Insulated Chimney

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See insulated chimney components available from Menards in zip file:

Photo of HabLab showing chimney exiting through wall. Photo taken in December of 2013.


Chris' Sketches for HabLab Chimney-through-roof Installation

Chris' original sketch sent to Marcin (basically identical to drawing Marcin later found that is posted at the bottom of this page):

Cathedral Box through Ceiling.jpg

Step-by-Step w/ Sketches

  • Cut cathedral box to match ceiling slope.

Cut cathedral box.jpg

  • Locate place in ceiling to cut hole. Using a plumb-bob is a good way to ensure that hole in ceiling will be above chimney outlet from stove.
    • One edge of this rectangular hole cut in the ceiling needs to lie along a rafter.
    • Use the cathedral box to mark the size of the hole to cut.
    • Edges of ceiling cut need to accurate but not perfect. Cathedral boxes typically come with a "finishing ring" or "trim ring" that is placed around the box and over the edge of the ceiling cut to make it look nice. If the hole is cut larger than this trim ring, the trim will not cover it, and there will be weeping and gnashing of teeth.
    • Slide the cathedral box into the hole and make sure it fits.
    • The photo on the right shows the cathedral box in the inside of my home. Finished ceiling is not yet installed, so you can see the box going through the rigid foam insulation that is on the underside of the rafters.

Chimney Sketch 2.jpg Cathedral box inside.jpg

  • Once you have the ceiling hole cut appropriately and know that the cathedral box fits into it well, take the box out and add blocking to create a second attachment surface for the box.
  • Add 2x4 (or 2x whatever-you-have) blocking to create attachments on at least two sides of the cathedral box. If the rafter spacing is the same as the cathedral box, this is unnecessary. If the rafter spacing is larger than the box, then one side will have to get built out to create a second attachment surface.
    • Note: the sample installation diagram at the bottom of the wiki page shows blocking added on the lower and upper sides of the box (perpendicular to the rafters). This can be done, but is not entirely necessary. If this blocking is put in, you can attach the box on all four sides, rather than just two. I think two is sufficient, though.

Cathedral box blocking.jpg

  • I like to make the hole from the roof side much smaller, and also circular. Locating where exactly to cut this hole is a little tricker. Here's how I have done it.
    • From the underside, eyeball where the chimney will penetrate through the roof and drill a hole through the roof large enough to begin cutting with metal shears.
    • Install the cathedral box from the underside. This can be tricky. You have to slide the cathedral box up through the hole in the ceiling, hold it in place with one hand and then reach through the hole in the box with your other hand and use the screw-gun to screw it into the rafter that is along one side of it and the blocking (or rafter) on the other side of it.
    • Once the cathedral box is screwed into place, climb up onto the roof and begin opening the hole with the metal shears. Use a section of the flue pipe to ensure that this hole is big enough and that it lines up with the hole in the cathedral box.

X Ray Cathedral Box.jpg

  • The cathedral box that I have used before has a coupler built into it. The flue from the top slides down onto this coupler.
  • Then, you can slide the flashing boot down over the top of the flue pipe and into place.
  • Here is a photo of the best-practice for installation of the boot.

Roof Boot Detail.png

  • As shown in the photo, the flashing boot must slide up under the ridge cap (or you can use a piece of sheet metal under the ridge that then overlaps the flat portion of the boot).
  • What is not shown in the photo is that where the boot and the flue pipe come together (the intersection of the truncated cone with the cylinder) needs to have the flashing ring installed and caulked with the high-temp caulk. The drawing at the bottom shows this - it's called the "storm collar" in the drawing.


  • At my home, I used a less fancy detail for the flashing boot. Instead of bending down all the sides, I just caulked the hell out of the ribs and made sure that there was a good overlap of the boot to the roofing ribs. About an inch up from the bottom, I used some "outside foam closure strips" that are made to seal between flashing pieces and the top of the metal roof. (NOTE: We have extra outside foam closure strips in the workshop - aisle with the power drills at the end - same side as the drills about halfway down the aisle and near the top.) I used two rows of foam closure on mine.
  • You can see that I screwed through the flashing boot and into the ribs (and decking below that) to compress the boot against the caulk tightly.
  • This detail only works when the position of the chimney hole creates the proper overlap between the flashing boot and the roof ribs.
  • Note the storm collar caulked into place at the junction of the boot and flue.

Chris' roof flashing.jpg

Sample page from an install manual