We’re lucky enough to have a double garage at our property, but it’s so full of bikes and other stuff that we rarely use it for cars. In fact, we’re thinking of converting it into an annexe and building a carport instead. But will this protect vehicles from freezing in winter?

Carports do keep frost from forming on your car and underneath it. As the carport roof is warmer than the outside air, it radiates heat down towards the vehicle and slows the rate at which your car cools down in freezing weather.

So let’s look at all this in greater detail, to discover exactly how a carport stops frost from building up on top of your car and underneath it – and also find out if a carport really is better than a garage.

Why Do Car Windows Not Frost Over When Parked Under An Open Carport?

Although it doesn’t have walls and still seems exposed to the elements, a simple carport can still prevent your car windows from frosting over. To understand why your car windows are frost-free after a night in an open carport, we need to understand how frost is formed.

Warm objects, like cars, lose heat quickly on a cold night. When that object’s temperature dips below the frost point, water in the air condenses on it. This then forms that layer of frost that we have to scrape off in the morning.

A carport may seem exposed to us; however, what it does is to slow down the speed at which the car loses heat. All it takes to slow down heat loss is that carport roof. Because the roof is warmer than the sky, warmth travels downward towards the car, and the carport stays at a higher temperature than the outside area. 

Added to this, the water in the air condenses elsewhere, because the roof is keeping the carport warmer. You’ll get frost on the outside of the carport, but not on the inside.

That simple roofed structure is enough to cut down on condensation and keep your car windows warm enough to prevent frosted windows.

Why Does Frost Not Form Under Your Car When it’s in a Carport?

Frost doesn’t form under your car because of the effect the carport roof has on the temperature beneath it. As with car windows, that open structure is enough to prevent frost, simply because the roof is warmer than the sky.

In cold weather, warm objects like the ground and the car lose their heat rapidly. When this happens, condensation forms on them, which eventually freezes and causes frost.

If your car is parked beneath a roof, this won’t happen because the roof will radiate heat downwards towards your vehicle. This prevents the air inside the carport from becoming as cold as the air outside. You’ll see the same process under an evergreen tree on a cold night, as the leaf canopy is warmer than the air above it.

Is a Carport As Good As a Garage That Can Be Closed? (Especially in Snow)

The main difference between a carport and garage is the strength of the structure. The carport is designed to protect the vehicle from the worst of the elements, and it does this surprisingly effectively, as that roof protects the car from frost, rain, snow and hail. But how does it fare in heavy snow?

A carport roof is not necessarily as strong as a garage roof, because the garage is a proper building and not simply a shelter, and the roof has sturdier supports. The biggest problem with snow and carports is a heavy snowfall leading to the roof sagging under the weight.

Guard against this by checking your carport every Fall. Are the beams sound? Are there any weak points in the roof? Now’s the time for any structural repairs, as you don’t want the roof collapsing onto your car under the weight of snow. Then when snow does fall, keep clearing it from the roof with a long-handled brush and clean out the gutters.

But what about the fact that a carport is open and a garage can be closed? Snow will generally only blow in if there’s a blizzard. Guard against this by siting your carport in a relatively sheltered spot (think about which direction the extra-cold weather usually comes from) such as close to your home or another outbuilding. An overhanging roof design also makes a difference to snow blowing in.

Do Cars Last Longer in a Garage Than a Carport?

The only real way a garaged car will last you longer than a car in a carport is that it is much harder to steal. That lockable door is the main advantage a garage has over a carport in many ways.

So, make sure your car’s security system works, don’t leave it unlocked and if you’re really concerned, install motion sensor lighting. You also can’t keep invading animals out of your carport – so watch out for those raccoons…

What about damage from the elements? A carport will keep the rain and snow off your car, and also go some way towards protecting your paintwork from UV rays (the carport roof helps to keep the sun off, preventing that unpleasantly hot feeling in the cab until the air con kicks in). 

Those open carport sides are actually a big plus when it comes to ventilation. Moisture can’t get trapped inside a carport, meaning that it’s actually a healthier environment for your car than say, a damp garage. 

An exception is if you live by the ocean, as that salty air is not good for the paint or bodywork. If you’re close to the sea, keep your vehicle regularly washed, and think about housing it indoors.

How Much is a Carport Compared To a Garage?

We took a look at some comparisons, and there’s a big cost difference between a garage and a carport. After all, the former is a building while a carport is simply a roofed structure. A 20 x 20 garage will cost around $33,000 (depending on materials, finish and what state you live in), while a carport of the same size is a fraction of that price, at about $7,000.

Garages have to conform to regulations as they count as part of your home. If you want it to have electricity, that’s a whole other set of regs. Because it can’t be used as accommodation or storage, a carport doesn’t come under the same rules.

Structurally, it won’t need the same foundations and can be assembled as a DIY project (although we always advise speaking to a local planning expert before diving into a structural yard project).

Is a Carport a Good Investment To Protect My Car?

A carport is definitely a good investment to protect your car, keeping the worst of the weather from it. It’ll keep off debris such as falling branches and bird poop, so should protect your paintwork.