Garage Insulation

[garybaldy]

Hi newbie to the forum here. I know its not a big project but any advice would be welcome.

I have a new timber frame garage, concrete base, to keep a classic car in. So I decided insulating it would be the best way to ensure its a good space to work in, and the right atmosphere to keep a classic vehicle in. I do intend on using a dehumidifier in the space. Any idea of what % of humidity you should aim for?

I'm having to keep the cost down so simple insulation to the walls and hardboard to cover followed by polyboards for the roof area (pitched felt roof).

I've looked at a few posts and damp/ moisture seems to be a possible problem doing the opposite of what I need, low humidity. It already has had condensation on the roof OSB boards during the winter, resulting in a little mold.

Any ideas / thoughts appreciated.

Cheers

 

[ajrobb]

As you say, a dehumidified garage is unusual. The normal method of controlling relative humidity for dwellings is heating. You can expect outside relative humidity to reach 100% at night. You can either pay for your dehumidifier to run at night or insulate the garage and use the thermal mass of a solid floor to keep the temperature up and the relative humidity down.

Did you damp-proof the floor to prevent damp coming up through the concrete? Otherwise this could be a source of moisture.

I don't know why you'd want to keep a classic car in a tinderbox lined with flammable hardboard. Plasterboard is hardly more expensive and resists combustion. You could use Duplex plasterboard or a separate vapour proof layer of polythene behind the board. In your case, a VPL will prevent ingress of moisture from outside, keeping your dehumidifier costs down.

Your garage will have 2 jobs:

• preserving the car from rust and mildew
  drying it out after excursions

You won't want the car to be warm while drying out as this promotes rust and mildew - lots of fans and ventilation. A sealed floor will prevent water soaking in and evaporating later. It will allow you to mop up the drips to remove the moisture from the garage.

As for the relative humidity setting, libraries might use between 30% and 50% and keep the temperature low.

 

[2929twin]

One of my customers keeps his ferrari in a not too clever garage - climate wise.He bought a purpose made, framed, plastic zip up tent thing. It is totally sealed with plastic floor complete and runs 2 small fans in the tent wall.
As far as I know, no dehumidifier tho.