Blown Insulation in the attic

[FastbackJon]

Okay, got a random question, wondering how anyone else would handle this.

Bought a house last year, built in 1910, but a 2006 remodel. Two story with an attic above that, that you can stand up and walk around in. But when they remodeled it they took a shortcut and sheetrocked over the opening to get to the attic. But that was no problem. I got up there and located the frame in the joists from the previous drop down ladder, got the reciprocating saw out and opened that back up again.

But now my issue is that I have about 372 sq ft of 6" to 10" deep blown insulation all over that I need to deal with before I can put down particle board and screw it to the joists.

What would you do?

[Musicman]

What's the problem Jon... If you have to put it somewhere, why not leave it where it is? I wouldn't use particle board though... I would use plywood. If it's a stand up attic, then it must have knee walls, so if you find that you really have way to much insulating material for the floor, then save some for the walls. Are you going to use this space for anything special, or just storage?

[FastbackJon]

Just too much of it I guess, it comes up a few inches above the joists so that even makes them hard to find when trying to secure the plywood down I would think. Short term would be storage, long term... who knows?

[PocketThunder]

I would put another layer of 2x6's over the existing attick floor (in the opposite direction of the existing) and then insulate that and then put down at least 5/8" tounge and groove plywood.  What are the existing attic floor joists right now?  2x6's?  If they are 2x4's, which they are probably not, then you would not have enough strength there to support living space above.
But with 2x6's and a second "grid" of 2x6's then you can get 11" of insulation over the first two floors and have strength to support living space in the attic.  Whatever you do dont stuff insulation directly to the underside of the roof and then sheet rock over it.  Make sure to add "attic chutes" so that air can flow properly from the soffit to the peak of the roof, where the should be vents.  Hopefully a continuous ridge vent..


Paul
in St. Paul

[Neal_J]

Had the same problem here when we bought our place.  Here's what we did.

First, I got a free used snow shovel off Craig's List to skim the insulation down to the top of the joints.  The excess insulation was bagged in big garbage bags and thrown in the garbage.  Before I laid down plywood, I stapled a layer of landscape fabric atop the joings.  This is important because it keeps the insulation from squirting out of the plywood seams whenever you walk across it - significantly reduces the dust).  I tehn used 5/8" plywood, cut into 2'x4' sections courtesy of Home Depot's panel saw, which made moving them up into the attic through our small trap door MUCH easier.   Drywall screws attach the plywood, in case I need to access wiring or plumbing.

We live near SF so the extra insulation above the 2x8 joists wasn't necessary.

Peace,

Neal

[Silver R/T]

they sell rolls of plastic at home depot, lowes that you can put right over insulation and screw plywood right on top of that

[FastbackJon]

Just some update pictures...

I'm going about it with Neal's approach. Got about six or seven bags done so far. What you see in the bottom (recent) picture is plywood I found underneath the blown in insulation that was up there.

BEFORE



AFTER

[Musicman]

Big improvement in the Before & After... that was one big ugly mess in the Before shot.

[BigBlackDodge]

Thats a big difference!


That old insulation looks like concrete with those cracks in it.


BBD

[bull]

I have to agree with Silver on this one. Just lay down and staple some plastic to the rafters and snap some chaulk lines where you want to put the screws/nails through the plywood to secure them. It shouldn't be hard to find the studs.

[Silver R/T]

also I would get a couple of sky lights in there and you can finish it off as another bedroom/kids room.

[Just 6T9 CHGR]

I have the same in my house......just screwed plywood to the joists over the insulation.  Mine is just storage space anyway

[NHCharger]

they sell rolls of plastic at home depot, lowes that you can put right over insulation and screw plywood right on top of that

Plastic acts as a vapor barrier. In a climate where you need to heat your house the plastic must go on the interior side of the insulation, otherwise when moisture migrates through the insulation and hits the vapor barrier/plastic it turns back into condensation and will cause water problems and possible mold.

[dodgecharger-fan]

Yep. Moisture barrier needs to be on the heated side of the insulation.

Jon, if you have plans to insulate the whole space, you could do away with all of that existing insulation. Although, it might work nicely as a sound barrier.

I was even thinking that you could put moisture barrier up on the roof joists with an opening up top and then scoop the insulation into that space. Cap off the moisture barrier with some more when you get done.
If you finish the peak of the roof so that you have a flat ceiling, you can just pile it up on top to finish off the insulation.

As mentioned though, always use a "chute" from the eaves to the ridge (or highest open area) to let air circulate under the sheathing of the roof.

[FastbackJon]

Update, about a year later....

Started working on it again. Plan is to get all the cellulose insulation out of there, currently working on that. Got a shop vac and some 30 gallon garbage bags to help out.

The framing is made up of rough cut 2x4's and 2x6's, so I bought some 2x2's to furr up the 2x4's with some 8D nails to anchor them. Then I need to wire in a couple outlets and a light, not sure where I'll get power from yet. Could tap it off one of my ceiling lights but I don't want to have to turn on a switch (or light) downstairs to be able to turn on another switch upstairs.

