Green Building Forum - Insulate MVHR metal intake/exhaust with sheep's wool

Insulate MVHR metal intake/exhaust with sheep's wool

Jeremy S — Thu, 16 Dec 2021 19:26:37 +0000

Hi,
Regarding the intake and exhaust 150mm galvanised spiral metal duct for MVHR:

I understand that the metal duct is usually insulated with foil-faced mineral wool.
And, in the light of GreenPaddy's comment in Is loft insulation sufficient to insulate MVHR ducting? , I know to provide a vapour-barrier.

... these do need a vapour IMpermeable (polythene) wrap around them whilst 
 inside the thermal envelope, as regular glasswool will allow moisture through, 
to condense on the duct surface in winter.

So, is there any reason not to use sheep's wool insulation rather than mineral wool?

Also, taking account of GreenPaddy's follow-up comment

 ... they should have the same Uvalue of insulation around them again as per your house external envelope

does the exhaust need to be as heavily insulated as the intake?

Insulate MVHR metal intake/exhaust with sheep's wool

djh — Thu, 16 Dec 2021 19:48:49 +0000

Posted By: Jeremy Sis there any reason not to use sheep's wool insulation rather than mineral wool?

Not as long as you're happy with sheeps wool in general, AFAIK. edit: the mineral wool products come pre-prepared for such use, so they're a bit easier.

Posted By: Jeremy Sdoes the exhaust need to be as heavily insulated as the intake?

Yes, they should both be at approximately the same temperature if the MVHR is working. i.e. outdoor temperature.

Insulate MVHR metal intake/exhaust with sheep's wool

Jeremy S — Thu, 16 Dec 2021 19:59:10 +0000

Thanks djh

We have some leftover sheep's wool, and some leftover vapour barrier, so this seems like a good use for them.