ᐅ Insulating a Garage Roof: Correct Order of Installation

So, it is more important to ensure proper ventilation than to focus on insulation.

Definitely in a room like that – I also find it very challenging.

Above all, everyone gives you different advice... whether my advice is good, I can’t really say.

In my opinion, proper ventilation in the garage is important. From my experience (I have an existing building), garage doors usually have ventilation slots, and ideally, there is also an exhaust vent on the opposite wall to create a slight cross-ventilation. A wet car in the garage brings in a lot of water, and if you drive in with snow on the roof during winter, it’s no surprise if damp spots eventually develop.

I also have a basement stairwell in the garage, and when humidity levels are high (like in recent days), condensation forms on the walls down there because the walls tend to be cold and are likely not insulated against the floor beneath the garage. The wall is covered with facing bricks, so the water runs down the surface, and sometimes a small puddle forms on the tiles in front of the basement door. It’s not ideal, but unfortunately, I can’t do much to fix it without demolishing half of the garage. Luckily, this only happens a few days a year, so I just have to mop it up then. At least I haven’t had any mold problems there so far.

Our masonry garage with a concrete flat roof has the following roof structure (from bottom to top):

• Concrete slab
• Bitumen membranes
• Insulation
• EPDM membrane (or whatever it is called)
• Gravel

For ventilation, the garage has a window that is usually left slightly open on the tilt setting. Otherwise, it’s probably a good idea to leave the garage door open occasionally for ventilation as well.

We are also getting a solid garage with a concrete ceiling, and now the question arises whether to insulate it or not.
The garage is unheated, outside the thermal envelope, and has no direct door to the house.
Furthermore, I want to maximize the height (car lift), and insulation would cost me 10cm (4 inches) of space. The architect says insulation is absolutely necessary, but I don’t agree – opinions are divided on this. I believe that insulation actually promotes a damp roof, especially in summer, when warm air meets the cooler ceiling insulated underneath.
In winter, the garage should remain relatively cool, since salt and heat accelerate rust.
Ventilation will be provided through the garage door, windows, and ventilation slots. If that is not enough, a duct fan can also be installed.
Are there any situations where insulation prevents condensation if adequate ventilation is already in place?

Hello, if I understand correctly, the garage is what a garage should be—a box where cars are parked.
Insulating an unheated space doesn’t really make sense anyway. Cold air will quickly enter the garage through the garage door and any open garage door. So what purpose would the insulation serve?
Insulation does not prevent a room from cooling down; it can only slow the process.
So I wonder what you ultimately want to achieve with the insulation?
In my opinion, it just costs money and serves no real purpose.

Personally, for a garage, I might install a fan at most. But even that I would only add later if necessary. I think you can create enough hidden gaps in a garage to provide sufficient ventilation, if ventilation is needed at all.
That means to me that a detached garage in particular should be as simple and functional as possible. Just a bit of paint on the outside and that’s it.