Air to Air Heat Pumps

[Coldwarrior]

That cannot be correct. If your home has genuinely gone from a D2 to A2, your energy use should be a fraction of what it previously was regardless of the type of heating system. Are you excluding the fact that with a heat pump you are now electricity only and have no gas bill??

I would guess they are comparing with the previous year, where they may have been at work out of the house most of the day with the heat off, to now where they are wfh and the house is maintained at a level comfortable temperature all the time?

dem_syhp am I correct? Otherwise I'd be surprised that the units of energy needed hasn't dropped a fair bit.

 

[_OkGo_]

They probably have photovoltaic panels, which would make more sense with a heat pump (offsetting the electricity the heat pump uses) than the solar tubes for hot water.

The same applies to PV. In a highly efficient A rated home, the only heating required during summer months (and late spring/early autumn) should be for water. If you need 8kWh of energy to heat water, your PV system needs to be sized to supply 8kWh during summer months. The same amount of heating with a heat pump can be achieved using 2.25kWh of electricity, of which a lot can be done at very cheap night rates

Basically your heat pump should not be running off an oversized PV as it is more economical and energy efficient to just use the grid. During winter months, the same PV is contributing very little to electricity, maybe 2-3kWh per day so it is not a good investment along with a heat pump.

I would guess they are comparing with the previous year, where they make have been at work out of the house most of the day with the heat off, to now where they are wfh and the house is maintained at a level comfortable temperature all the time?

WFH should only be a small contributor (5-10%) especially if it is A-rated. Going from D to A rated should have slashed the energy use so it is more than likely behavioral changes or incorrect use of the system (wrong settings, constant fiddling)

 

[Micks'r]

That cannot be correct. If your home has genuinely gone from a D2 to A2, your energy use should be a fraction of what it previously was regardless of the type of heating system. Are you excluding the fact that with a heat pump you are now electricity only and have no gas bill??

This, imo, is the flaw of the whole BER system for rating a dwelling especially when it comes to the heat retention characteristics, in that the rating achieved (BER) is a result mainly of a box ticking exercise rather than any kind of in-depth investigation.

I expect this flaw to come more to the fore when a lot of heat pumps are installed replacing convention heating systems and are found to be not up to the task (either very expensive to run and/or not able to deliver the heat when very cold) because the BER cert cannot be relied upon.

 

[dem_syhp]

Yes, sorry, photovoltaic panels, so yes, I'd absolutely expect costs to be lower in the summer (hence the comment, I can't really say for another 6 months how things will fare).

We still have a gas for cooking, albeit very low energy usage, but still have standing charges. [I know we can change, but for now things are staying as they are]

Yes, I agree we've someone in the house all the time, which wasn't the case a year ago, so I can't compare like with like. But I've no reference to how much other peoples bills have gone up with someone working from home.

Our yearly gas bill before, for heating + hot water, was about 500 Euro, this is based on the last two years - This was without shopping around as our figures were low, and shame to say on askaboutmoney I just didn't. But our most recent electricity bill (for two months) was in excess of 220 Euro (Estimated reading, but I'd the actual kWh used for the billing period month and just calc'd out difference). I didn't really expect our bills to go down, but hadn't expected it to go up....which by the time I've included summer it may not. I can only go on the data I currently have.

As has been suggested behavioral change is part of the problem....but its not one we want to make. (lack of research on our part before). How we previously liked to live is to turn on the heating when we were cold. So if actively working around the house - say working out, DIY, cleaning, moving around that is, I'd rarely need much/any heat. If sitting down, on the computer, in front of the television, I want a warmer room. I don't want a warmer room all the time - but that's how the set up is designed to run -I know its bad practice to be messing with it, so I don't..... but it doesn't suit me (yet! Maybe I'll go all soft and will want the additional heat ).

I'm not saying they're not efficient, I'm saying, so far, based on 4-6 months, the jury is out as to which way I'd go if given the choice again. The house is way more comfortable, we absolutely had rooms that were never comfortable, but that's the insulation.

 

[_OkGo_]

So if actively working around the house - say working out, DIY, cleaning, moving around that is, I'd rarely need much/any heat. If sitting down, on the computer, in front of the television, I want a warmer room.

That is one of the downsides to A-rated homes. Once you get used to the constant temperature, any level of moderate activity can suddenly make you feel very warm.

but it doesn't suit me (yet! Maybe I'll go all soft and will want the additional heat ).

