05:02AM | 11/16/04
Member Since: 09/11/04
14 lifetime posts
I have a house built in 1941 - small ranch with full attic and basement.

Insulation in attic is old with newspaper dated 1950 and probably old wool insulation on top. This insulation is between the floor Joists (?) and does not come up to the top of them. It is very dusty and just removing a small sends clouds of black dust into the room. I am very concerned about getting this dust into the rest of my house and would prefer to leave it putting a layer of insulation over it or using that pink styrofoam insulation and just resting that on top/across of the floor joists. The middle of the attic has a floor which I am not about to remove and old insulation under that as well but I'd at least like to add insulation to the open areas.

Is there any horrible reason why I cannot just ad insulation ontop of the old as long as we stay below the floor level or top of joists?


Ginny M.


03:01AM | 11/18/04
Member Since: 01/28/01
171 lifetime posts
The main concern would be moisture coming up through the ceiling and condensing in the insulation. Is there a vapor barrier of some kind under the old insulation? If there isn't, the guidelines I've found on the net say something like 1 sq ft of vent for 150 sq ft of attic for no vapor barrier. Check US Dept of Energy website.

I just redid my 1973 house insulation. Fiberglass loose fill without vapor barrier. Poor ventilation. Some dust dust but a good bit of fiber glass dust. I wore a tyvek suit with hood and an upgraded dust mask from a safety equipment supply house. Undressed in accessway with door closed to keep stuff from getting into house. Shovel and rake to move the loose fill. One layer of faced fiber glass batts laid between joists. Roughly smooth loose fill on top. Second layer fiberglass batts on top of loose fill laid across joists.

Other than the vapor barrier I see no problem with just adding insulation. I think I would put a thin batt along the top of the existing layer then a second heavier layer laid crossways to close gaps. When figuring how thick to add, I would just ignore the existing R value.


04:25PM | 11/28/04
Member Since: 11/27/04
172 lifetime posts
just a note. that 2 layers or more of oil paint is considered a vapor barrier. but you still have to use some spray foam to seal pipes and wires that come up into the attic. plus have good attic ventilation . also i like to use the wirlybird turbines for venting on the top of the roof as they do not get blocked up by snow in the winter like low profile vents do.

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