Insulating a house from the outside?
Our house was built in the 1850′s and the walls are just thin. Supposedly there is blown-in insulation but the walls still feel awfully cold to the touch even though we’ve sealed up drafts and leaks.
The (original?) clapboards are in so-so shape and so we’re thinking about ripping it all off, insulating, and re-covering with new clapboard. A contractor told me this would be the best way, rather than just slapping foam board and new siding over the existing siding. Is it really?
Also, what is the proper order of materials, and which materials are best? For example,
1. Batting insulation
2. Foam board as sheathing
3. Tyvek
4. Clapboards
does that sound about right?
My husband is pretty handy, is this something we could tackle ourselves with some guidance?
Be very, very, very (did I write "very"?) careful when you attempt to insulate a house from the exterior. The issue is where the dew-point takes place inside the walls. If it happens inside the insulation or inside the wall and there is no vapor barrier on the _interior (living space)_ of the house, water will condense within the wall cavity and in considerable quantity. Which will inevitable lead to rot.
Depending on the nature and age of the blown-in insulation and whether a vapor barrier was installed at the time (paint or some types of wall-covering) you may already be experiencing this – and it would partially explain the coldness of the walls.
Before you go any further, you need to investigate what you have, how it is performing, check for dampness or condensation within your walls and get a much better idea of your options.
Now – never, never, never, never, never (did I write "never"?) ever install vapor-impermeable insulation to the exterior of a house, as in foam board and new sheathing/siding: The inside face of that foam-board becomes the vapor barrier and condensation point. Not good. Yes, I am stepping all over a couple of (in my opinion questionable) industries – but them is the facts.
On the materials you mention: Tyvek is Dupont’s trademark for a infiltration-barrier, not a vapor barrier. So, it is perfectly OK to install it on the outside of the sheathing, but inside the siding. Any other form of insulation (except spray foam – expensive but a super-excellent insulation material) will require an interior vapor barrier to be safe to install. On foam – make sure that you are not sensitive to the chemicals that go into it and that it is approved for residential use, and that it goes all the way to the inside-of-the-wall face of the inside finish (plaster or drywall).
In any case, if I were you, I would suffer through this season and save for and plan for doing this work after the weather breaks in the spring – with the advantage that it will reduce your cooling costs as well.
What are your options? Here goes:
a) Install blown-in shreaded fiberglass insulation in the wall cavities. This has the virtue of being water and mold resistant and does not collapse or settle over time. The disadvantage is that if you ever have to open a wall to make a repair it is nasty stuff to handle.
b) Install the *new* blown-in treated cellulose insulation. Again as with the fiberglass it does not collapse or settle, is impervious to moisture or mold and also acts as a partial (but not complete) vapor-barrier. A bit more expensive.
NOTE: with either of the above, you should use an approved vapor-barrier paint or wall-covering on the inside of the insulated walls to eliminate condensation problems.
c) Install spray-in foam as previously noted. There are kits available for the DIY-types – but you need to be scrupulously careful when using them – and note the suggestion on chemical sensitivities.
d) Remove the _interior_ finishes and install batt insulation with the proper vapor barriers. No fun and a great deal of work but with care and attention will give excellent results using low-tech, proven processes.
Before you do any of this, indulge in the traditional simple solutions of caulking, tightening windows and other expedients. You will get a great deal more mileage stopping infiltration than you will with just insulation but still 1850s-style infiltration.
We keep an 4,000+ square foot three-story house built in 1890 which we moved into about 19 months ago from a 2,200 s.f. three-story twin built in 1895. I spent much of last summer tightening the house inside and out, insulating the crawl-spaces, installing storm doors (wood, "in keeping") and other refinements, replacing radiators (17 of 37), chimney dampers and so forth. That, together with a condensing boiler and some control refinements got our heating bill lower than the house we moved from. It works.
Good luck with it. Do some research on condensation, vapor barriers and how they work so you understand the process, needs and pitfalls. And be very careful.
Good luck with it.