I can confirm that's exactly what happens

My advice to get the most out of the system:

• Change provider every year for the cheapest rates
• Switch to a day/night rate if you have a night meter
• Do not let the room temperatures drop at night, it is very cheap to heat at night on the lower rates.
• Do set your bedrooms lower all day so they are not uncomfortable at night even if heating comes on
• Keep all doors open especially within the same heating zone to maintain the constant temp. (We benefit from a south facing living room with large windows that effectively keeps our stats at temperature during daytime even in winter so very little additional heat required)
• Check the temperature on your water tank and reduce it until the water temperature is comfortable. This is often a big mistake and waste of energy with heat pumps. To maintain a good COP, the water tank should be set as low as possible. It makes no sense to have really hot water coming out of taps that you then use the cold mixer to cool. There is a balance too between how low you can drop the temp and having enough water for all residents to shower etc.
• Similarly, the output temperature for your space heating is just as important. Dropping the temp by a few degrees means the systems stays on for longer but runs more efficiently
• Finally, if you do make changes to stats or other temperature settings. Let it 'settle' for a few days before adjusting again until everything feels comfortable
• You won't really see the impact of any of the above suggestions until next winter as your summer usage should be very low anyway

I'm not saying they're not efficient, I'm saying, so far, based on 4-6 months, the jury is out as to which way I'd go if given the choice again. The house is way more comfortable, we absolutely had rooms that were never comfortable, but that's the insulation.

That is probably where you frustration lies. As you already had gas, you didn't really need a heat pump. They would both be as effective at heating your home. Heat pumps are not necessarily better than gas, they are just another option in A-rated homes. Their benefits rapidly disappear if homes are not A-rated. Personally, I would be quiet annoyed with whoever spec'd your home to have gas, PV and a heat pump, it makes no sense.

 

[dem_syhp]

Thanks @_OkGo_ for the suggestions. Many of them we're already on our way to learning - I'm quite sure I'll be able to get back down to where we were, but I suspect it will take a bit of monitoring!

 

[Coldwarrior]

Check the temperature on your water tank and reduce it until the water temperature is comfortable.

Just on this, the temp of the tank should be brought up to 60 C at least once a week to prevent any legionella bacteria growing. Not sure if the heat pumps have a mode for this (I think some do? ), if not then a 7 day timer immersion could be used to give it a quick blast of a higher temperature.

 

[RobFer]

That is one of the downsides to A-rated homes. Once you get used to the constant temperature, any level of moderate activity can suddenly make you feel very warm.

I can confirm that's exactly what happens

My advice to get the most out of the system:

• Change provider every year for the cheapest rates
• Switch to a day/night rate if you have a night meter
• Do not let the room temperatures drop at night, it is very cheap to heat at night on the lower rates.
• Do set your bedrooms lower all day so they are not uncomfortable at night even if heating comes on
• Keep all doors open especially within the same heating zone to maintain the constant temp. (We benefit from a south facing living room with large windows that effectively keeps our stats at temperature during daytime even in winter so very little additional heat required)
• Check the temperature on your water tank and reduce it until the water temperature is comfortable. This is often a big mistake and waste of energy with heat pumps. To maintain a good COP, the water tank should be set as low as possible. It makes no sense to have really hot water coming out of taps that you then use the cold mixer to cool. There is a balance too between how low you can drop the temp and having enough water for all residents to shower etc.
• Similarly, the output temperature for your space heating is just as important. Dropping the temp by a few degrees means the systems stays on for longer but runs more efficiently
• Finally, if you do make changes to stats or other temperature settings. Let it 'settle' for a few days before adjusting again until everything feels comfortable
• You won't really see the impact of any of the above suggestions until next winter as your summer usage should be very low anyway

That is probably where you frustration lies. As you already had gas, you didn't really need a heat pump. They would both be as effective at heating your home. Heat pumps are not necessarily better than gas, they are just another option in A-rated homes. Their benefits rapidly disappear if homes are not A-rated. Personally, I would be quiet annoyed with whoever spec'd your home to have gas, PV and a heat pump, it makes no sense.

I guess hypothetically if carbon taxes are radically increased, this person's system may gradually become easier to justify financially.

 

[mike2017]

If it's vented, yes legionella is a risk
It it's unvented my understanding is no air can get into system so no risk of legionella
Interestingly as the thread is about Air to Air, Kore had a recent Daikan seminar online (youtube has a copy) and air to air systems can't heat water, air to water can. They are working on a system to deliver this next year as apartments would find this combination useful. They do supply heat emitters than can cool or heat which is interesting and can be mounted up high out of the way (with their A2W models).
If retrofitting A2W watch out for microbore - not compatible with that piping so more mess.

