Air Source Heat Pumps

[dhutch]

mcbook said:

Thanks for all the comments and the suggestion of the Home Energy Scotland loan. I'll look into it.

I suppose I have a fear that I'll build a new house (family forever home) and then be annoyed with the heating system.

I know that an oil boiler can cheaply and reliably meet my heating and hot water needs but I'm unsure that an ASHP will be able to.

I fully feel your pain here.

We are currently also going through significant refurbishment of a similar size Edwardian building which we also hope and expect to be out long term family home, full re-wire, full refit of central heating and other plumbing work, redecoration etc. And knowing what the best option is for each step of the process, who big to size the rads, what to do in terms of the boiler, etc is a mine field of mixed information.

The government don't know what the plan is, installers/plumbers training and experience is all very much on conventional system design. Even over-sizing for a reduced return temp for condensing boilers is largely an alien concept. Here you are willing to part with significant cash for something which is right on topic for what we should be doing and talking about, and the lack of clarity is astonishing.

We are on mains gas, and it might be that we should have fitted larger rads, planning for a gshp or the like. As it is we have gone as good pipe layout with multiple 22mm feeds, rads as large as the plumber (who is good) can be convinced will not end the world, and are moving the 7yo gas system boiler to a new location without replacing it. This should get us another 5-10years breathing space and we can re-access.

As you say, you want to future proof, you want to invest in a house and system that will last a lifetime, and in my case I even have an eco-steak a mile wide, but you also don't what to spend a lot of money on something which doesn't perform as required of a house.

One thing I would say if planning a new build, is to get the fabric of the house high spec. Good wall insulation (wider cavity?), watch out for thermal bridging, conventional plaster rather than dot&dab pb, that sort of thing which you just cant ever change.


Daniel

[mcbook]

dhutch said:

One thing I would say if planning a new build, is to get the fabric of the house high spec. Good wall insulation (wider cavity?), watch out for thermal bridging, conventional plaster rather than dot&dab pb, that sort of thing which you just cant ever change.


Daniel

Thanks for the comments.

Regarding the fabric of the house, I agree that it's worth doing this right. There's a lot to still to be decided but my preference at the moment is to have the structure factory-built and assembled onsite by the manufacturer, including windows. Put them on the hook for airtight-ness, hopefully doing it this way will help ensure quality but we'll see.

[mcbook]

Evanivitch said:

Look at it another way, the UK government has already indicated they are expecting to remove gas central heating from new builds within the next decade.

Using oil, already not used for grid scale energy generation, is a backwards step and how is that likely to be affected by future government steps towards decarbonisation?

Whilst your concerns are valid, they're nearly all born from poor retrofit experiences. A new build property can easily be optimised for heat pumps.

I'm not too bothered about making a 'backwards' choice if I can be sure it'll meet my needs Maybe I'm naive but I don't see the Govt banning fossil fuel sales in the next 20 years.

There's Govt meddling to be considered for heat pumps too... e.g. can I rely on RHI to be available at current levels when it comes time to buy the equipment?

I agree that a new build can be optimised for heat pumps but I'm still not sure that's the best way to go. I'd love to see a detailed case study to give me some confidence but what I've found so far is mostly fluff.

[herewego]

Indeed the no more fossil fuel boilers government review includes a review of insulation levels. It seems clear to me that it's insulation that is the answer to the problem and if they can find a way to get everyone's insulation up to a high level by encouragement, subsidy, regulation whatever then the source of heat is of much lower importance. Better to spend 10k on insulation and use small electric heaters.

[Equus]

herewego said:

It seems clear to me that it's insulation that is the answer to the problem...

It's a partial answer.

It's technically possible to design a dwelling that doesn't need a heating system at all - it can function purely from solar gain, incidental heat from things like cooking and showers, and the body heat of its occupants.

The problem is that it demands careful management of that heat, which in turn requires compromises on the part of the occupants in the way they use the building. We have similar issues with the water consumption regulations that are now part of the Building Regulations - yes, they work, provided you don't mind showers that are a pathetic dribble and toilets that don't flush properly. If you build to PassivHaus standards of very high airtightness, you can probably add an internal environment that in the long term is not conducive to occupant health, due to inadequate background ventilation that allows a build up of pathogens.

I suppose it depends on what price you place upon such relatively trivial improvements in the nation's carbon footprint.

Personally, I was brought up to design buildings that serve the needs of their occupiers, not the other way around, and if it takes a small overhead on energy consumption or carbon footprint to properly achieve that, then it's a price I'm willing to pay.

