Insulating Old (100 y/o) Stucco House
gh2
| Posted in Energy, Heating & Insulation on
I have a 100 y/o stucco home that I’m looking to insulate using fiberglass blown in insulation (ownings corning atticat). I’ve been reading that this may cause a moisture problem within the walls where there isnt one now. The house is stucco and needs some insulation; the boiler is trying to keep up. Should I not insulate this way? I can’t imagine ripping down the plaster walls and using traditional insulation..I’m also looking to replace the windows but over the next 5 years.
Thanks in Advance
Replies
An uninsulated wood frame building
can often tolerate a fair amount of moisture intrusion without a problem, because there's air movement thru the framing cavities, and they dry out seasonally. Add to that the fact that old buildings are often made of really good old growth lumber and you have a lasting deal.
When you insulate you are increasing the moisture storage potential of the cavities and reducing the drying potential. The insulation stores moisture and it slows the movement of air, slowing down the drying that would occur during dry periods.
My general opinion is that you can insulate walls in a lot of places without too much problem, but if there are leaks from around windows, doors, roof-to-wall flashings, outlookers, etc., you will soon have problems there.
Look into insulating your attic to the nth degree, insulate under your floor, do as much air sealing as you reasonably can (done in conjunction with combustion safety testing), add storm windows, weatherstrip your doors, and seal HVAC ducts. Do all that before dealing with the walls. If you're going to do serious energy rehab on an old house I think it's worth getting a skilled energy auditor to do an audit to BPI standards.
If you are going to do blown-in, I would do cellulose instead of FG.
I tend to agree w/ the other poster.
Generally you shouldn't have any issues. What is your location? Is your exterior finish weather tight (including e.g. seams around windows and doors). As the other poster said, if you have water intrusion issues now, you could make them worse. If you don't, IMO you should be good to go. If you live in a really humid area, there may be other issues. Also agree w/ other poster ... blow cellulose, not fiberglass.
Are you doing it yourself?
Re: I tend to agree w/ the other
I live in Northwest NJ.. Exterior seams around windows and doors are weather tight as I have never had any water intrusion problems. The windows are old and drafty (i have storm windows on all exterior old windows) but no water intrusion. I just stripped the walls in my sunroom (I thought I might do this to the entire house but after this experience I'd rather blow in insulation) and no sign of water. Should I redo the windows then blow insulation? Not sure if worth money.. Why cellulose over fiberglass?
I looked at a job at a historic church
that had shiplap siding over studs, no felt or anything else underneath. They had insulation blown in and a few years later were seeing water stains in places where they had never had any problem. I was asked to bid on residing the entire building and flashing all the openings.
I suppose it might be possible to look for problems before doing the insulation. Get a moisture meter like a Tramex MEP and scan the entire building, looking for areas that are wetter than average. Do this after blowing rain, when moisture-affected areas are likely to be wettest. You also might be able to find clues using infrared. Both would be worth a try and within the abilities of a good home inspector or energy auditor. I still wouldn't insulate the walls first, though, I'd do everything else and see how much improvement I got.
Re cellulose vs FG, what I have read and heard many times is that cellulose has a greater ability to absorb and then give off moisture during wet/dry cycles, whereas with FG the moisture will migrate down and sit on the bottom plate of the wall more readily, causing more structural damage.
I live in Central NJ and did this (FG blown in) in two rooms about 10 years ago. True 4" deep studs (clapboard exterior) and we removed baseboards, drilled a low hole and then drilled a high hole (you'll need two). In one room I ran crown over the holes and in another I patched the holes (made up pieces of 1/4" plywood w/ metal lath circles. inserted them into the holes (with the plywood ending up above and below the hole) and glue/screwed them in place, finishing with plaster.
Two years ago, part of this area was demolished for our addition and this area was uncovered - no moisture problems were evident in the area. The insulation was Certainteed Insulsafe FG which is great.
It was a great advantage to keep the old plaster since it is a stronger, smoother finish than drywall (by far) and helps with sound isolation from the exterior.
Jeff
What to do first? Not sure, but now is the time to think it through. Biggest question .... how will you be removing the old windows and what will you be doing to install new ones and finish them ... e.g. trim vs. repatch stucco up to the window frame, etc. This is the time to plan it out.
cellulose ... better R per inch, I think and is reasonable price, and will generally resist air flow more than the FG, I think. The other poster mentioned better resistance to minor moisture intrusion ... don't really know about that one way or the other.
Cellulose recycles newspaper, though, so that is good, too.