan in one of the gables.
 
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Old 05-22-14, 05:25 AM
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Hi alisha87,
There are some things you will need to do to avoid potential moisture issues. Although SC has some different climates I will assume yours is humid. Fill the attic with hot humid air and then allow the roof to cool at night from radiant heat loss and you have condensation in the attic. Probably not enough to rain down onto everything below, but a constant wet dry cycle is not good. It is important to have good air flow through the attic to vent some of that moisture before it can condense and then to dry it out when things warm up in the morning. Basically, good attic ventilation has always been good.

All that said, air seal the attic floor before you insulate. Raise the decking you mentioned above the insulation to prevent trapping moisture. I'll add a link on air sealing.

Soffit venting is about the best place to install low venting, but if you don't have soffits, there were some options before you installed that new roof, called edge vents. I know, too late .

One of the drawbacks of just having gable and ridge vents is the positive pressures that move the air out the upper vents will create a negative pressure at the attic floor increasing the air flow from the house into the attic through any leaks you missed. One way to reduce this pressure difference would be to extend those gable vents with some large insulated ducts down to the attic floor. Doing that makes the gable vents function like low vents.

Running long so I'll let you read.
Bud

http://www.efficiencyvermont.com/ste...ide_062507.pdf
 
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Old 05-23-14, 09:10 AM
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Thanks for the reply. One hiccup in that whole plan is the access to the attic is open. It is in a closet and has a permanent set of stairs up to the attic and there is no door or anything in the floor...hopefully that doesnt cause issues with insulation. But some insulation is better than none...right?

Also, would it be wise to install an attic fan to circulate the air? We can program it to operate an hour per day in the evening to circulate everything and hopefully keep that wet/dry cycle at bay.
 
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Old 05-23-14, 09:40 AM
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When you say access to attic is open, is there a door at the bottom to the closet?

With pull down stairs they build a coffer dam of sorts around the entrance to the attic to hold back the insulation so it doesn't fall into the stair in your case. But more importantly, you need to find a way to air seal between the conditioned space in the house and the attic. An open stairway would be high risk and expensive.

One of the tasks for making energy improvements is to define the envelope of the house and then insulate and air seal at that boundary. Now, the closet could be made part of the attic or part of the house, your choice.

Give me a better description if I sound lost.

Bud
 
 

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