I would like to know if I would benefit from insulating my steel Clopay 16 ft garage door and/or the garage ceiling (which is attic space above). Here is my home configuration:- Single-level new house (only 1500 sqft) with concrete block construction, with attached garage facing North (garage door faces north and never sees direct sun, but the garage still gets incredibly hot).- The conditioned airspace (living area) has a well-insulated attic (18 inches blown in fiberglass), but the adjoining attic over the garage is not insulated. There are two very large (4 inch by 20 inch) roof vents near the gable roof peak, one over the garage attic area and one over the living area, but there are no soffit vents or ridge vent in the house. There is a small vent (8 inch by 8 inch) in the garage ceiling into the attic, most likely used to provide air for the nearby gas-fired domestic hot water tank also located in the garage. I am an engineer and have read many contradicting articles on this subject, and therefore I still do not know what to do. I welcome your analysis and suggestions. I would like to keep the garage cooler without conditioning that space and wonder if insulating the garage door and/or attic might help, or would that trap heat in the garage. I wonder, did the builder cut costs by not insulating the attic above the garage, or was that the right approach considering the configuration of my home? Thank you!

 

Welcome to the forums!

Insulating should help but you need decent ventilation in the attic space to remove some of that hot air.

 

I'm not sure what the norm is for FLA, but for NC, I have the ceiling and walls of my attached garage insulated. Plus I have two gable vents, one on each end of the house with a temperature controlled fan covering one vent that kicks on when the temperature gets above 85 degrees.

Being you live in FLA, I can't imagine how hot your attic gets in the middle of summer. You definitely need to do something to remove the heat.

 

Would this be a case for adding radiant barrier under the roof to minimize the energy getting into the garage?

This is a product that I've read about but have no actual working knowledge!

 

I don't have any experience about the radiant barrier paint either but from what I've read I doubt it's worth the expense here in east tenn.
There is a farm house halfway to town that had that paint sprayed on the underside of their metal roof. It was a mess! the spray eeked out along the seams making the green roof look bad. I don't know who paid for it and it took several yrs but eventually the roof got replaced.

Fla attics and roofs do get extremely hot! Often fla houses have more vents in the roof/soffit than houses built elsewhere.

 

Sorry I was referring to the radiant barriers.

https://energy.gov/energysaver/weath...diant-barriers

 

Ok, I misunderstood 10-15 yrs ago SWP was pushing a radiant barrier paint - that was the first thing I thought of.

 

The problem I've found with putting a radiant barrier on the underside of the roof is that not only is the roof subjected to the suns direct rays, but now it's being subjected to all that reflected heat from underneath also. A much better solution is to insulate and have plenty of venting for airflow.