I'm upgrading a home I bought

Jack

A couple years ago. Have done the hvac change out. The place still has knob and tube and a stunning assortment of substandard elec. I'm getting this repaired in Nov and as soon as power is done I want to get the place injected with some sort of foam. There are about R19 batts in the attic bot nary a bit in the wall cavities. What concerns should I have while the insulation cures...if any. In your opinion, what is the best insulation method/type?

Brad White

My Default

approach would be Dense-Pack Cellulose. I am looking into J-M "Spider", which is an improved short-fiber fiberglass with similar density to dense-pack cellulose.



The key is density, not fluffing. Properly done, either insulation should be a firm, felt-like blanket to promote air blockage.



Another type I have seen once is magnesium oxide foam, which has a very light "meringue" consistency and is said to be ok to blow in when you have knob and tube wiring. It goes in like shaving cream and hardens. I am not certain regarding R values but the air sealing qualities were stressed. I know only one person who has had it installed this past year and so far no experience/data.

BillW

Insulation

I also favor dense-pak cellulose ,properly treated with insect control, water repellent and fire retardant.  Offgassing from the older foam spray products and the particulate from the "shaving" process could be a problem, but now the products have evolved beyond that point. If you live in a bitter cold, windy place like the Adirondacks, North Kingdom in Vermont , U.P. Michigan or Minnesota, make sure the R values are at the design requirements for the area, and you have a heat loss done to make sure.  Same for more moderate climates.  Insulation is part of the equation for comfort and efficiency...too much or too little can be harmful.  Pick a reliable contractor with experience.