Little Canada, Minnesota
By reusing roof materials, this replacement saved $16,000 on material and labor costs, and $4,000 in dumpster fees. Also eliminated was 400 cubic yards of landfill waste. But most important to the owner, by leaving the existing roof insulation in place, we also reduced the noise, smell, and dust usually created during roof replacement. This suburban Minneapolis facility required a clean-room setting, and uninterrupted manufacturing during construction.
The facility’s existing 23,000 square foot roof assembly was a 20-year-old, built-up roof featuring a metal deck topped with a 3-1/2 inch thick layer of expanded polystyrene. Because the polystyrene was not securely fastened to the deck during original construction, the insulation panels were separating between longitudinal joints. A lack of attachment of this insulation to the metal roof deck rendered the substrate unstable, allowing leaks and rusting.
A careful inspection determined we could reuse 99.8 percent of the polystyrene, or 22,770 of the 23,000 square feet, leaving just 230 square feet for disposal. The reused insulation provided a 16.6 R-value. The R-value was increased to 32 by adding additional layers of Isocyanurate insulation. The entire substrate was mechanically fastened to the metal deck to prevent recurring dimensional instability. A final layer of one inch rigid perlite was then installed in solid moppings of asphalt followed by a four-ply, built-up roof installation.