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Mvhr Installation


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14 replies to this topic

#1 JanetE

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Posted 26 April 2016 - 09:02 AM

We are installing our pipework at the moment, bit of a learning curve but it's going OK. Our installation guide advises that the plenums not be mounted to the floor above and I was wondering what everyone else has done. We are mounting ours on a solid piece of wood (the remains of the internal partitioning from the MBC install) and screwing this direct to the ceiling. What's the verdict??

#2 Calvinmiddle

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Posted 26 April 2016 - 10:22 AM

I put some bits of wood between the I beams and screwed the plenums to this. I had 100mm of service cavity below the airtight membrane to do this and so I could fit recessed spotlights.

The plasterboard was then screwed to the roof and the long parts of the plenum had holes cut round them. They were left long (and sealed off) until all the decorating was done and I then trimmed them back with a Dremel like tool and fitted the vents.

I got some nicer looking ones from BPC that are meant to be acoustical - but I got them for the look

http://www.bpc-direc...eq=133|9041168|

as opposed to any of the others

http://www.bpc-direc...?cgi_req=102|90

#3 jsharris

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Posted 26 April 2016 - 04:37 PM

I fitted one of ours to the top surface of the first floor, screwed to the floor boards, as it's in the eaves and out of sight, but can be accessed. I wonder what the reason is for stipulating that it not be fixed to a floor? There's no vibration or noise from the manifolds that I've ever noticed, and if there was I'd have heard it, as we also have a manifold fitted vertically to a wall in the services room, right at ear level.

Edited by jsharris, 26 April 2016 - 04:37 PM.


#4 notnickclegg

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Posted 26 April 2016 - 04:48 PM

Presumably if the floor flexes, there'll be movement of the outlet below, possibly causing cracks in the ceiling? Might be an issue with "bendy" floors.

Jack

#5 JanetE

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Posted 27 April 2016 - 07:35 AM

Thanks for this, I think we'll just carry on doing it the same way. I was also wondering what acoustic insulation everyone uses between the floors. We are insulating above the MVHR pipes where we have more than two running through the space between the joists (just using a bit of ordinary roof insulation at the moment which we had spare). Trying to get the insulation in after the pipes are in place would be too difficult. It's also pretty tricky trying to keep the stuff up, I would be interested to know how you lot have tackled this. :rolleyes:

#6 jsharris

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Posted 27 April 2016 - 08:13 AM

I put all the pipes in, then fitted dense 200mm thick rockwool between the joists. Our Posijoists are on 400mm centre and the 370mm wide dense rockwool was tight enough fit to be self0supporting. I stuffed it around the ducts as best I could, and it seems to have done a good enough job.

It was an absolutely horrible job, though. I wore a hooded tyvek suit, with tape around the ankles and taped on gloves, but I still found myself itching for hours afterwards!

#7 TerryE

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Posted 27 April 2016 - 08:54 AM

Our old farmhouse has elm floorboards on oak joists. It used to have directly attached with plaster and lath, which we replaced with plasterboard on 22mm spacer battens. OK the floor is pretty acoustically transparent, but this has never been a real issue in the 30+ years that we've lived here.

My personal view if that acoustic insulation in party walls and floors is important, but when it comes to internal walls then it's not worth going to overboard and minimum compliance to BRegs is the only constraint. We were planning to use a 100mm rockwool in the internal walls and directly under the floor boards between the joists.

I am interested in understanding why you decided to go to 200mm and what the pros of putting the insulation above the plasterboard, rather than under the flooring are.

Edited by TerryE, 27 April 2016 - 08:55 AM.


#8 TerryE

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Posted 27 April 2016 - 09:56 AM

To answer my own Q, the relevant section of BRegs (for our build) seems to be Part E section 5.18 Internal wall type B: an absorbent layer of unfaced mineral wool batts or quilt (minimum thickness 25mm, minimum density 10kg/m3) which may be wire reinforced, suspended in the cavity, and 5.23 Internal floor type C: an absorbent layer of mineral wool (minimum thickness 100mm, minimum density 10kg/m3) laid in the cavity. Though the wording doesn't specify where in the cavity this should be laid, the attached diagram 5.7 shows this directly above the plasterboard.

The Wickes 30mm (Rockwool) Acoustic Insulation Slab works out at £15.50/m² -- Ouch! Some of the glass fibre options are a lot cheaper (just over £2/m² for 50mm and under £4 for 100mm) but you have to handle glass fibre. Any suggestions appreciated.

Edited by TerryE, 27 April 2016 - 10:47 AM.


#9 jsharris

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Posted 27 April 2016 - 11:06 AM

You can increase the density of the mineral wool by compressing it, which means you can buy thicker and cheaper "loft roll" and then squeeze it into a narrower cavity to increase the density and it'e effectiveness as acoustic insulation. I did this with some of the internal walls, which had a nominal gap of 89mm between the plasterboard faces. There was an offer on 170mm thick knauf loft roll, and I just compressed it into the 89mm gap. I ended up with a much denser filling for less than the cost of the proper dense stuff.

#10 Alphonsox

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Posted 27 April 2016 - 11:43 AM

SWMBO is in the process of fitting 50mm Rockwool flexi-slabs into every internal wall in the place and 150mm Earthwool Omni roll into the ceilings.We were advised to leave an air gap and not to full fill. The Wickes price is crazy - We bought in bulk from the local builder merchant. A quick online check gives you around £3/m2
http://www.insulatio...mm-x-400mm.html

Edited by Alphonsox, 27 April 2016 - 11:43 AM.


#11 declan52

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Posted 27 April 2016 - 04:23 PM

She's going to love you for leaving her that Glamorous job to do.

#12 Alphonsox

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Posted 27 April 2016 - 04:42 PM

I've told her that what we save on labour she can spend on the new kitchen - strangely she believed me.

#13 JanetE

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Posted 30 April 2016 - 06:30 PM

Just for anyone interested, here is how we have configured our manifolds, and a picture of "Clapham Junction" from below. The MVHR will be in the services room to the left and this will all be boxed in. (There's a small sink and microwave going in here at the top of the landing. Our son's room is to the right, and this means that he doesn't need to carry coffee, etc. up two flights of stairs.)

Attached File  IMG_20160430_155814857.jpg   35.75K   19 downloadsAttached File  IMG_20160430_170509095.jpg   26.44K   19 downloads

#14 Woodgnome

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Posted 30 April 2016 - 07:40 PM

Is the manifold in your airtight side of the build?

#15 JanetE

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Posted 30 April 2016 - 09:25 PM

View PostWoodgnome, on 30 April 2016 - 07:40 PM, said:

Is the manifold in your airtight side of the build?

Yes it's on the top floor.