We are getting ready to build a house in Los Angeles area (about 1 mile from the beach, near LAX) I am having some issues deciding between Icynene and a blown insulation (like Owens Corning PROPink Complete).

Our exterior walls (that will be insulated) are 8". We are building with light gauge structural steel ("C" studs) which means that the studs are shaped like a "C", leaving a large gap in the middle of the stud that typical fiberglass bat insulation wouldn't fill. Also, the studs are spaced 24" OC (per structural engineer).

Icynene is rated at R-3.6 per inch, so our 8" walls would be R-28.8, but Icynene is also (from what I've read) about 2-3X the price.

Owens Corning PROPINK Complete Blown-In Wall (combo of loosefill and non-woven fabric) gives those same 8" walls R-31, at a lower price.

Either way, we will likely use Owens Corning PROPINK or Foamular 150 3/4" (R4) or 1" (R5) Rigid Foam on the outside of the house, layered with the OSB and wrap.

So, three questions here:
1. Icynene, PROPINK Complete, or Other and why?
2. What is the difference between the Owens Corning PROPINK and Foamular 150/250 rigid foams?
3. Would the outside of the house go OSB, rigid foam, wrap ... or OSB, wrap, rigid foam?

Thanks in advance for any any all input!

If ever there was a reason to use Icnene this is it. Using C studs limit the heat loss because of the little mass they offer. The issue with them is however that they can flex slightly if not properly cross braced. If your near the ocean wind is also figured into the design of the structure as that to flexes the building. My advice would be to use the foam. It adhears to everything and will help firm up the metal studs. Making the walls much stronger. Every bit helps when wind becomes a factor. While the blown in will work and cost less, I would stick to foam. Just be sure you have ALL the wires in the wall before you go ahead. Running wires into foam walls is a pain you know where.

Stay away from any EIFS exterior otherwise you will have issues. With eight inch thick walls your going to be quite tight anyway and do not want to sandwich the structural sheeting on both sides with foam. If any exterior water leaks behind the siding, and it will, you do not want to chance it getting trapped behind any foam boards installed on the wall.

There is such a thing as overkill on insulation. Ceilings are where the most of your loss is, so any additional amounts help, walls not the case. You get to a point where you will never see any payback for the cost of the extra stuff on the outside.

Thanks for the quick response. The structural engineer has plenty of cross bracing in addition to the OSB and has used quite a few hardy frames in the design... since we are in a #4 seismic zone ... he has also done all the wind calcs (as shown in the 450+ pages of calcs he gave me). Also, all wiring is in conduits.

I don't really want to choose an insulation based on it adding structural strength, since the house will stand on its own with or without the insulation. I think I should be choosing insulation based on price vs performance.

In the case of C studs, and Icynene verus Fomo HandiFoam + blown-in insulation, what is the real insulating benefit of Icynene (other than the 2x+ cost)?

Also, is the exterior rigid foam really considered EIFS? The Foamular and ProPink from Owens Corning are both listed as "hydrophobic, meaning it's practically impossible for it to be penetrated by moisture." (quote from http://www.owenscorning.com/around/insulation/products/foamular.asp). I thought EIFS was a special type of stucco like spray on.

Beware of falling into the pink trap of translating the R-value of any bulk insulation into the r-value of the wall. The R-value of the WALL is not the same as the R-value of the insulation between the members.

Steel studs are notorious for thermal "short circuiting" because of the high conductivity and the lateral heat flow through wall coatings. This has nothing to with the "mass" of the studs, but is related to the heat transmission or conductivity.

In some case, an R19 in a 6" wall can yeild an R11 wall. You should be able to find this in the ASHRAE (American Society of Heating, Refrigeration and Air Conditioning Engineers)documents that are the basis for codes. Some local codes provide for loop-holes by not including all of a referenced standards.

Only fools calculate the heat loss based on the percentage area of the various components. You need a series-parallel calculation or better yet, actual test results. In LA, you might be able to get away with this because of your climate, but it is not right.

The layer of rigid insulation on the exterior, in reality, may do more good than the stuff you put between the heat conducting steel studs. - At least you will be able to see the location of the studs in a year or two after the higher moisture content on the interior walls shadows the stud location (a common problem of differential heat loss).

Do not consider a surface application of rigid insulation with EIFS. EIFS is a wall surfacing system and the rigid insulation is just one part of the components covered by the EIFS syste. In some areas, EIFS is not permitted over wood fram construction, but it is fine over steel, concrete and masonry walls.

This message has been edited. Last edited by: concretemasonry,

Thanks CM... So, if I don't mention R values, would you say that the filling capabilities of blown-in insulation (after having used HandiFoam) would be the equivalent "fill" capabilities of icynene? Is Icynene worth 2-3x the price?


Also, I'm still looking for an answer on:

quote:

2. What is the difference between the Owens Corning PROPINK and Foamular 150/250 rigid foams?
3. Would the outside of the house go OSB, rigid foam, wrap ... or OSB, wrap, rigid foam?

I'm also confused where you said:

quote:

At least you will be able to see the location of the studs in a year or two

Did you mean that I will NOT be able to? ... or that I WILL be able to?

Shaun -

The high conductance of the steel studs can create a cool drywall surface that can attract moisture and dust that can create a "shadow" outlining the location of the steel studs.

It may not be a problem in your climate, but is common in colder climates. A layer of rigid foam can create a thermal break that will eliminate the problem. Wood studs do not show this as easily.

Thank you CM... I will plan to have the rigid foam on the outside of the house independently of choosing the in-wall insulation (icynene versus blown).