Should I insulate my attached garage?

[alex3610]

I have a 24x24 attached garage with a bonus room above it. The ceiling of the garage is insulated (unknown other than yellow fiberglass circa 1986) and has sheetrock. The other exterior walls are not insulated, and I guess the house was sheathed with what looks like a masonite product. Exterior wise the front and side of the garage have brick veneer and the back side of the house is vinyl sided. There are 2 wood garage doors with single pane glass in the top panel of the doors. There is a newer man door on the side of the garage. There are two double pane vinyl windows that are on the front of the garage. (rear entry garage).

The issue is the bonus room above. It's cold in the winter and hot in the summer. The duct work is fed from an electric furnace in the attic at the opposite end of the house. It's typically several degrees behind the rest of the 2nd floor of the house. My assumption is much of this comes from the unconditioned cold/hot air in the garage below.

So is it worth the expense to insulate and close in the 3 walls of the garage? I realize the wood garage doors will need to be addressed as well or we will never accomplish the goal. One of the bottom panels is starting to rot anyway. My one other concern is that once insulated, during the summer when we bring the cars in we will trap the heat given off by the cars. Thoughts?

 

[James-W]

Well, with it being hot in Summer and Cold in Winter you will need to do more than just have insulation. You will want to heat the space and air-condition it or you won't be able to work comfortably. Being located in Virginia you may want to look into a mini-split. I think they would work pretty well for you.

 

[matt_i]

My opinion from a former house with same issues are sort of what you've already outlined. A "bonus room" is kind of like an "el cheapo room" when it comes to the home builder. Its not a fully integrated part of the HVAC and is probably poorly insulated on top bottom and sides.

Easiest fix if its a room which gets sporadically used is probably the minisplit as mentioned. (Oversimplified...) Run a circuit for it, mount the parts, and done. If its going to be forever part of the house it probably deserves a bigger duct run or a booster fan and an air return, plus figuring out what the situation is in the walls, floor, and ceiling. What's happening in the garage isn't insignificant but as long as its basically closed in winter I don't think its the biggest factor.

 

[Markfothebeast]

In my experiences I've found that many homes or garages have leaks in the "rim joists" aka the gap between the edge of the floor joists or trusses near the intersecting edges of the home. This is one of the most leak prone areas that tend to receive a lack of insulating. It is usually in older homes or garages. There's really not much to a typical home.

My favorite tool is an infrared temperature gun. I paid about $20 for it. It helps determine what area is creating a draft or is lacking proper insulation. I also use it to diagnose car problems.

I use the small spray foam cans in the gaps and than put in fiberglass insulation, although fiberglass is a poor insulator and the term "R-Value" is probably the most stupid marketing ploy.

Be aware that if you decide to rip in to the "bonus room" truss area that the roof needs proper venting or the decking will eventually rot. There needs to be airflow between the areas that receive moisture. If it's that chilly just rip right into the drywall.

Sent from my SM-G920V using Tapatalk

 

[alex3610]

My opinion from a former house with same issues are sort of what you've already outlined. A "bonus room" is kind of like an "el cheapo room" when it comes to the home builder. Its not a fully integrated part of the HVAC and is probably poorly insulated on top bottom and sides.

Easiest fix if its a room which gets sporadically used is probably the minisplit as mentioned. (Oversimplified...) Run a circuit for it, mount the parts, and done. If its going to be forever part of the house it probably deserves a bigger duct run or a booster fan and an air return, plus figuring out what the situation is in the walls, floor, and ceiling. What's happening in the garage isn't insignificant but as long as its basically closed in winter I don't think its the biggest factor.

Yup there is no question why you see new builders advertising a "free bonus room" in a lot of new sub divisions. It's cheap square footage for them to add and the cheaper they can do it the more profitable it becomes.

The idea of a minisplit has already crossed my mine. I've noticed a few in the neighborhood (as well as a bunch of people with window units in the windows on the gable end of the room). I took out one of the access panels that lets me into the knee wall area from a closet in an adjoining room and can see that the side walls are indeed insulated. I also noticed that the joists above the garage are actually the engineered style (I should have measured) but that probably explains how I got a 24x24 with no support columns or large beam running across. There is an access to the attic above the room from the main attic so I can clearly see there is insulation up there as well. I think I need to get a thermal imager and go around and see whats what. But I am feeling like more than likely the HVAC system is the short coming rather than the building itself.

 

[DC73]

So is it worth the expense to insulate and close in the 3 walls of the garage?

It will certainly help. If you have access to a thermal imaging camera, you might find the insulation above the garage ceiling is missing in places. I'm betting it's not adequate anyway. One option would be to remove the ceiling in the garage and spray closed cell foam under the bonus room. This will provide adequate insulation and will also be a vapor barrier and an air barrier. Not the cheapest option for sure but one of the best ways to address the issue.

My one other concern is that once insulated, during the summer when we bring the cars in we will trap the heat given off by the cars. Thoughts?

Yes, this happens and it is a trade off for a warm garage in the winter. One option is to install an exhaust fan and an intake vent with a damper and put it all on a timer or thermostat to exhaust the hot air in the garage once the outside air temp cools down enough.

DC