Insulation: Round One

A week ago the crew from Expert Insulation put dense pack cellulose insulation in the exterior cavities of our house. It was an exciting day, and both John and I were there to watch the first of the two-part insulation process. Exciting, you wonder? Well, when you consider that the heating and cooling comfort of our daily lives will totally depend on three things—great windows that manage solar gain, how well the house is sealed against air leakage, and the capacity of the insulation to hold preferred temperatures—it’s monumental.

The house has a 5-1/2″ layer of insulation in the exterior wall and a thicker, 10″ layer of insulation inside the house in a truss-style wall. In this photo the gray areas of the exterior wall are already filled with insulation, and the brown areas are yet to be filled.

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Common to both exterior and interior walls, between the two layers of insulation, is 1/2″ OSB sheathing. As it’s installed, every piece of OSB is caulk-sealed at the edges, then covered with a secondary seal provided by Siga tape (photo below), a super-sticky, weatherproof product. Continuously-sealed OSB sheathing provides an extremely efficient air barrier, resulting in a near-impermeable wall between the outside and inside of the house.

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First, the Expert Insulation crew attached a translucent webbing called InsulWeb to the outside of the house.

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They pulled it tight, then stapled it to the stud walls.

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The insulation itself is Polar Barrier, made by a Minnesota company called InSolution. It feels like soft cotton, but is 100% recycled paper. This insulation provides terrific thermal performance (R value), uses little energy to make (up to 10 times less than fiberglass), is made from a renewable resource, and provides good fire protection. Because it’s packed so densely when installed, it also minimizes air filtration and controls sound.

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A big blower inside Expert Insulation’s truck shoots insulation from the truck to the house through a long, white hose. A narrower, pointed section of tube at the end of the hose pierces the webbing and pressurizes the insulation as it passes to the channel in the stud wall.

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Expert Insulation is certified through Minnesota’s Quality Insulation Program, which educates, tests proper dense-packing of cellulose, and ensures contractors use best practices in home insulation installation. Expert Insulation’s crew leader has Insulation Installer training from the Building Performance Institute, so they were careful to make sure the insulation was packed super tight in every section.

Jeff, Troy and JR, our contractors, followed along behind the insulators nailing 7/8″ BildRite fiberboard sheets over the stud walls. They are light-weight, breathable panels that will release moisture build-up, as necessary.

In the photo below, the contractors are using temporary 2x4s to secure the panels and keep them completely flat before nailing. Without them the densely packed cellulose made them bulge.

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It took the crew from Expert Insulation two days to insulate the exterior of the house. Part way through the process, they decided the cellulose would pack even more densely if the fiberboard went up before putting the insulation in the channels created by the InsulWeb. Here you can see how that looked. They drilled a hole in each stud wall channel, filled, then plugged the hole with foam insulation.

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The fiberboard was then covered with Tyvek and firring strips, which you can see in this photo (along with the first glimpse of our solar installation…details to come!).

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Comments
  1. Very cool to follow the building step by step. Pam and I are thinking of you and “rooting” for you to have everything buttoned up before the snow flies!

Location

Lanesboro, Minnesota
Climate Zone 6 (cold/moist)
Latitude: 43° 44' 18'' N
Longitude: 91° 54' 48'' W

House Size

Net Treated Floor Area: 1,514 SF
Gross Square Footage (House only): 2,210 SF

Building Envelope

Roof: R-99
Wall: R-61
Ground: R-53

Windows & Doors

Glazing: U-0.10 BTU / hour / sq. ft.
Solar Heat Gain Coefficient (SHGC): 0.48”
Frame: U-0.19 BTU / hour / sq. ft.

Modeled Performance

Specific Primary Energy Demand (Source Energy Demand): 12.1 kBTU / sq. ft. / year

Specific Space Heat Demand: 7.0 kBTU/sq. ft. / year

Peak Heating Load: 7,047 BTU / hour

Space Cooling Demand: 0.44 kBTU / sq. ft. / year

Peak Cooling Load: 3,625 BTU / hour

Pressure Test Goal: Whole House Air Changes Per Hour (ACH) = 0.4 ACH 50

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