Air-Sealing Retrofit for a Chimney Chase

Weatherization tech Scott Pillips air-seals a framing joint with gun foam before starting to install air-sealed metal flashing over the gap between the brick chimney and the wood-framed chimney chase.

Phillips measures the length of the chimney chase opening.

Cutting a piece of coasted aluminum coil stock flashing to length.

Phillips trims a piece of flashing to width using Cutco hardened steel shears.

Phillips displays his Cutco Su per Shears. "I can cut anything with these," he says. "I can cut a penny in half. They're like 85 dollars."

Phillips snips a corner off the strip of flashing to create room for a cable that leads out of the chimney chase into the attic.

To protect data cabling from damage from the sharp edges of the cut flashing, Phillips bends scraps of flashing over the cut edges at locations where the flashing may touch the wires.

Working at close quaters, Phillips wiggles a piece of metal flashing into place at the opening where the brick chimney penetrates the ceiling framing. With the roof sheathing removed and the ceiling exposed from above, according to Phillips, this is a relatively easy situation: often, the chimney-to-framing gap is less accessible.

Working by feel as much as by sight, Phillips eases a strip of metal flashing into place between the chimney and the framing.

After noting the location of some data cable by feel, Phillips bends a piece of metal around the sharp edge of the flashing in order to protect the wire insulation from damage.

Phillips works the metal into position in the small gap.

Phillips screws the metal flashing down onto the chimney chase framing.

Phillips applies high-temperature sealant caulk to the underside of a piece of flashing before setting the flashing in place. To achieve a good seal, caulking is installed between the metal and the wood framing, as well as at the joint between the metal and the brick chimney.

Phillips sets another screw to fasten the metal flashing securely to the ceiling framing.

Field expedient: to extend his driver bit to the length required to reach the awkward location, Phillips attaches several magnetized bit holders together and secures them with a temporary wrap of aluminum foil.

Once all the flashing has been screwed into position, Phillips caulks the joints between the flashing and the brick chimney with high-temperature sealant.

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