Open Cell Retrofit?

You pulling off the siding? Re sheeting the house?

No not adding sheeting. Only replacing cracked boards

southernxp said:

No not adding sheeting. Only replacing cracked boards

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So the open cell foam would be applied to the back of the siding boards ? What happens in the future when you need/want to replace more boards that have cracked ? I don't think I would go this route .

I would not. Reasons:
1. open cell absorbs water - in case of leak
2. injected, so you won't know if insulation TOTALLY covers the space - too unsure of air seal

3. Listiburek (well known for insulation) - his experience with sheathing touching the insulation wasn't good. Trapped vapor (from air leaking) condense into water which rots the sheathing.


I read that in hot regions vapor drive is from outside to inside. Another way that is said is "drying in" which always confused me.:smile: Your vapors are generally outside and your siding has many loose joints. I would just leave it uninsulated and dry. Create shadows on sunny side and power vent the attic to cool roofs or use whole house fan to cool in the evenings.

What are you actually doing? Spraying from inside to out or outside to in...?

Open cell is more suited to sound proofing. If you're paying for insulation, then you should do closed cell. An inch of closed cell gives you an additional R6-ish vs an inch of open cell only giving R3.5-ish. There isn't /that/ much cost difference not to get closed IMHO.


Typical T1-11 siding? Yeah, you should be able to do a pour into that.

By "plaster" inside you mean lap? I don't believe the "grow" on poured insulation is strong enough to pop anything. It doesn't pop out drywall nails so I'd imagine it'd be fine, but I'd want to call an installer just to be sure there wasn't any kinda reaction or anything. I'd imagine they'd done it many times and have a catalog of any troubles they've run into.

I'm pulling enough siding to be sure of completely filling the walls. I was quoted $2,000 for a 2,200 square house with 16 foot tall interior walls. Contingent on enough siding being pulled to do the job in one day. The contractor has great reviews explained what it would take. He has been in business 15 years. He said in our area it is not worth it to do closed cell in the walls. Plus he couldn't guarantee closed cell wouldn't leave gaps/holes. He recommended closed cell for the floor. GreenSouthInsulation.com.

I think on a scientific basis I'd disagree with him on the worth it part, works for hot as well as cold, but I'm certainly not an expert so take that for what it's worth

That's a really cheap price compared to what I'm used to seeing, planning to pay; my interior walls got quoted @ $30k for open cell... Hey you wanna ask him if he wants to visit Alaska as a tax write off?? We can totally debate open cell vs closed cell on the exterior LOL (Joking btw, I'm not ready for doing that yet heh)

Your contractor does insulation for a living. This is a free advice board Who would be more knowledgeable?

Mystriss said:

I think on a scientific basis I'd disagree with him on the worth it part, works for hot as well as cold, but I'm certainly not an expert so take that for what it's worth

That's a really cheap price compared to what I'm used to seeing, planning to pay; my interior walls got quoted @ $30k for open cell... Hey you wanna ask him if he wants to visit Alaska as a tax write off?? We can totally debate open cell vs closed cell on the exterior LOL (Joking btw, I'm not ready for doing that yet heh)

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Hey I will mention it to him, you never kn know:smile:

To put it in perspective for my area. I remember 4 freeze warnings this past winter. I don't think any warranted exterior spigot covers although I got mine on. And this past summer we had 100 straight days of 95 plus. So in this environment it is more about condensation on the exterior. Having no experience it sounds like I should fill the walls with open cell then caulk every piece of siding. Which is a no. Caulking fails, paint fails, everything fails. So back to square one, no insulation

If he has had good success with it, great. I am just hesitant if you don't have some sort of WRB in the case of a wood siding product. OC SPF is not a moisture or vapor barrier. In GA, its less of an issue than say, Minnesota, but you still don't want that moisture (relative humidity) pushing from either direction. Like I said, you are a pretty blended climate so it is less important.

hmmm Generally, in warm climates air born moisture condenses/comes from the /inside/ of the house (I believe especially air conditioning, showers, cooking, etc.)

As I understand it, in general, presuming rain water isn't getting into it, an insulated wall, with zero vap barrier, only rots/molds from moisture vapor penetration if there is not enough air flow in the wall cavity to dry it out. So as long as you have enough airflow to move the moisture out of the wall cavity before it can settle on the wood, there should be no problems...

If I'm not mistaken, which is entirely possible here cause I'm not getting any brain pictures on the subject - just a vague memory, wood siding and poured/sprayed poly foam have rather similar vapor permeability characteristics??

I'd research "Perfect Wall," "Passive House," and "house vapor protection layer" to get the scoop on insulation techniques. (Unfortunately, I have too much projects on the docket to do it myself atm.)

"I'd research "Perfect Wall," "Passive House," and "house vapor protection layer" to get the scoop on insulation techniques. (Unfortunately, I have too much projects on the docket to do it myself atm.)"

Thanks I will check this out