DIY Doctor

Insulating Cold Garage to Keep House Warm

Postby SteveGibbs86 » Fri Nov 15, 2019 11:22 pm

Hi there

New to the forum and just after some input.

We moved into our house in 2014 which is a semi detached property built around the 1960's. When we moved in we changed the windows and doors as they were past it and very draughty. Our rear door was an internal door. We have also changed out some radiators to more modern ones and more appropriate sizes for the rooms they were in. This has greatly improved the warmth of the property, however it does still seem to cool down fairly quickly.

The property was extended by the previous owners back in the 80's I believe where a garage was added and then 2 bedrooms built above it. When in our kitchen which has 2 walls backing onto the garage, it can feel really cold in that area as well as the 2 bedrooms above it.

Ignoring the crappy floor plan I have done of the ground floor attached, my dad and I are thinking of building 2 stud walls on the garage side on the 2 walls that back onto the kitchen and insulating these as they appear to be single skin walls. The garage wall that backs onto the stairs is the old harled wall before the garage was added - we may stud this as well. There is plenty head space in there so we can also look at insulating the roof to try and help with the bedrooms above.

My questions are:

1. Is this a good idea first of all?
2. If going with sheet insulation ie. Kingspan, would the foil side face the house or into the garage?
3. I assume for fire safety, the stud walls would need to be plaster boarded rather than plywood?
4. Any other pointers or tips?

My dad is a civil engineer so I am sure he will do plenty of research himself before we start but would like to get an idea myself.

The back personnel garage door is an old internal door as well so this will be getting changed next year.

Most of the houses round about have just had external insulation done through council/government funding but we did not qualify due to our extension bumping us up a council tax bracket outwith the qualify range unfortunately.

Apologies for the essay and many thanks in advance for any pointers and tips mentioned.
Floorplan (Custom).PNG
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Simply Build It

Postby AlwaysLearning » Sun May 17, 2020 11:12 pm

Hmmmm doesn't Kingspan have foil on both sides?

Ok, if you are using single sided board ...the foil reduces heat loss through radiation, the glass fibre reduces heat loss through conduction. The foil side therefore goes where the temperature difference is greatest, that is it should face the brickwork so lost heat is reflected back into the bricks.

If you build a stud and fill the gaps, you can still sheet over with OSB then put foil faced plasterboard over. That gives you plenty of anchorage if you want to hang things from the garage walls.

Alternatively, fix thin battens to the brickwork then Kingspan to the entire surface so you eliminate the cold lines where the wood is.

Little voice in the back of my mind is muttering something about vapour barrier and leaving a gap between the garage floor and the bottom of the insulation.
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