insulation worth the effort? 1.5 story 50's ranch


Old 08-05-12, 02:30 PM
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Join Date: Aug 2012
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insulation worth the effort? 1.5 story 50's ranch

hey there!
We own a 1.5 story ranch with two upstairs bedrooms (dormer) in northern NJ. In one upstairs bedroom, we removed the contact papered over wood paneling, thinking there was sheet rock underneath. This turned into a bigger job than expected, because only 1/3rd of the room was sheetrocked. I've already put in place the sheet rock for the entire room (except a piece or two).
A guy at work heard what I was doing, and is strongly incouraging me to upgrade the insulation (sad looking R13? between 2x6 roof rafters).
So now, I'm trying to figure out if we have the budget to insulate well enough to make a difference.

The roof has soffits along the eaves but no vent at the top of the roof. Most of the "attic" is the "insulated" bedrooms which is above the living spaces and about a third is open to the uninsulated attached garage.

Looking around, I'm not totally confused.

Fiberglass doesn't seem like it will do much and I'll have to take all the sheet rock down.

Spray foam seems great, other than the sheet rock needing to come down and it not being fire resisent (we heat with a wood stove whose chimney goes right through this room).

I heard of just putting 1" rigid foam up over the existing fiberglass/sheetrock, and then re-sheetrocking over that. Sounds to be a pain considering but an option. The plus is that it is also an air seal.
Hoping for some opinions here...

Our budget is nil at the moment, the cheaper the better. Another bun in the oven and such.
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Old 08-05-12, 08:04 PM
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Join Date: Mar 2012
Location: USA
Posts: 8,470
Welcome to the forums!

You need to add a ridge vent to exhaust the air entering through your soffit vents. If roof rafters are serving as framing for the drywall as well, rock wool insulation that leaves about 2" of airflow between it and the roof sheathing is probably the best option. Depending on where in NJ you are, R-38 above the flat ceiling and on the flat portions of the 1st floor ceiling behind the kneewalls is probably what you need. That leaves the kneewalls themselves - probably R-13; maybe R-15.

Entering the first 3 digits of your ZIP Code plus the specific information about your house's structure and your heating and cooling systems into the ZIP-Code Insulation Program will give you the information you need.

Post back and we can help you with material choices and techniques.
Old 08-06-12, 04:15 PM
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Join Date: Aug 2012
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The room we're currently working primarily has sloped walls (~45 degree if I'd have to guess) and is only 12' by maybe 12' between the knee walls, with the vast majority of that under the slopes. I don't think there is anyway to get to R39 without seriously reducing the headroom. The ceiling is only 8' in the very center.

Is ventilation definitely necessary? I'm afraid if I don't get a high enough R value with my current rafters and added a vent, it would cool the room down even more in the winter.
Old 08-06-12, 05:03 PM
Join Date: Aug 2009
Location: USA
Posts: 4,941
In your situation you have to do the best you can with what you have. Ventilation is necessary if you are insulating with anything except closed cell spray foam. The rigid foam board over the rafters is a good solution. It will actually be better than insulation between the rafters. I would remove the drywall in this case. That will give you an extra 1/2" to work with. If you go that route and only put 1" on, you should put 2 layers of 1/2" if you can get it. That way you can overlap seams in the ofam and reduce air infiltration. Also make sure you create a continuous thermal barrier. When you foam the ceiling, slanted ceiling, and knee walls, you will want to make sure the floor behind the kness walls is well insulated up to the insulation in the knee walls.

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