Insulation in 1970's Chalet-Style House

[JonThompson]

I live in a 1970's chalet style house. The two upstairs bedrooms are effectively a loft conversion. The soffits are open to the eaves and the floor void. I know the roof space needs ventilation, but this is really open. What can I do to insulate and stop draughts?

[stoneyboy]

Hi jonthompson
Insulating the room is easy, line all walls and ceiling with 100mm celotex, fit plasterboard on top and plaster.
The floor is more difficult because you will need access to the ground floor ceiling/first floor void and this you will need to seal at both ends. Use the celotex offcuts and use expanding foam to ensure an airtight fit.
Regards S

[JonThompson]

Thanks for your help. The ceiling, sloping bits and walls all have 100mm rigid insulation. It is the floor void I need to sort. So, I can seal them off, they don't need ventilation? And whether I can close off the eaves from the roof? The draughts are impressive. A few pictures to demonstrate. They're in reverse order but you get the idea.

[stoneyboy]

Hi JonThompson,
You must maintain ventilation of the area between the rafters i.e. below the sarking felt and above the plasterboard. You can seal the area between the dormer floor and the ceiling below it. The simplest way would be to seal the ends of this area working within the crawl space and pack loft insulation in the ends.
This is always a difficult one when done retrospectively but unless you do stop draughts you will have a cold floor in the dormer room and a cold ceilings in the rooms below.
Regards S

[JonThompson]

Hi, im going to see if I can drop the pvc soffit down to access the void from outside, might save my knuckles! Thanks for your help.