Insulating the garage

Jablite or similar.

Under 100GBP for 4 boards (40mm) from Sheffield Insulation. Each board is 2400 x 1800 mm IIRC.

Rockwool held up with chicken wire and covered with foil-backed=20 plasterboard?

============== Polystyrene (50mm thick) is quite cheap and effective. I used it underfloor.

Cic.

I went through this issue a couple of years ago. My 30m^2 garage was single brick wall with concrete floor and a pitched, felted tiled roof with access open from inside all the way up. There were up/over doors at the front (timber and ply construction with poor sealing around the edges).

I did the calculations for heat loss and to get the inside temperature up to a reasonable 18 degrees when it's around zero outside was in excess of 12kW. With electric heating, the implication would be a 50A supply and at 6p/kWh, a cost of 72p/hr to heat it. In practice, I could run two fan heaters and achieve about 10-12 degrees eventually but in a 3-4hour work session it really was hardly worth running the heating; plus for the 50A supply it would mean only

Therefore I did the calculations for using 50mm Celotex for the roof, walls and doors and nothing for the floor. This basically brought the heatloss down to about 3-4kW for 20 degrees inside and 0 outside.

I insulated against the rafters using Celotex attached with long drywall screws and flat washers, then joints taped with foil tape. I added soffit vents to allow ventilation behind the sheets.

For the walls I made a stud frame with a 25mm space behind for ventilation, infilled with Celotex and with 18mm ply over the top.

I improved sealing on the doors with special vinyl strips and again Celotex attached to the insides of the doors. It's light in weight.

FOr heating, I added a stainless steel plate heat echanger to the house CH system and added a secondary heating circuit for the garage so that the heat source is from gas rather than electricity. This results in a worst case cost of heating of about 5p per hour.

I used Celotex throughout because it provides good insulation for a given thickness and is light in weight and quick to fit. I was more concerned about space and running cost than capital cost.

To implement more cheaply, I would have kept with the Celotex for the roof and doors and used rockwool or fibreglass for the walls. I found it possible to get 50mm Celotex at £15-17 per 2440x1220 sheet by making a project including the timber and sheet materials and asking builders merchants to quote competitively for the lot.

The result is that I can use the workshop comfortably whenever I like and have adequate electrical supply for the machinery.

thanks all for the advice. if i can get celotex at that price i will do the roof with that. the walls i will probably do with thiner stuff because i cant realy lose the space. now the hunt is on for cheap celotex! if i cant get it that cheap, i will do the jablite thing.

steve

In terms of priority, I would do the doors and roof first, then move on from there.

You can get Celotex in a range of thicknesses.