Attic hatch

[Gordon Maney]

I have a hatch in the ceiling on one upstairs room. I just have a square piece of [insulated] material sitting on a ledge of dimension lumber, ripped to a reasonable width. I would like to make it seal better, so I don't get any drizzle of mineral wool dust past it due to air circulation in the attic, or changes in air pressure up there.

I imagine I could use strips of adhesive backed foam, but I wonder if there are any other stellar ideas out there....

[MoparNorm]

Is the mineral wool new or existing?

If the hatch works fine, I'd leave it and attack the problem using another method. It sounds like the hatch is OK from a visual point of view, so no need to install a new or air tight seal. I'd just get a piece of encapsulated fiberglass insulation (hard board insulation cut to fit or a glass batt bagged in plastic would work) and glue it or two sided tape it to the attic side of the hatch. For the mineral wool around the hatch, I'd either replace it with encapsulated formalgahyde free, fiberglass batts for about 24" ( or what ever the ceiling joist spacing is...?) around the perimeter of the hatch, or staple some Kraft paper to the joists, over the mineral wool in the same area to prevent it from moving around.
Never been a big fan of mineral wool, it's not the most efficient method since, as you found out, it moves around which changes the thickness and the R value. Most mineral wool attics that I travel into have material stacked in groups from either attic drafts or poor original installtion, with bare spots and thicknesses varying from 1" to 10". Also it compressed and settles over time. Nothing works better than encapsulated glass, properly applied and stapled to prevent movement.
MN

[Gordon Maney]

What is encapsulated fiberglass? Is this different from the common kind? Is it encapsulated in some membrane?

There was some mineral wool in it to begin with, and then I had more put in. That was in about 1979. I have considered having it vacuumed out and starting over with something better. I am told that the same equipment used to clean furnace ducts can be, and is, used to remove blown in insulation from attic spaces.

I can tell you it is really ugly stuff to work in. Though obviously you would know that, now that I think about it....

[Ugg013]

Gordon:

It's insulation covered with plastic or paper, fully enclosed.

Later
Ugg