There are non-fossil fuel alternatives to heat pumps, of course; biomass boilers will give you as much heat as you want, when you want it, and remain as near as makes no difference carbon neutral.

[silversurfer1]

I’m with Equus a house is for living in designing to passivhause standards would be to much for me it would be like living in a machine.

Ss

[Lemming Train]

mcbook said:

Thanks for all the comments and the suggestion of the Home Energy Scotland loan. I'll look into it.

I suppose I have a fear that I'll build a new house (family forever home) and then be annoyed with the heating system. I like to take hot baths, the kids have a bath every night - will i need to run an electric immersion heater to get the water hot enough for this? Seems like I will.

I know that an oil boiler can cheaply and reliably meet my heating and hot water needs but I'm unsure that an ASHP will be able to. It might be able to... but 'might' is not good enough when i'm thinking about a house that I'll probably live in for the next 20 years.

Maybe I'm looking at this the wrong way, I know there are environmental benefits with the ASHP but I don't really care about that. If anyone can point me in the direction of good case studies I'd appreciate it. I'd love to see some real data about the running costs for an ASHP in a new-build 250 m2 house.

My advice would be to ignore the nonsense from the ASHP sales reps in this thread and others. The argument that it works in Scandinavia is because when they build dwellings over there the walls, floors and ceilings are 13 miles thick in insulation. They stay warm because of that, nothing to do with ASHP. You could probably get the house warm just from breathing when you've got that much insulation.

In the UK? Nope. Never going to happen (as dhutch has said here and in other threads). The quality of house building here is to meet the absolute minimum legally required standard which means that it doesn't matter how many times you tell your builders you want it insulating up to the eyeballs, you'll get the minimum legally required standard, swiftly covered over with plasterboard and flooring panels whilst you're out of the way so you don't see any of it and then you'll be wondering why your house never gets above 15C and you're always shivvering.

ASHP/GSHP is the 2019 version of storage heaters with a fancy name. If you want to build your house with 40 year old redundant heating tech then go ahead but if the tech is so good then why are we not still using Economy 7/storage heaters still today instead of ripping them all out and replacing them with far superior gas/oil central heating with proper rads that are proven to work?

Do you want to be able to have a nice hot shower now, then bath your kids, do a load of washing and still have the rest of your house a nice toasty 20C, or, do you want to have to plan all that 24 hours in advance and cross your fingers and start praying that the weather doesn't turn a bit nippy in between times?

[mcbook]

Lemming Train said:

Do you want to be able to have a nice hot shower now, then bath your kids, do a load of washing and still have the rest of your house a nice toasty 20C, or, do you want to have to plan all that 24 hours in advance and cross your fingers and start praying that the weather doesn't turn a bit nippy in between times?

This is the crux of the matter for me. Having a house that is a nice place to spend time and enables family life, rather than restricts it.

[anonymous-user]

dhutch said:

One thing I would say if planning a new build, is to get the fabric of the house high spec. Good wall insulation (wider cavity?), watch out for thermal bridging, conventional plaster rather than dot&dab pb, that sort of thing which you just cant ever change.

Daniel

Just so I’m clear, I assume you’re saying conventional plaster because it’s a quality thing for you?

[caziques]

Lemming Train said:

ASHP/GSHP is the 2019 version of storage heaters with a fancy name. If you want to build your house with 40 year old redundant heating tech then go ahead but if the tech is so good then why are we not still using Economy 7/storage heaters still today instead of ripping them all out and replacing them with far superior gas/oil central heating with proper rads that are proven to work?

Don't pontificate about things you clearly know nothing about. Claiming a heat pump is a 2019 version of storage heaters is complete bks.

There are 10kWhrs of energy in a litre of heating oil, hence 1 kWhr costs about 5p in the UK.

If electricity is 12p per kWhr, a heat pump will cost 4p per kWhr (if the heat pump is 3:1).

ie the running costs are comparable - oil/gas are not "superior". Oil, gas, wood and heat pumps are alternatives, each have their place at the present time depending on circumstances.

[anonymous-user]

You’ve been away on holiday and just come back to your house. It was warm when you left so turned all the heating and hot water off.

Now there’s a cold snap and you need the house warm as quick as possible and a tank of water for the family to have showers later on.

Assuming UFH and an unvented hot water system, can anyone estimate what the typical time difference would be between a gas boiler and an ASHP to get the house as stated above?

To avoid confusion, assume 1600 sq ft bungalow with 2 bathrooms built to latest build regs.

