No experience with it (yet :-), but one thing to be aware of blowing insulation into old houses is that they tend to have more internal braces and blocking than modern houses. Each of the corners of our 1940's house has nice diagonal braces between the studs. So the placement of the holes needs to be done carefully, not just mid-level and high level, for example, but figure out where any internal blocks are, or you'll end up with large gaps in your insulation.

I got an estimate for Icynene in our former house, an 1867 Victorian. It seemed like an excellent product, especially for an old house.

It was my first choice but we couldn't afford it. Went with blown-in cellulose instead.

Reviving this old thread...

We are currently renovating, and I've gotten varying advice on insulating my 1896 four square/colonial revival with horse hair plaster and zero insulation is:

- Blown in cellulose or icynene in the walls
- Icynene in the rafters (attic is "finished" and we will add unico in a few years)

My concern that this along with air sealing will make my house too tight, primarily the attic. Worried about moisture, rot, sick house syndrome, radon, etc. I've been told by HVAC and other folks that I can't make this old house too tight.

Anyone have experience with either or both products in their old house? Any other thoughts or suggestions would be greatly appreciated! Thanks in advance!

Here are some general observations, four years (almost to the day!) after going with icynene in our c.1908 house.

Down-sides:
- icynene is expensive, probably the most expensive means of insulation per square foot
- as diygene points out, the frequent diagonal bracing in older houses leaves them sturdier against gale force winds, but does mean that you need to blow in the insulation in multiple holes, so you don't have big uninsulated gaps in the wall.
- We did have some patches of lath-and-plaster buckle under the pressure of the expanding icynene, making damaged wall sections as big as 2'x3', some patches were 18" square, and it did mean some extra work for our plasterer. As luck would have it, we were having all the walls re-plastered anyway, but if you're not prepared to deal with that kind of possibility, I wouldn't go with icynene.

Now the plus sides:
- Old houses tend to be pretty porous by nature. I don't think that putting icynene is going to lock in too much. It certainly has made our house hold on to heat or coolness for an extra day or three compared with before the icynene was installed.
- Because the house retains heat more efficiently, the winter after we put in the icynene, our heating bills dropped by a good 50%, so you will get some of it back in saved utility costs.
- Cellulose and fiberglass insulation are not waterproof, and lose insulation power if they get wet. Icynene serves as a natural vapor barrier, and keeps damp and dank from getting into the house (and hence mold and such).
- Bugs and pests hate the stuff, and won't eat it. I've noticed that our house has been remarkably free of infestations or invasions (apart from fruit flies), and I don't know if it's the icynene that is keeping them out, but I suspect that's part of it.

As a whole, we don't regret at all getting icynene insulation, and would do it again in a heartbeat. But those caveats do need to be kept in mind, and you shouldn't go with it if the cost or the wall issues are a problem.

Dr JimBob: Thanks so much for the update!! I'm reassured you had a good experience with icynene (esp since I also live in Boston metro). I'm not thrilled with the cost either and it's good to know about the plaster issue. I'm waiting to meet with the insulation company next week and will report back.

Make sure they will have access to an infrared camera to check for voids that did not get filled.

Once your house walls are insulated to R-13 you have just about maxed out your heat conduction resistance. Going to R-40, for example, gives you just 5% more conductive resistance.

Now the major problem is going to be heat traveling on air flow. Blocking this is a weather-sealing, not an insulation problem. Foams are good at weather-sealing.

So is cellulose. Foams are about 4-5 times more costly than cellulose, but not 4-5 times more effective. So if cost is not a factor, absolutely go with foams. If cost is a factor, dense-pack cellulose delivers more value for the buck.

Low expanding closed cell foams are a little dangerous to loose plaster, but seldom to properly adhering plaster. This risk is often exaggerated -- but if you want to find out where your plaster is loose, this is a good way to do it.

I would generally recommend cellulose, then spend some of the savings on weather-sealing around the windows, doors and house sills and pile up some more insulation in the attic. The overall improvement will be greater than if you just insulated with even the best foam without weather-sealing.

Keep in mind that either product is absolutely dependent on proper insulation -- so know your contractor and absolutely take infrared photos to verify full coverage with no gaps.

Best of luck with the project.

HulaGalj,
Get lots of info on UNICO. I tried that in a large older home and it was disaster! Hard to discern bad install/equipment or both. It stays broken and does not heat and cool properly when it runs. I have a 3 and 5 ton unit. The 5 was replaced 2 years ago and needs replacing again. I would not use Unico.