I've got sheets of 2.5" XPS (R-15). I'm considering placing a layer
on top of the existing blown-in insulation.

Any idea if this is a safe/sensible thing to do? The XPS will be
supported by trusses and won't compress the blown-in insulation.

Fire hazard?

Borrall Wonnell wrote:
I've got sheets of 2.5" XPS (R-15). I'm considering placing a layer
on top of the existing blown-in insulation.

Any idea if this is a safe/sensible thing to do? The XPS will be
supported by trusses and won't compress the blown-in insulation.

Fire hazard?

Probably that. Plus, it would trap moisture within your current insulation.

On Mar 11, 9:24*am, Borrall Wonnell wrote:
I've got sheets of 2.5" XPS (R-15). *I'm considering placing a layer
on top of the existing blown-in insulation.

Any idea if this is a safe/sensible thing to do? *The XPS will be
supported by trusses and won't compress the blown-in insulation.

Fire hazard?

Moisture barriers go down first, if any warm air leaks up into the
attic it will condense and mold up the insulation. The foamboard would
go down first, then the blown in.

Borrall Wonnell wrote:
I've got sheets of 2.5" XPS (R-15). I'm considering placing a layer
on top of the existing blown-in insulation.

Any idea if this is a safe/sensible thing to do? The XPS will be
supported by trusses and won't compress the blown-in insulation.

Fire hazard?

Your blown in may already be compressed. It should be over the trusses
at least a foot deep.

On Mar 11, 3:57*pm, LSMFT wrote:
Borrall Wonnell wrote:

Your blown in may already be compressed. It should be over the trusses
at least a foot deep.

It's not a foot deep, at least not where I measured. Methinks a
scouting trip to the attic is in order!

On Thu, 11 Mar 2010 07:24:13 -0800 (PST), Borrall Wonnell
wrote:

I've got sheets of 2.5" XPS (R-15). I'm considering placing a layer
on top of the existing blown-in insulation.

Any idea if this is a safe/sensible thing to do? The XPS will be
supported by trusses and won't compress the blown-in insulation.

Fire hazard?

If mold/mildew is of concern there should be one insulation barrier,
and that insulation barrier should be closest to the living quarter
planes in the attic space. Your insulation material above the
moisture barrier should allow water vapor to pass thorough it.

On Mar 11, 9:49*pm, Phisherman wrote:
On Thu, 11 Mar 2010 07:24:13 -0800 (PST), Borrall Wonnell


If mold/mildew is of concern there should be one insulation barrier,
and that insulation barrier should be closest to the living quarter
planes in the attic space. *Your insulation material above the
moisture barrier should allow water vapor to pass thorough it. *

Based on advice given here, I've decided to scrap the idea. If I'm
going to add more insulation it's got to be blown-in.

Borrall Wonnell wrote:
On Mar 11, 9:49 pm, Phisherman wrote:
On Thu, 11 Mar 2010 07:24:13 -0800 (PST), Borrall Wonnell


If mold/mildew is of concern there should be one insulation barrier,
and that insulation barrier should be closest to the living quarter
planes in the attic space. Your insulation material above the
moisture barrier should allow water vapor to pass thorough it.

Based on advice given here, I've decided to scrap the idea. If I'm
going to add more insulation it's got to be blown-in.

Why is that? It is easy to lay batts of fiberglass over blown-in insulation.