Insulation question

garlad

Hey,
Extension done on my house a while back for previous owner. Basically built 2 bedrooms over the garage. At the back, the room extends about 15 feet out the back, 5 feet wide (rest of room is over existing kitchen) and is held up by a pillar.
Hope that makes sense.
Basically a third of the back bedroom has nothing underneath it.
Now these 2 rooms used to get cold in the winter due to no insulation.
Got a job done on the walls last year, so they are now a fair bit warmer, but back room still cooler than front room.
I reckon the lack of anything underneath might be the main cause.
Is there anything I can do to insulate the underneath from the outside. Area is very sheltered, so I could screw/stick something onto the underneath if feasible.
Any advice greatly appreciated.
Gareth

10-10-20

I saw an overhanging office (supported by pillars) insulated with Kingspan Thermal-Pitch 10cm boards (expanded urethane between foil). This was retained with (mushroom?) plugs hammered up through the board.
You would maybe need to add a further sheet of thinner insulating board underneath this to prevent excess heat loss through the gaps, and then finish it with wooden lats or such.

I would have concerns about condensation, those boards need to be ventilated somewhat. I'll have a further look at what's done in other placed and see what I find.

GreeBo

Ive noticed in the car park in my office (basically the ground floor is the carpark, held up with pillars but no walls etc) the "ceiling" is basically that blown insulation stuff.
As you say its pretty sheltered so it seems to be ok.

that room will always be colder as its a) losing heat through the floor and b) not gaining heat through the floor like all the others...

garlad

Thanks for the info guys. Keep it coming

10-10-20

Here are two products which I found that will do the trick...
Sorry they are in French, but this is the best website for this stuff.

http://www.leroymerlin.fr/mpng2-front/pre?zone=zonecatalogue&backurl=%252Fmpng2-front%252Fpre%253Fzone%253Dzonecatalogue%2526ideilist%253D1188994469613%25261188994469613.pos%253D0%252601-comment-choisir-render%253Doff%252602-multicritere-render%253Doff%252603-zoom-produit-render%253Doff%2526eipublicationtype%253Dproduct%2526backurl%253Dpre%25253Fzone%25253Dzonerecherche%252526family%25253Disolation-murs%252526intuitiontodo%25253Dsearchproductsfamily%252526numberofitemperpage%25253D20%252526pageid%25253D71%252526presentationid%25253D2&idEIPub=1166000727
This is a semi-rigid batt available in 45mm, 75mm and 100mm.

http://www.leroymerlin.fr/mpng2-front/pre?zone=zonecatalogue&ideilist=1188993977204&1188993977204.pos=0&01-comment-choisir-render=off&02-multicritere-render=off&03-zoom-produit-render=off&eipublicationtype=product&backurl=pre%3Fzone%3Dzonerecherche%26family%3Disolation-combles%26intuitiontodo%3Dsearchproductsfamily%26numberofitemperpage%3D20%26pageid%3D71%26presentationid%3D2
This is a hemp batt with a single side foil faced.

You'll have to find out whether the insulation needs to be foil faced or whether that is that optional. Also, bear in mind that you may need ventilation...

Mellor

It is possible without venitlation.
What is the existing finish and structure?

It can be done like a warm roof (flat) construction.
Or a external insulation construction.
I would prefere a rigid board insulation, sealed membrane and suitable finish, mesh and render or torched on felt.

garlad

Thanks guys.
I'll try and put up a picture this weekend.
Basically the "ceiling" is plasterboard, then about 6-10" gap (filled with old attic type rolled fibreglass insulation), then the floorboards.
Ceiling is sheltered as the upstairs wall comes down about 18" further than the "ceiling" on the 2 external sides.