Attic insulation question.

[myopposablethumb]

Hello,

My attic has blown in insulation, about 10" deep (Grey fibrous stuff). I live in Utah, very dry year round, very hot in summer, cold in winter. Gable roof with about 7' inside hight, at highest point from top of ceiling joists to peak of roof. One of the problems in summer is that even with pretty good sized vents at either gable end, the attic space gets very hot (brown asphalt roof shingles). I'm sure that the heat in the attic space is responsible for the air conditioner working overtime, and the house taking a very long time to cool down at night.

My question is this... Rather than adding more blown-in insulation to the ceiling, what if I added insulation directly to the roof joists? The roof is framed with 2x6 (not trusses). I could add 6" of fiberglass insulation directly to the spaces between the joists that frame the roof. This would make a kind of 'cold space' in the attic... the insulation in the roof would be the first layer of insulation, and there would still be 10" of blown-in insulation on top of the ceiling joists. Does anyone see a problem with this? The area where I live is harshly dry, so I don't think I have to worry about moisture.

Thoughts?

Thanks, Daniel

[HayZee518]

houses with between the rafter insulation have ridge vents. In the rafter space is a polyethylene molded spacer that runs from the ridge to the soffit so as to promote ventilation through the attic space. purpose of insulation is to prevent air movement through hollow spaces. your ceiling insulation is relatively deep although I have seen deeper. blown in cellulose is quite dense and efficient. have you considered a gable end fan?

[myopposablethumb]

When there's a ridge and soffit vent, how big is the air space between the roof decking and the insulation? 2 - 3 inches?

If I installed the ridge vent and soffit vent, does that mean the rest of the attic would be enclosed (not vented)?

I thought about installing a power gable vent, but it seems that in July and August it would be somewhat worthless... if it's 125 degrees in my attic, and 104 degrees outside, I'm not gaining much. My goal was to try to stop the attic from heating up too much in the first place.

And, I re-checked the blown-in insulation (the ceiling joists are 2x6 (not 2x8 as I thought). The depth of the insulation is only about 7-8".

Thanks, Daniel

[HayZee518]

Attic cooling is accomplished with gable end fans , gable end louvers and/or rafter space vents. The rafter space vents are used in combination of manufactured ridge vents and manufactured or onsite constructed rafter spacers. The following diagram will show both types.