Large MVHR recommendations.

[ChrisDL]

Good morning,

 

I am wondering if anyone has any recommendations for a large single MVHR unit? Or would I be better off with two? I have had some preliminary discussions and quotes from suppliers which have all recommended two units... but I guess it is in their interest to sell more!

 

The property is quite large at 530sqm. Based on building regs 1.08 m3/hr that will equate to 572m3/hr - based on the advice I have read on this forum and running a unit at 50% I would need two, either Zhender Q600, Brink  (Ubbink) Flair 600, or at the more affordable end of the spectrum Vent Axia Kinetic High Flow. I don't want to spend more than is necessary, but quietness of the system is paramount, I would hate to have buyers remorse and wish I had purchased another unit.

 

I am about to start some calculations for duct runs to see if I will need to double up any 90mm semiflexible ducting - from the manifold to the extract/outlet the longest run would be about 15m. 

 

On a side note has anyone had any experience with Blauberg Blaufast ducting/manifolds? https://www.blauberg.co.uk/vents-ducts/semi-rigid-duct-systems  ?

 

Thanks.

 

[Kelvin]

The units themselves are generally quiet. It’s the correct attenuation on both supply and extract that needs careful thinking about. 

[ChrisDL]

  On 26/06/2024 at 11:10, Kelvin said:

The units themselves are generally quiet. It’s the correct attenuation on both supply and extract that needs careful thinking about. 

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Yes, reading the forums this is something not to be missed and I was planning to include decent attenuators between the MVHR unit and manifolds. If all the units will sound equally quiet at the valves that is great. At the unit itself won't matter being in a laundry/utility room at the rear of the house. Reliability and efficiency are probably the other considerations. 

 

Again one large unit if it existed would mean I don't have to double up on attenuators, manifolds, supply and extract atmosphere ducting either.

[Dave Jones]

  On 26/06/2024 at 11:10, Kelvin said:

The units themselves are generally quiet. It’s the correct attenuation on both supply and extract that needs careful thinking about. 

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i wouldnt say our zehdar unit is quiet. it's maybe a tad small for us running at 50% all the time, noise of a dyson from 10 feet away. Cant hear anything in any of the rooms though. the massive silencers certainly work.

 

Just make sure you slide in the ductng wehn you build in the pozi's/joists as you wont fit them in after.

[Kelvin]

As noisy as a Dyson hoover ? Our Q350 has a gentle white noise hum. 

[Blooda]

Our Vent Axia Sentinel is also a quiet hum, it's in the loft and when in the loft can hardly hear it, and have to listen out for it.

We hear it on when it ramps up to boost in room directly below, but it is soon forgotten when it is a constant speed.

Nothing like a Dyson vacuum cleaner. 

[JohnMo]

  On 26/06/2024 at 11:01, ChrisDL said:

530sqm. Based on building regs 1.08 m3/hr that will equate to 572m³/hr

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Not sure a single unit would be the best choice. You need to keep your max duct pressure drop below 100Pa. So you would need to do the pressure drop calculation for your longest duct run to make sure a single unit is practical.

 

A fan output drops as pressure drop increases on suction and discharge sides. The fan output is compensated by increasing fan speed (and noise). So be careful.

[Conor]

You'll need two. You want the fans running on allow speed 99% of the time. We're 350m² and have two units rated at 300mhr each.

[IanR]

  On 26/06/2024 at 11:01, ChrisDL said:

I am wondering if anyone has any recommendations for a large single MVHR unit? 

 

The property is quite large at 530sqm. Based on building regs 1.08 m3/hr that will equate to 572m3/hr - based on the advice I have read on this forum and running a unit at 50% I would need two, either Zhender Q600, Brink  (Ubbink) Flair 600, or at the more affordable end of the spectrum Vent Axia Kinetic High Flow. I don't want to spend more than is necessary, but quietness of the system is paramount, I would hate to have buyers remorse and wish I had purchased another unit.

 

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I'm happy to recommend the Airflow Duplexvent Flexi DV1100. It's the smallest of their Commercial PassivHaus units rated at 1100 m³/h. 

 

I'm only at 465m² foot-print, but have a 1650m³ internal volume. Airflow offer a free design service and then give you their recommended BOM for you to go and get the best price you can from their distributors. RRP is quite high, but discounts can be found amongst their distributors. The distributors get more favourable terms with Airflow based on their volume. For me Travis Perkins were cheapest, they had no idea what the were supplying, just went off the Airflow BOM. 

[ChrisDL]

  On 26/06/2024 at 16:13, JohnMo said:

Not sure a single unit would be the best choice. You need to keep your max duct pressure drop below 100Pa. So you would need to do the pressure drop calculation for your longest duct run to make sure a single unit is practical.

 

A fan output drops as pressure drop increases on suction and discharge sides. The fan output is compensated by increasing fan speed (and noise). So be careful.

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If I do end up with two units they will both be in the same central room in the home. Unfortunately no opportunity to have units either end of the house. I have measured today and the longest run to a bedroom will 16m. Which I could double up. 

[ChrisDL]

  On 26/06/2024 at 16:38, Conor said:

You'll need two. You want the fans running on allow speed 99% of the time. We're 350m² and have two units rated at 300mhr each.

