New houses with Air to Water Heat Pumps

yannakis

I was impressed to see newbuilds with no ventilation & no PV being rated A3. So digged deeper to see what's the story and realised there's a big difference compared to other developments - Air to Water Heat Pumps!

How impressively productive can they be to compare with gas heating+DCV+phtovoltaics at the BER scale? Maybe there's other elements I'm missing but I think these are the most important.

yannakis

I am very curious to see your input, so I'm bumping it up a bit

KCross

How can they have no ventilation?
If its an airtight house, which presumably it is at A3, you would have to have ventilation?!

yannakis

Here's an example development - more specifically, look at the top right in this photo, you can see the sky through the vent (which looks like an opening with grills).

Tefral

yannakis wrote: »

Here's an example development - more specifically, look at the top right in this photo, you can see the sky through the vent (which looks like an opening with grills).

A heat pump is completely separate to ventilation. The Air Source heat pump you mention takes the air from the outside and converts it. Think of a fridge in reverse.

I am wondering if you are confusing it with a MHRV system which takes the warm stale air from your house and uses that to heat the incoming fresh air in the house? In such cases you have no vents in the walls and the house is air tight.

The house you link to doesnt have that as it has vents.

Calahonda52

OP: what you are missing, perhaps, is the math behind the A3 rating, which, when clearly understood, shows why nobody responded first time out.

JohnnyB23

Got talking to a plumber , he tells me that I would also need to install a small oil boiler as well as an A2W heat pump. The boiler would kick in when external temps hit 0 degrees, as A2W heat pumps do not really work at these temps (not very efficently anyway). Anybody else told that they would need a secondary heat source as well as A2W HP?

Calahonda52

JohnnyB23 wrote: »

Got talking to a plumber , he tells me that I would also need to install a small oil boiler as well as an A2W heat pump. The boiler would kick in when external temps hit 0 degrees, as A2W heat pumps do not really work at these temps (not very efficently anyway). Anybody else told that they would need a secondary heat source as well as A2W HP?

In fact it would need to be a bit above 0 because once you get down below about 7 the HP will tend to frost up and they use elec to defrost which is Randle McMurphy territory so you need to quiz the supplier on this

murphaph

JohnnyB23 wrote: »

Got talking to a plumber , he tells me that I would also need to install a small oil boiler as well as an A2W heat pump. The boiler would kick in when external temps hit 0 degrees, as A2W heat pumps do not really work at these temps (not very efficently anyway). Anybody else told that they would need a secondary heat source as well as A2W HP?

?
We have only got an A2W hp in our house near Berlin and definitely do not need an additional heat source and we got down to -14 last winter. The immersion elements did not come on at all during winter.

Sure it's not as efficient at lower temperatures but it can certainly handle the relatively few very cold days a year without investing in a second heat source.

FrankGrimes

murphaph wrote: »

?
We have only got an A2W hp in our house near Berlin and definitely do not need an additional heat source and we got down to -14 last winter. The immersion elements did not come on at all during winter.

Sure it's not as efficient at lower temperatures but it can certainly handle the relatively few very cold days a year without investing in a second heat source.

Been trying to research A2W heat pumps and keep hearing this stuff about they need a separate heat source but is that really just guff and likely from those who haven't actually had such a system in their house? Could it be that murphaph is using a better pump in Berlin than is generally available in Ireland?

170sqm house, mostly bungalow, small two storey piece. Going underfloor heating up and downstairs. House will be well insulated and good sir tightness and using mechanical heat recovery. Want A2W as I like the idea of being less exposed to oil prices in the long term, so even if it's only marginally better than gas, would go for it. Would love if someone could put me out of misery and recommend an A2W pump that is proven to work well in circumstances similar to the above and doesnt need a separate secondary heat source.

One thing that woukd be a deal breaker though: currently staying in a house at a hotel and the hot water is incredibly hot but it's on a pump and dvery time hot water is used the noise of the pump can be heard throughout the house. Don't care what potential benefits such a system may bring but that noise would drive me nuts so no way I'd go with anything that has that setup. Is tgat a combi boiler setup? Does A2W cykinder work in similar manner or not? Concsious that we dont have much space to out in a tank upstairs to use gravity but must find a less noisy way of solving that.

Calahonda52

murphaph wrote: »

?
We have only got an A2W hp in our house near Berlin and definitely do not need an additional heat source and we got down to -14 last winter. The immersion elements did not come on at all during winter.

Sure it's not as efficient at lower temperatures but it can certainly handle the relatively few very cold days a year without investing in a second heat source.

