Replies

1. Expert Member
   MALCOLM TAYLOR | May 30, 2020 11:29am | #1

   Marty,

   i think it would help to draw that section with the blocking necessary to constrain the dense-pack cellulose at the top of the walls, and the fire-blocking required to separate the walls from the roof. That will make it clearer how the wall and roof insulation meet. That said, I can't imagine a situation where insulating the parapet walls is useful.

2. 
   Driven_5EM | May 30, 2020 01:18pm | #2

   I have revised the detail. It just means a lot of air sealing on the blocking, unless it would be ok to leave the space above the rockwool as a cavity and not vent it. I am in climate zone 5 in BC. 3000-3999 degree day heating with hot summers 30+ celcius.

1. Expert Member
   MALCOLM TAYLOR | May 30, 2020 07:18pm | #3

   Marty,

   You are in BC - that makes things easier. There is no requirement here for fire blocking if the exterior walls are filled with insulation the way I understand it is in the IRC. The only reason to block (using either wood, mesh or ?) would be to contain the top of the dense-pack cellulose, and I'm assuming that may be necessary simply for practical reasons, as I don't know how they would access the top of the wall to get a good fill above the level of the truss, but maybe they can.

   I'm not sure there is any advantage to connecting the exterior and interior air-barriers. They are separately continuous. The interior one running from the floor, up the walls, and across the ceiling, and down again. The exterior one running from the foundation, up the walls, over the parapet, across the roof (as membrane) and down again.

   Meaning you are good to go with your original section - and to finally answer your original question: No you don't need to insulate the parapet, but it would do no harm to do so.

3. 
   Driven_5EM | May 31, 2020 11:54am | #4

   thank you. I appreciate the insight and perspective from other professionals.