Stuffing the attic – Part 2

We got the attic toward the front of the building insulated, and with it I exhausted my annual allotment of crawling around. The center section of the attic had its own challenges with the space between the ceiling and roof joists becoming increasingly tighter.

Installing the rock wool between the roof joists toward the back of the building was a breeze. No crawling and no tight spaces, as we had removed the ceiling joists. Instead a wide open space with lots of freedom to move around.

Not only that, but we also had a process down that kept us moving along.

Harold, one of our neighbors, cut the rock wool batts to the sizes to fit them between the roof joists. To make the cuts quick, precise and easy, we had put together a cutting box with blocks that were used to adjust the dimensions of the batts in 1/2 increments.

With this system set up, on a good day we worked our way through ten bales of rock wool or 600 square feet of 3 1/2 inch thick batts.


Here is something that may make you giggle, but as German as I am, I have to throw it into the mix.

I attempted to be very particular when I calculated the total square footage of rock wool needed for the attic insulation. Too much rock wool left over would be a waste of money. Not enough rock wool would be – a pain in the behind.

I carefully subtracted the roof joist and roof joist reinforcements from the total interior roof deck area, and was delighted that we ended up with only 2 bails – or 120 square foot – left over. I felt that this was not bad considering a total of 3,880 square feet of rock wool batts that went into the attic. I take that 96.9076% accuracy rate any day.

(Would they give you an A for that in college?)

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About Marcus de la fleur

Marcus is a Registered Landscape Architect with a horticultural degree from the School of Horticulture at the Royal Botanic Gardens, Kew, and a Masters in Landscape Architecture from the University of Sheffield, UK. He developed a landscape based sustainable pilot project at 168 Elm Ave. in 2002, and has expanded his skill set to building science. Starting in 2009, Marcus applied the newly acquired expertise to the deep energy retrofit of his 100+ year old home in Chicago.

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