TL;DR – We got a huge discount on fiberglass, and had an air leak sealing product applied to the wood framing. We installed the insulation two weekends ago with a couple days off work:
The most popular options for home insulation are 1) fiberglass, 2) cellulose, and 3) spray foam. Foam also seals against air leaks (greatest cause of energy loss) and comes in two types – open cell and closed cell. Open cell matches the thermal resistance of fiberglass around R-3.5. Closed cell has a whopping thermal resistance of R-6.5. It has a low expansion rate and also adds structural support and is vapor impermeable.
I REALLY wanted to super-insulate this home, reducing the size of equipment and energy use to maintain it. Closed cell spray foam insulation would do it. However, it’s pricey, and most bankers and builders, ours included, see no benefit (ROI) in exceeding code minimums. We are an incredibly short-sighted culture.
There’s a hybrid method: spray a thin layer of foam to seal air leaks then fill the rest of the wall cavity with fiberglass or cellulose. It’s called “Flash and Batt” or “Flash and Fill.” Open cell foam expands too much, so this is only done with closed cell foam. As a vapor barrier, Building Science must be considered! Flash and Fill places a vapor barrier on the exterior side of the wall (appropriate for warmer climates), so in colder climates, the right depth must be provided to avoid condensation within the wall, or hello mold.
COST DROVE OUR CHOICE:
I got pricing to insulate several different ways:
Closed Cell – $21,900
Flash and Batt – $12,900
Open Cell – $12,600
Fiberglass + Installation through Builder – $6200
Fiberglass @ retail + Self-Installed – $4200
> Fiberglass with Trade Discount + Self-Installed – $1,000
> EcoSeal + Firecaulking – $1,600
> Odds and ends – TOTAL – $2800
The foams were too costly. But we still wanted superior air sealing. There are different versions of air sealing products to be paired with conventional batts and we used Knauf’s EcoSeal. We purchased insulation at a huge discount through a friend. Since we found nobody to install a product they didn’t provide (with the huge mark-up), we are also saving on labor costs by DIY. And learning something too. Cool.
R-21 High Density Batts w/ Kraft Face – Exterior Walls
R-49 Blown-In Fiberglass – Attic
R-51 Unfaced Batts – Attic where inaccessible
R-15 Unfaced Batts – Basement Walls
R-11 / R-19 Unfaced Batts – Interior Walls/Ceilings for Acoustics
R-38 Unfaced Batts – Garage Ceiling / Living Room Floor & Rim Joists
Day 1 – 2nd floor exterior walls
Day 2 – 1st floor exterior walls and all interior wall acoustic (with Melissa in the crew)
Day 3 – basement exterior walls, rim joists, garage ceiling and 1/2 the 1st floor ceilings. Huge thanks to Matt and Josh (Melissa’s brothers) for help!
Day 4 – remaining ceilings, mark studs for final framing changes, make/install vent baffles
I followed up during a couple lunch breaks, insulating the 3rd Bdrm and stair ceiling with spare batts after I realized the pain it would be to access, even for blowing in insulation. Overall, insulating is not rocket surgery, it just takes time. And when your glasses fog up from wearing a face mask, it doesn’t evaporate in below freezing weather. GrRr.