MVHR & ASHP best options

[James Allen]

Hi All new to forum, been watching as a guest for a while. We have finally started on our journey, site secured and existing house demolished. We have narrowed down our timber frame supplier to three and will be making a decision in the coming weeks. 

 

So far all three have suggested that we must have MVHR and that we should make a choice on our source for heating. We want UFH and are likely to go down the ASHP route.

 

Prior to this journey my knowledge was limited, I have done a lot of research online and to be honest there is so much choice and I really don't know what to choose, which companies are best to approach. So welcome suggestions from the community. This seems like a very important decision.

 

James

[JohnMo]

We started gas and quickly moved to ASHP. Really wouldn't bother going down the grant route for the ASHP you will just be ripped off with a unit way to big.

 

ASHP like it all kept really simple, this also reduces costs, so no need for thermostats, mixers or pumps, buffers or volumisers, do it all from the ashp circulation pump. So UFH on ground floor and in bathrooms only is a good choice. Keep it to single zone, run 24/7 in weather compensation mode is best way to run in a new build. Make provision for panel heaters in bedrooms. Electric towel rad in bathroom.

 

I would definitely look at Panasonic, easy to install and set up. You need to know your heat loss before progressing. So you need to understand your airtightness and ventilation strategy first.

 

MVHR is for ventilation, if your house isn't going to airtight (better than 3) it's not a good choice, demand activation MEV would be better.

 

Advice, go airtight, really well insulated, MVHR and ASHP. You may not be building a Passivhaus but read up on them, nearly everything is sensible and can be applied to any house.

 

I would steer clear of companies that want to design something and you hand over loads of money for kit you don't really need.

 

Once you get your head around MVHR it's pretty easy to design yourself. Same with the heating system, download LoopCad and design the loops yourself.

[JohnMo]

10 hours ago, JohnMo said:

Make provision for panel heaters in bedrooms.

Slight amendment, if you think you will need cooling in bedrooms install fan coils.

[James Allen]

Hi John, thanks for the detailed reply. First time I have heard someone suggest not to bother with the grant, £7.5k is a lot of money to ignore. Not quite sure why I would design for electric panel heaters and rads if I'm paying for an ashp?

 

Not going for PH cert, but aiming to the standard, so as airtight as possible. 

 

ASHP I would not feel comfortable doing myself (not within my skillset), though MVHR maybe....though would be concerned with getting it wrong and it all being behind plasterboard.

 

Any recommendations for MVHR manufacturers/suppliers?

[James Allen]

Cooling was something we were discussing actually, we had looked at doing through the mvhr

[JohnMo]

14 minutes ago, James Allen said:

Cooling was something we were discussing actually, we had looked at doing through the mvhr

Many have tried, but never heard anyone say it works as expected. Don't waste you time trying or your money - flow rates are too low to work. As I said deliberately MVHR is for ventilation. But you can do some heating with it max heat rate based on passivhaus flow rates at 10W/m2. But is way from efficient with a heat pump as the flow temps need to high.

 

Keep ventilation and heat/cooling as separate things. You can buy combined units but if one thing goes wrong, the whole lot stops working.

 

Keep it all simple.

[G and J]

We’ve had various MVHR and ASHP/UFH quotes from the high power sales outfits and they are educational, though I find their “don’t you worry your little brain, leave the details to us, just agree to pay lots and you’ll be fine” approach just doesn’t sit well.  It certainly doesn’t give me the info I need to incorporate the kit into our designs with confidence, especially as these companies typically demand a high percentage of the total cost upfront before doing the design.

 

Perhaps too many self builders have got hold of a free design then ran off and done it themselves thus teaching these companies not to be open.  I have found one company that charges a sensible amount for the design stage only, and when I ask them (pre sale) questions about what I need to allow for they are very forthcoming so that stands them in a good light - though no final decisions have yet been made.