[Lemming Train]

caziques said:

Lemming Train said:

ASHP/GSHP is the 2019 version of storage heaters with a fancy name. If you want to build your house with 40 year old redundant heating tech then go ahead but if the tech is so good then why are we not still using Economy 7/storage heaters still today instead of ripping them all out and replacing them with far superior gas/oil central heating with proper rads that are proven to work?

Don't pontificate about things you clearly know nothing about. Claiming a heat pump is a 2019 version of storage heaters is complete bks.

No, it really isn't. Your heat is being stored! There is no 'on demand' function to it, is there? It's Economy 7 for the year 2019. If you haven't "stored" enough heat then tough st, you're out of luck and you're not going to be having a hot shower, bathing the kids and doing a load of washing whilst mooching around your toasty 20C gaff in your T-shirt. You're going to be sat there in your house shivvering your tits off wishing that you hadn't listened to those green, eco, tree-hugger types on internet forums.

Any 'on demand' heating system is always going to be far superior regardless of what fuel source it's running on. Gas/oil are the 2 obvious choices because they just work without any messing about.

[Equus]

caziques said:

...the running costs are comparable - oil/gas are not "superior".

...Except that running costs are not the only criteria to consider.

Some people value flexibility, and this is where heat pumps fall flat on their ass.

[herewego]

Equus said:

herewego said:

It seems clear to me that it's insulation that is the answer to the problem...

It's a partial answer.

It's technically possible to design a dwelling that doesn't need a heating system at all - it can function purely from solar gain, incidental heat from things like cooking and showers, and the body heat of its occupants.

The problem is that it demands careful management of that heat, which in turn requires compromises on the part of the occupants in the way they use the building. We have similar issues with the water consumption regulations that are now part of the Building Regulations - yes, they work, provided you don't mind showers that are a pathetic dribble and toilets that don't flush properly. If you build to PassivHaus standards of very high airtightness, you can probably add an internal environment that in the long term is not conducive to occupant health, due to inadequate background ventilation that allows a build up of pathogens.

I suppose it depends on what price you place upon such relatively trivial improvements in the nation's carbon footprint.

Personally, I was brought up to design buildings that serve the needs of their occupiers, not the other way around, and if it takes a small overhead on energy consumption or carbon footprint to properly achieve that, then it's a price I'm willing to pay.

There are non-fossil fuel alternatives to heat pumps, of course; biomass boilers will give you as much heat as you want, when you want it, and remain as near as makes no difference carbon neutral.

As the majority of water used in a house goes straight down the toilet, the consumption can be significantly reduced by installing a catch tank and flushing with rain water. Mains water can take over in dry periods.

I don’t think trivial is a word that applies to domestic fuel burning. The national statistics figures that I can see are that the three largest individual CO2 figures are electricity production, passenger cars and residential combustion. Electricity and residential are improving every year and we clearly need to keep the pressure on. There are always people who want to keep the status quo, there were probably people who wanted to keep burning coal on open fires but most people do accept progress eventually.

[Vanordinaire]

I've fitted an ASHP to my house. It's a 250m2 single story farm steading conversion on a Scottish hillside 300m above sea level.

In a previous life I worked for a social housing provider and was involved in researching, trialling, specifying, monitoring, and evaluating various alternative heating systems. I've been to several courses and seminars on the subject and have some practical experience.

Our final conclusions at work were that in the right situation, a properly specified ASHP system can be cheaper to run than anything else other than mains gas so where, for practical or environmental reasons, mains gas is not an option, air source is worthwhile considering. We, however, had no existing properties where it was worthwhile retro fitting air source . I believe (since I left that job) that on the basis of my research, the organisation has gone on to successfully include ASHPs in some off gas grid new builds.

I've done the steading conversion almost entirely myself to my own spec and it is super insulated.
It's basically a new timber framed house built inside the old stone walls, concrete floor with 150mm kingspan, 150mm insulated frame with 50mm cavity between the stone walls and frame and insulated plasterboard inside, 170mm kingspan in roof, with insulated plasterboard inside.
I installed the ASHP (Nibe 12kW) last October and started running it before finishing the insulation because we've (naughtily) been using the building before completion.

