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Dakbupd
Attic insulation 1855 stone home, vapor barrier or not?
Dakbupd

We are purchasing a historic stone home built in 1855 in SE Wisconsin. There is very little insulation in the attic. What is there is loose and appears to possibly be something along the lines of a cellulose. There is no vapor barrier present. I am considering taking out what is there and starting from scratch. Should I put in vapor barrier? My other thought was to just add more cellulose insulation to level things out and then place batts of fiberglass over the top to get the desired R value. Do you recommend a vapor barrier and if so what type, polyethylene place between joist and stapled or placing paper backed fiber glass between joist? There is no mold or moisture issue at this time. I'm not sure of the width between the joist, it looked as though they are on 16" centers. Thank you for you time!,

dj1
Re: Attic insulation 1855 stone home, vapor barrier or not?
dj1

Considering the age of the house, I would remove the existing "insulation" out of the attic. Place it in plastic bags and get them out. Wear protection, it will be nasty.

Find out the R value necessary in your city (call your building dept). The batt insulation you will get will have moisture barrier (craft paper) - that side should be down first. Place each batt in a space between joists. Again, wear protection, body, hands, eyes and nose.

keith3267
Re: Attic insulation 1855 stone home, vapor barrier or not?
keith3267

If you upgrade the insulation, and I recommend that you do, you must also insure that you have adequate ventilation. Often those old houses had no ventilation in the attic and only a small amount of insulation. As a result, the attic would actually stay pretty warm so condensation did not occur. As you increase the insulation, the attic will be colder so you need more ventilation.

The more insulation you add, the more ventilation you need, up to a point. If you are going to R30 or less, the the usual dormer/gable vents with a surface area of 1/150 to 1/300 of attic floor space will be adequate. That would be a 1.6 to 3.3 square feet of vent at each end of the attic for every 1000 square feet of attic floor you have. You could also go with soffit vents and a ridge vent if you are putting up a new roof instead of the traditional gable vents.

With the proper ventilation, you do not need a vapor barrier. If you do not have the proper ventilation or it is undersized, then you need to remove the ceiling and install the vapor barrier under the joists, then put up a new ceiling.

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