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So the parents have asked me to take a look at their garage and see if i can make not as cold and stop things getting damp when they park their wet car in there
First step is to fit some kind of draught excluder to the bottom of the door as at the moment there is a big gap
Next thing is a dehumidifier to suck all the moisture out the air and rain from the car
The door is an up and over style door, one of the better ones and security isn't an issue but being an up and over door there isn't any insulation on the back of the door
Any ideas on how to add some insulation that looks nice and wont affect the weight of the door for the opening and closing mechanism?
Theres probably the least cost and complexity in just making sure the space is well ventilated. Seal the garage floor too.
Insulation won't have any effect on humidity
How waterproof are the walls? Ours is very porous bricks / mortar in quite a wet and exposed spot so rain pushes through and sits like a sponge. It has made a massive difference painting the outside with Stormdry masonry cream.
Insulation only helps keep heat in. If you are not generating any heat insulation is not going to make it warmer. The only advantage is stopping things like metal sheet walls or roofs becoming a place for water to condense against a cold surface.
As suggested sealing it from holding moisture would be a good plan. Paint a concrete floor maybe and look at the wall construction.
2nd, passive and active ventilation. When you are air drying hardwood you want as much air passing through the space as possible. You ideally just want walls that keep rain out but in every other sense are as open as possible. Cars are the same Id imagine - best place for a car returning wet is probably in a car port with no sides. In your garage...louvered wall panels maybe or just vents. Could you then install an electric fan on a timer to actively circulate the air. Or I guess combine the two and have one (or two) xpelair style motorised vents. Won't circulate the air quite so much as an actual fan though.
Conversely you could seal it tight and add your dehumidifier. Would need to be a desiccant type to work well in a cold garage. I probably collect a couple of litres a week in my unheated workshop used at night to take advantage of cheap electricity. But the door is leaky so I have a suspicion I might just partially be drying this planet as much as I am drying the workshop. It has made a difference - cardboard boxes on the mezzanine that have gone soft and started going a bit mouldy in the past are crisp and dry this winter.
There's probably a clever system where you have vents you can open for passive ventilation (maybe fan assisted) but then close in dehumidifier mode.
Insulation only helps keep heat in. If you are not generating any heat insulation is not going to make it warmer. The only advantage is stopping thing like metal sheet walls or roofs becoming a place for water to condense against a cold surface.
All insulating the door will do is move the condensation to the next coldest surface. The cold door is just identifying the humidity issue. Insulating is just shooting the messenger.
Having recently (as in two years ago) put an insulated suspended ceiling in my tin profile sheeted garage I disagree with some of the above comments. I also replaced the tin up and over door with a wooden framed and clad insulated front. The insulation has stopped the rapid temperature fluctuations that leave internal surfaces ( brick walls, concrete floor) as chilled surfaces for water vapour to condense on, particularly when a warm front comes through. Its much drier now. Before you couldn't keep books, paper, fabric in there, now no problem. Just by insulating.
Cheers for the replies
The garage walls and ceiling are cavity insulated and the floor has a heavy duty garage vinyl floor so the garage stays pretty warm even in winter but they say that the garage door gets quite cold and this transfers into the garage itself
They don't want me to start drilling holes and fitting ventilation hence why opting for a dehumidifier is their preferred option for removing the moisture coming off the wet car
I use a dehumidifier in our garage - collects a fair bit of water. You may want one with a long drain hose if they don't want to be emptying it. The one in my garage is old and a compressor type (we have a desiccant too, but that's used in the shed or conservatory. Certainly removes moisture and cardboard remains crisp and dry. Need it for the bikes and our tents.
First step is to fit some kind of draught excluder to the bottom of the door as at the moment there is a big gap
That's probably the last thing you want to be doing. If it's damp then you need airflow, not to be hermetically sealing in moisture. You can't just disappear 'wet,' it has to go somewhere.
In lieu of a dehumidifier sucking out far more liquid than you'd ever imagined (ask me how I know), you'd be better served by a big extractor fan. IMHO, etc.
Surely blocking the large gap (vent) at the bottom of the door is going to make things worse as air won't be circulating as easily?
Leaving car outside when wer would also help - but probably not what your parents want to hear.
Is the garage floor and walls painted? Those can help keep moisture out, but once it is in, it needs to be removed, so ventilation is useful. A dehumidifier would also be good but that might have to be on a timer switch if possible? Also ideally has a hose to mount to an external space.