On 21 Aug 2005 21:00:15 -0700, "caledon" wrote:

Hi, I need advice on insulating my old house (105 yrs. old). There is
virtually NO insulation in the attic at all. Between the joists you
can see the lathe and plaster. There are scatterings of insulation here
and there that is basically usless and likely should be removed (since
critters have used it as a urinal).

My question is, if I put down batts of insulation, should I FIRST be
putting plastic down as a vapour barrier. I think I read that some
types of insulation comes with a built in vapour barrier on one side.

You can purchase insulation that is unfaced (no vapor barrier), faced on one
side, or faced on both sides. If you buy the single faced insulation, there
should not be a need to put down a separate barrier. I have never used the
double faced in any application, but would be wary of it in an attic where you
need the insulation to be able to "breathe."

I thought that I would remove the old rotted insulation that is
currently there, put in batts of fresh insulation then blow in more on
top. Any suggestions

Removing the old insulation is probably a good idea. One never knows what has
lived in it, especially over a hundred year span.

If you place bats into the troughs between the ceiling joists, be sure to place
the barrier side down. Do not pour insulation over the bat material. Insulation
depends upon trapped air to provide the heat transfer stoppage between two
spaces. Placing a poured material on top of the (I am assuming fiberglass) will
crush the fiberglass and reduce its designed air volume and thereby reduce the
efficiency of the material.

If you really want to add to the "R" value of the insulation, and don;'t mind a
lot of work, you can cut slabs of Styrofoam insulation to fit be between the
joists and lay that in before putting in the roll material. In this scenario,
the independent vapor barrier would be advisable and unfaced bat material on
the top. Again, do not put anything on top of the Fiberglas that would crush it
down.



Bill Waller
New Eagle, PA