Considering an HPV (MVHR with heating/cooling) - any feedback appreciated

[Schoolboy]

We are looking to install an HPV system in our new build, timber frame property and just wondered if anyone had experience of such a system? 

 

On the face of it, by removing the need for an Air Source Heat Pump and underfloor heating, it seems to simplify the choice process, but we are keen to hear of any downsides / issues by going down this route.

 

[jack]

Supplying all of your heating via MVHR will likely require a much larger volume of air than you would otherwise be exchanging with an MVHR system set up for just ventilation. The system design is quite different and you may need a much larger MVHR unit. Having worked in offers where heating was provided via the air conditioning ducts, I personally really don't like air as a heating method.

 

If you aren't using an ASHP to provide the heat, what will you use? If resistive, then be prepared to pay 2.5-4 times as much per delivered unit of heat.

 

And what will provide your hot water?

[JohnMo]

Passivhaus say you can satisfy a heat demand of 15w/m2 based on their ventilation rates.  Anything more ends up with a burning smell as dust carbonises.  But you still need to heat the air from somewhere?

 

So if your heat demand is below this, you could go this route.

 

Other options could be A2A heat pump, heating cooling with a good CoP.

 

Nothing is easy all have downsides.

 

UFH doesn't need to be complex, we have 300mm centres, with 7 loops over 193m2.  Manifold with pump and mixer.  You need a buffer and heat pump, three way valve and hot water cylinder, a few other bits and bobs, but not a lot.  Run on Weather Compensation, you don't even need thermostats.

[Schoolboy]

27 minutes ago, jack said:

Supplying all of your heating via MVHR will likely require a much larger volume of air than you would otherwise be exchanging with an MVHR system set up for just ventilation. The system design is quite different and you may need a much larger MVHR unit. Having worked in offers where heating was provided via the air conditioning ducts, I personally really don't like air as a heating method.

 

If you aren't using an ASHP to provide the heat, what will you use? If resistive, then be prepared to pay 2.5-4 times as much per delivered unit of heat.

 

And what will provide your hot water?

I agree - the warmed air is a very different feel to a conventional heated home. I think the idea is that this would only work in a house with good air tightness. The central HPV unit contains the heating element, plus there are additional 'duct' heaters (if required) where the air enters the room. Bathrooms have heated towel rails. 

For hot water there is a separate tank.

[Schoolboy]

16 minutes ago, JohnMo said:

Passivhaus say you can satisfy a heat demand of 15w/m2 based on their ventilation rates.  Anything more ends up with a burning smell as dust carbonises.  But you still need to heat the air from somewhere?

 

So if your heat demand is below this, you could go this route.

 

Other options could be A2A heat pump, heating cooling with a good CoP.

 

Nothing is easy all have downsides.

 

UFH doesn't need to be complex, we have 300mm centres, with 7 loops over 193m2.  Manifold with pump and mixer.  You need a buffer and heat pump, three way valve and hot water cylinder, a few other bits and bobs, but not a lot.  Run on Weather Compensation, you don't even need thermostats.

Goodness 15w/m2 is low! We wont be quite at Passivehaus standard so this may not be the best route for us. Agree that all options have their downsides! You're right, the UFH is not so complicated plus heating from the ceiling does seem to go against the laws of physics!

[jack]

1 hour ago, Schoolboy said:

The central HPV unit contains the heating element, plus there are additional 'duct' heaters (if required) where the air enters the room. Bathrooms have heated towel rails.

 

So it's resistive heating, which is currently several times the cost of gas (I guess 2-4 times the cost - not sure tbh) per unit of energy delivered.

 

You say your house isn't going to be super-insulated/airtight. I think you'd really want to do your sums before committing to this approach. Your heating bills could be absolutely terrifying!

[Schoolboy]

3 minutes ago, jack said:

 

So it's resistive heating, which is currently several times the cost of gas (I guess 2-4 times the cost - not sure tbh) per unit of energy delivered.

