MVHR is Largely Bogus

[jack]

2 minutes ago, ProDave said:

II added up all the lights in the house, and if every single one is on, it's about 130W

 

Our pantry total is 12W, from memory. An hour with those lights on is 0.012 kWh, or about £0.0018 at £0.15/kWh.

 

Leaving them on 50% of the time would cost less than £8 a year. If it costs £60 to supply and self-install a motion sensor, the payback cost is something like 7.5 years.

 

I don't know how often a motion sensor needs replacing, but if it's every 10 years, it marginal whether it would ever pay back its costs. You also need to factor in energy consumption of the sensor, and the embodied energy of manufacture and disposal.

 

Worse, I doubt the light is on for more than an hour a day though, so even ignoring replacement costs it's more like a multi-decade payback.

 

This is the sort of maths that ends up applying to all those small rooms that you nip in and out of during the day: toilets, pantries, bathrooms, utility rooms. In the end, it's just difficult to make a financial case for it, so it comes down to whether you want to reduce your carbon usage to the absolute minimum, or consider motion sensors to be something that improves your life enough to pay for them.

[AliG]

3 hours ago, SteamyTea said:

Yes, lights are now 5W instead of 60W.

For most lights in the house that is true.

 

We have a lot of dusk to dawn lights that are on for hours and 5-8W each.

 

However there are 16 LEDs in my kitchen which the automation say use 185W when they are all on. I put them onto two circuits, but apparently people hate the idea of only one circuit being on.

 

Back on the topic of MVHR. I have turned my MVHR boxes down to level 1 as I didn't think any more air flow than that was needed. Perhaps it is the size of the house, plus lack of airtightness, but I have never seen condensation in a bathroom etc. One thing I note is that MVHR is cheaper than heating up cold outside air, but it still does not heat the air to the inside temperature during winter so it cools down the house if running too hard and increases heating bills.

 

 

[jack]

9 minutes ago, AliG said:

Back on the topic of MVHR. I have turned my MVHR boxes down to level 1 as I didn't think any more air flow than that was needed. Perhaps it is the size of the house, plus lack of airtightness, but I have never seen condensation in a bathroom etc. One thing I note is that MVHR is cheaper than heating up cold outside air, but it still does not heat the air to the inside temperature during winter so it cools down the house if running too hard and increases heating bills.

 

We have a Brink Excellent 400, which can run at up to 400m³/h. The regs say it should be run at (I think) 280m³/h, which is insane. 

 

I'd have to check, but I think we currently run it at 100m³/h, although it's been as low as 50m³/h without any apparent condensation issues.

[Levo]

On 30/12/2020 at 19:05, Levo said:

I am about to install an MVHR. All kit ready, waiting for marginally warmer weather.

The reasons for my installation are:

1- Pollen filter to help cut down on my son's Hay Fever.

2- Air quality. I suggest people invest in a CO2 monitor and check the levels in a couple of rooms. You would be amazed how quickly it goes to red without ventilation. Trickle vents would bring cold (bitter cold these days) air in and I hate the cold air flow. Example: TV room ~23m2. Begin at 400-500, two people watching TV, 2-3 hours later in red (1200+). CO2 PPM below 800 is deemed good, above 1200 it is bad and it is acceptable in between. Imagine a similar size or smaller bedroom with 2 people sleeping for 8 hours.

3- It will reduce the gas usage somewhat. I mention this not from cost perspective but environmental angle. Some may argue that the CO2 cost of manufacturing etc probably outweighs this.

I live in a 1970s detached house. It does have some gaps here and there which I will need to plug but the important rooms are reasonably airtight, so I am hoping it will serve to increase the air quality and remove the need to open windows and causing cold drafts and therefore providing better comfort.

Looking at this purely from cost perspective is wrong in my opinion. Anybody who does, I assume (as an example) has no TV in their house as one can argue a TV provides 0 £ value, and is therefore just cost...so impossible to justify.

