Detached garage insulation.

[Alexw1984]

Hi there,

I'm planning on insulating my prefab detached garage as I'm going to be using it as a workshop/garage. I've planned so far to put foam slabs between the rafters (which are 7cm deep and 73cm wide) and maybe some aluminium thermal foil over the top as well as I got a load of that cheap. The roof looks to be made of large chipboard sheets and has roofing felt on the outside. The thing I'm not sure of is ventilation?
Also the walls are a few inchs thick and I'd like to put something on them to help insulate - in summer the walls heat up and turn the garage into an oven and in winter the exact opposite! The only problem is I can't lose much space, i can only just open my car door and get out as it is.
So I was thinking of something like the mentioned aluminium thermal sheets and I've also seen insulated lining paper. I guess they won't do much but something has got to be better than nothing?
The garage has an electrical supply and I will be fitting a thermostatically controlled heater to stop it freezing. I just don't want it to be on pretty much permenantly as the heat just escapes.

 

[noseall]

There are no magic products out there that will insulate thinly and effectively.

Either you bite the bullet and insulate thoroughly (i.e. correct minimum thickness) or you suffer the consequences.

That is not to say that any insulation added to the garage will not improve it but be prepared to be disappointed if you merely add some as a token gesture.

Passive ventilation will help, i.e. louvered vents etc or even a mechanical extractor, but this needs to be included as well as the insulation.

I have mentioned before that it is probably better to build a timber cell within the garage then insulate this rather than mess about trying to fix stuff to concrete panels.

 

[mointainwalker]

...........I've also seen insulated lining paper. I guess they won't do much but something has got to be better than nothing?

Well, not if the effect is so small - which it will be with what you are proposing - that you can't feel the difference or it still doesn't make it possible to work.

Forget about trying to stop summer heat by insulation alone : it is just not possible.

 

[dhutch]

Im reading this having found it in a search so you may have done something already, but a lot of the summer heat will be coming in from the roof. If it where mine i would put 50mm foam board (XPS or simular) on the roof as you suggest and look to adding ventilation.
- If you then need to take the chill off to work, consider infrared halogen heaters or just sucking up the cost of a large heater if very occational use.

If you want it to be warm and dry to house grade frequently, knock it down and start again.

Lining paper will do nothing, but if you really want to insulate the walls 25mm of foamboard and some 5mm play over the top will do a lot more than nothing. Use closed cell board to prevent it taking on damp.


Daniel