 

You say your house isn't going to be super-insulated/airtight. I think you'd really want to do your sums before committing to this approach. Your heating bills could be absolutely terrifying!

Thanks Jack - I will check this out. There are examples of these units in the Build It Education House at Graven Hill  and Potton show home, so hopefully they should have feedback in terms of cost. 

[SuesieG]

Very interested to read this thread as we are in exactly the same position. We've lived with underflooor heating downstairs & upstairs plus MVHR for the last 25 years and are now building our second house which will be approaching passivhaus standard and considering our options for all systems. I think we have decided that whilst we may go for the HPV unit for the ventilation side of things we are not prepared to risk it all on that so will have wet underfloor downstairs provided by an outdoor ASHP plus heated towel rails in bathrooms . we are also having 12kW of solar pv, batteries and solar diverter to immersion heater in hot water tank. I might add that we are quite a large build at 350sq m but this is a house & granny flat. There will be no other heat sources (log burners etc)

You thoughts very welcome too

[Radian]

2 hours ago, jack said:

Having worked in offers where heating was provided via the air conditioning ducts, I personally really don't like air as a heating method.

You know there's been a great deal of improvement in A2A - especially domestic units. We often hear similar reports of experiences with office type A/C but it would be a shame if it put people of unnecessarily. With good insulation and airtightness, the sort of air velocities from the indoor units is going to be barely noticeable. And many systems now use thermal imagers to direct the airflow away from people. Getting heating and cooling with SCOP of 5 beats any other heating system I know of, not to mention the relatively low cost of the kit.

[Schoolboy]

1 hour ago, SuesieG said:

Very interested to read this thread as we are in exactly the same position. We've lived with underflooor heating downstairs & upstairs plus MVHR for the last 25 years and are now building our second house which will be approaching passivhaus standard and considering our options for all systems. I think we have decided that whilst we may go for the HPV unit for the ventilation side of things we are not prepared to risk it all on that so will have wet underfloor downstairs provided by an outdoor ASHP plus heated towel rails in bathrooms . we are also having 12kW of solar pv, batteries and solar diverter to immersion heater in hot water tank. I might add that we are quite a large build at 350sq m but this is a house & granny flat. There will be no other heat sources (log burners etc)

You thoughts very welcome too

Yes - it's a real gamble not having ANY underfloor, isn't it! If you are going for an ASHP anyway, then I guess you will just go for a more standard MVHR system (as opposed to the HPV which costs a lot more but does the heating and cooling as one unit). We are going to visit someone who has taken the gamble and installed the HPV system and apparently loves it, so I will report back! We are also thinking 12kw solar pv, but will need to pay the DNO £10k to upgrade  .    

[Schoolboy]

1 hour ago, Radian said:

You know there's been a great deal of improvement in A2A - especially domestic units. We often hear similar reports of experiences with office type A/C but it would be a shame if it put people of unnecessarily. With good insulation and airtightness, the sort of air velocities from the indoor units is going to be barely noticeable. And many systems now use thermal imagers to direct the airflow away from people. Getting heating and cooling with SCOP of 5 beats any other heating system I know of, not to mention the relatively low cost of the kit.

Absolutely right - we need to make sure we experience it before dismissing. The system efficiency is quoted as "efficiency varies between 300-1,200% depending on flow rates and environmental conditions." The only real way is to see for ourselves and ask those using it what their experience is in terms of real world efficiency.

[JohnMo]

7 minutes ago, Schoolboy said:

pay the DNO £10k to upgrade  .    

Why would anyone sane do that?  Do it via G99 and export limit to 16A.

 

The bigger the house the less the incremental contribution to heating you get from humans and appliances, unless you cram the house full of humans.  So the more likely you are to need some sort of heating.  Even the best insulated house is always loosing some heat to the outside.

