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I arrived here on a bit on a tangent. I had considered installing sun pipes with built in extractor fans in our ensuites, although I'm not entirely sold on the sun pipe idea in general. An alternative could be MVHR.

 

The property is 1850s built, solid wall and no wall insulation, the floor is a new slab with 100mm PIR insulation (and UFH throughout downstairs, radiators upstairs). We're currently working through an extension design which will more than likely be 150mm cavity wall (EPS bead) and 200m EPS under slab, at which point all existing (1980s) upvc windows and doors will be replaced too.

 

Once done, we plan to do an air tightness test, I'm not expecting miracles, but the original part of the building is wet plastered and the skirts have been sealed top/bottom when they were fitted last year, so I think we can get something "OK".

Do you think we'd be suitable for an MVHR system as part of the extension? We could possibly install it to the existing upstairs room too, but it would predominantly supply the extension.

 

 

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28 minutes ago, jayc89 said:

Do you think we'd be suitable for an MVHR system as part of the extension? We could possibly install it to the existing upstairs room too, but it would predominantly supply the extension.

probably but if full house system have you considered how to run the pipework?

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8 minutes ago, Simplysimon said:

probably but if full house system have you considered how to run the pipework?

The existing ground floor rooms would be problematic (AKA near impossible without making a mess), this would mean some of the downstairs wouldn't benefit from MVHR, but the extension could and all of the upstairs could.

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10 hours ago, JohnMo said:

dMVHR

Decentralised Mechanical Ventilation and Heat Recovery.

AKA Single Room MVHR.

11 hours ago, jayc89 said:

I had considered installing sun pipes with built in extractor fans in our ensuites

Who makes them, do you have a link please?

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2 hours ago, SteamyTea said:

AKA Single Room MVHR.

 

.. But noting that some can operate in unison ie one sucks whilst the other blows (stop that sniggering at the back please!) so as to get through flow of air between rooms. 

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7 hours ago, SteamyTea said:

Decentralised Mechanical Ventilation and Heat Recovery.

AKA Single Room MVHR.

Who makes them, do you have a link please?

 

These are what I was looking at for our en-suites in particular - https://www.roofingsuperstore.co.uk/product/ztv-014-ventilation-outlet-for-use-with-twr-014-2010-twf-014-2010-only.html but according to the Velux site, they're only suitable for tile fitments, not slate.

 

18 hours ago, JohnMo said:

Have you thought about either, dMEV or dMVHR

 

I hadn't mainly because the extension will likely double the footprint of the existing property so assumed MVHR would likely be justified. In reality it's only 2x downstairs rooms (plus hallway) that would be difficult to retrofit, which I think we could live with.

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4 minutes ago, jayc89 said:

 

These are what I was looking at for our en-suites in particular - https://www.roofingsuperstore.co.uk/product/ztv-014-ventilation-outlet-for-use-with-twr-014-2010-twf-014-2010-only.html but according to the Velux site, they're only suitable for tile fitments, not slate.

 

 

I hadn't mainly because the extension will likely double the footprint of the existing property so assumed MVHR would likely be justified. In reality it's only 2x downstairs rooms (plus hallway) that would be difficult to retrofit, which I think we could live with.

I cannot get the link to open so can’t see the item.

if you can tile around something, you can usually slate around it too as slate is much for forgiving and trimmable.

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6 minutes ago, markc said:

I cannot get the link to open so can’t see the item.

if you can tile around something, you can usually slate around it too as slate is much for forgiving and trimmable.

 

The link says;

 

Quote

Ventilation outlet ZTV supplements the existing ventilation in the room. The ZTV can be installed with 14" TWR and TWF Sun tunnels.

 

TW* are apparently for tile, whereas TF* are for slate, according to the Velux side - https://www.velux.co.uk/products/sun-tunnels/pitched-roof

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54 minutes ago, jayc89 said:


 

I hadn't mainly because the extension will likely double the footprint of the existing property so assumed MVHR would likely be justified. In reality it's only 2x downstairs rooms (plus hallway) that would be difficult to retrofit, which I think we could live with.

Have a look at coanda effect nozzles, these will make the air travel from one side of the room to the other, so routing pipes is easier.