We've been keeping the building at 19°C throughout November to now,occasionally through some pretty chilly weather. My electricity usage was ridiculously high ( £20 per day) at first with virtually no insulation in the
building then as I've completed each room, has come down steadily. Almost finished now ( still got some insulated plasterboard on the ceilings to do) and it's down to about £4 per day. Getting close to Nibe's estimate of £1200 per annum. That's with 4 adults living here at the moment keeping whole house at 19°C and a 300litre hot water tank at a constant 55°C. Hot water is via the ASHP but we also have a 3kW immersion heater which I leave on at all times. The heat pump alone is supposedly able to heat the 300l tank from cold in under 30 minutes, but as it doesn't seem to make much difference to the consumption, we just leave the immersion on too. Haven't ever been lacking in hot water.

Not sure what the underfloor pipework cost as I did it myself at the same time as doing everything else but probably around £3500. The pump and everything else associated was done by an approved installer for just under £10000. Being in Scotland, I can get a 10 year £10000 interest free loan for the system and I can also get around £1300 per annum free money for 7 years via the government's RHI scheme.

Conclusions:- Works for me in my situation, doesn't make sense for everyone.

[anonymous-user]

Vanordinaire - do you run the ASHP continually?

What I don’t understand is how these things operate, i.e. do you use them in the same way as a gas boiler (turn them in when needed or when the thermostat calls for heat) or do they need to run all the time? Do they generate heat as quickly as a gas boiler?

So many questions!

[Equus]

herewego said:

I don’t think trivial is a word that applies to domestic fuel burning.

You misunderstand me: as I said, I accept that higher levels of insulation can be a partial solution (where they are viable - not always the case on existing housing stock, which represents the vast majority of UK housing).

I am suggesting that the overhead on carbon footprint (or running cost) between specifying a heating system that offers a flexible and healthy living environment, compared to one that requires significant compromise on the part of its users, is trivial.

[herewego]

garyhun said:

You’ve been away on holiday and just come back to your house. It was warm when you left so turned all the heating and hot water off.

Now there’s a cold snap and you need the house warm as quick as possible and a tank of water for the family to have showers later on.

Assuming UFH and an unvented hot water system, can anyone estimate what the typical time difference would be between a gas boiler and an ASHP to get the house as stated above?

To avoid confusion, assume 1600 sq ft bungalow with 2 bathrooms built to latest build regs.

I expect you'd use your phone to tell the system when you expected to be home.

[Equus]

garyhun said:

What I don’t understand is how these things operate, i.e. do you use them in the same way as a gas boiler (turn them in when needed or when the thermostat calls for heat) or do they need to run all the time? Do they generate heat as quickly as a gas boiler?

Think of them as an inside-out fridge or freezer: instead of sucking heat out of the insulated box and dumping it outside, they suck heat from outside, and dump it into the insulated box. Otherwise, their operating principle and the technology they use is virtually identical.

They will run on demand, to do that, but the level of demand depends on the difference in temperature between the 'inside' and the 'outside', and the rate at which heat is being transferred from one to the other (which comes down to insulation levels and airtighness), versus the capacity of the unit.

The main difference is that food doesn't need to breathe, and doesn't get sick from build up of pathogens, whereas humans ideally need the entire volume of air in their living space to change ~6 air changes per hour, to keep it fresh enough to be healthy. So no matter how well you insulate, you need to allow for that level of 'overhead', to maintain a healthy internal environment (and my beef with PassivHaus is that it doesn't - a PassivHaus will operate at much lower levels of ACH, which there is growing evidence to suggest are unhealthy). You can recover some (not all) of the heat lost in that air change process by using MVHR, but apart from the loss due to efficiency, MVHR isn't capable of delivering 6 ACH, with sufficient dispersion, without becoming unacceptably noisy and draughty.

And no, they don't generate heat anything like as quickly as a gas boiler - that's their main limitation.

With a gas boiler, you can afford to let the heat be lost via the fabric and background ventilation when you're out of the house, because it has the capacity to ramp the temperature back up quite quickly when you get home. If you do the same thing with a heat pump, it will take all night to warm back up again, so you have to program it to run to maintain something close to the desired temperature even when you're not using the building, so that it doesn't have far to ramp back up when you return.

[mcbook]

Vanordinaire said:

I've fitted an ASHP to my house. It's a 250m2 single story farm steading conversion on a Scottish hillside 300m above sea level.

...loads of interesting details.

Thanks Vanord, that's really helpful information. I'd expect to have a similarly sized water tank so that detail is especially helpful.

Seems like by using the interest free loan and getting RHI, the capital cost is covered. What happens to the loan and RHI if you want to move house?

Still seems like it uses quite a lot of electricity though...

I really want to develop some sort of modeller for this but have no idea where to begin.