 

If you have a screed floor its a no brainer to install loops, cost is small I only have 500m of pipe in the floor over 193m2.  So a small cost adder overall and flexibility for heating you can't install later.  Cheap to install would be a Willis heater (more costly to run).

[Schoolboy]

2 minutes ago, JohnMo said:

Why would anyone sane do that?  Do it via G99 and export limit to 16A.

 

The bigger the house the less the incremental contribution to heating you get from humans and appliances, unless you cram the house full of humans.  So the more likely you are to need some sort of heating.  Even the best insulated house is always loosing some heat to the outside.

 

If you have a screed floor its a no brainer to install loops, cost is small I only have 500m of pipe in the floor over 193m2.  So a small cost adder overall and flexibility for heating you can't install later.  Cheap to install would be a Willis heater (more costly to run).

Sorry - forgot tho say the upgrade is to three phase. Apparently that is cheap. Our electrician has been quoted 4 times that! You're right - it's a sensible precaution just to add the UFH pipework even if you dont connect it up & use it initially.

[Gone West]

4 hours ago, Schoolboy said:

We are looking to install an HPV system in our new build, timber frame property and just wondered if anyone had experience of such a system?

We built a PH a while back which was heated with electric towel rails in the bathrooms and a MVHR with built in EASHP. The whole house was kept at 23C comfortably. It was very well insulated and according to PHPP required 13kWh/m2a or 9W/m2 for space heating.

[SuesieG]

1 hour ago, Schoolboy said:

Yes - it's a real gamble not having ANY underfloor, isn't it! If you are going for an ASHP anyway, then I guess you will just go for a more standard MVHR system (as opposed to the HPV which costs a lot more but does the heating and cooling as one unit). We are going to visit someone who has taken the gamble and installed the HPV system and apparently loves it, so I will report back! We are also thinking 12kw solar pv, but will need to pay the DNO £10k to upgrade  .    

I would be very interested to hear what you find out from the visit & how big the house is & how many occupants. Luckily our DNO upgraded our area to 3Phase recently!! however we did pay to have our cable put underground. 

[jack]

2 hours ago, Radian said:

You know there's been a great deal of improvement in A2A - especially domestic units. 

 

I didn't know that - interesting, thanks.

 

2 hours ago, Radian said:

Getting heating and cooling with SCOP of 5 beats any other heating system I know of, not to mention the relatively low cost of the kit.

 

From his description, it sounded more like resistive heating.

 

1 hour ago, Schoolboy said:

The system efficiency is quoted as "efficiency varies between 300-1,200% depending on flow rates and environmental conditions." The only real way is to see for ourselves and ask those using it what their experience is in terms of real world efficiency.

 

1200%? That seems optimistic.

 

You mentioned not needing an ASHP, but you'll still be paying for the heat pump in the unit you're looking at buying. The main advantage would seem to be system integration.

[Schoolboy]

15 hours ago, jack said:

 

I didn't know that - interesting, thanks.

 

 

From his description, it sounded more like resistive heating.

 

 

1200%? That seems optimistic.

 

You mentioned not needing an ASHP, but you'll still be paying for the heat pump in the unit you're looking at buying. The main advantage would seem to be system integration.

Yes - effectively you are combining the ASHP with the MVHR unit. One of our biggest concerns, therefore is noise. The supplier does provide details of how to soundproof the plant room (utility room) walls and floor.

[Schoolboy]

16 hours ago, Gone West said:

We built a PH a while back which was heated with electric towel rails in the bathrooms and a MVHR with built in EASHP. The whole house was kept at 23C comfortably. It was very well insulated and according to PHPP required 13kWh/m2a or 9W/m2 for space heating.

That sounds great! We’re there any downsides? Was the unit noisy? How were your electricity bills?

[joth]

18 hours ago, Schoolboy said:

Sorry - forgot tho say the upgrade is to three phase. Apparently that is cheap. Our electrician has been quoted 4 times that! You're right - it's a sensible precaution just to add the UFH pipework even if you dont connect it up & use it initially.

