Air quality with mvhr

[Jeremy Harris]

Just now, P1234 said:

Thank you. And wow that is dirty. I live in a block of flats. Was informed the ventilation system for all the flats are connected. I am hoping this means that all flats use the same incoming fresh air duct and filter which has been cleaned by the block management elsewhere in the building. And that the only filters in my flat are the extract filters.

 

Worth checking, but extract filters don't usually get anywhere near as dirty.  You should be able to check whether you have an intake filter quite easily, as they are user-serviceable components, and a dirty one does tend to look obviously dirty, as the photo above shows!

[P1234]

16 hours ago, TottenhamFC said:

@P1234

 

my manual says to service the mvhr system every 12 months but I think this seems unreasonable albeit living in London may mean this is needed more often. 

 

I feel that if you if you can change and replace your mvhr filters (or hrv - not sure what the difference is between the two definitions) more regularly you could probably get away without servicing it for years ! 

Thank you. My block management has confirmed that it is ok to service once a year although 6 months is preferable. They last came in January and all they did was open the ceiling hatches and look at it.....

 

Did a bit of research:

HRVs and ERV/MVHR s both supply air to the home and exhaust stale air while recovering energy from the exhaust air in the process. The primary difference between the two is that an HRV transfers heat while an ERV/MVHR transfers both heat and moisture.

[jack]

21 hours ago, P1234 said:

HRVs and ERV/MVHR s both supply air to the home and exhaust stale air while recovering energy from the exhaust air in the process. The primary difference between the two is that an HRV transfers heat while an ERV/MVHR transfers both heat and moisture.

 

Moisture is only transferred in a so-called enthalpy MVHR. When used alone, MVHR generally means just heat recovery. Enthalpy units are rarely used in the UK.

[P1234]

I see thanks. 

29 minutes ago, jack said:

 

Moisture is only transferred in a so-called enthalpy MVHR. When used alone, MVHR generally means just heat recovery. Enthalpy units are rarely used in the UK.

I see. I always thought that after showers with the bathroom door closed, the air in the whole flat felt damp..

[jack]

Sorry, I misunderstood your earlier comment.

 

MVHR does transfer moisture in the way you're talking about. It delivers fresh air to living areas, and pulls air from areas such as kitchens and bathrooms, including moisture in those rooms. I don't know what HRV is that's different to this: wikipedia thinks HRV and MVHR are synonyms.

 

 

[NSS]

On 05/09/2018 at 10:51, HerbJ said:

For anyone with  a PAUL MVHR, Paul Scotland offer very competitive prices for single sets of filters  at the moment - see https://www.paulheatrecovery.co.uk/shop/  

 

Yep, I ordered enough for the next 2 years from them last week ?

[Dreadnaught]

This scientific paper addresses internal air quality in Passive Houses with MVHR. It suggests a significant source of internal PM2.5 is cooking and that MVHR may be inadequate in removing such contaminants, even in boost mode. It also looks at contributors to air quality, such as CO₂ and formaldehyde.

 

It is a current paper, with a forthcoming publication date of 15 October 2018. The houses monitored for the study are in Colorado, USA.

 

https://www.sciencedirect.com/science/authShare/S0360132318305183/20180907T163100Z/1?md5=5e4246e165b6c901268110a047c99c37

[joe90]

I,m buggered when I burn the toast then?.

[ProDave]

Interesting and timely observations.

 

I am about to connect the boost function of my MVHR (a timer switch upstairs and downstairs, nothing complicated)

 

For the upstairs boost, I am going to connect that at the maximum mvhr speed to clear condensation and moisture as quick as possible.

 

Downstairs, we have been cooking in the house for 2 months, without even a recirculating cooker hood and the mvhr just running at normal speed. I can't say we have had any issues or particularly notice cooking smells lingering long.  Obviously fitting a recirculating cooker hood with carbon filter is on the "to do" list.

 

but when it comes to the downstairs mvhr boost, I was going to connect that one so it runs the mvhr at a faster speed, but not necessarilly the fastest one.

[joe90]

I am yet to wire up my MVHR, we do get a little condensation after a shower and we have been cooking fir 4 months and not noticed any real problems. We do however need bedroom windows open at night and suffer a little if we don’t. It’s on my very long to do list !!!!  If I remember correctly we have a humidity sensor that should boost the MVHR automatically.

