Insulate all ducting in a warm roof?

[Happy Valley]

Got asked a question by the chap doing my SAP calculations:

 

Is all your ducting insulated?

 

Well that got me thinking as all the ducting to plenums (75mm plastic flexi pipe) is within the fabric of the house having a warm roof and the garage where the inlet and exhaust exit to. 

 

Is there any worthwhile advantage to this?

[JohnMo]

If the duct (75mm) is with the insulated envelope of the building, I see no advantage to them being insulated.  The extract duct work will have inside building temperature air within it, so no heat transfer in or out.  The supply ducts, will have cooler air within it (on a cold day) so there will be a heat transfer to the duct, which is a good thing as you are less likely to feel drafts.

 

Ducts (75mm) outside the insulated envelope of the building, needs to be insulated, mostly for condensation and or heat loss reasons, plus building regs require it.  

 

Large ducts to and from outside to MVHR unit, insulated, inside or outside insulated envelope of the building, mostly for condensation and or heat loss reasons, plus building regs.   

 

Large ducts MVHR to plenums treat same way as 75mm ducts.

[joe90]

I certainly have not and was not asked the question. The only ducts I insulated were the ones from the MVHR Unit to the outside, the incoming one developed condensation on it so wrapped it in rockwall. 

[Happy Valley]

Yes everything is within the insulated envelope of the building so just the inlet and exhaust from the outside to the unit to insulate. 

Edited April 11, 2022 by Happy Valley