 

Do you actually need 3phase? I was quoted about £4000 for the upgrade, over and above the £2k it was going to cost anyway to move the existing single phase meter head, and I couldn't bring myself to pay it even though it would have made my solar installation a bit simpler (no need for G99 permission).

in retrospect Installing 3ph would also have added extra project risk (time line to close and dig up the road, during lockdown as it turned out, and delays in getting a 3ph smart meter, etc).

 

Obviously if you have a hard requirement for 3ph then go ahead, as you say £10k is not the highest quote ever for what is in essence a complete new supply 

 

[Gone West]

6 hours ago, Schoolboy said:

That sounds great! We’re there any downsides? Was the unit noisy? How were your electricity bills?

We didn't find any downsides but the house was very highly insulated and was designed not to need a conventional CH system. The air from the MVHR vents was only warm, so the EASHP had a high CoP. The EASHP also heated the DHW tank to 45C. Our electricity bills were very low, but that was pre 2021.

[Schoolboy]

On 04/11/2022 at 10:47, joth said:

 

Do you actually need 3phase? I was quoted about £4000 for the upgrade, over and above the £2k it was going to cost anyway to move the existing single phase meter head, and I couldn't bring myself to pay it even though it would have made my solar installation a bit simpler (no need for G99 permission).

in retrospect Installing 3ph would also have added extra project risk (time line to close and dig up the road, during lockdown as it turned out, and delays in getting a 3ph smart meter, etc).

 

Obviously if you have a hard requirement for 3ph then go ahead, as you say £10k is not the highest quote ever for what is in essence a complete new supply 

 

Slightly off topic but you are absolutely right to question the need. Regarding PV, we have never seen such a variety of professional advice, ranging from 3kw to 14kw, battery & no battery, single & three phase. I think it comes down to a) what we believe is going to happen to the price of energy and b) how much we are going to use. If we end up with a house with four busy adults running two electric cars, a three phase system may be worth the investment. If it ends up being just me and the wife, we may have overcooked it!  

[Schoolboy]

On 04/11/2022 at 15:55, Gone West said:

We didn't find any downsides but the house was very highly insulated and was designed not to need a conventional CH system. The air from the MVHR vents was only warm, so the EASHP had a high CoP. The EASHP also heated the DHW tank to 45C. Our electricity bills were very low, but that was pre 2021.

Wow - the EASHP did the hot water as well - brilliant! As you say high insulation levels (and airtightness) is key.  

[Cognis0]

On 04/11/2022 at 15:55, Gone West said:

We didn't find any downsides but the house was very highly insulated and was designed not to need a conventional CH system. The air from the MVHR vents was only warm, so the EASHP had a high CoP. The EASHP also heated the DHW tank to 45C. Our electricity bills were very low, but that was pre 2021.

Hi @Gone West.. Can you recommend EASHP unit? Vaillant do the aroSTOR which looks interesting. Would you recommend a single supplier/installer for all MVHR and EASHP together? Thanks

[Gone West]

@Cognis0 I used a Genvex Combi 185L which was a combined MVHR and EASHP which heated the DHW and the air through the ventilation system. I wouldn't necessarily use a single supplier for both MVHR and EASHP. I contacted ADM Systems who were very helpful when I was looking into MVHR systems. Genvex were also helpful. I can't recommend an EASHP for heating DHW but from what I have read the aroSTOR seems OK. I would check that which ever EASHP DHW system you use doesn't have an anode in the tank.

[Cognis0]

Thanks, that's helpful.

Can you please clarify what the issue would be with an anode?

I am a bit mystified by EASHP which also reheats the ventilation (or some with wet heating). Most of the heat coming through the MVHR is recycled by the heat exchanger back to supply; by the time the DHW is heated it's difficult to understand what energy can be left to provide any meaningful contribution to space heating!

Cheers....