Church MVHR

[siwatkins]

Hi,

 

I live in a church conversion.  Two storey plus a basement level with level access (sloping site).  Approx 340sq m with highish ceilings.  fully internal wall insulated at conversion.
 

house has mvhr when we bought it 8 years ago.  Poorly installed using foil flexi.  Big unit - Kair Big Bertha in the attic. Fans died around the 5 year mark, and I sourced new ones from Papst.  But have yet to turn it back on.  Church is not airtight!

 

fast forward to now, and I’m refurbishing the basement storey (more a storey than a basement due to level access) - around 75sq m and forming a new toilet, and moving the utility to the one central, windowless room.  I’ve decided to deal with the new wet room extract requirements by splitting mvhr services into two due to the size of house.  Existing attic system, and new system in the basement level utility room. Basement level has two wet rooms, and 3 habitable spaces.  I can also feed to the giant dining room above which then equates to about a third to half of the house  habitable space dealt with by the new basement system.  I’ve sourced a Nuaire xboxab eco3 unit, and intend 75mm radial feeds and extracts to the basement level rooms.  That’s the rough plan, all diy by me.

 

my question:

 

necessarily the central location in the services room is 6m away from outside walls - same elevation for intake extract. Can achieve abou 2-3m between them.   I want to duct that to atmosphere and can route 150mm pipe for this input and output.  I don’t know what pipe to use - Round spiral steel, plastic pvc, or possibly rectangular.   Or even insulated flexi - but I’m not sure what to use.  Could also use semi rigid alu.  It’s tight but doable with any option.  Because it needs to be insulated and I’m trying to do this on a tight budget, what is recommended?  I know the flexi and semi rigid options for intake exhaust aren’t ideal but insulated mass volume pipe isn’t cheap!

The scope of this new mvhr unit, if I do the dining room, neatly segments the house, and means I can reduce the demand in the loft system and disuse some of the 100mm foil ducting to the furthest reaches.  As I refurb the rest of the house I can move to a radial system for the other half.  Though I may not need to given the reduced demands - it seemed to work ok before the fan burned out, even with the flexi duct.

 

i know mvhr works best in an airtight building which this isn’t though the basement level won’t be bad at all.  I’m really needing ventilation as the stained glass windows don’t open,  and there are just three DG sash window in basement level, thus any heat recovery is viewed as a bonus.   

sorry for length of text for context - main question really is about what 150mm insulated pipework to use?

 

cheers,

 

Simon
 

[MJNewton]

1 hour ago, siwatkins said:

Because it needs to be insulated and I’m trying to do this on a tight budget, what is recommended?  I know the flexi and semi rigid options for intake exhaust aren’t ideal but insulated mass volume pipe isn’t cheap!

 

[...]

 

sorry for length of text for context - main question really is about what 150mm insulated pipework to use?

 

Might the approach I took below be of any use? Cheap and cheerful, but I think it does the job?

 

Edited August 12, 2020 by MJNewton

[siwatkins]

That looks really neat - and a great solution.   I need to shop around, but I could do either plastic, or spiral steel using the same approach.  (The spiral steel seems really quite cheap, and aside from weight not a bad option).   I could use the sleeve approach you have with either that, or plastic.  I suppose the other option is to use rockwool foil faced wrap, but I suspect your approach might be cheaper (and easier!).

 

Is that silencer on the supply or extract plenum?  Any recommendations for that?   I have room for a silencer and understand they are highly recommended.   I could probably fit quite close - just above - the wall mounted MVHR in the utilities room, and saw there are some semi rigid options for this too, but if push came to shove, I could mount in the ceiling void as I will have enough room once I've dropped the ceiling for the 150mm pipe (and insulation!).   Also, you've used 125mm pipe - my MVHR has 150mm spigots, so I've assumed 150mm is best for my situation, but 125mm would help me by lowering the ceiling less (I'll be at 235cm finished ceiling height with 150mm).   Are your spigots 125mm or have you used reducers?

 

Cheers,

 

Simon

[PeterW]

3 minutes ago, siwatkins said:

The spiral steel seems really quite cheap, and aside from weight not a bad option

It is cheap for a reason ..!! It’s a pig to cut and fit and used on big commercial jobs where ease of access isn’t a concern as they can put it in when the shell is empty. 

[MJNewton]

6 minutes ago, siwatkins said:

Is that silencer on the supply or extract plenum?  Any recommendations for that?

 

It's on the supply side (only) and I'd read various manufacturers/retailers recommendations that this is all that's required. I don't think we get any fan-related noise in the extract vents, but I'm sure someone here did and found that they benefited from fitting one on the extract side also. I seem to recall they're not that expensive (mine's a Blauberg silencer) so you could be worth making provision for one in both if you've got the room?

 

Quote

Also, you've used 125mm pipe - my MVHR has 150mm spigots, so I've assumed 150mm is best for my situation, but 125mm would help me by lowering the ceiling less (I'll be at 235cm finished ceiling height with 150mm).   Are your spigots 125mm or have you used reducers?

 

125mm spigots here. I think I'd be worried about using reducers as presumably the size of a unit's spigots is a reflection of its size/throughput and therefore implied requirement of ducting?

Edited August 12, 2020 by MJNewton

[siwatkins]

1 hour ago, MJNewton said:

 

It's on the supply side (only) and I'd read various manufacturers/retailers recommendations that this is all that's required. I don't think we get any fan-related noise in the extract vents, but I'm sure someone here did and found that they benefited from fitting one on the extract side also. I seem to recall they're not that expensive (mine's a Blauberg silencer) so you could be worth making provision for one in both if you've got the room?

 

 

125mm spigots here. I think I'd be worried about using reducers as presumably the size of a unit's spigots is a reflection of its size/throughput and therefore implied requirement of ducting?

 ok, that's helpful thanks!  Yes, I'd concluded that reducing might not be the best idea!

[siwatkins]

1 hour ago, PeterW said:

It is cheap for a reason ..!! It’s a pig to cut and fit and used on big commercial jobs where ease of access isn’t a concern as they can put it in when the shell is empty. 

 

True - I have good access at the minute though - a clear run under my ceiling joists, with only a bend or two at each end needed.   I've got an angle grinder, so I figured it wouldn't be too prohibitive all else being equal.  So it's really about cost/performance differences in my case.  I get the sense that plastic is a whole lot more friendly though!

[JFDIY]

Have a look at the uubink foam ducting, about £10 a meter all ready insulated, easy to install as well.