I moved to the UK nine years ago from Cayman, where AC is everywhere (for obvious reasons) and central AC is built into the designs of homes for many decades now. Water heating used to always be done by immersion heaters (typically well insulated and just left on all the time), though after we had a hurricane in 2004 that flooded the ground floor of many homes, a lot of people now have "instant" water heaters. Still electric (so not like the UK combi boilers), but work well when sized correctly.
Anyway, I was a bit shocked when I bought a "new build" home on the southern edge of London to find how hot it gets. As we all know, the UK almost mandates homes to be designed to soak up and retain heat, but in summer, that meant for me that a 26c day and 16c overnight (pretty common) gave me bedrooms that would not cool below about 27c overnight on a still evening.
So, AC was on my mind right away. My house came with (basic) solar already, so that helps a bit, but I invested £10k in total on two air-to-air heat pump solutions (good news is that all domestic AC is already able to heat as well as cool, so that makes the parts and labour zero-rated for VAT when dual use is spec'd, and that means that this is the default for AC installers in the UK already). This was before the £2500 grant, so now each system would be less.
Each system handles three rooms, so de facto the whole house is cooled. In flat out use this week (with temps yesterday at 34c and only dropping to 25c ovenight), it used only about an additional 10kwh over and above the usual daily summer electricity use.
So far so good, but what about the future?
- when my gas boiler dies (useful life around 10 years, so for me that is a couple of years away), I take it out, turn off the gas, then simply use the hot water tank already in the house. For the bathrooms in winter I remove the (hot water) heated towel rails and put in electric ones. That is all I have to do and then I am using an all electric system for heating and cooling
- I will move to an electric car soon enough and will make sure that one has bidirectional charging, so will charge up the car overnight using cheaper electricity and use it as a battery during the day.
- I may upgrade my solar panels for summer AC use, but with the car as a battery, no need for additional battery installation.
All in all, I will be off carbon-based power (gas) soon enough, and with the inexorable transition to renewables, I can see that within a reasonable time I will be heating and cooling my house efficiently (as you note) with air-to-air heat pumps, devices that will use renewable power.
Oh, and given that I am very familiar with AC compressor units outside homes and businesses in Cayman, I was astonished to find that my 10kw exterior unit runs so silently (55dba). At a distance of over about 3m from the unit, the birdsong is louder. Oh, but my neighbour has a portable AC unit running now next door, it is much louder ;)
Went with the AC company recommendation, Samsung Cebu. Very happy with them. The last few days, at 34c peak, the two exterior units (total of 16.8kwh) and six interior units (total of 17.5kwh) have been going all the time (for about 12 hours per day at least). Incremental electricity usage, astonishingly, only a net 8kwh per day.
I put this down to a few things. First, the rating on the units is peak rating, indoor units cycle on and off based on thermostat. Second, we have a battery of basic solar panels that were installed when the house was a new build. Total rating only 1kwh, but that helps. Third, heat pumps (whether cooling or heating) are pretty efficient these days ;)
The government grant for air-to-air heat pumps, apart from being less generous is entirely wide of the mark. You can only get it if the heat pump entirely replaces your existing heating system. Yet adding an air-to-air unit would provide both air conditioning and a more efficient form of supplementary heating than the existing heating system, allowing reductions in the gas or oil consumed in operating it. Exactly what government policy is intending, yet failing, to do. Associate an air-to-air heat pumps with solar panels to power it, and there is no added load on the grid from the aircon mode because the aircon will mostly be operating in sunny weather.
UK and for that matter all of Europe going “net zero” is a grim joke once you understand that China, India, Africa and the Middle East will *never* embrace the Western obsession with “carbon”. It’s simply not a thing in most of the world, other than participating in fancy conferences and entering into treaties with naive Europeans that confer some advantage. The wealth of a society correlates directly with the availability of cheap, abundant power. The UK will eventually sink below China in per capita wealth, and for what?
They're going from a basic uk medieval level in the 1970s to the leading world superpower in the 2020s, with a population of over a billion. That's not a shock. The average American is ridiculously higher use in every area. What is amazing is how little it has increased per capita in China.
China is making and deploying the energy technologies of the 21st century and in doing so decoupling themselves from dependence on fossil fuel imports whilst reducing CO2 emissions. If that’s why they will over take the UK in per capita wealth then we might want to think about emulating their success rather than trying to resist progress. All new electricity generation in countries like India, Pakistan and Namibia comes from renewables. Ethiopia has banned the import of petrol and diesel vehicles. Electrification of heat and transport coupled with cheap electricity from renewables is what we should be going hell for leather on if we want to remain competitive.
You are missing a large part of what China is doing though. They are also bringing on a large number of coal power plants (they have large coal reserves unlike oil) and nuclear plants. They are installing a large amount of renewables but it is by no means their entire energy policy.