 

 These are what I used these for our supply nozzles.  Zehnder 990326254

 

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17 hours ago, JohnMo said:

Have a look at coanda effect nozzles, these will make the air travel from one side of the room to the other, so routing pipes is easier.

 

 These are what I used these for our supply nozzles.  Zehnder 990326254

 

 

For clarity I supposed that is for side wall installation, at high level as close to the ceiling as possible?

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Pretty much.  Photos of mine in the lounge.

 

The MVHR unit is in the plant room the other side of the wall.  Pipe run approx 3m, to one nozzle on the other is about 8m. Also have one in the hall, that pipe run is also 3m.  The air comes down after approx 4 to 6m depending on flow rate.  So is in effect the same as having the nozzle on the other side of the room.

 

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On 07/02/2022 at 20:06, jayc89 said:

Do you think we'd be suitable for an MVHR system as part of the extension? We could possibly install it to the existing upstairs room too, but it would predominantly supply the extension.

I say yes, as that's what I did before: I ran MVHR ducts only where I could. Building airtightness was poor, but it nevertheless brought noticeable difference to air quality inside. The reason is it provides/extract air where you want and how much you want, natural draughts are temperature and pressure dependant. You loose a lot of heat recovery component, so go with as cheap unit as it gets, as efficiency (long term economy) will be of less importance vs upfront purchase cost.

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On 07/02/2022 at 20:06, jayc89 said:

Do you think we'd be suitable for an MVHR system as part of the extension?

 

I'll play devils advocate and say probably not.

 

It's unlikely that your final air tightness will be better than 5m³/m².h @50Pa. Maybe your extension will be built to a level that could achieve slightly better, but it is unlikely that in combination with the existing house that the overall air tightness will be better.

 

Down to an infiltration rate of 3m³/m².h @50Pa, building regs imply that mechanical ventilation is unnecessary since there is sufficient background air changes for reasonable air quality.

 

Yes, these back ground air changes are uncontrolled and have no heat recovery, but they are there whether or not you fit MVHR.

 

If you do fit MVHR you are creating additional air changes, although you should recover 80% - 90% of the energy, but you loose the 10-20 percentage points unnecessarily, since you don't need the mechanical ventilation for air quality. For me, with a ventilation rate above 3m³/m².h @50Pa, MVHR is an unnecessary expense that requires future filter changes and occasional servicing. Room extractors in bathrooms and trickle vents in the new windows are more cost effective.

 

If you want to be sure, pay a couple of hundred pounds for an air tightness test prior to the extension starting and see what your baseline figure is. If it is close to say, 5m³/m².h @50Pa, then maybe it's worth doing the extra detailing on the extension to try and bring the overall figure down to somewhere near where an MVHR system adds value.

Edited by IanR
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1 hour ago, IanR said:

 

I'll play devils advocate and say probably not.

 

It's unlikely that your final air tightness will be better than 5m³/m².h @50Pa. Maybe your extension will be built to a level that could achieve slightly better, but it is unlikely that in combination with the existing house that the overall air tightness will be better.

 

Down to an infiltration rate of 3m³/m².h @50Pa, building regs imply that mechanical ventilation is unnecessary since there is sufficient background air changes for reasonable air quality.

 

Yes, these back ground air changes are uncontrolled and have no heat recovery, but they are there whether or not you fit MVHR.

 

If you do fit MVHR you are creating additional air changes, although you should recover 80% - 90% of the energy, but you loose the 10-20 percentage points unnecessarily, since you don't need the mechanical ventilation for air quality. For me, with a ventilation rate above 3m³/m².h @50Pa, MVHR is an unnecessary expense that requires future filter changes and occasional servicing. Room extractors in bathrooms and trickle vents in the new windows are more cost effective.

 

If you want to be sure, pay a couple of hundred pounds for an air tightness test prior to the extension starting and see what your baseline figure is. If it is close to say, 5m³/m².h @50Pa, then maybe it's worth doing the extra detailing on the extension to try and bring the overall figure down to somewhere near where an MVHR system adds value.

I must agree with you, hence my first suggestion of dMEV. Very little running cost, good ventilation, as long as you have good cross flow.  For way less cost than MVHR, you have condition based dMEV.  Some light reading attached.

Atamate_SDAR+Paper+2019+(1).pdf

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