So our house is built on a hill so the garage is underneath the kitchen.  The garage has an up-and-over door with minimal insulation and a concrete ceiling which is also the floor of the kitchen above.  Which means when it’s cold outside the garage is cold so the kitchen floor is cold.

I’ve installed fairly pathetic brushes along the edges of the door which has helped reduce the breeze but it’s still damn chilly.  I can think of two options:

1) replace door with something which fits tightly and is insulated.  An insulated roller door?

2) Insulate the ceiling of the garage. There are concrete “joists” so filling in between those with an insulating tiles seems like it shouldn’t be too difficult.

Any opinions?

Do you want it to be warm in the garage, or warm In the house.

that tells you where to put the insulation.

Insulate the existing door with Kingspan-type boards?? You can get damaged boards from various places

A wooden floor can be affected by condensation if done badly, I don’t know whether insulating a concrete floor carries the same risks, or if dry rot could start here

You need to insulate all of the concrete under the kitchen, not just the gaps with some celotex insulation or similar, 100mm boards should do it. Thats the modern standard for loft conversions so should be similar for what you want.

Also try and seal up as much as possible round the door. Fit a roller shutter door with side brushes and a rubber bottom seal instead of an up and over maybe.

As well as insulating the ceiling, if I had the money I’d fit a sectional garage door like a Hormann.  They are insulated, and available in different thicknesses.  They are great, and you can seal them up pretty well.  An uninulsated thin metal garage door is just a big heatsink.

Yeah I guess 3) both is the best solution but I was trying to find fixes that didn’t involve *too* much money.

Not sure I want 100mm reduced off the height of the garage to be honest, it’s low enough as it is…  Maybe 100mm in the gaps and then 50mm on top?

50mm of Celotex would.still be a huge improvement. On a solid wall 50 or 60mm reduces heat loss by around 85%.

Don’t think interstitial condensation would be a risk here either as any vapour would condense in the garage.

Insulated my external garage wall with 25mm celotex (limited clearance at side of sectional door) and the boarded over. It has made a noticeable difference. As did the 40mm insulated sectional door with decent seals to reduce draughts.

Slight thread hijack but where abouts did you get your sectional door from? Did you fit yourself?

Not sure I want 100mm reduced off the height of the garage to be honest, it’s low enough as it is…  Maybe 100mm in the gaps and then 50mm on top?

I’ve got a good friend lives outside Calgary where its often -“a lot”

He has a huge metal framed workshop and its insulated with 120mm (available in Canada not here easily)

He reckons he keeps the whole place above freezing with a single oil filled radiator on a thermostat.

50mm is huge … 25mm will be WAY better ….

Its obviously better to insulate the joists as well but even if you don’t it will still be way better.

You could easily get away just using 25mm on the joists and fill the gap…

Real Kingspan is fantastic… but Wickes do some way way cheaper foam insulation .. you can always back this with a roll of the radiator stuff for places like the garage.  Kingspan is better for the same thickness but if you are doing the jots you could probably just do the joists with Kingspan and fill the between with cheaper.

I had my sectional door fitted by a local (Bristol) firm. It’s a Novoferm door, they are made in Germany.

Slight thread hijack but where abouts did you get your sectional door from? Did you fit yourself?

Got mine from a garage door shop in Cardiff, fitted it myself. Was pretty easy, took me a relaxed day to rip out the old one and fit new, with a helper. Cost something like £500 for the door and £300 for the opener IIRC.

Mentioned up there about risks of insulating with king span, I’m looking at insulating a wooden floor and brick internal cavity walls.  Is there a good site for advice to make sure I do it right?

DT78: Cavity walls are pretty easy. The recommendation is just to put a vapour barrier on the warm side. Often foil backing on the likes of Kingspan would be sufficient but you can always tape the joints.

Wooden floors are more complicated if they are over a vented cavity.

Look on the self build and eco forums for good advice.