Hybrid Insulation: Spray Foam and Wet-Applied Cellulose
I’m located in zone 5 northwest Ohio. I have a 2 story house. In the county on a hill so I get a fair amount of wind. I’ve received multiple quotes from insulation contractors. I have 2×6 walls with 2 sheets of 1/2 osb on the exterior. I’m not sure why the previous owner did this but it is what it is.
One contractor wants to spray foam 1″ closed cell on everything then go back and wet cellulose the rest of the cavity. I asked about moisture problems and he said” I’ve been doing this for 13 years with no call backs”
#2 wants to just spray stabilized wet cellulose everything. With 2″ closed cell on the sill plate.
#3 just wants to spray 3″ of closed cell spray foam in the cavities and 2″ around the sill.
#4 wanted to just spray foam 2″ closed cell spray foam from the sill plate all the way to the roof peak for an unvented roof…. I did not like this option since the low R value of only 2″ and the hot roof deck.
I’ve tried finding actual studies on the stabilized cellulose. The only one I found was one done on a chicken coop. After 7 years there was minimal settlement. I’m still a little Leary about it settling and having a couple inches of air gap at the top of my walls after 10 years. Also I’m planning on living at the house for 40+ years so I want to do it right now. I’m just looking for some input on my 4 options. My main concern is just moisture and mold in the wall. I’m ok will paying a little more on heating and cooling cost. Since spray foam is around 7k more. I’m not sure I’ll re coop that in savings given the R values are compatible for the amount of spray foam I was quoted. Unless cellulose degrades quite a bit after 20 years.
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Replies
Before we talk about the specific solutions, two questions:
1. What insulation do you have now?
2. What is your goal, or what's the problem that this is intended to solve? Is there other work going on that means you have your walls opened up anyway? Or would you be opening them up to do this?
Charlie makes good points.
Spray foam is not needed to make a tight house. Passive House levels of air infiltration, .6 ACH50 or less is achieved without foam.
So would you recommend just stabilized cellulose? My biggest concern with it is settling over time. I just don't want to have to mess with drilling holes and topping off in 15 years. And I'm not sure what the life is on it for R value does it degrade in 15 years?
I find it interesting a lath and plaster wall is 2x6. What was the original insulation? I agree, a wind exposed building needs special attention for airtightness. A robust air barrier somewhere in the wall assembly is needed. Batt insulation should be considered. If there is room inside, a strapped wall would give more R-value and a plane for a smart air barrier exclusive of wires and electrical openings. What is the exterior sheathing?
Sorry about not including that. Sometimes when I'm focused on something and have been working on it for a long time I forget to include stuff like that. Yes the house is completely gutted ripped all the old plaster and lath out. My goal is to have an R 20 or greater in all my walls. I don't want my outlets to frost up on a cold winter night like my old house. I'm looking for some air sealing and to not have problems with moisture in the wall cavities.
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I'm thinking of going the 1" of spray foam for air sealing with the stabilized cellulose option. It's about 3k more for the spray foam but I think the air sealing will be beneficial to me. Looking at the flash and batt chart 1" will be just enough so I'll have to be very particular and possibly go back and fill any low spots. Any one have any reasons why I shouldn't go this method?