Floor Insulation

[diynoob]

Hi. I'd like to insulate a first floor suspended timber floor. The space below is unheated and very cold. The floor is 20cm deep.

I have enough 5cm thick celotex to do 2 layers and also a load of spare loft insulation. Any tips on how best to utilise it, eg sandwich loft insulation between the celotex? Or lay the loft insulation with 2 layers of celotex on top? Or forget the loft insulation and buy more celotex to fill the void completely?

 

[cjard]

What is the heat source for the room above the floor?

 

[^woody^]

Put the foil faced insulation closest to the room you want to insulate.

 

[Blagard]

I agree with Woody - with the foil face nearest the room it serves in part as a vapour barrier, and will reduce the amount of water vapour that can pass through your insulation towards the colder space below. Whilst it probably won't matter in practice for your situation, it is none the less the right way to build so you would be wise to do it that way.

You may find it practical to sandwich the loft insulation, always providing the top layer of celotex has its foil facing nearest the room,

Edit:
Do not overlook electric cabling. If you start to bury it in insulation you will alter the circuit design. While probably not a problem in most domestic situations I would be very careful not to bury high load cables like cooker or shower supplies. Try to leave them as you find them.

 

[diynoob]

The room has central heating and also a wood burning stove. Only one or the other is ever on, usually the central heating.

Thanks for the tips, I will put the celotex as the top layer.

There is only electric cabling at one end of the floor so I can easily avoid insulating it.