It's not possible to build a garage the right way

[Johan Larsson9794]

One thing that confuses me is garages, and especially heated garages. I thought it was a no-brainer and I'm pretty sure it's not entirely uncommon to have a garage. However, it seems difficult to build a garage the right way, and I wonder if not everyone has garages with moisture damage.

Ideally, you shouldn't have a garage because it causes rust on the car. Then you bring in a lot of snow and dirt, which damages the entire structure. You also can't have it insulated, because that creates even more moisture. But if you do have it insulated, you shouldn't have a vapor barrier, yet you should still have a vapor barrier. It might be good to have drainage for all the water that comes in. But at the same time, it's not necessary. Sometimes you might need ventilation, but overall it's quite overrated since the doors allow natural airflow.

 

[Fotografen]

Mja...my tips:
- If you put the car in a warm garage, it should dry out completely before you take it out again, i.e., if it's used every day in winter, it's better off in a carport or outside
- If you're building an insulated warm garage using the modern gypsum method with wooden frame walls, plasterboard, and insulation, you should have a vapor barrier, but the garage must be heated and cannot be left cold
- I recommend having a drain, and if the garage is over 45 or 54 m2, I can never remember which, it should have an oil separator. Garage drains are connected to stormwater drains.
- A garage needs ventilation, at least natural ventilation with a vent at each end up/down, but then it depends on how advanced it is and what you're willing to spend, there's nothing preventing exhaust air-FTX-exhaust air heat pump, etc.
- An unventilated unheated cold garage becomes a moisture chamber, no matter what you do.

 

[Johan Larsson9794]

Mja...my tips:
- If you park the car in a heated garage, it should dry out completely before you take it out again; if it's used every day during winter, it's better off in a carport or outside.
- If you build an insulated heated garage in the modern gypsum style with wooden stud walls, gypsum boards, and insulation, you should have a vapor barrier, but then the garage must be heated and cannot be left cold.
- I recommend a drain, and if the garage is over 45 or 54 m2, I can never remember which, it should have an oil separator. Garage drains are connected to stormwater systems.
- A garage needs ventilation, at least passive with a vent at each end top/bottom, but then it depends on how advanced it is and what you want to spend, there's nothing preventing exhaust-FTX-exhaust heat pump, etc.
- An unventilated unheated cold garage becomes a moisture chamber, no matter what you do.

But isn't a vapor barrier less ideal when it's warmer outside than inside the garage? Then the moisture has no place to go.

 

[Fotografen]

But this thing with a vapor barrier is less good when it's warmer outside than in the garage? Then the moisture has nowhere to go.

Yes, exactly. That is why a vapor barrier garage cannot be kept cold during the winter, it needs to be at least 10-12 degrees. Then you bypass the periods, in early spring, where it gets warmer outside than inside. It is usually 5-7 degrees outside and 0 to a few degrees above zero indoors. Keep the heat on and maintain 10-12.

 

[Argastesnickaren]

I built a new house 3 years ago and finally got drains installed in the garage on the basement floor, 3 in total, one under each car and one for the heat pump and the washbasin.
70 sqm and no oil separator.
Supply air through the wall and exhaust air to the heat pump.
Underfloor heating throughout the slab and a bone-dry garage.
Always at least 20 degrees warm.

 

[Johan Larsson9794]

Yes, exactly. That's why a vapor barrier garage cannot remain cold during the winter, at least 10-12 degrees. Then you get past those periods, in early spring, when it becomes warmer outside than inside. It’s usually 5-7 degrees outside, and 0 to a few above zero indoors.

Okay, but about the drainage. It's only meant to divert water from the inside, right? You can solve that by having a slope or by "jackhammering" a channel that goes out?

There isn't more water to divert just because it's a garage instead of a carport.

 

[Fotografen]

Yes, it works, but if you lead it out under the gate, it becomes an icy road outside, with a frozen gate, etc.

 

[Huddingebo]

It also depends a lot on how thick the insulation is. I don't think many people insulate like a permanent residence.

If you don't run an eco warm car, there's quite a lot of heat accumulated in the drivetrain, exhaust system, cabin, etc.

But a dehumidifier might not be a bad idea.

 

[Argastesnickaren]

Where the gate is, I have added a slight outward slope both inside and outside so that if it rains and the wind blows toward the house, it will not flow inside but stay outside.

 

[Johan Larsson9794]

Yes, it works, but if you let it out under the gate, it will become an ice rink outside, frozen gate, etc.

Good point.

 

[Johan Larsson9794]

Okay, but if I understand correctly, it is actually the moisture in connection with the large snow accumulation that can occur in winters that is the biggest culprit?

If the garage has its own air source heat pump, isn't this quite easily managed? The air source heat pump dehumidifies quite effectively, right?

If needed, you can also break up the concrete to install a channel without an outlet? For example, this https://www.purus.se/purusranna-avdunstning-guide

Comment?

 

[Argastesnickaren]

Ok, but if I understand correctly, it's actually the moisture in conjunction with the large accumulation of snow that can occur in winter that is the main culprit?

If the garage has its own air source heat pump, this should be fairly easy to handle? The air source heat pump dehumidifies quite effectively, right?

If needed, you can also break up the concrete to install a trench without an outlet? For example, this one [link]

Comments?

Then you have moisture in the garage for a longer time than if you can (are allowed to) install a drain in the garage.
Building new makes it easier to solve problems directly instead of afterwards.
Rust problems are worst at about 7-8 degrees with high humidity, so the worst place to have a car is in a cold garage with little insulation and poor ventilation.

 

[Johan Larsson9794]

Then you retain the moisture in the garage for a longer time than if you can (are allowed to) install a drain in the garage. When building new, it's easier to solve problems directly instead of afterwards. Rust problems are worst at about 7-8 degrees with high humidity, so the worst place to have a car is in a cold garage with little insulation and poor ventilation.

The plan is to have a heated garage. I'm more concerned about mold in the garage than rust on the car. The garage is connected to the house, so it's important to keep the moisture in check.

 

[moo7e]

Heat up the garage and install a proper dehumidifier. It always goes below 50% every night, even with an extremely wet car. Have never had issues with either rust or moisture.

 

[Johan Larsson9794]

Warm up the garage and put in a proper dehumidifier. It always goes below 50% every night, even with an extremely wet car. I've never had a problem with either rust or moisture.

Do you need a separate dehumidifier? Doesn't an air source heat pump take care of dehumidification?