 

[Foreveramber]

That is one of the downsides to A-rated homes. Once you get used to the constant temperature, any level of moderate activity can suddenly make you feel very warm.

I can confirm that's exactly what happens

My advice to get the most out of the system:

• Change provider every year for the cheapest rates
• Switch to a day/night rate if you have a night meter
• Do not let the room temperatures drop at night, it is very cheap to heat at night on the lower rates.
• Do set your bedrooms lower all day so they are not uncomfortable at night even if heating comes on
• Keep all doors open especially within the same heating zone to maintain the constant temp. (We benefit from a south facing living room with large windows that effectively keeps our stats at temperature during daytime even in winter so very little additional heat required)
• Check the temperature on your water tank and reduce it until the water temperature is comfortable. This is often a big mistake and waste of energy with heat pumps. To maintain a good COP, the water tank should be set as low as possible. It makes no sense to have really hot water coming out of taps that you then use the cold mixer to cool. There is a balance too between how low you can drop the temp and having enough water for all residents to shower etc.
• Similarly, the output temperature for your space heating is just as important. Dropping the temp by a few degrees means the systems stays on for longer but runs more efficiently
• Finally, if you do make changes to stats or other temperature settings. Let it 'settle' for a few days before adjusting again until everything feels comfortable
• You won't really see the impact of any of the above suggestions until next winter as your summer usage should be very low anyway

That is probably where you frustration lies. As you already had gas, you didn't really need a heat pump. They would both be as effective at heating your home. Heat pumps are not necessarily better than gas, they are just another option in A-rated homes. Their benefits rapidly disappear if homes are not A-rated. Personally, I would be quiet annoyed with whoever spec'd your home to have gas, PV and a heat pump, it makes no sense.

Do you have to leave all the doors in the same heating zone open? I'm thinking of replacing my Grant's oil burner replaced with the air to water heat pump but it wouldn't suit me to leave all doors open

 

[_OkGo_]

Do you have to leave all the doors in the same heating zone open? I'm thinking of replacing my Grant's oil burner replaced with the air to water heat pump but it wouldn't suit me to leave all doors open

The 'keep the doors open' comment is in relation to passively keeping an even temperature in A-rated homes. Not specifically for a heat pump but it all helps. Basically there is no point letting some rooms overheat by closing doors while sunlight is streaming in and your heating system is on bringing a room up to temperature at the other side of the house.

From your other post, a heat pump is probably not a good option for you until you have addressed all the heat loss issues ( in particular the convective heat loss) as pointed out by @Micks'r. Heat pumps are only a part of the overall heating system. Putting one on an old house is a bad idea unless all heat loss issues have been addressed.

 

[roker]

I had assessment done with a retrofit company to measure heat loss when a full insulation job is done e.g attic insulation, floor insulation external insulation ( in my case). A BER would then be achieved and the idea in order to achieve a BER rating to B2 at least for houses built before 2011.

 

[David_Dublin]

That is probably where you frustration lies. As you already had gas, you didn't really need a heat pump. They would both be as effective at heating your home. Heat pumps are not necessarily better than gas, they are just another option in A-rated homes. Their benefits rapidly disappear if homes are not A-rated. Personally, I would be quiet annoyed with whoever spec'd your home to have gas, PV and a heat pump, it makes no sense.

Is the above pretty much undisputed?

We're planning an extension and refurb job. We're gas at the moment, but need to replace boiler, and extension part of house will be UFH. Wondering if we should plan to stay gas, or run as A2W.

Other downstairs rooms may also be UFH as they are draughty suspended floors, old house, so a good opportunity to cut joists and pour concrete. So would make sense to go UFH in that case.

Some people I talk to are adamant that A2W is the way to go. Elsewhere I read thats only for A rated, and even then running costs can be high. I'm just so confused! Also, we have decent rads upstairs, so going A2W would mean changing these to alu ones.

 

[Micks'r]

Comparing gas or oil fired ch to a heat pump system is like comparing apples to oranges. Yes, they are both heating systems just as apples & oranges are fruit but that is really where the comparison ends.
The main function of a heating system is to supply heat to the house at a higher rate than the heat is lost from the house.

High temperature heating systems such as gas / oil were developed for houses with a high heat loss rate. These systems work well because they are capable of delivering large amounts of heat energy in a short period of time. They can deliver heat at a higher level than the house loses it so the house heats up.