It has been 2 years since I installed a Brink 300/325. My main reason was 1- Hay Fever, 2- cleaner air and finally try and reduce the gas bills to help saving the environment and reducing the cost to achieve the first two. I have checked the gas bills the other day and it seems we were averaging 16K KWHr annually before Brink and it is in the 11K KWHrs afterwards. That is a 5,000 KWHr a year reduction helping the environment and a £500 saving a year for my pocket. So the payback for my DIY install at £3600 will be ~7 years.

Just wanted to share.

Edited March 15, 2023 by Levo

[JohnMo]

 

7 minutes ago, Levo said:

That is a 5,000 KWHr a year reduction helping the environment and a £500 saving a year for my pocket. So the payback for my DIY install at £3600 will be ~7 years

You need to take account of running costs (electric) and filters also, for the complete cost saving.

[Dave Jones]

running cost isn't relevant. What's the running cost of  a £20k kitchen compared to a £40k kitchen ?

 

 

 

 

[Levo]

50 minutes ago, JohnMo said:

 

You need to take account of running costs (electric) and filters also, for the complete cost saving.

Good point. I figured around £65 a year (20Watts continuous at 35p/KWHr) for electricity. Some of this will be offset by the central heating operating less so less electricity for the burner fan, the water pump etc. Say down to £42. Add two sets of G4 at £4 each set, so totals to £8 a year.  That is 500 - 50 = £450. Still a good saving.

[JohnMo]

1 hour ago, Dave Jones said:

running cost isn't relevant. What's the running cost of  a £20k kitchen compared to a £40k kitchen ?

Of cause it is, we are not talking cost of a kitchen.  If you install something to save on gas as @Levo did (his 3rd motivation), that being MVHR, its running cost is relevant.  If it cost £100 to run and maintain and saved £50 in gas consumption, it would be a waste of investment and would fail to achieve his 3rd motivation.  In this case, gas saved is greater than electric used and filters, so win win.

[SteamyTea]

MVHR needs to be compared to the alternative, which is uncontrolled ventilation.

If MVHR is not fitted, the air leakage has to be >3 ACH (I think).

 

Edited March 15, 2023 by SteamyTea

[Nickfromwales]

2 hours ago, Dave Jones said:

running cost isn't relevant. What's the running cost of  a £20k kitchen compared to a £40k kitchen ?

There is no "running cost" of a kitchen?! Do try to say something relevant, it helps a lot  

[Post and beam]

2 hours ago, Dave Jones said:

running cost isn't relevant. What's the running cost of  a £20k kitchen compared to a £40k kitchen ?

 

 

 

 

It is if the person making the statement considers it to be so

[Dave Jones]

11 hours ago, Nickfromwales said:

There is no "running cost" of a kitchen?! Do try to say something relevant, it helps a lot  

 

kind of my point duh.

[Sparrowhawk]

17 hours ago, Levo said:

It has been 2 years since I installed a Brink 300/325. My main reason was 1- Hay Fever, 2- cleaner air

What's the impact been on your hay fever? If MVHR means sleeping without issue during hay fever season plus a large reduction on symptoms indoors, that'd be worth a few thousand to me.

 

For those debating running costs, Acrivastine (antihistamine) is £6 for 12 and you can need up to 3 a day. Plus nasal spray, plus... So a reduction in medicine costs plus reduction in lethargy and reduced productivity should be taken into account.

Edited March 16, 2023 by Sparrowhawk

[Levo]

1 minute ago, Sparrowhawk said:

What's the impact been on your hay fever? If MVHR means sleeping without issue during hay fever season plus a large reduction on symptoms indoors, that'd be worth a few thousand to me.

 

For those debating running costs, Acrivastine (antihistamine) is £6 for 12 and you can need up to 3 a day. Plus nasal spray, plus... So a significant reduction in needing these should be taken into account.

It was for my son and his life quality has definitely improved, as long as he stays inside 😟.

But you need to get a system that will take M5 filters as a minimum. I have the Brink Flair with F7.

In the autumn/winter I go to 2x G4 and once the Hay fever seasons starts (in about a months time for my son; grass and silver birch), move to F7+G4.

