When it comes to insulating a garage, there are many ways and many materials that can be used to get the job done. There are also variables to consider too, such as is the garage heated or not? Does the customer want storage in the attic space? What type of trusses are installed?
Ultimately, the customer’s budget tends to be the deciding factor on which route to go.
Below are a few different cases of what materials to use and where, depending on the garage set up.
Heated Garages
In a heated garage, the best solution would be to spray foam the entire building: the walls, the underside of the roof, to make everything airtight. The benefit of spray foam is that it holds the air inside the building, so the heat inside will stay inside.
Alternatively, spray foam can be installed on the underside of the roof, with batt and poly installed inside the walls. This works really well because in a heated garage the majority of the heat is going to be rising, so with that airtight barrier at the roof, the warm air won’t escape; it just stays in the building for longer.
This leaves the overhead door and perhaps the windows where air might escape, but everywhere else will be completely sealed.
Having spray foam, on the underside of the roof allows the attic to be used for storage as well.
Spray foam costs more upfront, so it's more of an investment than fully batt and poly.
A less expensive option is to install a traditional attic insulation. With a drywalled ceiling, the attic can be filled with a loose fill blow in insulation on top which will give an R50 or R60 R-value. The loose fill will still do a good job at keeping the heat inside. Adding fiber glass batt and poly to the walls will also help keep the space warmer.
Non-Heated Garage
A garage that is not heated has a few less recommended options. Spray foam is a better barrier against the cold, but it needs heat inside the building to work well, so in a non-heated garage, loose fill blow in insulation in the attic space and batt and poly in the walls is a better solution.
If a garage is not heated, clients probably don't want to spend too much on insulation anyway, so using blow-in loose fill and/or fiberglass batt and poly is great as an inexpensive option.
One could also put batt and poly in the ceiling, but that will not be as effective as blown-in insulation because it comes in individual batts that can allow vapor to transfer between pieces. Blow-in insulation is like a blanket that sits on the ceiling, which provides a more effective insulation, whereas in the same metaphor, batt and poly would be like individual pillows, not quite as effective at keeping your garage comfortable.
Windows and Doors
As for those sneaky air gaps around windows and doors, if the garage is spray foamed, our crews can take care of those spaces and make sure they are filled in, but homeowners can also use canned spray foam to take care of it themselves if they prefer.
Canned foam is good for sealing around electrical boxes or other holes in the framing.
Sealing around any penetration that the wires have made in the wood frame with canned spray foam is a good idea when you have batt and poly insulation as well.
"Blow-in insulation is like a blanket that sits on the ceiling..."
Rigid Foam Board
Rigid foam board is another option for insulating a garage. With good thermal resistance (between R4 and R6 per inch) and soundproofing abilities that will help in not annoying your neighbours for those days you’re running the air compressor, saws and any other noisy machinery.
Rigid foam boards are made from polystyrene, polyisocyanurate (or polyiso for short), or polyurethane foam and comes in panels that can be cut to fit the space, so it’s helpful in awkward areas.
This type of insulation is ideal for heated garages in ceilings and walls, as it offers moisture resistance (as long as it is sealed properly) and high thermal resistance, which means it’s good at keeping the temperature steady.
That said, rigid foam boards are good for added insulation in non-heated garages too.
Every joint, edge, and penetration should be sealed to ensure the rigid foam remains airtight and resistant to moisture.
Some foam boards are also fire retardant offering an extra layer of peace of mind for your garage.
Attic Storage and Truss Design
Turning a garage ceiling space into storage space isn’t as easy as putting up drywall and insulating the space. If there are regular trusses or rafter trusses holding up the roof, they will need to be replaced with specific attic or storage trusses in order to not only reliable hold up the roof and provide proper storage space, but also for safety.
Conventional truss and rafter framed roofs are not designed to support any sort of storage, so turning the space into attic storage might get homeowners into trouble, either through the paperwork side of things, or it could just plain collapse.
The solution is to install proper attic trusses or hire an engineer to investigate if there is adequate support for storage before moving ahead.
"...for those days you’re running the air compressor, saws and any other noisy machinery."
To Heat or Not to Heat? Garage Set Up Determines Type of Insulation
Whether the garage is heated or not will likely depend on what the garage is used for, may that be just to store cars or as a workshop, or as storage space. And what the garage is used for will also decide on the type or combination of types of insulation used.
The benefits of spray foam within a heated garage are many. When it's used for the entire building, you create an airtight space where heat can’t escape. Even using a combination of spray foam on the underside of the roof with batt and poly in the walls can provide a comfortable space.
Having attic storage space is always a bonus for car parts, seasonal yard equipment, Christmas decorations or junk you’re not ready to let go of yet. With proper trusses and insulation it can be a prime space for storing just about anything without the worry of colder temperatures ruining your precious goods.
On the flip side, a non-heated garage is better suited to be insulated with loose fill blow-in in the attic space and batt and poly in the walls.
Still not sure what might work best for your garage? Give our team at Beyond Group a call today!
