Vaulted ceiling insulation

[Lee66]

My new extension(kitchen/diner/lounge all open), 10m x 5m with a 3mx2.4m Oak section on rear, will have a vaulted ceiling with a 45degree pitch. haven't got as far as building regs drawings yet but wondered what you would do for insulation if it was yours? ( I want to be one step ahead of architect and builder) 

[Cpd]

External insulation would be the best. 

[nod]

Most of the ones I do are 100 mill kingspan or similar between the rafters and insulated plasterboard below 38mil 

On our own home we intend to double up the insulation 

 

[SimonD]

37 minutes ago, Lee66 said:

My new extension(kitchen/diner/lounge all open), 10m x 5m with a 3mx2.4m Oak section on rear, will have a vaulted ceiling with a 45degree pitch. haven't got as far as building regs drawings yet but wondered what you would do for insulation if it was yours? ( I want to be one step ahead of architect and builder) 

 

Are you having visible oak beams in the ceiling?

[Lee66]

6 minutes ago, SimonD said:

 

Are you having visible oak beams in the ceiling?

yes, king trusses but below the finished ceiling hopefully as a feature rather than structurally supporting the roof 

[Lee66]

32 minutes ago, Cpd said:

External insulation would be the best. 

sorry, what do you mean by external insulation?

[Dudda]

External insulation is when the insulation is on the outside and it's plastered or rendered over. You mentioned architect. They'll be able to advise you best as you may have a very exposed site or be  in a conservation area or be looking for a specific finish externally or have some other requirement we're not aware of. I wouldn't go to the architect suggesting external insulation. See what he proposes first and then consider your options. Under no circumstances should a builder be making this decision. 

 

Are you doing any work to the existing house or what age or quality of insulation and airtightness does the existing house have? Not much point going overkill and having a super insulated passive house standard extension if all the heat is lost through the existing house.

[Lee66]

50 minutes ago, Dudda said:

External insulation is when the insulation is on the outside and it's plastered or rendered over. You mentioned architect. They'll be able to advise you best as you may have a very exposed site or be  in a conservation area or be looking for a specific finish externally or have some other requirement we're not aware of. I wouldn't go to the architect suggesting external insulation. See what he proposes first and then consider your options. Under no circumstances should a builder be making this decision. 

 

Are you doing any work to the existing house or what age or quality of insulation and airtightness does the existing house have? Not much point going overkill and having a super insulated passive house standard extension if all the heat is lost through the existing house.

Think cpd must have miss read my question or meant something else? I was referring to the vaulted ceiling rather than the walls. Existing is a 1960s bungalow with at present probably no insulation, certainly not in the floor or walls. We intend to re-roof this to match in with the new extension and sort loft insulation. hoping then to clad the outside with an oak feather edge board, firstly as the bricks are ugly and we need to brick up some window/door openings and secondly to help with heat loss through the walls. most floors are suspended except for current kitchen and bathroom which are solid, so unsure what we plan for with these yet

[Cpd]

Sorry i may be operating with a dull brain today..... 

I interpreted your question as - you have a nice 45 degree pitched roof with exposed oak rafters and you were wondering how best to insulate the roof..., 

my quick response was to go external insulation.... but what I should have said was - look at external insulation for the walls and link it into a warm roof design so that all your oak can be on display. Still not sure if I have got the wrong end of the stick.....

I think I just need to sleep.....
https://www.helifix.co.uk/blog/warm-roof

[Lee66]

11 hours ago, Cpd said:

Sorry i may be operating with a dull brain today..... 

I interpreted your question as - you have a nice 45 degree pitched roof with exposed oak rafters and you were wondering how best to insulate the roof..., 

my quick response was to go external insulation.... but what I should have said was - look at external insulation for the walls and link it into a warm roof design so that all your oak can be on display. Still not sure if I have got the wrong end of the stick.....

I think I just need to sleep.....
https://www.helifix.co.uk/blog/warm-roof

Thanks, not heard of this before, wasnt sure if there was some fancy insulated tile or something i had missed. I will certainly bare this in mind. Only just getting my head around the potential issues of vaulted ceilings with heat loss through timbers! Would never have thought of that in a million years.

[SimonD]

On 13/04/2021 at 11:37, Lee66 said:

yes, king trusses but below the finished ceiling hopefully as a feature rather than structurally supporting the roof 

If it's an oak frame, the trusses are highly likely to be structural. Essentially you'll have something like trusses, purlins above and then rafters. As @nod said, you'll likely go for insulation between the rafters. You can go for warm roof but with this roof buildup you could end up with a very thick roof structure which may be undesirable from an aesthetic point of view.

 

 

Here's an example pic randomly sourced from web:

[Lee66]

9 minutes ago, SimonD said:

If it's an oak frame, the trusses are highly likely to be structural. Essentially you'll have something like trusses, purlins above and then rafters. As @nod said, you'll likely go for insulation between the rafters. You can go for warm roof but with this roof buildup you could end up with a very thick roof structure which may be undesirable from an aesthetic point of view.

 

 

Here's an example pic randomly sourced from web:

the build isnt an oak frame, we are going brick and block but were putting the oak trusses in for appearance only. Obviously the architect and builder will decide how to accomplish this but we are hoping that the trusses dont actually touch the ceiling on the slope sides 

[nod]

I’ve just stated the boarding seven houses out and the warm roof comes as a cassette with roof lights in and all insulation already in the gables and roof all held in place with 9 mill OSB Its just a case of boarding with 15 mil fire board 

[SimonD]

45 minutes ago, Lee66 said:

the build isnt an oak frame, we are going brick and block but were putting the oak trusses in for appearance only. Obviously the architect and builder will decide how to accomplish this but we are hoping that the trusses dont actually touch the ceiling on the slope sides 

 

Confusion from use of terminology as I'd read " 10m x 5m with a 3mx2.4m Oak section on rear" in the OP while assuming trusses are normally load bearing. Never mind ?? Best thing to do then is speak to your architect before he does the details to understand what he's planning compared to what you desire. ?

Edited April 17, 2021 by SimonD

[GaryM]

It's not quite the same, the oak and steel is structural, but above is rafters with 150mm of insulation

 

 

 

[SimonD]

3 minutes ago, GaryM said:

It's not quite the same, the oak and steel is structural, but above is rafters with 150mm of insulation

 

 

 

 

Nice, I've always really liked oak trusses with those steel ties.

[Dave Jones]

need to make sure you leave 50mm gap from the top of the insulation to the underside of the breathable membrane under the tiles. Many make the mistake of pushing the insulation between the rafters as high as it will go which is wrong and can lead to issues.