Remove old insulation in attic?
 

Background: House built in 1984, 1200+sf, Oklahoma City, Ranch style.

While installing a bathroom fan and duct for the main bath from the attic, I realized that there is old (blown in?) gray insulation under newer pink (faced) rolled insulation all over the attic.

There is a lot of small debris from when the roof was re-shingled in July, along with lots of old mouse droppings as well. I'd like to clean up the droppings and debris, but I feel that the old gray stuff should be removed as well.

I realize that this could be a long and time consuming process for me, but as the weather warms in the next couple of months, I'd like to get it cleaner up there as my wife has some health problems.

Any thoughts to removing the old insulation?

Thanks!

Leave it in place. The gray is most likely rock wool, and the fiberglass on top is a waste. Get an insulator to come in a blow cellulose...add 6 inches or so, and you will notice the difference, as well as "mouse proof" the attic, since mice cannot tolerate the borate treated cellulose....it is also extremely fire retardant.

Why would the fiberglass on top be a waste?
Ron

I don't agree that it is a waste in terms of insulating value, but it shouldn't be faced.

Is the faced insulation layed with the facing up or down? If it is down go ahead and add celulose on top as it is acceptable to have 25% or so of your insulating value on the inside of the vapour barrier (face). Of course this only applies if you don't already have a vapour barrier in place (typically plastic between the drywall and rafters).

If it is facing up, or if there is another vapour barrier in place, peel off the face or at least slit it before adding cellulose.

Don't worry about cleaning it. The attic should be sealed from the rest of the house.

It is faced down.

Thanks for the replies. I'll look into adding cellulose.

The greatest myth perpetrated by advertising and misinformation is that fiberglass will insulate anything. At best, it creates a trapped air space, and slows the transfer of heat....at worse, it only slows the migration of air...meaning if it isn't faced, it does nothing. There is a lot of information out there that basically exposes fiberglass for what it is, and the industry that manufactures it still opposes complete disclosure of testing.

It is faced, as described in the original post. Where would you use fibreglass without some type of air barrier? All the fibreglass I've seen says right on the package that it is for use with an air/vapour barrier.

There are 'home gurus" who have fiberglass blown in...same way we do cellulose. Same machine will do it.

I've heard that the small critters don't like borate (the big box guy talked about "boric acid" in their blown in product - so I assume he was talking about the same thing...?)

wondering if I should consider a layer of this just for add'l mouse protection. My attic is critter proofed like crazy (galvanized harware cloth along ridge vent, soffit vents, etc.) - but the little ba$tards can still find a way to get where they want to go...

do you know if rock wool is also treated with borate (I have rock wool batts in the attic space now) - I don't see this listed on any of the materials or packaging but I though I once heard one of those home repair shows talking about this being the case...?

thanks

blown in insulation is really easy DIY. you can rent the machine from HD. its especially easy for attics where you don't even have to cut holes between joists - like you do for walls.

as for the mice ... are you sure its not BAT droppings?

i wouldn't bother trying to make my attic mouse proof. you must stop how they get into the house from the outside, probably ground level.

the attic must be sealed against bats entry.

then bait & trap the mice and/or bats until they are gone. no more problem.

thanks knucklez - for me, mice, bats, squirrels, etc. - they're all a pain in the a$$ and they all seem to want to live in my house (fwiw I've had mice in the rafter vents in my original roof - i think they came in from top side via bad section on the ridge vent opening because when I fixed that part they stopped - my mantra has become that they take whatever opening you leave them. I also had bats come down the chimney (stove pipe) - I fried a couple one time when I lit the fire - didn't even realize they were hanging in the flue. Squirrels used to use my roof as a patio before I took down the small trees near the corners of the building. They were chewing at the walls under the soffit. It's a constant battle - I feel like Bill Murray in Caddy Shack :laughing:

so now I just go paranoid and seal the crap out of everything - stop 'em all - galvanized screen mesh wherever I need airflow. and lots of traps everywhere too - just in case. If the insulation is something they hate, then I'm all for more of it, beyond the heat gains.