mvhr MVHR Efficiency

[sonicboom]

3 hours ago, MikeGrahamT21 said:

went up after work and decided to tackle it whilst it’s still cold out, doing work under the eaves is no fun at the best of times!

 

found quite a few bits which I’ve now corrected, where the ceiling joists end was warmer than I’d expected it being, so the wool is clearly doing it’s job, was just too patchy in places, fingers crossed it’ll do the trick anyway. Managed to cut out some excess pipe too from the supply runs, around 3m in total which should help also

Its probably useful to understand the purpose of the different types of insulation. Wool type insulations do not stop airflow, they slow it down. This allows for the trapped air to heat up but also for moisture to escape. Its primary use case is in attics because you want moisture that has seeped through to escape otherwise you risk mould growth.

 

Foam type insulations stop airflow completely and convective heat loss is substantially reduced i.e. > 95%, and the primary focus is on conduction/radiation. Pipework should be using some type of foam insulation for this reason. Wool type insulation will help but you are losing heat through conduction, radiation and convection. You just won't get the numbers you want.

 

[MikeGrahamT21]

9 hours ago, sonicboom said:

Its probably useful to understand the purpose of the different types of insulation. Wool type insulations do not stop airflow, they slow it down. This allows for the trapped air to heat up but also for moisture to escape. Its primary use case is in attics because you want moisture that has seeped through to escape otherwise you risk mould growth.

 

Foam type insulations stop airflow completely and convective heat loss is substantially reduced i.e. > 95%, and the primary focus is on conduction/radiation. Pipework should be using some type of foam insulation for this reason. Wool type insulation will help but you are losing heat through conduction, radiation and convection. You just won't get the numbers you want.

 

I know foam insulation is the gold standard for this type application.

 

had a quick look online and can see climaflex 76mm bore for not much money, but only seems to be 9mm thickness, probably wouldn’t make a worthwhile difference for the immense amount of effort I’d need to put in to install it.

 

hopefully my efforts yesterday which I’m paying for today will work some, there’s no gale force winds up there

[Marvin]

On 29/11/2024 at 10:18, G and J said:

Good grief there’s a warning for me.  I’ll be running ducts in the loft and had intended to run on top of the first level of fluffy stuff, underneath a couple more.  Ok your 100mm of PIR is more insulative than our 100mm of fluff (technical term!) but still, methinks I need to rethinks….

My humble opinion is that you insulate the ..... out of any of the system which is outside the building thermal envelope. I have 400mm of fluffy over the MVHR box and about the same over the ducts...

 

Good luck M

 

[JohnMo]

Nice discussion but isn't duct supposed have a vapour barrier also? So any type of insulation is fine. Stuff like Climaflex is closed cell so additional vapour barriers are not needed.

[G and J]

1 hour ago, Marvin said:

My humble opinion is that you insulate the ..... out of any of the system which is outside the building thermal envelope. I have 400mm of fluffy over the MVHR box and about the same over the ducts...

 

Good luck M

 

If you are M is JohnMo really Q?

[G and J]

1 hour ago, JohnMo said:

Nice discussion but isn't duct supposed have a vapour barrier also? So any type of insulation is fine. Stuff like Climaflex is closed cell so additional vapour barriers are not needed.

Hmmmm. I’ll have a vcl directly below my bottom level of fluffy but I’m now thinking condensation risk when on summer bypass….

 

Goodness it boils the brain!

[JohnMo]

1 hour ago, G and J said:

when on summer bypass….

Think I would be more concerned about winter, than summer. If summer bypass is on its likely your loft would be unbearably hot. Any condensation would vapourise.

[G and J]

1 hour ago, JohnMo said:

Think I would be more concerned about winter, than summer. If summer bypass is on its likely your loft would be unbearably hot. Any condensation would vapourise.

And in winter the ducts will be warmer than the loft in our cold loft…..  ok, condensation panic over.

[sonicboom]

9 hours ago, MikeGrahamT21 said:

I know foam insulation is the gold standard for this type application.

 

had a quick look online and can see climaflex 76mm bore for not much money, but only seems to be 9mm thickness, probably wouldn’t make a worthwhile difference for the immense amount of effort I’d need to put in to install it.

 

hopefully my efforts yesterday which I’m paying for today will work some, there’s no gale force winds up there

I use https://www.ebay.co.uk/itm/335374071609

 

[Fiona Brick]

On 29/11/2024 at 09:38, MikeGrahamT21 said:

its 75mm semi rigid stuff, currently buried under around 300mm of wool insulation, but the loft is cold, very cold, almost no heat from the bungalow gets up there as under the 300mm wool, there is 100mm PUR insulation board. The manifold boxes (made from metal) are also up in loft, again buried under a lot of insulation. Theres definitely improvements to be had, and those figures were at -3C outside, so loft will also have been near this. I agree though, it is a lot of heat loss, and i hope to improve on this.

Hey, what changes did you make? We also have some of our duct work running through a cold attic space and we are experiencing really big temperature losses at the supply air points serviced by this duct work. 

[MikeGrahamT21]

14 minutes ago, Fiona Brick said:

Hey, what changes did you make? We also have some of our duct work running through a cold attic space and we are experiencing really big temperature losses at the supply air points serviced by this duct work. 

 

I managed to reduce some of the pipe length in some cases, some of my routes weren't optimal it turns out, the 125mm pipe from the plenum to the ceiling was also too long in some cases, meaning that the plenum sat raised in the loft space, causing the insulation to sit poorly. I went up with the thermal camera on a cold day and found some areas where the insulation wasn't well placed around the pipes too, ended up buying some more and topping up around those areas, was definitely an improvement but i didn't get any figures

[Fiona Brick]

Thanks for that. We're just at the point of going back over the pipes and doing further insulation. Thinking of overing with wool insulation and boxing them in with PIR. We have another section of the house where ducting is within thermal envelope and no issues with that vent air temp. 

[Mike]

11 hours ago, Fiona Brick said:

Thinking of overing with wool insulation

Anything except wool, unless the new Ionic Protect treatment is as good as it claims.

[MikeGrahamT21]

12 hours ago, Fiona Brick said:

Thanks for that. We're just at the point of going back over the pipes and doing further insulation. Thinking of overing with wool insulation and boxing them in with PIR. We have another section of the house where ducting is within thermal envelope and no issues with that vent air temp. 

yeah the lofts are definitely a challenging for pipework, you can only do what you can. If you are able to box in using PIR that would all help.

 

how near are the pipes to your ceiling to work as a heat source? I’ve got 100mm Phenolic between the joists before the pipes so don’t get much heat input, although it’s scary how much gets through the timbers