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Discussion Starter #1
Hi everyone,

We are in the process of finishing off our bonus room and I was looking for a little advice on the insulation.

The floor is already insulated with blown in insulation but we are looking at options to insulate the roof sections. From what i've been reading, spray foam is the best route to go, but for cost purposes, i was looking at doing rockwool batts. We are located in Wisconsin. We will be using a mini-split heating/cooling system in the room.

When insulating, do we need to run baffles all the way from the floor to the ridge vent on the ceiling? If so, should we do that on every section on both sides?

Any insight would be great. Thanks!
 

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retired framer
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You want to leave the outside the need wall cold and insulate the nee wall. Yes you would need chutes in every bay from common space below to common space above.
The space between rafters below the edge of the floor should be solid blocked.
The walls should be made 2x6 depth and the insulated section of trusses above should be made to be 9" deep.
This is a storage, bonus room. A living space bonus room has 2x10 for the rafter section.
 

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Discussion Starter #5
Okay, sorry if I sound dumb, I’m a novice when it comes to this. What do you mean leave the area outside the knee wall cold? Only insulate the knee wall section, and the 6 feet of rafter space outside the knee wall going to the peak should be left uninsulated? If so, why? Are you recommending not making this a living area bonus room? What would be the downfall of making it one? Difficult to control the temps?
 

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Wisconsin has 2 climate zones, cold and colder and both require R-49 if using the 2009 energy codes. You'll need to verify when you pull your permit what code they are currently following.

But, as Neal said, current rafters are not deep enough for batt insulation and the necessary ventilation gap, minimum 1" preferred is 2". If you were to go completely over to an unvented attic space then even at the max r-value per inch (R-6.5) you would need 7.5". 2x8's are only 7.25" and we don't know whether your local authorities have moved beyond the 09 codes.
https://energycode.pnl.gov/EnergyCodeReqs/?state=Wisconsin

Before we get into a lot of details you need to talk to those local authorities to see what they want you to do with your plans.

As Neal said, great storage, but it may not be convertible to living space.

Bud
Sorry I type slow
 

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Discussion Starter #7
Ah okay, so what you’re saying, is it may not be able to be convertible as living space because we may not be able to reach the correct R value of insulation that is required by code. Is this correct?
 

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retired framer
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Okay, sorry if I sound dumb, I’m a novice when it comes to this. What do you mean leave the area outside the knee wall cold? Only insulate the knee wall section, and the 6 feet of rafter space outside the knee wall going to the peak should be left uninsulated? If so, why? Are you recommending not making this a living area bonus room? What would be the downfall of making it one? Difficult to control the temps?
Adding lumber to get enough insulation in the space is the trick. but were the trusses designed for the extra weight to make it living space.

If you were to insulate the roof all the way down past the nee wall on each side then you have to heat and cool it and that creates all kinds of other problem. so best you insulate the walls and then up on the ceiling over the room. Much less mold problems that way.
 

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Discussion Starter #9
And to verify, would we need to run baffles all the way up the 9 or so feet from bottom to top? Or just have the baffles in the lower section, as that are there now, and then leave a 1”-2” gap behind the insulation the rest of the way?
 

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retired framer
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And to verify, would we need to run baffles all the way up the 9 or so feet from bottom to top? Or just have the baffles in the lower section, as that are there now, and then leave a 1”-2” gap behind the insulation the rest of the way?
1 to 2 " or baffles, same, same.
 

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Discussion Starter #11
Ah okay, so no need to do both? A baffle AND a 2” gap between the baffle and insulation is not needed? A baffle and the gap serve the same purpose? I’m getting in contact with the builder to verify that the space has strong enough trusts to support a living space. He knew what our plan was for the space and never said it wasn’t doable. But I want to be safe with this.
 

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retired framer
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Ah okay, so no need to do both? A baffle AND a 2” gap between the baffle and insulation is not needed? A baffle and the gap serve the same purpose? I’m getting in contact with the builder to verify that the space has strong enough trusts to support a living space. He knew what our plan was for the space and never said it wasn’t doable. But I want to be safe with this.
They are engineered by the truss company and you should find that name on the trusses, call them, they won't have a reason to stretch the truth.
For a few bucks any truss company would look at the style of truss and would know the max weight. They would likely need the total length outside wall to outside wall.
 

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