Roof insulation is important in terms of energy efficiency, which in turn lowers heating and cooling costs. Insulating around a chimney is in both the exterior and interior space. The exterior consists of sealing air leakage, while the interior consists of creating a barrier between a hot flue pipe or chimney and adding insulation.
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Things you need
- Caulking gun
- High-temperature resistant caulk
- Tape measure
- Aluminium flashing
- Metal shears
- Vice grips
- Heavy-duty stapler
- Furnace cement
- Unfaced insulation
Load a caulking gun with high-temperature resistant caulk and run a bead of caulk into gaps around the exterior chimney where the chimney meets the roof to seal air leaks.
Build a damn around the existing flue pipe or chimney with aluminium flashing. Measure the size of the chimney or flue pipe and cut aluminium flashing 6 to 8 inches larger than the flue pipe or chimney with metal shears to create a sleeve. Check all local codes to determine the exact size of the insulation damn. Generally, codes require a 1- to 2-inch damn around metal flue pipes and 3 to 4 inches around a masonry chimney. Building a damn prevents insulation from coming in direct contact with a hot flue pipe or chimney.
Cut the aluminium flashing at the bottom and top of the every 2 inches all around, and each cut will measure 3 inches deep in order to create tabs on the aluminium sleeve.
Grasp each cut on the bottom with vice grips and pull up to form a 90-degree angle.
Grasp the tabs on the top and fold them in to create a 90-angle.
Place the sleeve around the chimney or flue pipe and staple the tabs into the attic floor with a heavy-duty stapler. The top-folded tabs will keep the sleeve sitting back from the flue pipe or chimney the appropriate distance.
Seal the seam on the sleeve with furnace cement.
Place insulation without a paper backing, known as unfaced insulation, around the damn.
Tips and warnings
- Check all local codes prior to building a damn.
- Obtain all necessary permits and schedule all inspections to ensure safety.
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