[SteamyTea]

25 minutes ago, Levo said:

was for my son and his life quality has definitely improved

Moving from the home counties to Cornwall improved my hayfever.

[Levo]

On 18/12/2019 at 22:10, Jeremy Harris said:

There's little hope that a house built ten or twenty years ago could be made adequately airtight to allow MVHR to work efficiently, without a great deal of major improvement work to the core fabric of the house.

While I agree that the MVHR will benefit more in an airtight house, my 1970s house (50 years old now) has definitely benefited:

1- Pollens filtered out: You just need to increase the intake rate so you have positive pressure inside. That means some air leaks but on the plus side you reduce the amount of pollens coming through gaps.

2- Nice clean air, reduced CO2 etc etc

3- Bonus energy saving. Perhaps not as much as it would have been in an airtight house but still a respectable 30%+ (1-11k/16K) saving.

 

Filters are not that expensive. I have just ordered some G4 filters at €22 for 10 (€26.5 including shipping). That is ~£4.60 per 2xG4 filter change.

[Levo]

@JohnMoStrictly speaking my motivation wasn't saving money, it was saving Gas for the environment.

On 30/12/2020 at 19:05, Levo said:

3- It will reduce the gas usage somewhat. I mention this not from cost perspective but environmental angle.

But I would never say no to money😁

 

 

[JohnMo]

On 15/03/2023 at 16:11, Levo said:

and finally try and reduce the gas bills to help saving the environment and reducing the cost to achieve the first two

Sorry didn't go all the way back to your older post 2020, just read the above.  Where you mentioned bills and reducing costs.

[Adsibob]

22 hours ago, JohnMo said:

Sorry didn't go all the way back to your older post 2020, just read the above.  Where you mentioned bills and reducing costs.

I’m really surprised by the title to this thread. I think MVHR is amazing. Probably one of the best “green” aspects of my renovation. I went out for dinner with some friends the other day who were complaining about how much it costs to heat their house, and how they have lots of draughts but still have condensation problems. I couldn’t help feeling smug that my bills haven’t been too bad this winter and the house never feels cold, smelly, damp or draughty (especially now we got the window fixed).

[Oldsteel]

Agreed. This is the second house I have built fitted with MVHR (Zehnder Q350), and yes we struggled to meet the 8 ACH required by our BCO on our airtghtness tests (APT), vented cavities being the main culprit. However, after 6 months I have the balanced MVHR turned down to 1/3, all rooms in the house are dry, warm where required and fresh. We dry clothes regularly and fast inside, bathroom steam and smells clear within minutes, and my wife is looking forward to improved hay fever symptoms come the season. I have a recirculating extractor in the kitchen which stops cooking smells from escaping to the rest of the house and doesnt impact the MVHR airflow. The next test will be a warm summer, do I switch off the MVHR when windows are open?

[MJNewton]

1 hour ago, Oldsteel said:

The next test will be a warm summer, do I switch off the MVHR when windows are open?

 

I keep it running throughout as often in the summer - particular on warm sticky nights - there isn't much wind around and so the MVHR can really help keep the air moving. In some situations the heat exchanger will also reduce the temperature of the incoming air, but only by a couple of degrees or so and given the low volumes it's no air conditioner, but I think every little helps psychologically!

[Gus Potter]

Good thread.

 

But for the younger members from an "old crusty".. may save you money.. choice is yours.

 

My thoughts and a bit of back ground. I worked at Torness Nuclear power station, and have designed stuff for the decomissioning of Bradwell Nuclear Station so apreciate the decomissing costs. Mostly now I do domestic stuff.. Part of my Masters was to do with the energy supply in the UK.. I started out as a local builder.. so did not go into Uni right away..

 

I also had a spell at designing farm buldings with 40 kW pv when the grants were good. Yes I was right into it.. how the grants worked and so on.

 

Have to say one at least went on fire as the invertor did not do what was written on the tin. Lucky for me I was not in the firing line.. but it burnt well and no one got hurt.

 

Yes, I'm near sixty but I still practice so have not quite turned into a fossil... and can't see me going woke any time soon.

