I have been looking at the "superior wall" type insulated precast panel for an addition I would like to do.  I have also been reading some stuff on the ORNL building research site about thermal mass that led me to think about taking the precast panel and turning so that the concrete side faces inside the structure and the insulated side faces outside.  This would give the best possible interaction between the thermal mass of the concrete and the interior living space.  You could then add insulation in the cavity of the panel that faces out and place your siding over that.  Has anyone seen something similar done?  Any pitfalls I don't see?

Thanks.

Sweetlew I have recently started my project using Superior Walls and i think you would add several extra steps to your build by reversing your walls. I assume you are not backfilling against your walls but you would still need to sheath and side your walls and fur out your interior walls for electric. You may still need a vapor barrier to keep you insulation moisture free. If i understand your question, these are the pitfalls i could think of. I doubt they would warranty that either.

If you look carefully at the Superior Wall system, the actual concrete is relatively thin. The 'thermal mass' is very low when compared to a standard masonry wall. Their thin coat of concrete is more for waterproofing than anything else. If you wish to reverse the system and use below grade, the finish and waterproofing process will become very similar to any other metal framed wall. Above grade would be similar to finishing any other wall system. In short, considering the price of the Superior Walls system to start with, and then the added expenses for finishing, there are several better and more cost effective ways of achieving your goals. I think Royal Building Systems has a most interesting alternative.

Insulating, sheathing and waterproofing the outside would be tricky (expensive). Why not use ICFs? And don't stop at the foundation, do all the perimeter walls with ICFs all the way to the roof.

I think some ICF forms are able to have one side of the foam removed to reveal the concrete. Also look into shotcrete panel systems that have concrete shot inside and outside w/ a foam core.

But why would you want less insulation?

Because insulation on the inside insulates the interior from the benefits of the concrete's thermal mass.

Why would you want to do that??

You can just put up a cmu wall up on the inside of the wall or brick? Just puting it out their, I would not use superior myself don't like it at all.

robinnc, what is your question - why wouldn't one want to do what?

Wow, this is getting confusing ;). Ok, if you want to use the thermal mass of the concrete, you don't want it insulated on the inside. That defeats the purpose of a thermal mass. However, slight caveat, you need to have a way to 'charge' that thermal mass(direct sunlight is one way), if you don't then you will probably end up with a space that is actually colder due to the thermal mass. Remember, the wall(thermal mass) is connected to the ground, and what is the ground temperature at that location?

Good point JC, what is sweetlew's climate? If it's cold then one might benefit from insulating under the foundation. But the thermal mass can also be charged by whatever method is used to heat the house (and the opposite in the summer, the mass can be charged by air conditioning).

This an interesting discussion.  Thanks for all the replies.

As usual, I did not give enough info in my original post.  Climate would be East TN (mixed humid) and the structure I was going to build would have a crawlspace with the "superior walls" on top, completely above ground.  With the concrete toward the interior, the cavity would be insulated further on the exterior and then a hardi board material would be applied for siding.  They make two different kinds of wall, one has more insulation and some different details in its construction, but both have 1 3/4" concrete.  I think JC's correct that it would be best to have the thermal mass in contact with a large heat source, but in reading the literature from ORNL (http://www.ornl.gov/sci/roofs+walls/) I think they were allowing the actual interior living space temperature to charge the thermal mass.  I could be wrong.  I think if that is the case, then the thinner concrete would be charged more easily, of course, it would also discharge more easily.

" Remember, the wall(thermal mass) is connected to the ground, and what is the ground temperature at that location?"

It is best to have a thermal break between the mass and the ground but it is not alway possible. The thing to take in to account is that heat and cold move very slowly through concrete and if the mass is properly placed, it will be recharged faster than it will leak through a wall.

Sweetlaw

Have a look at http://www.tfinsulatedconcreteforms.com/, vertical insulated concrete forms.

To acheive unisulated interior thermal mass, you can put all the insulation on the exterior and use Magboard as the interior sufrace of the form. They have clients that have done this already, so they can walk you through the process.

It also insulates the house from the humidity and moisture that will collect on a concrete wall. If you are using a regular heating system, It will cost you more to charge the wall then you will re coop from it. Go with an ICF wall with rock on the inside, and hardi on the outside. You will be much more pleased.

There is another thread on Superior Walls on the ICF forum. Check it out but some of the things discussed there are the lack of additional waterproofing and footing, which Superior Walls promotes. I would not use them, superior walls are inferior in almost every way to ICFs.

The iGreen Construction system has 10" of 1.5# density foam for the exterior walls and roof. How much more thermal mass do you need? They put structual aluminum "I" beams and "C" channels inside the foam to frame the structure, it is very strong. The wall and roof has a R value of over 45, that is pretty high...

Kelly

From what I see it has no thermal mass?