Cost of a double stud wall with dense packed cellulose
Matt_Salkeld_PEng
| Posted in General Questions on
I want to compare the cost of a ‘conventional’ 2×6/batt/rigid foam wall to a double stud wall with dense packed cellulose. Wall should be around R35 to R40-effective.
Are there any estimates or data available for Canada or northern USA?
Also one advantage of the double stud wall would seem to be eliminating most of the thermal bridging thru studs and therefore eliminating the need for a continuous exterior foam. That should simplify labor.
Thanks in advance, Matthew
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The best way I figured wall pricing was to determine how much material was needed for 100 sf of wall space, so say 8'-1 1/8" pre cut wall height you would need 12'-4 1/4" of linear feet of framed wall. In that length you would need a certain amount of studs, plates, sheathing, insulation etc, and then you can narrow that down to a per square foot cost for the material. Labor figures are going to vary a good bit so starting with just material should be pretty easy.
You may find this of use. NREL determined the double wall to be the most cost effective for Denver, CO.
>"NREL determined the double wall to be the most cost effective for Denver, CO."
That was a double studwall with a pair of R13 fiberglass walls space 3.5" apart with stacked R13 fiberglass installed horizontally in the gap, with and an interior side polyethylene vapor barrier and fiber cement siding (sans-rainscreen).
The approach was taken to minimize the MATERIAL cost while making the assembly volunteer-labor friendly, completely writing off the labor cost (since it was a Habitat for Humanity house the majority of the labor being volunteer.)
The assertion that double studwalls are "...the most cost effective..." isn't well supported by the document. A zero labor cost triple batt double studwall is pretty different from dense packed cellulose double studwall in technique, material, & total cost, even if the labor were at standard construction rates rather than presumed to be zero.
Matthew,
if you are DIYing the house it's pretty simple to price the materials. If you are getting it built for you, the only way to know what the two will cost is to get quotes. There is no formula that will give you a useful answer independent of the variables brought by each contractor.
Just got quotes back from my insulators and framers. For an R43 2x6 wall with exterior insulation (4 inches of XPS foam) framing and insulation came in at 44,500. For a R45 double stud 2x4 wall framing and insulation was 39,000. Both were using Zip sheathing and liquidflash. I do not have anyone near me to quote dense packed cellulose so cavity insulation for both walls is rock wool. These numbers are in SW MT for ~3200sf home so use at your own risk.
>"Just got quotes back from my insulators and framers. For an R43 2x6 wall with exterior insulation (4 inches of XPS foam) framing and insulation came in at 44,500."
XPS is about as bad as it gets compared to any other insulation from an environmental point of view:
https://materialspalette.org/wp-content/uploads/2018/08/CSMP-Insulation_090919-01.png
Worse still, it's performance declines over time to that of EPS of similar density & thickness, even though it's usually warranteed to 90% of labeled-R for 20 years or more. The HFCs responsible for it's early-years performance are also what is responsible for it's disparate CO2e footprint. As the HFCs slowly diffuse out over a few decades it loses that performance edge.
Thanks all, I'll send the designs out for the pricing. I am trying encourage carbon storing materials wherever possible!!