 

Anyway my thoughts are.. Marcro and from an SE / designer point of view looking to the future.

 

If you are an environmentalist and into PV.. or any other home automation just to be blunt you have a living in a bubble. For the following macro reasons not least:

 

1/ China are becoming dominant to the extent that they are going to influence what happens in fifteen/ twenty say years time, unless they invade Taiwan.. then we will have much more to worry about.

 

2/ The stuff that we rely upon comes from mostly China and the "belt and braces"  and most importantly hegemony that they have fostered. I also grew up in Africa and follow how the Chinese  have weaved their way in that continent.. and some think the British Colonials were bad!

 

3/ All this stuff we are introducing.. electronics.. EV cars requires for example, mining and invites destruction of the environment..

 

4/ Have you thought about getting replacement parts and how much these are going to be in say 10 - 20 years time? Remember washing machines don't last that long.. you MHVR is intrinsic to the house so should be able to preform in the long term. Do you honestly expect that you MHVR is going to last the design life of the house? You'll be lucky if it works for five years and each ear yoy need to change the filters..

 

 

 

Look folks you have to wake up and realise that while we are trying to save every extra penny in the UK other countries are shafting the environent and the global eco system we need to produce the "air we all breathe"

 

You also need to recognise that you are buying filters, the running cost.. and inherant redundancy.

 

Get your head round this. If you think strategically...

 

The best thing we can do is to try and adapt our building systems to use the materials we have in the UK. We have lots of clay.. if we supported our Farmers and brick industry we could have  bricks and wool.. good for insulation in the right combination. Also all locally sourced and provides jobs... I could list more but we have in the uk many of the things we need to protect the environment without haveing to ship in stuff.

 

Look there is word that in the south of the UK they is Lithium for batteries.. in Scotland we have the wind to charge them up.

 

Just maybe we could start to think.. hey... see in the south of the UK our houses are getting a bit to hot in the summer.. can we pinch ideas from Adobe houses that rely upon passive stack ventilation. Yes there is a bit in the building regs about this but if you think about it.. it's a controlable chimney. They do it in Spain for example just here BC don't help. 

 

Anyway.. kids need fresh air not filtered air.. just think about it if you are a parent.

 

Yes you may think I'm off the mark here.. but see in ten years time when you can't find replacement parts for you MHVR and home automation other than from China.  I'll get the last laugh.. if I'm still here. If not well you made you own bed.

 

I have a house with UF and  some nice bells and whistles.. but these come at a cost.. there is not a couple of weks that goes by when something does no break down.. You'll end up saying.. the house was great for the first month.. but there are loads of things not working and it is getting on my tits.

 

When I go to see a Client I point out the good bits and the bad..

 

For example just this weekend two dimmer light units have failed out of about 16.. and that is in the first 18 months of installation .. and they have to come from China. 

 

I can fix this myself but what if you are not OK with diving into electrics.. how much is the spark going to cost you?

 

To finish.. I'll appeal to your wallet. Do you think that having MHVR is a good or bad selling point? Can you demontrate to a buyer that it all works, what value is a Surveyor going to attach to it.. is it like a dodgy gas boiler... at least a gas boiler has a Gas safety certificate .. your MHVR just has.. cowboy written all over it!

 

 

 

 

 

[MikeSharp01]

6 hours ago, Gus Potter said:

But for the younger members from an "old crusty".. may save you money.. choice is yours.

 

My thoughts and a bit of back ground. I worked at Torness Nuclear power station, and have designed stuff for the decomissioning of Bradwell Nuclear Station so apreciate the decomissing costs. Mostly now I do domestic stuff.. Part of my Masters was to do with the energy supply in the UK.. I started out as a local builder.. so did not go into Uni right away..

 

I also had a spell at designing farm buldings with 40 kW pv when the grants were good. Yes I was right into it.. how the grants worked and so on.

 

Have to say one at least went on fire as the invertor did not do what was written on the tin. Lucky for me I was not in the firing line.. but it burnt well and no one got hurt.

