Garage insulating

[robby71]

I had a new prefab 24ft x 10ft garage errected 3 years ago and the last couple of winters it has been so cold inside the car had condensation and the water based products in a plastic cupboard had frozen
I use a small oil filled radiator but it isn't enough to heat the garage and i just want to stop some of the extreme cold comming through.

A couple of months ago i fitted some plastic floor tiles to help with the ground cold and yesterday i fitted some batons to the walls in prep for some moisture resistant chipboard flooring which i have ordered for next week - this will be fixed to the batons on the walls.
I also fitted some poly insulation in the wall recesses which i'm hoping will help?

I'm also next week fitting Kingspan insulation panels (25mm) to the roof which will be screwed to wooden batons i fitted and i've used expanding foam on the biggest gaps between the roof panels and the wall tops - the eves fillers are fitted all araound.

I've attached some pics of the progress so far and would welcome any further recommendations or comments as to how i can improve things further.

tape holding poly in place until chipboard is in place - should i seal the poly together to cover joins?

roof batons ready for Kingspan - should i seal the roof joins with silicon?

 

[Deluks]

Polystyrene doesn't look very thick. And you should consider doubling the kingspan thickness (at least) The problem you may create, is that condensation could form on the underside of the kingspan and drip back down. Adequate ventilation would help prevent this.
Also before you board over the walls, cover the lot in polythene, taped at all joins.

 

[robby71]

The polystyrene is 25mm thick which i thought would be ok?
If i use polythene directly behind the chipboard wouldn't that create condensation from the wall side and drip down?

Should i paint the interior side of the chipboards with an anti-condensation paint (as used on bathroom ceilings) to further reduce the risk of dampness?

 

[robby71]

Well little update - with this freezing weather i've found the moisture resistat chipboard on the walls is allowing damp to come through
I'm guessing it's from the outside so maybe the polystyrene isn't doing its job? should i pull the board off and place another layer of kingspan/ celotex (20-25mm) then refit the chipboard?

If i paint the wood with moisture resistant paint will this stop the damp comming through or will it flake off?

I've ordered a dehumidifier which will arrive this week - i'm thinking of running this through the cold weather as it has a permanant drain so should drive some moisture out

 

[Deluks]

Also before you board over the walls, cover the lot in polythene, taped at all joins.

Did you do this? If not there's no way of knowing whether it's ingress or condensation. If you did then its condensation and you need to ventilate.
Running an extract fan on a timer would be cheaper than running a dehumidifier.

 

[noseall]

Why are you trying to make a silk purse out of a sow's ear?

Why the pre-occupation with damp?

You also have a great big draughty cold admitting garage door that you can't possibly insulate or make draught-proof.

It seems a bit bonkers to build a low end budget building then expect it to perform like a full spec building.

 

[robby71]

Also before you board over the walls, cover the lot in polythene, taped at all joins.

Did you do this? If not there's no way of knowing whether it's ingress or condensation. If you did then its condensation and you need to ventilate.
Running an extract fan on a timer would be cheaper than running a dehumidifier.

No i didn't use polythene as i thought any damp/ condensation would run down behind the wood

I can redo the insulation and use a polythene if it will help - any recomendations on what to use?

 

[robby71]

Why are you trying to make a silk purse out of a sow's ear?

Why the pre-occupation with damp?

You also have a great big draughty cold admitting garage door that you can't possibly insulate or make draught-proof.

It seems a bit bonkers to build a low end budget building then expect it to perform like a full spec building.

bit harsh?
i'm working on a budget so couldn't have a stone garage built with insulating bricks, etc.
The door was the standard offered with the sectional garage and i was told i couldn't have a roller door ue to not enough space above the opening?
I'm not expecting a sauna but i would like to keep most of the cold out so i can work in there (car detailing) and not have my materials ruined by condensation/ cold

 

[limerockconstruction]

Harsh but fair I reckon - 25mm of polystyrene isn't worth anything, the lack of polythene has made it impossible to tell where the damp has come from, but also why would the damp run down the back of wood? Wood loves a bit of moisture!!

But even being on a budget, there are still some minimum requirements you are going to have to hit before you get anything remotely insulated / damp proofed.

But as nose says, the garage door isn't gonna help!

The more money you spend on not doing it properly, the more money you will spend putting it right again!