Insulating MVHR Unit Ducting

[MJNewton]

Given the need to to insulate the ducting going to/from the MVHR unit (which, in my case, is installed in an unheated loft space which is a bit cramped given it's what's left of the roof space in our 2.5 storey house) I was wondering how best (read: easiest!) to do this.

 

Here's my unit which as you can see I went with rigid smooth-wall piping for the unit-to-manifolds where possible and aluminium semi-rigid ducting for the final connections so as not to transmit vibration-induced noise (the whole unit is sat on a frame sitting on rubber exhaust mounts so is fairly free-floating):

 

 

I did consider flexible insulated ducting for these final connections but didn't fancy wrestling with it to ensure it was taught enough to avoid flow restrictions. The idea did however occur to me though that it would make an ideal outer insulation layer for my ducting and as I hadn't heard of others doing so (maybe for good reason!) I thought I'd share what I did...

 

My ducting is 125mm and so to ease fitting of the insulated ducting - particularly round bends - I bought the next size up (150mm) and taped the ends to keep things clean and easy to handle (the inner core, vapour barrier, insulation and outer layer are all separate and can move around a bit when manhandled):

 

 

After stretching out the insulated ducting and cutting to length I then compressed it back over a section of rigid ducting:

 

 

I then refitted the ducting, taped up the inner ducting joints...

 

 

...and expanded the insulation round giving what I thought was quite a neat final installation with no joins:

 

 

Not only was it easy to fit but with the ends taped it provides what I assume to be a decent vapour proof insulation layer, which I believe is important. I also went for the acoustic insulation option (it has small holes in the inner core to allow sound through to be absorbed by the insulation layer) although this was more down to 'why not?' than any particular need as the unit is fairly quiet in operation.

 

As I said, just though I'd share this in case the method is of use to anyone else.

Edited April 11, 2020 by MJNewton

[ProDave]

Just a thought.

 

You are going to want regular access to that, in what looks like an awkward loft space that is going to be insulated.

 

I would suggest you make a raised walkway above the height of the insulation to make easy access to it.

 

This is how I did it in our previous house

 

 

 

[MJNewton]

Great minds think alike! That's exactly what I was thinking of doing as whilst I've become quite adept - cat-like in fact - navigating the trusses I am sure it's only a matter of time before I fall through, and no doubt right above the stairwell too!

 

The horizontal joists like you've fitted were what I had in mind, and I've got loads of 11mm OSB sheet offcuts which I figured I could double up on? Need to experiment with how strong a base that provides.

Edited April 11, 2020 by MJNewton

[ProDave]

Those are just 2" by 1" battens fixed accross the trusses and 22mm chipboard floor panels.  Just use whatever you have.

[Savage87]

This is what I've done in my loft, It's still work in progress..

[Savage87]

And this is how I insulated the 5inch ducts.

[MJNewton]

Good job!