The Berlin spec and configuration of a HP and the HP for here is going to be different, same as air-con units in UK and Irish cars, not the same as Mainland Europe

FG: where is the booster pump?

murphaph

FrankGrimes wrote: »

Been trying to research A2W heat pumps and keep hearing this stuff about they need a separate heat source but is that really just guff and likely from those who haven't actually had such a system in their house? Could it be that murphaph is using a better pump in Berlin than is generally available in Ireland?

170sqm house, mostly bungalow, small two storey piece. Going underfloor heating up and downstairs. House will be well insulated and good sir tightness and using mechanical heat recovery. Want A2W as I like the idea of being less exposed to oil prices in the long term, so even if it's only marginally better than gas, would go for it. Would love if someone could put me out of misery and recommend an A2W pump that is proven to work well in circumstances similar to the above and doesnt need a separate secondary heat source.

One thing that woukd be a deal breaker though: currently staying in a house at a hotel and the hot water is incredibly hot but it's on a pump and dvery time hot water is used the noise of the pump can be heard throughout the house. Don't care what potential benefits such a system may bring but that noise would drive me nuts so no way I'd go with anything that has that setup. Is tgat a combi boiler setup? Does A2W cykinder work in similar manner or not? Concsious that we dont have much space to out in a tank upstairs to use gravity but must find a less noisy way of solving that.

Sounds quite similar to us-new build with n=0.7 air tightness, very well insulated.

We have cellar + dormer bungalow on top, 220m² heated floor area (UFH on all three floors)

We have a bog standard Thermia Atec Total 11kW and like I say, it did not need to fall back on any of its 3 immersion heating elements at all last winter. It only ever used them during the screed drying phase of the build and since then they have never come on.

We haven't even fitted our stove (just for the comfort of a fire the odd time) yet, so we definitely didn't assist the HP that way.

There's no way that a HP in Ireland in a well insulated, airtight new build with UFH throughout should need a second heat source. I wouldn't bother with the HP at all if that was the case. The air temps in Ireland are higher in winter than Germany. The downside is that it hovers around freezing a lot in Ireland so you presumably have more defrost cycles on an A2W unit, even though it's warmer (same reason roads in Ireland break up so easily in winter due to freeze-thaw effect).

If you go ahead with the HP just make sure you get a modulating one that can precisely match the heat demand of the house, rather than cycling on and off (leads to premature compressor failure).

JohnnyB23

Thanks for the info guys, I'm not sure I'm in the right forum/thread for my next query.
I'm thinking of going with A2W heat pump, heat recovery system and go for high level of airtightness in our new build We're building a 200sqm storey and a half, ufh on both floors. My question is this...

JohnnyB23

Would there be much of a difference costwise between a regular build and building with a high level of air-tightness in mind? I got a price before I decided to go air tight/ heat recover system and I'm curious about the difference.

murphaph

There's no point building without a high level of airtightness. All the insulation in the world will do little good if draughts can simply bypass it.

I'd rate airtightness as just as important as insulation, especially in a low temp system with a heat pump as heat source.

FrankGrimes

murphaph wrote: »

Sounds quite similar to us-new build with n=0.7 air tightness, very well insulated.

We have cellar + dormer bungalow on top, 220m² heated floor area (UFH on all three floors)

We have a bog standard Thermia Atec Total 11kW and like I say, it did not need to fall back on any of its 3 immersion heating elements at all last winter. It only ever used them during the screed drying phase of the build and since then they have never come on.

We haven't even fitted our stove (just for the comfort of a fire the odd time) yet, so we definitely didn't assist the HP that way.

There's no way that a HP in Ireland in a well insulated, airtight new build with UFH throughout should need a second heat source. I wouldn't bother with the HP at all if that was the case. The air temps in Ireland are higher in winter than Germany. The downside is that it hovers around freezing a lot in Ireland so you presumably have more defrost cycles on an A2W unit, even though it's warmer (same reason roads in Ireland break up so easily in winter due to freeze-thaw effect).

If you go ahead with the HP just make sure you get a modulating one that can precisely match the heat demand of the house, rather than cycling on and off (leads to premature compressor failure).

Thanks murphaph, the sound advice I've come to expect from you (lurker on politics forum and suffice to say am often in agreement with your posts!). Any thoughts on what models offer the modulating functionality you refer to? Knowing 11kW works for you in Berlin has me inclined to go for similar high powered unit (vs typical unit many suppliers in ireland might spec) and run it underpowered rather than at high utilisation ( the opposite of overclocking a PC if you will), so just want to nail down some models to shortlist (tight on time since baby #2 arrived!).