[epsilonGreedy]

On 08/09/2018 at 13:43, Dreadnaught said:

This scientific paper addresses internal air quality in Passive Houses with MVHR. It suggests a significant source of internal PM2.5 is cooking

 

 

The report doubts (though not tested) the effectiveness of recirculating cooker hoods and adds they are unsuitable for gas cookers.

 

With this in mind is there a product that effectively seals a genuine exhausting cooker hood when the fan is off?

[Nickfromwales]

21 hours ago, epsilonGreedy said:

With this in mind is there a product that effectively seals a genuine exhausting cooker hood when the fan is off?

Ive looked into this for my house and was in a volley with an EB member before numbnuts pulled the plug. Can’t get that back now as it was by PM  

I looked into 100 and 150mm electromechanical dampers to stave off free airflow from room to atmosphere and did find a LOT of hideously expensive ( over-priced ) units. ‘We’ did find a cheaper robust unit but the cack hit the fan and I didn’t think to copy my stuff before being unceremoniously locked out. 

Something for anyone without mvhr or indeed with an extracting cooker hood, especially with 150-200mm ducting !

[ProDave]

Fire valve springs to mind, I believe they are energise to open. Or were they the stupidly expensive option?

[Jeremy Harris]

Hard to engineer an external extract duct valve that both works effectively and isn't a thermal bridge when closed, I think.  The valve really needs to not only seal well when closed, but also be as well insulated as the skin of the house it's located in.  It's a bit like the passive house cat flap, or letterbox, conundrum.

 

You also have to add in the unbalancing effect on the MVHR, as when the extract is on the main source for air to get into the house will be via the MVHR fresh air intake, and with the much higher intake flow versus the exhaust flow through the MVHR heat exchanger my guess is that the MVHR won't do much to warm the incoming fresh air.  Using such a system in winter will probably create cold drafts, as well as some noise from the MVHR fresh air terminals.  In summer, a window could be opened to compensate for the high extraction flow rate, perhaps.

 

There seem to be a few things to look at first, though, I think.  First of all, are the PM2.5s from cooking harmful?  We know that PM2.5s from things like wood and coal smoke, vehicle engines, etc are harmful, but we also know that PM2.5s from natural sources may not be harmful at all (the open countryside air is full of particulates on a breezy day - everything from spores and pollen to fine dust from soil).  I'd want to see some evidence of harm from cooking related particulates before getting concerned, and I also suspect that there are a wide range of them, from very fine water and oil droplets that are probably pretty harmless, to particulates created from combustion during cooking that may not be so harmless.

 

Perhaps our diet is untypical, but with an induction hob, very little frying (maybe once a month), food that's mainly steamed, boiled or baked, I suspect the highest risk particulates may come from the occasional bit of burnt toast.

 

Finally, there are a range of different filters available for recirculating extractor hoods, and it may well be possible to fit an F7 filter as the final one in order to filter the exhausted air that's returning to the room down to about 1µ or so.

 

 

[MortarThePoint]

Saw this and thought it may interest this discussion if someone comes here. I don't know mch about MVHR, but the height of room extraction may be a factor.

 

https://www.novofibre.com/health/indoor-aqi.php

[SteamyTea]

7 minutes ago, MortarThePoint said:

Saw this and thought it may interest this discussion if someone comes here.

I will bite.

So is this a manufacturer that is selling a product that does not contain legal amounts of formaldehyde, by rubbishing the opposition and playing on peoples fears?

[MortarThePoint]

4 minutes ago, SteamyTea said:

I will bite.

So is this a manufacturer that is selling a product that does not contain legal amounts of formaldehyde, by rubbishing the opposition and playing on peoples fears?

 

Probably, but if the formaldehyde concentration being higher near the floor is true, then it's a consideration for anyone who is interested in the formaldehyde part of this thread so I thought I'd share it.

[ToughButterCup]

Quote

According to data collected by the China Building Decoration Association in 2014, China's household indoor formaldehyde exceeded the average worldwide levels by 70% -80%. The highest detected formaldehyde emissions level exceeded the national standard by 4.2 times.

https://www.novofibre.com/health/indoor-aqi.php# (downloaded 29/04/2021)

 

In other words, formaldehyde concentrations are already lower in the world outside China.

And the author is also lazy enough not to specify which national standard  has been exceeded and where it was exceeded. 

 

Lazy, possibly self-interested, sloppy thinking condensed into a couple of sentences.   Fake Noos! (How I miss you Donny)

Edited April 29, 2021 by ToughButterCup