Comments on: How to Kill the Performance of Your Insulation

By: Steve Perry

Steve Perry — Tue, 14 Mar 2023 00:13:38 +0000

I took my beach house with 2600 sq ft, added zip wall, 2 inches of 6lb mineral wool with a rain screen and cement siding.
I also replaced all and increased all the window sizes by 20 percent.
Made the attic a conditioned space and insulate the crawl space floor with 4 inches of foam.
Changed to geothermal.
The house is super quiet and the electric bill went from a maximum of 450 a month to a max 150 a month.
I can’t even hear the neighbors run their lawn mowers or the 70 mph wind gust.
The walls are now 11 inches thick.
I used Marvin windows with lamented glass to get mostly 40 STC rated windows.

Amazing home now.

By: Paul Szymkiewicz

Paul Szymkiewicz — Sat, 11 Mar 2023 15:10:46 +0000

Thank you Allison, I learned something new from the RDH report: the chi-value.

Also referenced here: https://www.passivhaustrust.org.uk/UserFiles/File/Technical%20Papers/2022.02.21%20Steel%20frame%20briefing%20note%20v1.3%20Patrons.pdf

One point from the above I’ll have to remember: “the Chi-value for a bracket is specific to the insulation type and thickness it penetrates AND the substrate it is fixed to”.

The devil is in the details. It is crucial to have reliable thermal performance data for any clips, screws, brackets, etc. in order to be able to reliably compare assembly u-values for different options. Calculating u-values for these elements is no walk in the park.

By: John Gellatly

John Gellatly — Sat, 11 Mar 2023 12:13:53 +0000

In reply to Todd Witt. Your comments reflect why I believe an integrated design and construction team is important. Being able to identify early in the design the forever penalty of oversized windows might help folks make the decision to right size them to balance all the goals of why we build in the first place, ideally in a more sustainable fashion than our traditional solutions. Thank goodness for code changes requiring us to collectively conquer these challenges!

By: Todd Witt

Todd Witt — Thu, 09 Mar 2023 14:27:38 +0000

My company works mostly in Northern Alabama and Southern Tennessee. When I started in this business years ago, I did numerous things to eliminate thermal bridging. It is my opinion, that in most of the homes we design the HVAC systems on and spray foam, thermal bridging is rarely an issue. Most of our homes are large custom homes with a lot of windows. We have found that in cooling climates, R-value overkill in the walls and overkill on thermal bridging does not help the home much. You printed a chart not long ago showing the differences in walls and exterior sheathing and my takeaway is that is really doesn’t matter when you have walls loaded with R3 to R5 windows. We are good with 2 x4 walls or 2 x6 walls. We highly recommend the Zip System exterior system and open cell foam with a great air sealing package. Size, design, install, and commission a multi-stage all-electric heat pump in the encapsulated attic or encapsulated crawlspace and much of your energy efficiency worries all over. In commercial construction, most of it is so poorly done that it does not matter what you do.

By: Rick Duncan (SPFA)

Rick Duncan (SPFA) — Wed, 08 Mar 2023 10:57:32 +0000

In reply to Robert Jordan.

On occasion, pictures in our magazine do show SPF as a cavity insulation between framing as an alternative to air-permeable fibrous cavity insulation. SPF provides required R-value and air barrier in a single application step. If closed-cell SPF is used, it may also provide a vapor retarder for colder climates and a durable water-resistant cavity insulation in flood-prone areas that can also improve the structural performance of the assembly.

The photos in question show SPF installed between metal studs. I completely agree that insulation between any framing does not optimize the R-value of the assembly due to thermal bridging. The thermal bridging impact is magnified when metal framing is used because of high thermal conductivity of steel. Prior to air leakage limits introduced into energy codes, it was not uncommon to see metal framing with only continuous insulation and no cavity insulation.

To meet modern energy codes, the optimum assembly would consist of a layer of continuous insulation applied outboard of the framing, augmented by cavity insulation. The entire assembly also needs to be air sealed. One of the best designs that addresses maximizes thermal resistance and minimizes air leakage is continuous insulation (PIR, XPS, EPS) with an air-impermeable, self-sealing cavity insulation like SPF.

By: JC

JC — Tue, 07 Mar 2023 20:24:04 +0000

This is a perfect example of how fixed costs, in this case labor, are transferred onto the tenants in the form of variable cost of energy usage.

What a waste of $$.

By: Robert Jordan

Robert Jordan — Tue, 07 Mar 2023 19:30:25 +0000

In nearly every issue of SprayFoam magazine there is a highlighted project that uses steel studs and spray foam between them. After seeing many projects like this, I emailed Rick Duncan P.E., their technical director, and complained that the magazine should point out how inefficient that was. By then Rick had become the Executive Director of the Spray Polyurethane Association. His response was it provided a good air barrier. I could just imagine the outrage from chemical companies advising against using tens of thousand of pounds of chemicals.

It probably doesn’t even provide a good air barrier unless there is a conscientious effort to ensure it is continuous.

I renovated a duplex from the outside. The siding needed to be replaced and the interior plaster was in good shape. I ran 2 X 4s on edge 2′ on center. None of them were located at a rim joist. Other than where the 2 Xs crossed there was at least 3 1/2 ” of spray foam everywhere and mostly 7″. In the addition part, I sheathed the outside and insulated from the inside. I don’t think this was very much additional work. But no one has said they thought it was a great idea.

I participated in a Kwik Model Manual J through D webinar. They used a .15 framing factor. I protested. Oak Ridge had measured actual framing factors and found them to about .25 and frequently much worse. Considering the cost of framing material, this is an easy place to save significant labor and material. Insulation is usually estimated on total wall area, so it wouldn’t increase the insulation cost.

By: Hugo Vargas

Hugo Vargas — Tue, 07 Mar 2023 16:59:22 +0000

“Will those long screws be able to hold up the insulation and whatever cladding you install over the insulation? ” Of course, in the world of mechanical engineering, the study of Joint design is one in which some people dedicate their entire careers. “Flexible fastener, stiff joint!” was something one of my professors used to say. In this application, the long screws through the wood and foam and into the hard material (wood or masonry) creates the stiff joint that does’t slip.