Seriously – Blow-in Cellulose or not?
Redoing the interior rooms of my house, one room at a time. I’m taking down crown molding to replace cracked plaster ceilings with gyp. board. My new crown molding detail begins with a 5-1/2 wide baseboard (inverted), so I have about 5 inches or so at the tops of the walls where it doesn’t matter if I tear up the existing wall plaster (which for the most part is staying).
At the base of my walls, in many places the baseboard is removed already and in some places, I’ll be cutting out plaster to install new outlets, so I have ready access to the inside of my exterior walls at the bottom, too.
I wasn’t planning on it, but I now have a unique opportunity: I could blow in cellulose insulation from the interior while my walls are torn apart anyway.
My question: Is it worth it?
Conditions:
I live in the Kansas City, Missouri area, so we have cold winters and hot, humid summers.
The house is 120 year old wood claps over some sort of tar paper over 3/4″ 1x sheathing over 2×4 studs with 3/8″ lath and 3/8″ plaster. No existing insulation.
We have renovated the doors and windows and they are extremely tight. We have abated most air leaks in the house and blown in lots of cellulose attic insulation already. The house already performs thermally as well as an old house can be expected to without wall insulation.
Would I see much improvement in thermal performance if I blew in cellulose? How about sound? Do I need to be concerned about moisture condensation inside of the wall cavity?
Replies
Any insulation is better than none, but blown in cellulose wouldn't be my first choice for your house.
Moisture will almost certainly be an issue since there's no way that your exterior is really air tight. Blowing any type of insulation may become more difficult since you probably have fire blocking in the stud bays.
Are you stripping off the old interior walls? If you're taking it back to the studs, I would try lining the stud bays with plastic and using batts. Blown in insulation will settle long before batts.
No. Existing plaster, for the most part is to remain. We will not tear out the existing plaster at this time, so we will not be about to add a vapor barrier.If it gets down to it, we'll leave the exterior walls be (no insulation) for another 10-15 years until its time to paint again, then we'll tear off and replace old siding.My initial investigations, with the first room in our house, is that there is no fire blocking. The house is one story with ~10'-0" walls.Perhaps there are ways around the cellulose settlement issue?
And don't get me wrong, I have been a longtime proponent of the "forget the insulation, it's the air leaks that waste energy" school of thought. Our house is no slouch when it comes to heating and cooling performance. I think that's due mostly because of our diligent air sealing and window/door work, but also due to thermal mass of plaster walls.However, for the next few days, before I start repairing plaster and putting up crown, I have a once-in-a-lifetime opportunity to get some cellulose in the walls with almost NO extra work. That is... IF it will help any and not create other new problems.Advice?
I say do it. It WILL help with your heating bill and make the house more comfortable. You will want to do the dense pack method. Has a smaller diameter hose with higher velocity.
You may also consider one of these, they are only $200:http://www.ridgid.com/Tools/SeeSnake-micro
FWIW, existing plaster with several coats of oil paint is a pretty good vapor barrier. Moisture will get through the cracks and around the edges, but very little through the plaster.
If your view never changes you're following the wrong leader
> If it gets down to it, we'll leave the exterior walls be (no insulation) for another 10-15 years until its time to paint again, then we'll tear off and replace old siding.
If you do blown-in now, what becomes of it in the future when you do the siding job?
-- J.S.
I did this on mine and I definately think it was worth it. No, there's no vapor barrier, but there's no house wrap either, so I'm not worried about vapor condensing in the cells. Besides, it's been about 6 years now and subsequent renovations have shown no sign of dampness.
It's pretty cheap, so I say "do it."
Mike Hennessy
Pittsburgh, PA
Blown-in cellulose is a good fit in terms of ease of retrofit installation and it's ability to seal air leaks. And you're far enough south that condensation in the walls (in the absence of a vapor barrier) shouldn't be a major worry.
The only question would be whether the existing structure is water-tight enough to prevent any serious leakage of rain/snow into the cellulose. The stuff can stand an occasional wetting, but shouldn't be subjected to continual drenching.
(Well, there's also the question of whether the access you're providing is sufficient, but that's partly up to the skill of the operator plus specifics of your house.)
Dan, what's the access question? Just that we don't know all of the details about what kind of framing is in the wall?
I was sort of hoping that I would be the operator of the blow-in machine and that I could just use the Home Depot / Lowes products.
The question is whether you can get good fill from those access points.And you'll need a pro blower, not the HD toy.
If your view never changes you're following the wrong leader
Dense pack cells Needs no VB as it does not let air move through it like FG batt wall filters do . I would not worry about water from ext. as you have siding,tarpaper and t&g sheathing.
And, good point about water infiltration from the exterior... I suppose the exterior is pretty well sealed at the trim and ends of clap boards, but there is no sealing at the bottom edges of the claps. I wonder how much water actually can be blown into the wall cavity...
Dense pack cellulose must be bought into these proceedings so now it's homework time for rasher.
Seeing you've been around on the forum a while I'll forego the how-to spiel about the search function and just say there are 200 messages dealing with dense pack cellulose in the archives.
cheers
94386.16 79167.1
Edited 10/29/2007 7:05 pm ET by rez
Yes,
Blow in cellulose.
Look for cellulose treated with borates rather than sulfates... it retains it's fire retardant properties if it gets wet and dries back out.
Garett
I did similarly when I bought my first house many years ago and would do it again today. I used a HD type pump, we fluffed the stuff well and it worked. Fire blocking, windows, etc, are annoyances but it's really pretty easy to do the bust out and patchwork on the plaster in general.
I've seen/done jobs where the cellulose was dumped in and rodded because no pump was available, and even after settlement, it was pretty well packed.
Don K.
EJG Homes Renovations - New Construction - Rentals
I wouldn't hesitate a second in a house that has sheathing. Dense-packed cellulose will perform well in mixed climate. Better not to have vapor barrier on one side or the other in a mixed climate anyway. The wall benefits from being able to dry out to either side depending on the season and moisture-drive conditions. Dense packed won't settle. Residing problems down the road won't be an issue, as you have sheathing in place already. It'll make the house quieter too.Steve