So after the studs are furred up and the wiring is done, I bought some R-19 to go down between the joists. Joists are 15" or 16" on center and so is the R-19 so that's good. After the insulation goes down then does the plywood.

Got my fingers crossed I don't run into anything funny!

[Steve P.]

You will more than likely find it easier pre-drill and use screws rather than nail the 2x2's. The older wood gets the harder it gets. This way will also be  LESS DAMAGING to the ceiling below it.

Good luck....

[PocketThunder]

You will more than likely find it easier pre-drill and use screws rather than nail the 2x2's. The older wood gets the harder it gets. This way will also be  LESS DAMAGING to the ceiling below it.

Good luck....

You got that right!   

[dodgecharger-fan]

So, this space will be unheated?
If this is just storage and not heated, keep going. You're on the right track - insulating the floor will insulate this space from the heated living space below. The only issue I see is that you haven't mentioned vapour barrier in the floor. Ideally you want it below the floor joists as well but that means taking down the ceiling below - not fun. So, at least lay plastic down before the insulation - wrapping it up and over the floor joists and make it continuous - taping any seams. Wrapping up over the joists isn't ideal, but the alternative is not pretty. This is better than no barrier at all.

If it's more than storage space, you want the insulated envelope of the house to come up around this space.
That means insulating the roof, end gable walls and the knee wall. That would make the attic part of the heated space below.
This makes the floor part of the heated space and thus does not need the vapour barrier - because the vapour barrier will be on the roof, gables, and knee wall, right?
As mentioned, make sure the roof can breathe from the soffitt to the ridge or you'll end up with ice dams and/or curly, lifting roof shingles.

You can still have insulation in the floor - but it's more for sound than heat unless you insulate the entry point as well - then you've got some temperature control between this space and the space below. If it's living space, I wouldn't want that because now you need to treat each space separately for heating. If you don't, and the temperature difference is enough, you'll be back to needing vapour barrier again because the warmer air below will condense against the colder surfaces in the floor, the moisture will pool causing rot and mold.

[FastbackJon]

Space will be unheated on it's own, except for the radiating heat that gets upwards into the space from the rest of the house.

Good thinking on the screws instead of nails, the nails I bought were sinker nails so they do go in a little bit easier, but hammering away I might disturb the existing ceiling (sheetrock into plaster and lathe) more than just using screws.

The attic ceiling and the knee/gable walls for the most part is already insulated. But I'm not sure what the point was there since there are 6"x6" vents right to the outside on either end of the attic.

No plans for a vapor barrier. There wasn't one there before, and for what it's worth I think it would be way too much work to put one up and down over every joist. To do it right I'd have to remove the existing ceiling and staple it to the underside of each joist like you said, but that would be far too involved.

[dodgecharger-fan]

Space will be unheated on it's own, except for the radiating heat that gets upwards into the space from the rest of the house.

Good thinking on the screws instead of nails, the nails I bought were sinker nails so they do go in a little bit easier, but hammering away I might disturb the existing ceiling (sheetrock into plaster and lathe) more than just using screws.

The attic ceiling and the knee/gable walls for the most part is already insulated. But I'm not sure what the point was there since there are 6"x6" vents right to the outside on either end of the attic.

No plans for a vapor barrier. There wasn't one there before, and for what it's worth I think it would be way too much work to put one up and down over every joist. To do it right I'd have to remove the existing ceiling and staple it to the underside of each joist like you said, but that would be far too involved.

So with those vents, this is a cold space no matter what the roof and walls have in them.

Without a vapour barrier, the warm, moist air below will rise up, hit a cold surface and then condense. That condensation will drip back down on your ceiling or collect up in the nooks and crannies of the insulation. It could freeze, or worse, allow mold to start.
The vapour barrier - as close to the warm side as possible - will stop the movement of the moist air. With it on the warm side of things, there's no chance for condensation.
If you've ever seen condensation on your windows in the winter or on the uninsulated tank of the toilet, you know what will happen inside your ceiling. It's amounts to a lot of water.

[FastbackJon]

Where I live though, we have pretty dry air. It's not like in Houston or Georgia where it's muggy. The only time I ever see condensation on the glass when I take a shower and forget to turn on the fan. I've never seen it on the tank of the toilet.

[Just 6T9 CHGR]

Looks just like my attic.....same plaster ceilings, same 2x6's, same brown "fluff" insulation  It was built in 1920
When i moved into my house the particle board was already screwed down to the joists over the insulation

[Charger_Fan]

Hey, congrats! You made it a whole year without accidentally sticking your foot through the ceiling (like Christmas Vacation).

[Steve P.]

Many homes do not have a vapor barrier above normal rooms. Bathrooms and some kitchens mostly. As long as the attic is well ventilated it should not be a problem.

I live in Florida where it is humid for 8 months of the year. OR MORE...    There is no vapor barrier in this house ceiling or in my last house. The last one was build by/for the the track owner.

[Silver R/T]

are you planning on getting some sky lights later on?