insulating attic room

[jonyy]

I’m in the middle of a remodel (completely gutted) and want to insulate the attic room.Currently I have 360deg access of the room.


Build specifics:
House is 100 years old
Floor or attic room is 2x8 16” centers.
Attic floor is 1”x3” T&G
Knee wall are 2x4 2’ centers
Rafters are 2x4 2' center (I don't know that kind of wood was used but it is like iron)
2 small dormers with a window each

Below (2’) the attic floor joists is the ceiling for the downstairs living. This ceiling is 2x4” braced to the 2x8s above. The plan is to blow insulation between the two cavities. However, this will settle over time so first questions should I batt between the 2x8s with the batts pressed firmly against the attic floor or is the attic floor even a concern here?


----------attic floor

2’ space

---------- lower level ceiling

The attic room itself I’m debating between traditional batts or just use xps? Or maybe a combo, batts between the 2x4s and ¾ xps on top across the 2x4s? I’m not sure if there is an issue with two different types of insulation contacting each other.

Thank you for your time. I look forward to your responses.

 

[nealtw]

The big thing to look for is good venting on one side of the peak and at the soffit area.
Adding another 2x4 under the rafters will allow 6" of batt and an air flow above that. Adding insulation between floor and ceiling would for noise and not really needed.

 

[jonyy]

t. Adding insulation between floor and ceiling would for noise and not really needed.

In this case it is needed for more than noise. The liveable attic room does not cover the whole lower story (not even close). It is in the center of the house with with quite a bit of non useable attic space around it, so the insulation is needed for the ceiling on the lower level. I'm just not sure how concern I should be with the attic room floor.

thanks.

 

[nealtw]

I understand now. I think I would be looking at extending the pony walls down to the ceiling and insulate that so the space between is part of the envelope.