How to insulate a Butterfly/London roof?

[mjsx]

What's the right way to insulate a Butterfly/London roof?

 

It looks like this on the outside:

 

 

And this on the inside:

 

 

There's two parts I'm especially wondering about:

 

1. The red bit toward the bottom of the "valley", where the roof and the ceiling comes to a point. There's obviously not enough height to put a great deal of insulation here. Also, completely filling this area would block airflow.

2. The green bit that's the main rafter, at the very lowest point of the roof (under the gutter). This is cold, solid, wood bridge.

 

I'm planning to board up the ceiling with insulated plasterboard so all areas have some (meagre) insulation. Is it worth filling the red area with insulation, or leave it unfilled, for better ventilation?

[Dave Jones]

i would fit an eaves ventilation tray first to keep good airflow then cram as much insulation as physically possible into the void.

 

https://www.roofingsuppliesuk.co.uk/collections/eaves-ventilation

 

[j_s]

Consider also adding insulated plasterboard after you have insulated between the timbers? 

[mjsx]

  On 09/02/2023 at 09:23, Dave Jones said:

i would fit an eaves ventilation tray first to keep good airflow then cram as much insulation as physically possible into the void.

 

https://www.roofingsuppliesuk.co.uk/collections/eaves-ventilation

 

Expand  

 

@Dave Jones Sorry, which tray did you mean? None of those seem suitable. I don't think there's any ventilation there.

[yellowchair]

Hi mjsx, 

I'm looking to DIY insulate a butterfly roof mid terrace in London. Did you just leave the bottom of the V without insulation? Did you add any ventilation? Thanks!