If your hatch rests directly on the moldings like ours did add 2 1 2 in wide stops around the opening.
How to seal chimney in attic.
You have to start from the bottom and spray the sealant on the bricks evenly.
Some of the repellents will drip down.
After the air sealing work was complete including wiring vent and plumbing penetrations throughout the attic the attic received an r 60 blanket of blown cellulose insulation.
That material is not allowed to contact the masonry chimney so after blocking the bypass jerome fit pieces of 2 inch roxul mineral wool insulation around the chimney to isolate the masonry from the cellulose.
I installed it upside down with the drop leg pointing up.
Remember that all chimney flashings need to be masked off prior to applying the sealer.
Sealing an air leak around a chimney in the attic 1.
This folded leg strengthens the unsupported edge and created a perfect little trough for firestop caulk.
Set up a cordless drill with a.
As you note the chase on the attic floor is not as much of a problem because your basement and your attic are both inside of your thermal envelope.
Then finish up by sealing the access hatch with self sticking foam weatherstrip photos 10 and 11.
Measure and cut the flashing for each side of the chimney using sheet metal cutters.
So you should certainly seal the air leaks around the chimney at this location by installing metal flashing with sealed seams around the chimney on the underside of the rafters.
I used pieces of various widths up to 6 in.
Put on work gloves.
Access the attic through a crawl space in the ceiling using a stepladder or use or the attic stairs.