Building Codes and Inspections/Garage Insulation



Thank you for taking the time to help with my question. I have an attached garage with block walls and a dry walled ceiling. I will be pulling the dry wall, doing some rewiring and reinsulating, then installing new drywall. My question is about the best way to insulate and seal the garage from the finished room above. There are 5 HVAC ducts in the ceiling, and as far as I can tell now, no other openings to the living space above. I planned to use fiberglass insulation with vapor barrier, but I've heard that the expanding foam is better for this type of application. Any thoughts on which to use? Also, are there any special precautions to take with the HVAC? Any other suggestions would also be appreciated.

Thanks again for your time.


A few thoughts...

Either type of insulation is fine so long as at least the minimum required r-value is installed.  The spray foams are great product, but pricier; you'll have to weigh the cost benefits there.   Closed cell insulation would really seal the ducts when sprayed on them, but it takes specialized equipment, as would pumped in cellulose or other loose fiber insulation. If you insulate it yourself with fiberglass, be sure the vapor barrier faces the heated side, the living area (up).

Keep the ducts on the warm side of the insulation as much as possible to avoid heat loss to the unheated garage. Also, don't have the ducts up against the underside of the floor above, as this could cause noise when weight is put on the floor and the ducts flex.

You must maintain the the code required separation between the garage and living space above. Modern codes usually require a 5/8" gypsum barrier, where 1/2" drywall may have been used in the past.

Specific questions regarding the code and required r-values at your location can be answered by your municipal Building Official, as required insulation levels are location specific, and the municipality could have amendments to their code that I wouldn't know about.

Good luck!

---------- FOLLOW-UP ----------

QUESTION: Thank you for your detailed, quick reply. I would have installed the fiberglass incorrectly. I will take all of this into consideration. One follow-up question- When the drywall is installed, how would you suggest sealing the gap between the drywall and block? Silicone?

If you are speaking of the gap between the ceiling drywall and a wall block, then you would want to seal that with the red fire caulk that's available and building supply stores like Lowes and Home Depot. You can use the same product to seal around any ceiling electrical boxes, like if you have a garage door opener or light in the ceiling between the garage and the room above.

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Keith Fuller


I'm an ICC Certified Master Code Professional fielding general building code questions. My experience has been heavy in fire related issues.


I've been employed since 1985 as an inspector and plan reviewer, and am a municipal Assistant Building Official and Deputy fire Marshal. I've had fire service experience since 1972, having served as a three time Fire Chief and Fire Marshal in years past. The increasing workload, mandatory certifications, and continuing education requirements in recent years have caused me to concentrate my efforts on code related issues. I hold national fire service certifications as well.

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