 

Yes, I'm near sixty but I still practice so have not quite turned into a fossil... and can't see me going woke any time soon.

 

Anyway my thoughts are.. Marcro and from an SE / designer point of view looking to the future.

 

If you are an environmentalist and into PV.. or any other home automation just to be blunt you have a living in a bubble. For the following macro reasons not least:

 

1/ China are becoming dominant to the extent that they are going to influence what happens in fifteen/ twenty say years time, unless they invade Taiwan.. then we will have much more to worry about.

 

2/ The stuff that we rely upon comes from mostly China and the "belt and braces"  and most importantly hegemony that they have fostered. I also grew up in Africa and follow how the Chinese  have weaved their way in that continent.. and some think the British Colonials were bad!

 

3/ All this stuff we are introducing.. electronics.. EV cars requires for example, mining and invites destruction of the environment..

 

4/ Have you thought about getting replacement parts and how much these are going to be in say 10 - 20 years time? Remember washing machines don't last that long.. you MHVR is intrinsic to the house so should be able to preform in the long term. Do you honestly expect that you MHVR is going to last the design life of the house? You'll be lucky if it works for five years and each ear yoy need to change the filters..

 

 

 

Look folks you have to wake up and realise that while we are trying to save every extra penny in the UK other countries are shafting the environent and the global eco system we need to produce the "air we all breathe"

 

You also need to recognise that you are buying filters, the running cost.. and inherant redundancy.

 

Get your head round this. If you think strategically...

 

The best thing we can do is to try and adapt our building systems to use the materials we have in the UK. We have lots of clay.. if we supported our Farmers and brick industry we could have  bricks and wool.. good for insulation in the right combination. Also all locally sourced and provides jobs... I could list more but we have in the uk many of the things we need to protect the environment without haveing to ship in stuff.

 

Look there is word that in the south of the UK they is Lithium for batteries.. in Scotland we have the wind to charge them up.

 

Just maybe we could start to think.. hey... see in the south of the UK our houses are getting a bit to hot in the summer.. can we pinch ideas from Adobe houses that rely upon passive stack ventilation. Yes there is a bit in the building regs about this but if you think about it.. it's a controlable chimney. They do it in Spain for example just here BC don't help. 

 

Anyway.. kids need fresh air not filtered air.. just think about it if you are a parent.

 

Yes you may think I'm off the mark here.. but see in ten years time when you can't find replacement parts for you MHVR and home automation other than from China.  I'll get the last laugh.. if I'm still here. If not well you made you own bed.

 

I have a house with UF and  some nice bells and whistles.. but these come at a cost.. there is not a couple of weks that goes by when something does no break down.. You'll end up saying.. the house was great for the first month.. but there are loads of things not working and it is getting on my tits.

 

When I go to see a Client I point out the good bits and the bad..

 

For example just this weekend two dimmer light units have failed out of about 16.. and that is in the first 18 months of installation .. and they have to come from China. 

 

I can fix this myself but what if you are not OK with diving into electrics.. how much is the spark going to cost you?

 

To finish.. I'll appeal to your wallet. Do you think that having MHVR is a good or bad selling point? Can you demontrate to a buyer that it all works, what value is a Surveyor going to attach to it.. is it like a dodgy gas boiler... at least a gas boiler has a Gas safety certificate .. your MHVR just has.. cowboy written all over it!

 

Somewhat down beat way to start the week, but hey, food for thought and you are correct, every day is a school day - thanks Gus.

[SteamyTea]

@Gus Potter

You alright mate?

[Kelvin]

I have a lot of sympathy for Gus’s position. It’s never great when a country is able to become dominant. It’s likely I’ve swallowed the increasing anti-China propaganda but I actively try and avoid buying Chinese made products, which isn’t easy. 
 

When we first started looking at building a house we started from a position of very simple, no technology, simple heating systems etc. Every extra device, pump or valve is another point of failure. We’ve not ended up there as the house will have a lot of stuff in it some through necessity some through choice. I hope it all still works in 20 years. In 30 years it’ll be a problem for my offspring. 😂