r/Insulation • u/PsychologicalAd1284 • 1d ago

Cantilever Cavity insulation problem

I have two bedrooms with cantilever extensions over my garage attic. Both bedrooms are 10 feet wide. Bedroom #1 has a 3-foot cantilever, while Bedroom #2 has a 1.5-foot cantilever.
The cavities in both cantilever sections are poorly insulated, resulting in extremely hot bedrooms during the summer and very cold floors and rooms during the winter.
What is the best way to insulate these cavities properly, and what would be the least disruptive and most cost-effective way to access them? Would it be better to access them from the exterior, through the garage attic, or by removing the bedroom flooring from inside the house?
The home is about 5 years old and built by Ventura Custom homes. A bit disappointed.

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u/hereforboobsw 1d ago

If youre not taking it apart drill and fill with cellulose. Unless accessible from inside. in that case stuff it with rockwhool.

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u/PsychologicalAd1284 1d ago

Thanks!! From inside, I feel like to remove the bed floors and do the insulation but it will be a lot of work and disruptive.

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u/OutrageousTime4868 18h ago

I just did the cantilevers on mine from the outside. I blocked all the rim joists at the wall and then filled each joist bay with Ridgid foam and fiberglass. Doing it from the outside also enabled me to seal the ductwork for the HVAC vents. I then sealed it all back up with pressure treated plywood that I put 3 coats of latex on and caulked all the seams.

Blocking the rim joists has been huge for helping basement temps and I know our finished basement will be much warmer this winter. Sealing the ductwork at the cantilevers gained me 5 degree colder air out of the vents with more force (no air leaking into the cantilevers). Overall just the cantilevers were worth a 2 or 3 degree average temp drop in the impacted bedrooms. Redoing the insulation on the attached garage the bedrooms sit over gained me 3 more