Insulating wooden frame

[dave_sch]

The Bottom and sides of my house are brick with cavity which is insulated. The top half, being dormer style is wooden construction. It seems beyond the plasterboard there is a 4inch or so gap then felt and tiles on the outside. I must be losing a huge amount of heat through this.

The obvious thing (to me at least) would be to put Celotex or similar sheets next on the outside of the plaster board between the joists, but it would mean that all the tiles and wood they are nailed on plus felt would have to come off. Given that it's all in small sections, it would be a hell of a job and the cost of paying someone to do it would likely take a long time to break even on what I save in heating cost.

So I'm wondering, seeing as I'm about to decorate the upper rooms whether there is the option to make some small holes at the top of the plasterboard and drop or blow in some insulation. My main concern though is that filling the void completely might lead to moisture problems. Could someone please comment on that ?

The things I'm thinking of are:
Cavity insulation ( is there a way of blowing it in DIY ? )
Loose lay rockwall insulation dropped through holes
Polystyrene beads, blown or dropped in
Polystyrene packing chips
Canned foam, though would probably be difficult to measure right.

What do people think of these ideas, or is there a better way ?

 

[Chukka63]

doing what youre suggesting is not really practical and risks creating condensation.

 

[dave_sch]

That's what worries me, hence why I asked the question.

What is the normal way to insulate in this situation ?

 

[geraldthehamster]

That's what worries me, hence why I asked the question.

What is the normal way to insulate in this situation ?

You'd have to do it from the inside, not the outside.

The way of least disruption would be to fix (glue or screw) insulation and new plasterboard over the existing, then skim. Either 50mm Kingspan, and board, or an insulation-backed plasterboard. That's below the current standard for this application but would make a noticeable difference without losing too much interior space.

Bear in mind that a vapour barrier must be involved - either in the form of foil backing to the Kingspan, or a separate plastic sheet on the warm side of the insulation. Otherwise moisture in the warmer air inside the room will condense as it moves to the cold side.

A more thorough, but also more disruptive way to do it, is to remove the existing plasterboard, then install Kingspan between the stud work, as well as over it, up to a depth of 5 inches (which is the current standard). Previous remarks about a vapour barrier apply. Then you'll be toasty warm.

Theoretically, if you interfere with the "thermal element" of a building, as you are here, it is notifiable to Building Control and must be done to the current standard. I suspect most people don't worry about it, though

Cheers
Richard