MVHR Sizing and Brand Recommendations

[ChrisDL]

Couple of questions regarding peoples experience with MVHR Sizing and whether they have any brand recommendations (quietness being my main concern). I have only been in a property with a DOMUS system and admittingly did not notice it. I have been looking at and quoted for Vent Axia units and wondered what real life opinions of them are? Zehnder I been quoted for as well and I am sure they are dood but - but considerably more expensive and if I have to buy two.... I have also heard the brand Brink on these forums but can't find many opinions on them.

 

Back to the sizing. We admittingly are a large barn conversion, 500m2, internal volume is basically 1500m3 with a large vaulted space. So far all the designs I have had back have recommended 2 units... and I would probably err towards the side of caution and go with that. But wondering whether if in reality I could get away with one to keep things simpler. I found this on PAUL Heat Recovery which suggests that a 500m2 property will need 375m3/hour to maintain a good Indoor Air Quality - anymore and it will be too dry. The Vent Axia recommended has a a 575 m3/h Airflow rate @ 100Pa which would mean it would be running at 65% of its potential. Would this be too noisy or overstretching one unit?

 

Also whilst at it. Oiler boiler flue siting in respects to the MVHR. I can potentially house the oil boiler in the garage 35m away from the inlet of the MVH eliminating any risk of fumes... however it will be easier to site the boiler just behind the plant room, where the MVHR inlet/outlet will be, and I am wondering if I have a flue extension rising up to the eaves of the barn will said fumes be taken away enough not to get sucked back into the house. Wondering if anyone has any real world experience on this.

 

Appreciate the opinions and recommendations.

 

[Adsibob]

32 minutes ago, ChrisDL said:

it would be running at 65% of its potential. Would this be too noisy or overstretching one unit?

Absolutely! The max flow rate of my Brink Flair 400 is 400m3/hour. Standard operating rate is 175m3, so just  under 44%. It would definitely be audible at 65%.

Remember that you will increase flow rates above your standard operating rate when you hit the boost switches, so you need plenty of spare capacity so that when boosting it isn't getting too close to 100%. My system is only audible when boosting and even then it is not too loud.

 

Although you might be thinking it is overkill to have two units, I think this is an excellent idea. You can locate them in different places making for shorter duct runs. They will both run at such low rates that you'll get more longevity out of the units.

[ChrisDL]

45 minutes ago, Adsibob said:

my Brink Flair 400 is 400m3/hour

You have confirmed my gut feeling and obviously the recommendations from suppliers. You pleased with your Brink though? It obviously operates quietly. Is it Vent Axia priced or closer to Zehnder products?

[jack]

18 hours ago, ChrisDL said:

You have confirmed my gut feeling and obviously the recommendations from suppliers. You pleased with your Brink though? It obviously operates quietly. Is it Vent Axia priced or closer to Zehnder products?

 

Brink (I have one) are more expensive than the Vent Axia equivalent. They're generally considered quiet and good quality. I had a minor issue with some internal water build-up in mine and Brink sent out an engineer something like 3 years after we bought the unit, so I can't fault their support. I know others on here (maybe @Nickfromwales?) rate Brink highly as well.

 

The airflow rates quoted above are overkill imo. They're quoting for 5 bedrooms, 7 wet rooms, and 12 occupants (perhaps that's what you'll have, but it seems unusual compared to typical British living arrangements).

 

From memory, the building regs rate for our 289 m² house with higher than average volume was 180 m³/h, which in practice is far more than needed. We tend to run it at 80 m³/h year round, and that leaves us with perfectly fresh air (two adults, two teenagers, and a dog). 

 

Edited to add: I forgot to mention that some of the Brink units are rebadged under other brands. Envirovent (which might actually be a Brink sub-brand) and Ubbink are two that jump to mind - I think there used to be others. It might take some comparing to make sure you're getting all the same features, but I suspect there may be savings to be had if you can find one of these rebadged units. It's generally pretty obvious from the pics. 

[Nickfromwales]

 

[ChrisDL]

Thank you @jack and @Nickfromwales. 

12 hours ago, jack said:

They're quoting for 5 bedrooms, 7 wet rooms, and 12 occupants (perhaps that's what you'll have, but it seems unusual compared to typical British living arrangements).

Ha, No we are a family of 5 with 2 dogs. We will have extended periods of time with family from abroad staying with us but no more than 10 people for more than a few days max... that's more than enough of the in-laws! 

 

It would appear I would probably be pushing it to drop to one unit... and may very well regret it - it won't be desirable to retrofit another unit in once we have moved in.

 

Does anyone have an opinion on the boiler flue positioning?

[Adsibob]

Go for two units. Run them very low when you don’t have guests and on low when you do.

 Do not retrofit. Much easier to get all the ducting in before you board up your walls and ceilings. The ducting design should really be done before you finalise your wall and ceiling positions, if possible. We had to drop a couple of ceilings to get around RSJs that our SE wasn’t happy for us to cut through. Other option is for SE to overspecify steels and approve the position and size of the cuts (usually 90mm diameter), and then your steel manufacturer can supply them ready-drilled. Posi joists also make life easier.

[Nickfromwales]

20 hours ago, ChrisDL said:

Does anyone have an opinion on the boiler flue positioning?

The boiler MI’s will give you pictures and distances from other openings / terminals / opposing or adjacent walls etc so just use those to show your options. 
Well away from the MVHR inlet is of course a given. 

[ChrisDL]

Just received back a design based on two Vent-Axia High Flow units which I thought I would share. A lot of the runs are pairs of ducting (denoted by the number below the diffuser), I wondered if one 90mm would suffice for these long runs but two 75mm will allow more volume. I haven't got much to compare against other than one branch design which I have dismissed. Does this look sensible to people? Tweaks/suggestions I can ask to make?