Velux in vaulted ceiling

[Paul84]

Hi all,

I've read a few posts on the vaulted ceiling insulation, notably a one on the first page about large vaulted ceiling. 

It got me thinking about the best methods for my roof as looking at the drawing it looks minimal for insulation. 

It's a 4m x 8m room with 4.5m bi-folds on the outside wall and 4 standard veluxs in the ceiling. 

It's going to be the main area of the house and I'm now thinking I need to pay more attention to roof structure. The rafters are actually 50 x 200 with 400cc and I'm putting double Romans on the outside.

What's your thoughts people. 

[PeterW]

Insulation is fine as it has 40mm kooltherm backing on the plasterboard under the rafters. You could increase the TP10 to 150mm and reduce the insulated plasterboard to 20mm to reduce the cold bridging but it’s fine as it is. 

[ProDave]

Alternatively make it a warm roof. Put insulation above the rafters rather than under them, then you can full fill the gap between rafters without needing a ventilation space.

[Dudda]

Have you a vapour control layer or airtight layer planned?

[PeterW]

48 minutes ago, ProDave said:

Alternatively make it a warm roof. Put insulation above the rafters rather than under them, then you can full fill the gap between rafters without needing a ventilation space.

Doubt that will fit - look how close it comes under the first floor windows

[ProDave]

35 minutes ago, PeterW said:

Doubt that will fit - look how close it comes under the first floor windows

You just set the rafters 100mm lower at both ends so they are position for insulation above them rather than below them.  The net effect is the same with finished roof surface in the same place.

 

Assuming it has not been built yet.......

[Paul84]

It's not built ProDave, the pitch is already struggling without lowering the rafters. I've got Redland tiles which can go to 17degrees. 

 

Don't know what you mean by vapour or airtight layer, the roof will have the membrane fitted obviously, I was wanting to put a service layer in to fit the led downlights if that's what you mean. 

[Dudda]

13 minutes ago, Paul84 said:

Don't know what you mean by vapour or airtight layer, the roof will have the membrane fitted obviously, I was wanting to put a service layer in to fit the led downlights if that's what you mean. 

Yes. You have tiles and timber battens, roof membrane then timber and insulation then Vapour / Airtight layer then timber battens to create service void and then the plasterboard. I'm wondering where you're putting the vapour control layer if you don't have the service void.

[ProDave]

1 hour ago, Paul84 said:

It's not built ProDave, the pitch is already struggling without lowering the rafters. I've got Redland tiles which can go to 17degrees. 

 

Don't know what you mean by vapour or airtight layer, the roof will have the membrane fitted obviously, I was wanting to put a service layer in to fit the led downlights if that's what you mean. 

I am not suggesting changing the pitch.  Lower BOTH ends of the rafters 100mm so the pitch is the same, then you can put 100mm insulation above the rafters and full fill the gap between them, finished tile level exactly the same. and inside plasterboard straight onto rafters, no insulation under them.

 

This gets you more insulation into the same space, easier to detail and harder to get wrong, and no need for ventilating anything but the space between the external insulation and the tiles.

[Carrerahill]

6 hours ago, Paul84 said:

Hi all,

I've read a few posts on the vaulted ceiling insulation, notably a one on the first page about large vaulted ceiling. 

It got me thinking about the best methods for my roof as looking at the drawing it looks minimal for insulation. 

It's a 4m x 8m room with 4.5m bi-folds on the outside wall and 4 standard veluxs in the ceiling. 

It's going to be the main area of the house and I'm now thinking I need to pay more attention to roof structure. The rafters are actually 50 x 200 with 400cc and I'm putting double Romans on the outside.

What's your thoughts people. 

Make consideration for lighting, we have a very similar roof makeup but I opted to use indirect light sources for all our lighting - our whole kitchen is lit from light sources on top of cabinets up-lighting the ceiling which in turn reflects down giving a good quality of light which is nearly impossible to create shadows in and creates a very clean look. So the ceiling is totally bare which is what we wanted. 

 

If you use the above makeup then start trying to punch downlights into it just forget it and think about a battened out service void and second sheet of PB or something which also then gives it some fire rating.

 

 

[wozza]

We have 150mm rafters with 100mm PIR between and 75mm PIR below. We then have a 75mm service void for lighting etc.

 

We have Redland Regent tiles so not too dissimilar to your Double Romans. We used a lot of half tiles between the Velux to get the tiles to finish better so a full or fullish tile is adjacent to the window rather than a small strip of tile.