Thermal insulation for garage door

Garage is coming along nicely now, and my attention is drawn to trying to improve the thermal characteristics a little.
Possibly the most significant problem to try and do something about is the huge expanse of two up-and-over doors for this double-width garage. Made of the usual thin steel sheet they must conduct thermal energy in both directions with gay abandon.
I've seen references to using selotex in this forum, which I assume to be a sheet lagging material (polystyrene sheets maybe?). Haven't found that stuff in the local DIY sheds so far. I guess it's not so hard to shape to the door.
Another idea I've come up with is that we've got a large roll of bubblewrap which could be easily cut to the door shapes, and stuck on with double-sided sticky tape. Whilst I doubt it would have equivalent thermal properties to something like selotex any form of improvement has to be worthwhile. Does that sound feasible?
PoP
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Sorry, forgot to add this one:
http://www.enigma-insulations.co.uk/garage.asp
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This any good to you :
http://www.cardale.com/html/thermaglide.html
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On Sat, 13 Sep 2003 05:23:48 +0100, PoP

Celotex is very effective and available in lots of thicknesses. It is a polyisocyanurate foam with glass fibre reinforcement strands. You will find it at builders merchants for about 15-18 for a 2440x1220 sheet of 50mm material, which is plenty. I have never seen it in DIY places. It is foil covered on both sides as a vapour barrier. You can also get a metal foil sticky tape for sealing the gaps.
It is extremely light in weight and with better characteristics for insulation than styrofoam. You can cut it with a saw (e.g. a circular saw, or a knife.
I cut pieces to fit within the steel frames that run across the back of my doors and left gaps for the rods and cables which I later ran in plastic pipes. The pieces of sheet were attached to the doors with Gripfill. I later installed the pipes to carry the operating rods and then taped over the top of them filling with polyurethane foam as I went.
In addition, I fitted weather strips on all sides, tops and bottoms of the doors to eliminate draughts. The overall effect is good and the garage requires heat at less than the values calculated to maintain the required temperatures.

Feasible, but not very effective. I think that if you are going to do this job, it's worth doing with a decent material.

.andy
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On Sat, 13 Sep 2003 05:16:15 GMT, "BigWallop"

Wow! Multiple answers in one reply....! Thanks!
PoP
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Why?
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On Sat, 13 Sep 2003 16:13:48 +0100, 666 snipped-for-privacy@hack.powernet[dot]co[dot]uk (Simon Gardner) wrote:

In previous winters it has been a bit parky to try and work in there. Whilst I'm okay with the idea of putting a small fan heater in there to help warm things up a little there seems little point if the garage doors represent an open goal for heat to escape.
I appreciate there are lots of places where heat can escape from a regular garage, and those would need to be tackled in due course. But it strikes me that a significant loss area would be two 7x6 ft (approx) thin metal doors which conduct heat readily.
PoP
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On Sat, 13 Sep 2003 19:48:16 +0100, PoP

Absolutely. When I calculated the heatloss for my garage, the loss through the (wooden) doors was the highest of any of the surfaces. Metal would be even worse, so this is definitely worth doing. The second greatest loss was the roof area and lastly the walls.
Having insulated the lot, I can now maintain the whole thing at room temperature of 21 degrees (-1 outside) on 4-5kW; although generally when I'm working I run it at about 18 degrees.
.andy
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wrote:

Sorry if you are repeating yourself from another recent thread, but what approach did you take with respect to insulating the roof area?
I have a regular apex roof on my double garage just like a typical loft (very useful for hiding all those useful things that you don't really want to chuck away....). Though I've boarded the main areas to make it usable for storage I have made no attempt to board it completely - so air can flow no problem at all.
Wondering whether you've done something to insulate the sloping sides of the roof?
PoP
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On Sat, 13 Sep 2003 22:15:07 +0100, PoP

That's OK.

I have the same thing. The sloping roof is felted and tiled similarly to the house although the roof pitch is a bit lower.
Celotex's usual suggestion for insulating this type of roof is to use two sets of sheet. One set is cut and placed between the rafters, while the other goes on top. I called their helpdesk and explained that I wanted to insulate the roof of a garage workshop. Their suggestion for this, to save some effort and cost, was to use a single sheet and fit that over the top of the rafters.
I chose to use 50mm material, which would have fitted between the 75x50 rafters and left an air gap behind, but it was simpler to fit it to the tops instead and loses very little space.
So the procedure was to fit vents into the soffits between each pair of rafters all the way along on both sides. The Celotex sheets were cut and fitted with long dry wall screws with large washers screwed gently into the rafters. The joints were then taped with foil tape.
The soffit vents allow ventilation to the space behind the Celotex.
The trussed roof timber frames provide "ceiling" joists. I boarded onto these over the entire area, but did not insulate. At one place, I fitted a loft hatch with ladder between two joists and this is used for regular access. Behind it (i.e. facing you at the top of the ladder), I created a removable panel of boards so that larger items like bicycles could go up there. There is a hoist arranged over this to help lift awkward items.
Then in the lower part below the boarded ceiling, the walls are insulated using 75x50 studding with 25mm air gap behind. This time, the Celotex is fitted between the studs and taped and ply is screwed to the front.
The doors are insulated as described before.
The effect is that the area below the ceiling can be kept quite warm if required. There is a deliberate heat loss into the space above which lifts the temperature slightly and keeps the area dry for storage.
I did consider doing the floor as well by making a platform. This would have had the advantage of having a space to run services as well, but I haven't implemented it and probably won't for a number of reasons.
- The (concrete) floor to joist height is only 2500mm or so. To make it interesting to run services, I would have wanted to run dust extraction ducting for woodworking machinery. Some of the ducts would need to be 125 and 150mm, thus taking away a lot of height. I've run electrical services using a combination of three compartment dado trunking and conduit on the walls and across the ceiling, so there was no reason to have electrical services under the floor.
- The floor had the lowest heat loss of all the surfaces, so there was no real need to insulate it.
- Adding the height would have made it difficult to take things in and out through the front doors.
Before insulation, I calculated that over 12kW would be required to achieve a reasonable temperature, which was crazy. Now, as I said, it's 4-5kW and that's when it's really cold. This is provided by a radiators run from the CH but on a separate circuit through a heat exchanger.
.andy
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wrote:

Thanks for the detailed explanation. I think maybe I'm going to be a bit cold in my garage this coming winter, but maybe next year.....
You've certainly gone to town on the insulation!
PoP
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On Sun, 14 Sep 2003 09:20:37 +0100, PoP

You're welcome.
I looked at the time I might spend in there - let's say 3 hours in an evening and 8 hours each day on Saturdays and Sundays - say 30 hours per week total.
Over the year (say 50 weeks) that's 1500 hours. Let's say without insulation, I needed to heat it to the tune of 8kW for 6 months of the year (12kW was the peak requirement when it was -1 outside)
That adds up to 750 x 8kW = 6000 kWh.
At 7p per kWh, that would be 420 per annum.
If I insulate and heat as I am doing with gas, I need an average of 2.5kW on the same basis as 2/3 of peak requirement for 6 months.
So we have 750 x 2.5 = 1875kWh
At 1.5p/kWh that comes to 28.
400 pays for a fair chunk of the Celotex to do the job.....
.andy
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wrote:

My goodness, you certainly carried out a cost-benefit analysis on this garage insulation. I have to congratulate you on the level of detail you've gone to!
PoP
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How do you maintain it at 21 degrees when it's 37 outside?
Plant a geranium next to it?
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Oh right. Yes, that would be a reason.

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