FrankGrimes

Calahonda52 wrote: »

The Berlin spec and configuration of a HP and the HP for here is going to be different, same as air-con units in UK and Irish cars, not the same as Mainland Europe

FG: where is the booster pump?

Can you elaborate on the ways in which the HP is different here vs mainland Europe? Genuinely interested as would have thought with seemingly few of them being Irish made it was very much a case of tdking products designed in other countries (with more severe weather extremes in genersl such as Scandinavia) and using them here.

murphaph

FrankGrimes wrote: »

Thanks murphaph, the sound advice I've come to expect from you (lurker on politics forum and suffice to say am often in agreement with your posts!). Any thoughts on what models offer the modulating functionality you refer to? Knowing 11kW works for you in Berlin has me inclined to go for similar high powered unit (vs typical unit many suppliers in ireland might spec) and run it underpowered rather than at high utilisation ( the opposite of overclocking a PC if you will), so just want to nail down some models to shortlist (tight on time since baby #2 arrived!).

Don't "underclock" a traditional heat pump whatever you do. A big powerful unit can satisfy heat demand quickly, so it goes on and off again quickly and then it cools down a bit and it goes on and off again...this is "cycling" and is bad for traditional heat pumps, which is why they should be specced to closely match the actual expected heat demand.

Perhaps calculating the heat demand is the bigger issue in Ireland. We have dozens of pages of calculations for each room based on size and what adjoins it etc. This is then used to choose an appropriate unit.

A modulating unit like a Panasonic Geisha (quite popular here) means you can slightly over spec and not pay this cycling price.

Dcmb1984

Hi guys I was just reading all yere previous posts and I'm currently getting ready to give my house out to a builder and I'm wondering has anyone here a opinion on MHRV units combined with a heat pump to heat your domestic water. I believe they use the exhaust air to heat the water. Anyone have an opinion on them?

KCross

Dcmb1984 wrote: »

Hi guys I was just reading all yere previous posts and I'm currently getting ready to give my house out to a builder and I'm wondering has anyone here a opinion on MHRV units combined with a heat pump to heat your domestic water. I believe they use the exhaust air to heat the water. Anyone have an opinion on them?

That's news to me. They are separate systems. MHRV brings in fresh air to the house. The heat pump heats the water and the underfloor.

I'd say do a bit more googling and get some companies to quote you some prices and give you info on the systems.

BryanF

Dcmb1984 wrote: »

Hi guys I was just reading all yere previous posts and I'm currently getting ready to give my house out to a builder and I'm wondering has anyone here a opinion on MHRV units combined with a heat pump to heat your domestic water. I believe they use the exhaust air to heat the water. Anyone have an opinion on them?

Not a good idea unless your have super insulation and even better air-tightness. These systems were first introduced as being efficient in passive houses where the kw/hr heating requirements were really low.

Unless you've set a 0.6ach in the contract and calculated your heat loss with something better than the BER software, be cautious of these systems

Dcmb1984

BryanF wrote:

Unless you've set a 0.6ach in the contract and calculated your heat loss with something better than the BER software, be cautious of these systems

BryanF wrote:

Not a good idea unless your have super insulation and even better air-tightness. These systems were first introduced as being efficient in passive houses where the kw/hr heating requirements were really low.

Thanks Bryan. My build is not passive but A3. I aim to achieve slightly better on all values set out in my BER but probably not good so for this system.
My just stick with the straight forward air to water heat unit.

Dcmb1984

BryanF wrote:

Not a good idea unless your have super insulation and even better air-tightness. These systems were first introduced as being efficient in passive houses where the kw/hr heating requirements were really low.

Hello again Bryan
Just to confirm the exhaust air heat pump is just to heat the domestic hot water. The air the water heat pump which is also part of the system I've priced then just does the underfloor heating. Just confirming we're talking about the same system, and not just the exhaust air heat pump for the buildings entire heating requirements as in some passive house's.

BryanF

Dcmb1984 wrote: »

Hello again Bryan
Just to confirm the exhaust air heat pump is just to heat the domestic hot water.

What are your buildings heat loss, what is the expect airtightness figure and what is the w/m2/yr expected heat load

The air the water heat pump which is also part of the system I've priced then just does the underfloor heating. Just confirming we're talking about the same system, and not just the exhaust air heat pump for the buildings entire heating requirements as in some passive house's.

How have you priced a system, if you don't know the above?

The system may work, but you better make sure it's accurately sized to suit your house, The only way to do that is to accurately assess the above parameters