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Good to know. What brand unit and ducting did you end up with and are you pleased with it?

[ChrisDL]

  On 26/06/2024 at 17:07, IanR said:

I'm happy to recommend the Airflow Duplexvent Flexi DV1100. It's the smallest of their Commercial PassivHaus units rated at 1100 m³/h. 

 

I'm only at 465m² foot-print, but have a 1650m³ internal volume. Airflow offer a free design service and then give you their recommended BOM for you to go and get the best price you can from their distributors. RRP is quite high, but discounts can be found amongst their distributors. The distributors get more favourable terms with Airflow based on their volume. For me Travis Perkins were cheapest, they had no idea what the were supplying, just went off the Airflow BOM. 

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This is interesting, I had wondered if a commercial unit might work... But have assumed it would be noiser and since it was likely to be in less noise sensitive areas, office, school etc. I will call them though. Did they also supply you ducting or did you use another brand for that?

[JohnMo]

  On 26/06/2024 at 18:31, ChrisDL said:

longest run to a bedroom will 16m.

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If it's only 16m all good. 

[ChrisDL]

  On 26/06/2024 at 14:41, Dave Jones said:

 

i wouldnt say our zehdar unit is quiet. it's maybe a tad small for us running at 50% all the time, noise of a dyson from 10 feet away. Cant hear anything in any of the rooms though. the massive silencers certainly work.

 

Just make sure you slide in the ductng wehn you build in the pozi's/joists as you wont fit them in after.

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Hi Dave your experience sounds unusual as I believe Zehnder are one of the most premium brands... Might go to show that I don't need to spend top £. I see few people have complaints with the Vent Axia's and buying two units could save me a lot. 

[ChrisDL]

  On 26/06/2024 at 18:39, JohnMo said:

If it's only 16m all good. 

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Good to know... but as a single or double run?

[IanR]

  On 26/06/2024 at 18:36, ChrisDL said:

This is interesting, I had wondered if a commercial unit might work... But have assumed it would be noiser and since it was likely to be in less noise sensitive areas, office, school etc. I will call them though. Did they also supply you ducting or did you use another brand for that?

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iirc the PassivHaus certification has a max noise requirement, so assume it will be similar to other domestic units. I've got nothing to compare it to, but I'd call it quiet. On boost @ 60% is the only time I hear it, and that's if I'm in the room adjacent.

 

I used all Airflow ducts, manifolds, terminals etc. except connection to outside which require Ø250 ducts, where I used Lindab.

Edited June 26, 2024 by IanR

[JohnMo]

  On 26/06/2024 at 18:41, ChrisDL said:

Good to know... but as a single or double run?

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Depends on 75mm or 90mm and how many bends etc, and flow rate through that duct - assuming semi flex manifold system. All the info should be on the data sheets for duct system, you choose.

[Dave Jones]

  On 26/06/2024 at 18:40, ChrisDL said:

Hi Dave your experience sounds unusual as I believe Zehnder are one of the most premium brands... Might go to show that I don't need to spend top £. I see few people have complaints with the Vent Axia's and buying two units could save me a lot. 

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i would give it a 5/10. To be fair Miele have been utter crap as well. The days of a real premium brand are long gone i think.

[JohnMo]

  On 26/06/2024 at 11:01, ChrisDL said:

anyone has any recommendations for a large single MVHR unit

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Titon HRV20. In reality, unless you are crammed with people, building regs flow rates will be way to high you could end up halving them after sign off. So with a large house don't go overboard with sizing the unit.

 

Titon are UK company, good support and spare parts if you need them. Good technical info readily available on their website. You call they pick up the phone, you get to discuss any issues and concerns with technical people.

[ChrisDL]

Thank you for the recommendations. I will follow up the suggestions.

[Russell griffiths]

Just flicked through this, so just a quick point I have. 
 

in a house that size I would think you need a dedicated plant room, fitting one unit in a laundry it will take up a huge amount of space, fitting two units will be an insane amount of pipework and manifolds. 
 

I’ve been on a few jobs these last few years and it never ceases to amaze me how much room we need to allow for the MVHR. 

 

the silencers are chunky things, then put them on some 180mm pipe work and it all gets very space consuming. 

[ChrisDL]

  On 27/06/2024 at 10:00, Russell griffiths said:

Just flicked through this, so just a quick point I have. 
 

in a house that size I would think you need a dedicated plant room, fitting one unit in a laundry it will take up a huge amount of space, fitting two units will be an insane amount of pipework and manifolds. 
 

I’ve been on a few jobs these last few years and it never ceases to amaze me how much room we need to allow for the MVHR. 

 

the silencers are chunky things, then put them on some 180mm pipe work and it all gets very space consuming. 

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16m2 is the allowed for space. But granted it will be gobbled up. Again, the preference for one unit if possible.

[Kelvin]

Plenty big enough. Mine is < 5m² plus about the same again space in the garage. 

[Mike]

  On 26/06/2024 at 11:01, ChrisDL said:

recommendations for a large single MVHR unit?

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You may well be better off with 2, but here's the PassivHaus database for large units:

 

https://database.passivehouse.com/en/components/list/ventilation_big?page_count=50