I am thinking of buying a REALLY old home. (built in 1830) I was wondering if you all would advise me to foam insulate this house? Obviously, a house this old can’t have much insulation left in the walls…so something has to be done.
Wikipedia says that “spray polyurethane insulation typically has an R-value around R-5 to R-6 per inch. In comparison, blown fiberglass typically has an R-Value of only R-2 to R-4 per inch.”
The house is 3500 square feet…so it isn’t going to be cheap.
Mike Holmes, a Canadian contractor with TV shows Holmes on Homes, Holmes Inspections, and Holmes Makes It Right regularly uses spray foam insulation for his Canadian-based homes. He swears by it.
Are you in Canada? I think the answer might depend on what the temperature differential is going to be in the winter.
There are companies that do this - this is one that I have heard of. Looks like they have done a few old buildings.
More than just insulating, spray foam seals, and a 180-year old house will have tons of leaks, cracks and holes. The problem is that it’s best done when the inside surface of the wall is down. It may be possible to foam a wall with the plaster still up, but it’s an iffy proposition thanks to obstructions in the wall like fire stops, pipes, etc. Then, you have a bunch of holes to patch where the foam was injected, and it is possible to pump in too much foam, leading to bowed or cracked walls or jammed doors and windows.
Another note - make sure you have done all your other renovations first. You will probably need to add things like electrical upgrades and vents. These are much easier to do before the insulation goes in.
What kind of electrical wiring is in this house? Is it new or at least post 1950 or so? A house this old may still have knob and tube wiring and you can’t insulate that because it needs to dissipate heat. It probably has been upgraded because it is hard to get a mortgage or insurance on a house with K&N, but it still does exist. Do not blow insulation into walls that have knob and tube.
Another question to ask, is this house in a historical zone or registry? A house built that long ago might be and there are limits to your options for upgrading or remodeling a historically registered home.
I had to look up “knob and tube wiring”, wanting to know what the deal is.
Question : was the insulation over the actual single-conductor wires so bad that the ceramic was mandatory? Or are the ceramic components designed more to insulate the heat of the wires from the wood?
It looks like K&T lets you get away with using a lot less copper because the air around each wire, and the ceramic insulators mean the wire can safely get much hotter.
Foam insulation acts as a vapor barrier. Saving the tedious task of stapling plastic sheeting on the walls. That labor savings should offset the extra cost of spray foam.
Cite: Mike Holmes. He’s mentioned no vapor barrier is needed with spray foam many times in all his series.
There is a down side that Mike fails to mention. If you ever have to go into that wall to change the wiring or plumbing then you got one heck of a mess. Imagine scraping that foam away. I’ve learned that from other DIY shows like Disaster DIY with Bryan Baeumler. Bryan often does his own spray foam. He’s got a small tank and suits up in one of those white suits. I guess it’s cheaper on a small job.
Check your local codes. I recall Mike built a house in New Orleans after Katrina. They used spray foam, but also had to use regular insulation. Apparently the local codes were a bit out of date.
Spray foam is the future. Not only is it an effective vapour barrier, it is a vastly superior vapour barrier to poly and sheathing tape, especially for complex areas like joist spaces. It is also a uniform vapour barrier that is indifferent to what side is hot or cold; it keeps humidity out of the wall space whether driven from the inside or outside. Polyurethane formulations have a decent fire rating as well.
There are a variety of products with different insulating properties but they are all higher R value that fibreglass for a given volume. The draw back is the expense; at least double the price of fibreglass insulation and poly vapour barrier.
I expect fibreglass batt insulation to be phased out eventually for occupational health reasons. Nasty stuff.
I don’t think that heat was the issue that caused the use of ceramic ‘knobs’. At least, it doesn’t seem to be mentioned in this Wiki article on knob and tube wiring.
