Foam / celluose hybrid?
Foam insulation is great but expensive and has little or no ability to absorb moisture prior to seasonal drying and ends up with a lumpy rough surface that sometimes must be trimmed — which makes me wonder the following: Could a method be developed to add cellulose (using a third hose or by wetting the cellulose with one part of the foam mix) to the foam as it’s being blown in?
The ideal mix I would be looking for would have the consistency of paper mache, consisting of say 90% cellulose and 10% foam. It would not need to dry like wet spray cellulose, would have the air sealing properties of foam (but slightly more permeable) and the moisture retaining and affordability of cellulose.
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Replies
Andy,
Your suggestion should be taken to an R&D lab, not a builder's forum. Maybe the engineers at BASF, Dow, or North Carolina Foam Industries would be interested in your idea.
It takes a few inches of open cell foam to achieve tightness of air barrier status. If you have a 10% foam mixture, that's a half inch in a 2x6 wall cavity. Moreover, it would be dispersed by the cellulose, so that the air sealing property you are looking for likely would not be achieved. I suspect that dispersal would mean also that closed cell foam in that proportion also would be insufficient for an air barrier. This is pure speculation on my part.
I do wonder, however, if the use of a small amount of foam mixed with cellulose would provide enough stiffness for the cured mixture (to prevent settling) so as to achieve good R value in a vertical wall cavity while also using lower density than with dense packed dry cellulose. It's just a thought, and my first criticism of the idea is that maybe the cost of the foam added would be more than that of the cellulose saved by not having to dense pack.
I love the idea. One drawback. The best attribute of cells is how green it is and how easy it can be dealt with during and after its useful life.
Still, I may have to get my insulation guy to play with the idea. I hope somebody does and gets back to us.
This sounds like a solution in search of a problem. I think a far better solution is 90% cellulose + 10% cellulose = 100% cellulose....and make your air barrier at a different layer than your insulation.
John, the automatic transmission had nay sayers too.... but I bet you have and love yours. I know I do. I could see cellulose used in thick assemblies being improved greatly by adding a stiffening agent to stop it from settling. Would be nice if the additive was a renewable non toxic agent.
Seems _really_ messy as a field-operation; would probably end up with a very non-homogeneous assembly that was impossible to put a real R-value to, which we often want to do... So I second the R&D punt. Besides that it's mixing 'technical' with 'biological' nutrients [even 'soy-based' foams aren't really biodegradable/compatible, right?] a cradle-to-cradle no-no, if you have stock in that.
But if someone wants to try...it's one way to learn. I agree with AJ, a stiffening agent that was non-toxic might be better to explore than foam; but doesn't dense-pack solve the settling issue?
Gut says better to use each material separately, each as it's best suited. Like keeping solar thermal and PV separate...?
David/OK
AJ,
I drive a 2003 VW Golf TDI...54 mpg on my last tank. It's a 5-speed manual. I hate automatics.