 

As for the MCS/grant issue I’m sure I’ve heard of instances where peeps haven’t been ripped off.  I suspect there’s an awful lot of ‘oversize to inflate the price and up the labour charge to keep the grant’ type cowboys but there also appear to be good guys who are happy to do a fair job - ok getting in their diary might be tough but ever it is thus in the building trade.

 

The MCS process though also appears to have mild oversizing of ASHP built in presumably partly as a reaction to standard thinking in gas combi boilers and partly to ward off complaints when the heating systems the run aren’t properly designed.

 

For me, boning up and becoming a just about informed enough client is the only viable option.  This forum is invaluable for that but it does take a lot of time reading (as J will testify lol).

 

 

[ProDave]

1 hour ago, James Allen said:

Hi John, thanks for the detailed reply. First time I have heard someone suggest not to bother with the grant, £7.5k is a lot of money to ignore. Not quite sure why I would design for electric panel heaters and rads if I'm paying for an ashp?

 

The point about electric panel heaters in bedrooms, is a well insulated air tight house with mvhr most of us find does not need any heating at all in the bedrooms, even up here in the Highlands.  But a lot of people are not comfortable with no heating so installing electric points for panel heaters just in case you find you do need some bedroom heating, is a comfort blanket and cheaper to install a few cables that never get used, than a whole lot of upstairs UFH pipes that never get used.

 

If you think you want upstairs cooling look at fan coil units that normally go in the ceiling and will do heating and cooling.  The cost of them has put me off and so far we have only had one spell of weather when I might have liked them for cooling.

 

Re the grant.  I bought all the parts and installed my own ASHP for WAY less than £7.5K.   You only have to look at posts on here on the subject of heat pumps and grants to see it does not seem to work in the customers favour.  You might naively think the installer would charge a fair price for the materials and a fair price to install them, then deduct £7.5K leaving the customer with a very small or even zero bill.  Sorry to say that optimism will soon be dashed when you start getting real quotes and one is left wondering how can they charge that much?

[Andehh]

You want cooling? Fit air con, nothing else works as effectively, and a well Insulated house does risk over warming!

 

MVHR and ashp is a good base line, don't rule out the Grant just watch for cowboys artificially inflating the price to take advantage of it.

Edited August 18 by Andehh

[James Allen]

Thanks lots of responses - really appreciate the help. 

 

We are aware cooling through MVHR is limited and we have been advised that there are no significant overheating risks on the house - we have designed most out with overhangs etc. Though FCU in the main bedroom is something we might look into, with MVHR cooling just to bring the temp of the air that isn introduced into the house down. 

 

@G and J who is the company that you have found helpful? When it comes to choosing suppliers, I favour quality over price and do like an element of hand-holding. 

[Andehh]

Still fit air con!

 

Small price for very effective 'feel good feeling' for those few weeks of the year. Never be able to retrofit it properly after the fact. Paperwork no overheating risk is always optimistic IMO. Also acts as a warm boost on a cold winter night! Never hurts resale value as a premium feature as well.

[G and J]

3 hours ago, Andehh said:

Still fit air con!

 

Small price for very effective 'feel good feeling' for those few weeks of the year. Never be able to retrofit it properly after the fact. Paperwork no overheating risk is always optimistic IMO. Also acts as a warm boost on a cold winter night! Never hurts resale value as a premium feature as well.

Oh ok, I’ll install aircon then. 
 

My aircon will be a split system with separate heat pump to internal distribution system.  AKA ASHP and a fancoil. 
 

There, everyone is happy lol

[JohnMo]

2 minutes ago, G and J said:

There, everyone is happy lol

Not us that needs to be happy, it your house🙂

[G and J]

53 minutes ago, JohnMo said:

Not us that needs to be happy, it your house🙂

I want everyone happy, me.  Everywhere. All at once.  Oh, and I only want it to rain at night.  

[Dave Jones]

15 hours ago, James Allen said:

Thanks lots of responses - really appreciate the help. 

