Mold on the ceiling in your garage?

If you have mold on the ceiling in your new garage, it might be because it is too humid in there.

In the winter when you bring your cars into the garage they are usually covered in snow and ice. By the time the morning comes all the snow and ice has almost melted off the vehicles. This is because it is actually warmer in your garage then it is outside, it’s warmer in your garage even if you do not heat your garage. All this moisture from your vehicles is what creates the humid environment in your garage.

Most garages aren’t entirely insulated because of cost and most people believe that if they aren’t going to heat their garage why would they bother to insulate it at all.

The modern garage is so well sealed now that you almost never have air leakage into a garage space. Garage doors in modern custom homes are made to be extremely airtight. They do not allow water or snow to blow in around the doors, the rubber seals on new garage doors are better than most man doors into the actual home. Since the garage doors are so air tight there is virtually no air exchange in the garage.

Since most garages are attached to the home making it more convenient, then the walls of the garages are sealed to stop the carbon monoxide from entering the home and causing health problems. This air seal is good and bad when it comes to humidity. If the garage isn’t completely insulated then the warm moist air in the garage will travel up to the ceiling, as it meets the drywall it also meets the cold air coming from the attic, the warm air rapidly cools, this creates moisture and the moisture ends up on the drywall of the ceiling where warm and cold air mix. As this process happens repeatedly day after day and with little air movement in the garage mold starts to form on the surface of the drywall.

There are a couple ways to avoid this;

1. Insulate your entire garage regardless if you are heating it, walls and ceilings.
2. Install an exhaust fan that is run from a humistat.

A humistat fan is a fan installed high up on the wall that has a humidity detector, when the air in the garage reaches a certain humidity level the fan turns on and expels the air outside. This helps keep the humidity level in the garage down and also helps air exchange in the garage.

Since you are removing air from the garage then you need to add air so that the garage doesn’t become depressurized. Since your humistat fan is mounted high on the wall then you need to add fresh air on the opposite side of the garage as low as possible. All you need is an air vent that can be adjusted by hand; these are the same vents that you would install in a cold room.

These two simple things will help you keep your new garage mold free.

Rob Abbott
Operations Manager
Village Builders Inc.