DIY Bonus Room Knee Wall Insulation Tips

Having a hot bonus room with knee walls can seriously affect your comfort. Many bonus rooms and rooms over the garage have knee walls that are under-insulated or not insulated at all and certainly not air sealed. In this video, Michael shows a different way to insulate, air seal, and properly ventilate the roof around that hot bonus room with knee walls.

✅ If you are a DIYer, here are products that can help you get your attic cool:

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[sparkwebdesign]

Where is the link to the video you mention at 0:53- how to insulate knee walls?

[RJG]

Ninjas: not clear whether the baffles are below are above the spray foam? so do you sprayfoam, then baffle, then rigid foam, then edge foam? or is it baffle, sprayfoam, then rigid foam?

[mar]

I see info about issues with two vapor barriers.. would it matter in this scenario that you have paper faced batt installation in the 90 degree wall and then the roof rafters are also vapor barrier ? I have this exact scenario with a slope roof that i need to keep ventilation at the roof rafters considering foam board right over top of those roof rafters which will leave an ventilation channel all the way up to ridge vent then also insulation in that 90 degree wall

[chris-p-Bacon]

Cool Beans ! Would you put reflective behind the foam board ?

[marctappa]

If I already have bat insulation on the roof side of the knee wall and in the floor of the knee wall, can I also install it inside the wall of the knee wall? I have a bedroom upstairs and in the winter it's very dry. So we need to use a humidifier but that humidifier is causing moisture going through the knee wall up into the attic. The ventilation is fine but it's causing an issue upstairs

[erics]

Why can't we see the whole process from beginning to end? If you spray foam to get a base, don't you lose that air gap?

[danielkilligrew]

On the angled part of the ceiling is there insulation on that? Mine has insulation blocking the passageway at the top of the knee wall and up along the angled part.

[yvonnecleveland]

What if the bonus room is over the garage?

[philindeblanc]

What do you think works better? This rigid foam(1 or 2"?) or the foild sheet Radiantgaurd material? We do not have ridge vents, but we do have a gable fam (3K CFM. We likely can use a intake fan as well) plus a Whole House fan.

[breakfastclub]

does that foam in the updraft area of the truss not make the shingles hold heat on a sunny day?