overboard with insulated plasterboard directly onto existing sloping ceiling?

[Tirglas_7]

is it possible to overboard using insulated plasterboard directly onto the ceiling of a dormer bedroom in the areas shown, then replaster on top of that?

looking at ways of improving the insulation up there as it is pretty cold.

 

[vinn]

Insulation keeps any warmth thats already present in the room - it doesn't make the room warmer, it retains the heat.

Given that you have a double dormer with presumably flat roofs - are the flat roofs warm or cold roofs?
And presumably much fenestration (windows) in both dormers then I would doubt that, without a careful site inspection much could be done to improve things.

But my experience in this kind of thing is limited, and perhaps others on here would think and suggest differently, & more helpfully?

 

[Tirglas_7]

The dormers are being converted to a warm roof design, with kingspan on the cheeks, front faces and the flat roof section.

All the windows does are being replaced with new upvc.

I want the rooms to retain heat better, will Overboarding in the areas shown improve the insulation?

 

[vinn]

As I mentioned above - a site inspection is the way to go.
And given the proposed work to come then carry out a proper survey at that time.

 

[Tirglas_7]

thanks for the reply.

sorry to keep asking what are probably stupid questions.

do you mean when the dormers are being converted, look at the current insulation in the areas i've shown in the pic? and then if there isn't deemed to be suitable insulation then it could be worth doing?

i realise the dormers will lose heat even when converted to the warm roof design etc, i'm just looking to improve where i can. If overboarding is used can it cause any issues with damp? or as it'd be installed over the top of the current plasterboard it isn't a problem?

 

[vinn]

I cant go any further in answering your questions.
Maybe overboarding will improve the insulation or maybe it will be worthless in the scheme of things - but, IMO, there's no particular reason why it would make things worse.

 

[Doggit]

Of course it's possible to increase the insulation to make the room warmer, but the problem you've got, is knowing where to fix it to. If you were starting the job from scratch, then you'd add 70mm of insulation between the rafters, and them overboard with insulated plasterboard to bring the insulation up to 135mm, but you'd know where the rafters were to fix the insulated plasterboard to.

So the question becomes, how much insulation was used in the first place, and can you find the rafters under the existing plasterboard.

 

[Tirglas_7]

i'm assuming the insulation is the same as in the eaves which is this polystyrene type sheet


so would it be best to just rip down the old plasterboard and start as if from scratch?

we have only just purchased the property and don't plan on moving again, i want to improve the insulation up there as much as i can now before we decorate and have new lighting installed etc. also energy prices are only going one way, so i hope anything spent now will eventually pay for itself.

 

[Doggit]

It's not clear from the picture, but some of it looks like celotex, and others like polystyrene, so they may have tried to improve things at some stage. I'd be inclined to suggest you rip things out, and start from scratch, as you could end up making things worse. You want an airgap going up and over the roof, so you wouldn't want the celotex up against the tiles. You'd insulate the dwarf walls, and leave a cold space behind them for airflow. You're not doing a loft conversion, so it doesn't need to be up to current spec, not under building control, but you could have quick chat with building control, and they'd tell you want they'd want, and then you can talk to the builders. You also need to make sure you have trickle vent in the new DG to stop moisture/mould problems in the room.

 

[Tirglas_7]

I'm thinking that is the way forward.

What is the DG?

 

[Doggit]

Upvc Double Glazing