You can certainly buy insulated garage door of the roller-shutter type. How draught-proof they are I don't know, although it should be possible to use brush-type draught-excluders all around, inside and out.
I've seen insulated bi-fold side-hinged doors on an integrated garage.
I've not seen a garage fitted with double-glazed patio doors but there's no reason why they couldn't be used by someone keen to show off their cars.
The former owner of our current house did exactly that. He was a sign-writer and "pub decorator" and simply replaced the garage door with uPVC patio doors with the extra glazed side panels. Quite bizarre as the garage was still just an external single skin garage with a flat felted roof. No insulation anywhere but a small radiator tapped off the C/H.
We added a new garage to the front and incorporated the old garage into the new front extension. Walls were internally insulated, insulation added on top of the slab, UFH pipes on top and screed on top of that.
It's now a nice warm gym. :)
Let's disregard the fact that it's a garage. Does anyone have any thoughts on if insulation is better above or below the slab with UFH in a screed. There is no question a screed can take the weight of a car so just thinking about energy use and energy loss in the slab.
Do you a) want a quicker response or b) do you want to be able to turn the heating off and for the building to stay warm longer ?.
If a) then put the insulation on top of the slab (but you might need to use ?blue extruded polystyrene used for insulating cold stores) and/or use a stronger type of screed . Do not use cheapo white expanded polystyrene, even if you put a secondary DPM on top of the insulation. It doesn't have the strength and if any moisture gets into it, it loses all its insulative properties and also tends to disintegrate
If b) then put the insulation below the slab, this time you won't need (probably *) the high-compresive-strength extruded poly but just use normal 'celotex' or pink extruded poly. If you use the white
*expanded* poly to 'save' money then the main DPM must go below the insulation and you absolutely *must* have a second DPM on top of the insulation before you pour the slab otherwise water and cement fines will migrate inside all the voids in the poly and render it ineffective.Also with b) there is some argument over whther the DPM goes below the celotex or above it. Since it is 'closed' cell, water theoretically cannot migrate into it. It really depends on what sort of soil you are on and where the water table is during the winter.
(*) Depends on the weight of the vehicles that will be parked here. You need to think about the point loading, including the use of car jacks.
Just had to go and check. The original garage walls had 2 additional block courses added which gave lots more headroom. There used to be 3 steps down from the from the internal floor to the garage floor, now there's just the one with 255cm from new floor to new ceiling.
Having added UFH to the old garage i.e. insulation on slab and the 2 new rooms i.e. slab on insulation I wasn't so happy about not being able to get a greater thermal separation between screed and slab on the latter as all levels were built not accounting for additional insulation but with UFH pipes running in egg-crate and a 7mm multifoil under the egg-crate it seems to provide enough separation and I would have to say there's not much to compare between the 2 from a users perspective.
Given the choice I'd have insulation on slab every time just because it makes far more sense to keep hot things only radiating into the room where the heat SHOULD be.
Bizzarely, being built on a hill and "upside-down" the UFH I put in the original 5 rooms of the house (16-ish years ago) are individual room manifolds and 10mm fast-flow on cellotex betweeen the joists with chipboard and engineered wood on top. These rooms take far longer to warm up than the new rooms and cool down quicker so by far the worst performing but the old house is early 70's with big windows and wood isn't the best medium for heat transfer so nothing is really comparible even when all circuits and installation methods are are next to one another.
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