 

We are aware cooling through MVHR is limited and we have been advised that there are no significant overheating risks on the house - we have designed most out with overhangs etc. Though FCU in the main bedroom is something we might look into, with MVHR cooling just to bring the temp of the air that isn introduced into the house down. 

 

@G and J who is the company that you have found helpful? When it comes to choosing suppliers, I favour quality over price and do like an element of hand-holding. 

 

put supply and condensate drains in all the bedrooms and just leave them capped off. Will cost a few quid at first first but come the mega heatwaves the climate loons tell us are coming you may be glad you did.

[NSS]

Re Fan Coil Units, when we fitted ours 7 years ago, Panasonic called it an Air Rad. We went for it to provide spot heating/cooling in the main (and only) upstairs bedroom. What they didn't tell us was that, in heating mode, the valve in the unit is thermostatic and will only open when the water reaches a particular temperature (circa 50C iirc). Of course, with the ASHP running UFH for the rest of the house, the water never reaches that threshold. It works absolutely fine for cooling, but we ended up adding a small flat panel electric radiator for the odd occasion we need to heat the room.

 

No idea if this is something that has been solved in more recent FCUs, but worth checking specs before purchasing.

[James Allen]

Based on my online research the following units are the best options. Does anyone have any suggestions, I want to start getting quotes this week and want to put together a list of companies to approach for quotes.

 

ASHP: Heliotherm (though very expensive). Viessman and Stiebel Eltron

 

MVHR: Zehnder, Brink

 

 

[JohnMo]

32 minutes ago, James Allen said:

ASHP: Heliotherm (though very expensive). Viessman and Stiebel Eltron

You have chosen everyone that carries a huge price premium.

 

Nothing wrong with Grant, but hook up as per Chofu (original manufacturer), my only choice would be Panasonic if buying at full retail.

 

But really depends on how the system is designed, good heat pump in poorly designed and/or operated system is a p*ss poor heat pump. Mediocre heat pump can be a really good one in the correct system.

 

MVHR, nothing wrong with a Titon HRV unit, UK manufacturer, good technical support and spares if you need it. Also remember MVHR is ventilation it runs 24/7 365 days, it doesn't need lots of bells and whistles, once your house dries out boost is rarely needed so a simple momentary switch is all that is needed. Also look at the cost of filters as you will be changing every 6 to 12 months. Costs can soon mount up.

[Mike]

3 hours ago, James Allen said:

MVHR: Zehnder, Brink

For other options, see https://database.passivehouse.com/en/components/list/ventilation_small? - the Efficiency Ratio is the most important number.

 

[G and J]

On 18/08/2024 at 17:01, James Allen said:

Thanks lots of responses - really appreciate the help. 

 

We are aware cooling through MVHR is limited and we have been advised that there are no significant overheating risks on the house - we have designed most out with overhangs etc. Though FCU in the main bedroom is something we might look into, with MVHR cooling just to bring the temp of the air that isn introduced into the house down. 

 

@G and J who is the company that you have found helpful? When it comes to choosing suppliers, I favour quality over price and do like an element of hand-holding. 

Sorry about the delay, wanted to have a quick word with them before I posted.  It’s a company called Heat, Space and Light.

[Nick Laslett]

36 minutes ago, G and J said:

Sorry about the delay, wanted to have a quick word with them before I posted.  It’s a company called Heat, Space and Light.

There website is very good. Huge amount of useful material. I think about 50% of my MVHR install answers came from reading their blogs. Often their replies to people in the comments is equally as useful. They said enough positive stuff about the ComfoPost to swing my decision to install one. 

[JohnMo]

23 minutes ago, Nick Laslett said:

They said enough positive stuff about the ComfoPost to swing my decision to install one.

But have you actually read the data sheet?

 

Does it do what you think it will?

