Attic insualation suggestions?


Old 07-09-12, 09:37 AM
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Join Date: Jul 2012
Posts: 1
Attic insulation suggestions?

I'll try to explain what the house has without making a huge wall of text...

The house is a split level with a protrusion off the front that has half the basement and the master bedroom. Half of the main attic is a finished room (left side of the pic).

Walls are mostly uninsulated except for the ~20ft in the kitchen (had the drywall down, installed R15). Brick facade, a layer of fibrous sheathing, open stud wall otherwise.

Ceilings facing the attic have presumably 1954 vintage fiberglass batts a few inches thick (R13, 15, who knows) plus unknown vintage loose cellulose which seems to be 8-9 inches thick except a small area where the whole house fan has moved it. The sloped parts of the attic room ceiling just have the fiberglass with an air gap between it and the roof sheathing. The attic over the master bedroom is very low, under 3 ft from rafters to peak. There is a similar height tunnel above the attic room.

The bedroom attic has 2 turtle vents in the roof and the main attic has a continuous ridge vent and 2 gable vents. Both attic areas are open to each other. The soffits are fairly narrow and were unvented but I recently cut them out so air inlet is as good as it's going to get. From what I can tell the cellulose is now now longer blocking any airflow and almost every rafter space has a clear path between the soffit and attic area.

The problem: on really hot days like this recent east coast heat wave, the attic insulation heat soaks right through by 3pm or so especially over the master bedroom. Of course the attic room also gets hot very easily. From what I can tell, the fiberglass plus all that cellulose should have a reasonably good R value.

Should I be considering redoing/adding to/whatever the attic insulation or not? Otherwise, I know I should probably seal off the gable vents to let the soffit/ridge system do its thing. Also the roof over the bedroom is a hip roof so I could block the turtle vents and probably get 6ft or so of ridge vent installed instead. If I get really motivated I may take drywall down in the attic room to put better insulation in the sloped ceiling part.

Any help would be greatly appreciated!
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Last edited by iwfur25; 07-09-12 at 10:00 AM.
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Old 07-09-12, 04:06 PM
Nashkat1's Avatar
Join Date: Mar 2012
Location: USA
Posts: 8,470
Welcome to the forums, and thank you for including a picture with your first post!

First thing, you should run the Zip Code Insulation Program, entering all of the specific information about your house, your heating and cooling systems, etc., to determine what your insulation needs are. I would go ahead and enter R-38 for the attic, given what you say is there.

It sounds like you've made some real progress on the ventilation. Yes, you can block off the gable vents. You might also replace the turtle vents on the hipped roof with a ridge vent, but that's not a sure thing since it ties into the main roof rather low down. Did you open the soffit around the hipped roof? Hard to tell from the picture.

Insulating the walls - possibly by blowing it in where you don't have access, or by replacing the drywall on the sloped walls, looks like your best bet for adding R-value in a cost-effective manner.

I'm wondering about your windows. Have you upgraded them? Or have you installed shades - not blinds - on the ones facing south? I don't see any awnings on your house - they might help a lot.

If the real problem is that heat is collecting upstairs because it rises, and that the upstairs is gaining heat through the windows, then adding more insulation around the upstairs might just make it worse.

One quick idea: If your house has intakes for the return air on more than one level, then blocking a good portion of the lowest one, and about half of the middle one (if you have three) should help you balance the air supply to the demand.

Second quick idea: Install a programmable thermostat designed for your heating and cooling systems, if you haven't already.
Old 07-09-12, 04:13 PM
Join Date: Aug 2009
Location: USA
Posts: 4,941
His problem is not going to be fixed with window blinds. The problem is the roof gets real hot in the sun. You are getting a lot of heat via radiation. I don't know how much ventilation you have or really need. I know there is a formula for figuring out sq in of vent area. I don't think blocking off your gable vents will do anything for you. You may want to add more ventilation to the area that only has the turtle vents. I'm sure the attic room is very underinsulated.
Old 07-11-12, 09:46 PM
Join Date: Mar 2009
Location: WA
Posts: 1,167
I agree with the previous post. You need more insulation to protect the conditioned rooms from the solar gain roof. The '60's had fiberglass batts of R-9, I'd hate to find out what yours are...

If you have access to the side attics, air-seal any wiring/plumbing holes before adding more insulation. This will help find those openings;

Install some soffit vents (intake) as you have plenty of exhaust now; Air Vent: Continuous Soffit Vents Specifications

Close off gable vents? - Fine Homebuilding Question & Answer


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