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Do I Need To Install A Vapor Barrier?


Hi, I bought this house and my utility bills are sky high, the house was built 1964, ceiling joists are 2x6 and the insulation doesn't fill that either, the insulation is double faced with foil. My plan is to pull out old insulation, add 2x4's to existing 2x6's bringing the total to approx. 9" and put new R-30 insulation (and of course baffles where roof meets ceiling). Now my confusion is with the vapor barrier, do I need it or not? (faced or unfaced). Our winters give us approx. 25 f and can reach a low of 0 f on a couple of nights (Monsey, NY 10952). I would appreciate your advice. 

Also, I am planning on turning half of the garage into a room with a vaulted ceiling. What's the best way to do it as far as ventilation and moisture control. Thank you for your consideration.


Hi NM,

I love those old houses but so many of them are under insulated or not insulated at all.

Replacing the old insulation is a good idea. You say you will have a 9" depth. You will probably need to opt for R-25 fiberglass batts instead of R-30 as I don't think it will fit without compressing it. Once compressed it can lose some of it's R-value making it less effective.

Regarding the vapor barrier, when using fiberglass batts any insulated ceiling over a living space should have a vapor barrier installed. In your case you should purchase kraft faced batts. The kraft (paper) facing serves as a vapor barrier. If you were using blown in insulation a vapor barrier may not be required.

For your converted garage you have a couple of options as far as ventilation. I wrote several articles a few years ago regarding ventilation procedures that will answer your questions.  Since your garage will be a living space you would also want a vapor barrier added, both in the ceiling and walls.


Related Tips and Advice:

Insulating An Attic Hatch Cover
How To Install Baffles Or Vent Chutes
Wall Vapor Barriers

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