Low temperature systems such as heat pumps are used to deliver a much lower level of heating over a much longer period of time. Therefore they work best when married to low temp distribution systems such as uf, high thermal mass buildings and also where the heat loss from the house is very low to start off with. Also they are designed to be running constantly so the house doesn't swing madly from cold to hot to cold etc but rather stays as a constant comfortable temperature.

The issue (confusion) arises when you try to shoehorn a hp system in a house with high levels of heat loss. You end up with v high electricity bills or not being able to heat the house or in some cases both!

This is why it is vital that before a hp is considered, serious attention must be paid to the significant reduction of the heat losses in the first place.

 

[David_Dublin]

Comparing gas or oil fired ch to a heat pump system is like comparing apples to oranges. Yes, they are both heating systems just as apples & oranges are fruit but that is really where the comparison ends.
The main function of a heating system is to supply heat to the house at a higher rate than the heat is lost from the house.

High temperature heating systems such as gas / oil were developed for houses with a high heat loss rate. These systems work well because they are capable of delivering large amounts of heat energy in a short period of time. They can deliver heat at a higher level than the house loses it so the house heats up.

Low temperature systems such as heat pumps are used to deliver a much lower level of heating over a much longer period of time. Therefore they work best when married to low temp distribution systems such as uf, high thermal mass buildings and also where the heat loss from the house is very low to start off with. Also they are designed to be running constantly so the house doesn't swing madly from cold to hot to cold etc but rather stays as a constant comfortable temperature.

The issue (confusion) arises when you try to shoehorn a hp system in a house with high levels of heat loss. You end up with v high electricity bills or not being able to heat the house or in some cases both!

This is why it is vital that before a hp is considered, serious attention must be paid to the significant reduction of the heat losses in the first place.

Thanks Mick. I've a good understanding of the above, all makes sense.

In my case, though we most likely have sufficient thermal mass in the ground floor floors, the issue I have is that when undertaking a big refurb, including new windows, doors, insulation, airtightness measures, I don't know if the result of this work will deliver a house suitable for hp, i.e. what the heat loss will be and how much running a hp will be/how effective it will be.

I know what the likely answer to this is: make it so, only go for hp if the result will support efficient use of hp by engaging with the right professionals and design for a specific BER rating. Maybe that is my answer.

 

[noproblem]

I had assessment done with a retrofit company to measure heat loss when a full insulation job is done e.g attic insulation, floor insulation external insulation ( in my case). A BER would then be achieved and the idea in order to achieve a BER rating to B2 at least for houses built before 2011.

Hopefully you got this done with one of the companies on the SEAI list? You will pay for this and it's quite substantial, but if you chose the company to do the work they'll allow you this cost against the overall job. The quotation they give is very, very, detailed and the company I saw and was involved with on behalf of my sons job in Dublin really knew what they were doing. It wasn't a quotation given with a quick look and a few figures.

 

[Micks'r]

I know what the likely answer to this is: make it so, only go for hp if the result will support efficient use of hp by engaging with the right professionals and design for a specific BER rating. Maybe that is my answer.

Yeah, this is it really. Concentrate in doing the best job you can on the building fabric and then how the place is heated becomes a much simpler problem to solve.

 

[David_Dublin]

Will probably avoid risk, do as good a job as we can and stay with gas heating. Seems like a sensible choice for a 100 year old house that we're not going to be overly focused on air tightness.

 

[Leo]

Seems like a sensible choice for a 100 year old house that we're not going to be overly focused on air tightness.

Only choice in that case!

 

[Coldwarrior]

The same applies to PV. In a highly efficient A rated home, the only heating required during summer months (and late spring/early autumn) should be for water. If you need 8kWh of energy to heat water, your PV system needs to be sized to supply 8kWh during summer months. The same amount of heating with a heat pump can be achieved using 2.25kWh of electricity, of which a lot can be done at very cheap night rates

Basically your heat pump should not be running off an oversized PV as it is more economical and energy efficient to just use the grid. During winter months, the same PV is contributing very little to electricity, maybe 2-3kWh per day so it is not a good investment along with a heat pump.

Just on this about the PV solar again, I'm hopefully soon going to be moving to a new build (A2 or A3 BER) that'll have an air to water heat pump, underfloor heating downstairs and radiators upstairs. I'll be working from home most of the time and will probably go for an electric car the next time I change cars. The house won't come with any solar panels as standard, though I was considering asking the builder to install PV. From what you've said it sounds like it may not be worth it, is there any merit to installing PV in this case?