Spray foam vs. other kinds of insulation in a house

[Zachary Hoyt]

Thank you all for the further information. The foam guy mentioned needing an air exchanger, and when I asked he said they cost around $1000 and are not hard to install, so that sounds doable.

It is partly a labor of love and partly of necessity, since I have been planning to leave here this summer and time is running out. The house is tall and narrow and awkward, so I look just like the sort of person who should live in it.

The house was listed as having been built in 1920 by the county records in the tax auction, and it has to be close because there was nothing in the area till 1893 when the paper mill was built, and the house was built before it closed in 1933. The green foam sounds good, and I noticed today that the foam for the basement walls is listed a $1.80/bf rather than $1.40 like everything else, so maybe that's why. I don't mind hanging drywall in the attic if needed, it's cheap enough and not that much work. Thanks for the tip on sealing penetrations, I'll bear it in mind. I asked if I should be putting in wooden fireblocks at the second floor level, and that's when he said he would do it with the foam.

That's odd that CA doesn't require the higher insulation value. It's good to know that rockwool won't burn. He said that was what code required around a metal chimney installation for 2" before the foam begins.

[Bill Dufour]

They do make special high temperature fiberglass for home ovens. It is just pure white fiberglass with no glue. So it does not burn.
I bought a new unused stove from c-list. It had mice in the insulation so I took it all part and replaced the insulation after washing everything inside and out. It is just draped over the firebox and hangs down the sides.
Bill D

[Jim Becker]

There are special collars that go around the stovepipe when it needs to penetrate insulation. It provides the required clearance plus it's metal for additional protection. This collar is in addition to using code compliant double-wall stove pipe.

[Zachary Hoyt]

Yes, I bought the kit with the attic insulation shield among other helpful components. I don't think it will fit where the chimney is going through a 12/12 roof that is insulated, so I think that is why the rockwool would be used, if I understand correctly. I went with SuperVent from Lowe's for both chimneys since it is relatively cheap for a double wall stainless pipe. All the bits are stashed under the stairs in the house, waiting till I have time to put them in.

[roger wiegand]

In MA, and I suspect most other places, foam needs to be covered with something to protect it from fire. Drywall is the usual choice, but intumescent paint is a better choice in the attic because then the foam contractor can spray over top of the rafters, blocking thermal bridging through the wood (R value of wood is 1/in or less, and framing can comprise 20% of the surface area of a structure, so it's a big deal if you're going for a highly efficient house. The paint is pretty expensive.

[Ronald Blue]

I don't envy your project Zach. Old houses have lot's of character and also lot's of challenges. Balloon construction definitely has it's draw backs. How out of square is it? As for insulation that seems high for a 900 hundred square foot home but it is quick and allows you to move on to other things. If you only do 2 inches in the wall that would allow you to still run electrical. The attic needs much higher R value though. At least R 38. Just my opinion though and it has little value. Good luck.

[Jim Becker]

Yes, I bought the kit with the attic insulation shield among other helpful components. I don't think it will fit where the chimney is going through a 12/12 roof that is insulated, so I think that is why the rockwool would be used, if I understand correctly. I went with SuperVent from Lowe's for both chimneys since it is relatively cheap for a double wall stainless pipe. All the bits are stashed under the stairs in the house, waiting till I have time to put them in.

You can use the rockwool where it's needed for the fire resistance and use other methods for the rest if you prefer.

[Brian Elfert]

I don't envy your project Zach. Old houses have lot's of character and also lot's of challenges. Balloon construction definitely has it's draw backs. How out of square is it? As for insulation that seems high for a 900 hundred square foot home but it is quick and allows you to move on to other things. If you only do 2 inches in the wall that would allow you to still run electrical. The attic needs much higher R value though. At least R 38. Just my opinion though and it has little value. Good luck.

In my house I had the back of ceiling sprayed with just enough foam to air seal everything. The insulation contractor then blew in insulation to something like R-60.

[roger wiegand]

In my house I had the back of ceiling sprayed with just enough foam to air seal everything. The insulation contractor then blew in insulation to something like R-60.

This works great, you just need to be sure that the foam layer is thick enough (and consistent enough) so that you don't create a condensing surface inside the wall. Your foam contractor should know that number for your area. There were some early disasters with flash and batt where the foam coat was too thin and the insulation ended up soaked and moldy with condensation.

[Bill Dufour]

I do not know if the economics is still correct but at one time it was cheaper to do flash and batt with spray foam and rigid foam sheets. Cut the rigid foam 1/2" narrow between the studs then foam all edges to seal it. Claim was factory made foam bard was cheaper per cubic foot then made in place product.
You can buy used roof foam panels on c-list and ebay.
Bill D

[Jim Becker]

Maybe the economics might work that way, Bill, but you'd compromise one of the important advantages of spraying the foam directly on the structure which provides both an infiltration and vapor barrier as well as some additional structural stiffness. There's no place for any condensation to form, either. The foam panels "could" be less expensive in some cases, but don't seal to the structure in the same way.

[Scott T Smith]

I have spray foam in several buildings - both open as well as closed cell. When I had my attic sprayed the summer electric bill dropped by over $50 per month.

A decade or so back I did a total remodel on a Sears kit house fro 1939. The house was built from pre-fabricated panels that were assembled on site. We gutted the interior of the house and filled the 3" wall cavities with open cell spray foam. A second floor was added and the footprint increased 8' to 24' x 42' with an entire second floor added.

Electric bill (all electric) runs around $125 per month in the summer.

One of the most efficient spray foam installations was in a friend's shop. He used 2x6 construction, with 1" of closed cell sprayed in the wall cavities, and standard R13 installation in the wall. There is around a 1" air gap between the fiberglass insulation and the spray foam. The three story shop is close to 4000 sq ft (around 1700 sq ft per level) and he cools the entire building on a couple of mini-splits. Impressive, to say the least.

[Zachary Hoyt]

Thank you all for your help. It's great to hear of the energy savings, though it may work out a little differently in this case since we mostly need heating and only a little cooling.

The walls and roof of the main part of the house are still quite square and vertical, though the second floor is a bit droopy in the middle since there are no interior walls on the ground floor and at least 80 years ago someone cut one of the main joists without connecting the cut ends to the adjacent ones in the usual way. I jacked it up last fall and added sistered joists so it's better, though still not fully straight. The one story kitchen on the end had sagged a couple of inches in one corner due to the sills rotting away, but I've got it mostly straightened too.

I have wondered how they framed the walls when the house was built. The 2x4 studs are about 18 feet long but the house is only 16 feet wide. No doubt they had a method, since the paper company built all the houses.

[Jim Becker]

The center section of our previous home was balloon construction. What was really interesting was that it clearly was all heart pine and still had "that resinous" smell, despite being there for so long. The other notable thing was that since there was no blocking and poor insulation, those bays were like a superhighway for rodents over many decades. It was interesting to find so many, um...treasures...