Insullation between knee-walls

42nat1

Hello. Been lurking for a while, but decided to bite the bullet and ask an actual question / get confirmation.

I am in the process of finishing an attic. It will be a fully built out space, 7' 7" ceiling, approx 600 sq ft of floor (minus walk up stair). The house was built in the 50s and has never been finished. I am in the process of putting in ridge vent (no small task in MN at this time of year) and opening the soffits.

There are knee walls on each side and flooring in place between the knee-walls (2/10 pine planks) and plywood between the knee-walls and the soffits. Blown insulation has been put in the floor joists throughout.

My questions: when creating the envelope for the new space, should I remove the insullation under the floor between the knee-walls? If I do remove it, where should I seal the joists off at -- at the knee wall or a foot or two to the inside envelope? I have read conflicting things on this.

Thanks in advance.

Windows on Wash

No need to remove it but you do want to seal off the joists with blockers and foam where they meet the vertical wall.

Insulation should still be in the floor joists in any locations that are over conditioned space.

Air seal the sill plate on the kneewall as well as any other top plates and penetrations.

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HomeSealed

... A very important step that I see guys skip on a regular basis... That is unless their work is being checked by a blower door and thermal cam.

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42nat1

One follow-up. It had been suggested to me by one person that I wanted to remove the joist insulation between the knee-walls because one you seal off the joists with rigid if you leave the insulation you will have two climates to manage rather than a single one, even though the attic stairs will be open. Any thoughts on this -- will the stairs (standard) be adequate in equalizing the whole envelope?

Windows on Wash

Not sure I am understanding what you are saying here but I cannot envision a scenario where you would not want blockers in the joist bays if they are exposed to ambient air.

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42nat1

I was planning on the blockers.

What I am wondering about is whether to remove the insulation from the rafters between the knee walls that will become the living space (the rafter use to make up the top of the envelope for the house).

Thanks again for your input.

Windows on Wash

No need to.

The insulation is not really insulating anything at that point but it will dampen sound. Leave it in.

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