What I do know is that over time the insulation on the wires, which consists of paper with an outer ‘fabric’ covering (rubber was also used), will become brittle and crumbly and will disintegrate and literally fall off of the wire if it is disturbed or handled much. :eek:
Spray foam causes health problems for a number of homeowners:
A bit more on the subject:
There are two types of spray foam. Open Cell and closed cell. In non contractor terms think of one as loose and pliable and the other as rock hard once cured.
Spray foam is flammable so there is an extra charge to put an ignition barrier on the inside exposed surface of the foam. Advisable to do.
Spray foam will get into cracks and crevices other types of information will not. This is good and very air tight.
As one mention already, some people not tolerate this well.
Per another mention make sure all and every embedded utility in the wall is up to code and technology once you spray this stuff on. A hell of a mess if you have to pull out after for repairs.
Is best to use with open exposed walls, in your case a full tear down and start over renovation.
good luck
Which can be good… or bad. In some applications, you do not want a vapor barrier.
And this is why I’ll never use it. I often find myself snaking wiring and cables through walls, and it’s fairly simple when the wall contains fiberglass insulation.
I just had my attic spray-foamed, followed by a layer of blown-in insulation. The spray foam isn’t just for insulation, it’s to seal the attic to avoid air leakage through the interior walls and heat leakage at the tops of walls where insulation can have gaps. Adding the blown-in on top of it puts the R-value at the needed level. It reduced our unwanted leakage of air by about half. It’s making a big difference this winter for us, and our home is only 40 years old.
Great thoughts. Thanks so much!
That’s good enough for me. I would love to have a home built by Mike Holmes.
Note that Holmes says he always installs a heat recovery ventilator too so that the house doesn’t end up retaining too much moisture, since foam seals up the house tightly. You don’t want a house to be completely air-tight. This device lets indoor air out and brings outdoor air in, but heats the incoming air (in part using the heat from the warm air that’s going out).
A house built in 1830 would probably have plenty of air exchange (i.e., leaks) even after spray-foaming, so you probably wouldn’t need this, but you can test it to make sure.
My sister had her attic done with foam. It cost her $4k. To do it with fiberglass would have cost $2.4k. I’ve decided to have my attic done as soon as practical next spring. One downside is that you have to be out of the house, so don’t leave any valuables lying around. Also, the house stunk for a few days and continued to have occasional odors for a few months.
On a related note … My house is 50+ years old. I purchase it in 1983. I immediately had cellulose insulation blown in. Does cellulose insulation last, or does it tend to settle and leave areas at the top that are uninsulated. I’m considering re-siding my house with fiber-cement in the spring. While the exterior is exposed, it would be a good time to beef up the insulation if it is needed.
I tend to be conservative in these matters, fiberglass works and it doesn’t burn (the paper backing will, but the 'glass itself doesn’t). I’m sure spray foam works as well, but does it work in the 50 year time frame? We won’t know for sure for another 25 years or so.
I recommend first going over the entire outside of the heated area with a good quality chalking filling in all the cracks and crevasses. There’s a bit of economy to be had with materials of the same kind (like wood and wood, metal and metal), but spend the money for a high quality, 100% silicone chalking for dis-similar material (wood and metal, wood and cement). This is because different materials expand and contract at different rates, thus we need a very flexible chalking to keep the seal.
A little off-topic, but the cost of re-wiring will be offset by reduced insurance costs. It seems many house fires start with faulty electrical connections. So at least hire a professional electrician to look the systems over.
You say the house isn’t insulated? It may be well overdue for pulling down the wallboard (or is it still lathe and plaster), new wiring, new plumbing, new coaxial cables, new telephone cables, new heating system and replace any and all rotting wood parts.
Everything else being equal, I’d hire a skilled professional to spray in the foam. There’s special equipment to be used, experience to get the right amount in … probably not a good DIY project. Using fiberglass on the other hand is real easy, just need a sharp bread knife and a stapler. The only real pitfall is compacting the 'glass into the spaces, it works best when it’s fluffy. Cut the 'glass to fit the odd-ball space, never just stuff it in.