Best solution for insulating attic space

[djcdan]

Our attic space is currently planned to be uninsulated. However, we will be installing our MVHR unit in to attic and the plan was to wrap the necessary ducting/pipework in insulation. The other option would be to insulate the entire attic space instead. If we were to do that, as well as no longer needing to wrap pipes in insulation, I would have thought it would have wider benefits to the properties overall heat loss. For clarity, the attic floor (upstairs ceiling) will already be insulated and am referring to the apex of the roof between the trusses.

 

What would others recommend and if you'd insulate the apex what type of insulation would be suitable? The simple option would seem to be insulation board. Would CWB do the job? This seems to be more competitively priced compared to general PIR boards.

[tonyshouse]

No, increasing the heated volume will increase heat losses, increase heating bills 

 

plus it is bound to introduce air leakages. 

[joe90]

1 hour ago, tonyshouse said:

plus it is bound to introduce air leakages. 

not sure I would agree with that. I have a warm loft, wanted a large storage area with MVHR in it as well. The roof is built with 400mm I beams, filled with rockwall and inside glue bonded OSB sheeting. The air test found virtually no air leaks from the loft hatch (indicating loft was well sealed.). It’s all about the detail, I am a fussy bugger and bubble glued and foamed every join. 
 

if you don’t want to go to that trouble you could always create a large box over the loft hatch, MVHR, and insulate and seal that with the insulation at bedroom ceiling height.

[Oz07]

You'd probably want warm roof if going down this route. Which is not something to change on the hip it will have knock on effects with detailing and sizes

[tonyshouse]

On the hop?
 

[Oz07]

Yes bloody auto correct