Replies

1. 
   Armando Cobo | May 06, 2010 12:31pm | #1

   Eric,
   I would be happy with 2-1” rigid insulation on the outside and 4” of cellulose on the inside; that’s ±R24 wall assembly, that’s good, and it would allow your wall to dry to the inside. If you are in humid climate as well, make sure you install a dehumidifier. Also, you could install 2x2s @ 24” o.c. horizontally, adds 2” more of insulation for ±R31. I would spend my money on the attic or roof insulation and better windows first.

   On the brick, have you thought about the cost of using thin brick veneer vs. digging and pouring a new brick ledge, or even using a different type of cladding like stucco or fiber cement bd.?

   I’ve searched for quite some time the structural capabilities of attaching cladding over more than 2” of rigid insulation and have not found a single study to support it. I’ve talked to two commercial brick ties manufacturers that would not guaranteed their products in such applications, but as a precaution they said, with great QC it can be done making sure all ties are in the studs at least twice the length than the length on the foam. In NM, the state code prohibits the installation of cladding (stucco generally) over more than 2” rigid insulation without an engineer report. Most builders I know have walked away from this practice. It all has to do with the rigid insulation not been able to support the cladding weight through the foam and the ties “bending”.

2. 
   Daniel Ernst | May 06, 2010 03:44pm | #2

   Eric - I'm not entirely clear on your question. If you are considering the costs between interior and exterior methods, my "shoot from the hip" answer is that the interior renovation would be cheaper AND more cost effective.

   As Armando said, you might consider other options first. Air sealing the existing structure, improving your ceiling / attic insulation, replacing windows, etc. Gutting walls is expensive anywhichway you cut it!

   Waiting for PV costs to drop is not the answer. PV is extremely expensive. It's doubtful that we'll ever see a day when PV will affordably power a building that is not first made to be efficient in its use of that energy - whether it's by reducing your plug / appliance load or improving your insulation level.

   Whatever you decide, remember that as you add insulation to the wall cavity you reduce the drying potential. Adding insulation without airsealing first could also lead to increased risk of condensation (likely on the interior surfaces in your climate).

   Armando - Have you seen this product?

   http://www.heckmannbuildingprods.com/PWing75.htm

   They primarily sell to the commercial market. Their Pos-I-Tie is designed for exterior insulation up to 3 1/2" thick (plus 1/2" sheathing). The shaft and pintle tie are available in both galvanized and stainless versions. They're not cheap (> $3 / each for stainless), but they are significantly stronger than the corrugated ties used in most residential projects. As to code requirements, I'm sure they vary from state to state.

3. 
   Armando Cobo | May 08, 2010 01:01pm | #3

   Thank you Daniel. I had not seen heckmann's and seems to work great on brick veneer applications up to the 3 1/2" of rigid bd., however it doesn't help in siding or stucco applications, also it appears to be rather expensive, ouch!!! Eric may have to bite the bullet to do it right.