Replies

1. 
   Walter Ahlgrim|Oct 23, 2020 02:39pm|#1

   Have you read the articles on the website about how to design a wall?

   As to your question of the cost vs. benefits much of that is dependent on your contractor. Naturally when you ask for something they have not built before they need and rightfully expect to charge more than normal to cover the time they will spend learning.

   Your best bet is to get bids from contractors that have use exterior insulation on past projects.

   Consider getting bids for the Zip+R system as most contractors will see it as something somewhat familiar.

   The only way I know to compare the cost per square foot of different wall systems vs. their ability to save you money over time is to model your house in a computer program called BEopt.

   https://beopt.nrel.gov/home

   Walta

2. 
   navroz|Oct 23, 2020 02:50pm|#2

   Thank You Walter

3. Expert Member
   Dana Dorsett|Oct 23, 2020 05:46pm|#3

   Virgin stock foam is not climate or environmentally friendly, and neither is glass or mineral fiber insulation. If those things matter to you limit your options to cellulose for cavity insulation and only reclaimed goods for the foam if you can, not virgin stock SIPs or nailbase. It saves money, and it saves the planet, since no new polymer or blowing agents are created when re-using insulation, and there are several square miles of used roofing foam available from multiple vendors in upstate NY.

   Run this search from time to time to find a source near you:

   https://syracuse.craigslist.org/search/sss?query=rigid+insulation

   With 2" of reclaimed roofing polyiso (labeled R11.2, derate it to R9-R10 for age and temperature from a design point of view) there would be sufficient dew point control at the structural sheathing to go with 2x6/R21 fiberglass, R20 cellulose or R23 rock wool on the structural wall and NO vapor barriers, detailing the OSB or plywood structural sheathing as the primary air barrier. If building 2x8/25 fiberglass or R30 rock wool insulated structural walls bump it to 2.5" of reclaimed roofing polyiso to be fully safe after derating for age & temperature.

   From a lifecycle energy cost rationality point of view, in zone 5 the 2x6/R23 + R10-ish foam is edging into the gray zone, but if using cheap reclaimed goods on the exterior, R25 batts or R27 blown cellulose (the greenest approach) in the wall cavities and 2.5-3" of reclaimed foam can still make financial sense.