40 degree flow, for a 200m² house at typical flow rates is just over 1kW heating. If you have UFH your max flow temp should be lower than 30, which represents a 0.4% CoP hit.

 

Cooling flowing 7 degs would yield 1.88kW, on a 20 deg day that would give a CoP of about 5.1, while a fan coil or UFH flowing at 14 would give a CoP of 8.1, so a CoP hit of 3.

 

If you are actually a Passivhaus that maybe ok? Otherwise it could be a waste of more than a £1000.

[joth]

On 19/08/2024 at 12:05, James Allen said:

Based on my online research the following units are the best options. Does anyone have any suggestions, I want to start getting quotes this week and want to put together a list of companies to approach for quotes.

 

ASHP: Heliotherm (though very expensive). Viessman and Stiebel Eltron

 

MVHR: Zehnder, Brink

 

 

I know it sits uncomfortably as a tech consumer, but for ASHP in my experience it's much less about the brand of the equipment (within reason) and much more about the quality of the install. If you can find a reputable installer in your area that can do the design and come back a year (or whatever) later and do a high quality install, then yes, trusting them to select the actual kit used is probably going to be just fine. Also in the timelines of most (self) builds, the "best" option can actually change as ASHP is still fairly fast moving.

 

2 hours ago, G and J said:

It’s a company called Heat, Space and Light.

pretty sure this is a new company from some of the fragments of the old Enhabit team (before it was acquired by GBS)

Yep... Patrick Chester is the director of the company, same name as the chap that designed our MVHR install at Enhabit.

Kasper who used to do their ASHP designs (and did one for also, although we went elsewhere in the end) also has his own company now: https://www.nextstepheating.co.uk/

 

[Chanmenie]

I used the BUS Grant and got a Veismann system installed for a total cost to me of £1800, the retail on the system alone would be in the region of £10k so I was well happy.

The best advice I can give is to design your house so the ASHP is just the other side of the wall from the plant room.

My installer said mine was the simplest install he’d done, hence the labour cost was low, and he only charged me cost on the system 

[Nick Laslett]

16 hours ago, JohnMo said:

But have you actually read the data sheet?

 

Does it do what you think it will?

40 degree flow, for a 200m² house at typical flow rates is just over 1kW heating. If you have UFH your max flow temp should be lower than 30, which represents a 0.4% CoP hit.

 

Cooling flowing 7 degs would yield 1.88kW, on a 20 deg day that would give a CoP of about 5.1, while a fan coil or UFH flowing at 14 would give a CoP of 8.1, so a CoP hit of 3.

 

If you are actually a Passivhaus that maybe ok? Otherwise it could be a waste of more than a £1000.

@JohnMo, I only got it for the cooling, we have solar, so expecting that to cover the energy costs. System not yet commissioned, but my expectation is for it to knock 1°c degree off the internal house temps, if it achieves that I will be very happy.
 

Currently only have the ASHP commissioned, in the recent August heat wave we had down south, we had 2 days of 30°c weather. The house temp upstairs reached 23°c. The bedrooms are in the roof, there is no attic. The ASHP cooling is just running on weather compensation, I think I set the lowest water temp at 13°c. Also, we have not moved in yet, so I don’t feel comfortable having the windows fully open when we are not there. 
 

In the design stages, I discounted installing AC, and went with alternative cooling strategies. The Fancoil approach had not matured on BuildHub at that point in 2019, with very few members having installed it. I have nothing against Fancoils and think it is a good solution. But my wife is anti having radiators outside of bathrooms, so not something I could easily retro fit if I wanted to satisfy that criteria. 
 

I was originally going to install the Zehnder ComfoCool Q600, which is about twice the price of the ComfoPost. In discussion with Paul Heat Recovery, they recommend the ComfoPost as being more effective. Zehnder actually replaced the ComfoCool with ComfoClime 36 during our build and the ComfoClime on top of the ComfoAir is too tall to fit in our plant room. 

Edited August 21 by Nick Laslett