Why don’t we have more forward thinking? Every house but every new house should have disabled access and facilities. And downstairs! Even a lift. We all get older! They should have specific pipe runs for electricity and gas. So reading meters should be easier. Not ad-hoc pathways for pipes underground. Basements to should house air to air HVAC systems. Solar panels on roofs and sheds in gardens. Even a windmill at each street corner. If possible ground source heat pumps and air source heat pumps. Back up generators. Car chargers. Great insulation and triple glazing. In fact any modern convenience. Room to park more than two cars comfortably. We have kids who drive! ID card readers at the front door so we know who is knocking on your door. Similar technology to make a phone call so we know who they are! Has anyone got more ideas?
Your correct Nigel. That’s why we all need a leveller to ensure that if he gets such money he has to spend it back. We can’t allow money to keep going one way. The rules need to be changed. And that’s why I’m trying to tell those interested that money flow back by spending is key. In fact it’s the only way to perpetuate a monetary exchange of payment for work.
What that should tell us Nigel is that we are underfunded and underpaid!
There is apparently £19 trillion pounds out there in the aether.
If all that were to be SPENT in just one rotation. Once, not millions of times a day but once in one whole year, we should be able to supply £3.8 trillion pounds to our government from vat alone! One tax only, no other taxes, just one on one spending rotation in one whole year.
Our government gets £1.1 trillion pounds from all taxation from all spending now.
So we could have a surplus each month instead of a deficit. We could have four times our tax take four times!
Now that’s not just our government, it’s also us!
The revenue could increase our incomes by four times easily.
We have had a cash flow problem since the war. Money isn’t the problem we should have sufficient based on population and need. So the key is SPENDING money.
We have had so much money outside our daily economy that we have been underfunded. And the flow is small because the vast sums are unspent! Unused and idle.
What could have been? What could we have now. We just need those holding money to spend it continuously. Earn as much as we can. But spend it is the key to growth.
Well, actually... It should tell us that the UK money is getting pumped away to other countries very rapidly, and the majority of the wealth left behind isn't liquid, but rent seeking.
Thatcher took away exchange control regulations and allowed money to move abroad.
So yes our daily productive economic pot is devoid of freely spent money. Instead it’s full of money resupplied by debt. Loaned by those holding that money here and abroad.
So the sort of change we need is to reinstate exchange controls. Reintroduce a new currency. You have to swap all sterling here and abroad for a new uk only digital currency.
Then when all money is in the uk we put a spend by date on that new currency.
This would mend our economy overnight.
The tsunami of spending would give that cash flow we all need. Higher wages and so no need to borrow on a daily basis for necessities.
But our politicians don’t have that sort of vision!
Inflation grows when money is short. When those needing it want more from the meagre pot. When taxes are high and costs are high.
When plenty of money is around profits are guaranteed. No need to profiteer. If they have to spend it they begin to realise they don’t need it all! How many shirts can a man need? If there is an abundance of goods prices fall. Inflation is reversed.
It’s counterintuitive I know. But reason should prevail.
How can we sustain a position in a democracy that allows the few to hold all the money? That’s undemocratic. The money has to be valueless ti be a token of fair and full exchange?
Is David Beckham worth 10000 nurse? Of course not. Is it fair he earns his best? Yes if course but we need a leveller. And forcing spending ensures that. Ensures the constant return of money to the pot or to the government pot. One way you get a fair exchange. The other? The return of money that’s always needed.
Be rich off the stuff we buy! Not money itself. Every successful business does it! And nearly every family in the uk do it, spend all their money each month. So where is the problem? Rainy day money is for a drought. But if money is ensured to revolve in higher amounts then it’s a flood every month!
You can buy Midea portable split air con units for £1k. They give proper aircon performance because the heat exchanger is outside. Very popular in Germany - good for renters including apartments with balconies. https://www.midea.com/uk/air-treatment/porta-split
They were about £850 before the hot spell. We got one for our office - which just about kept us alive, and I’m going to get one later in the year when prices have gone back to normal!
A great article and lots of things to digest here, I’d like to make a few points.
Both A2A and A2W system work by increasing pressure of a refrigerant gas, the pressure increases is generated a compressor driven by an electric motor driving, the compressor accounts for 95% of the energy used.
Motor technology and efficiency have improved, but the main gains have come from speed-controlled compressors and fans. Historically, compressors were driven by AC motors that needed separate speed-control devices, many of which delivered little energy saving at reduced speeds.
AC motors had a limited minimum operating speed because they relied on airflow over the motor for cooling.
EC and DC motors have built-in speed control and remain highly efficient at reduced speeds. With the latest IE4 and IE5 motors already around 95% efficient, future gains are likely to be minimal.
Commercially, A2A systems are widely installed, and the UK market is mature, with around 750,000 units sold each year.
These include single-split, multi-split, and VRV/VRF systems, all of which provide both heating and cooling.
The problem is that around 99% of the estimated 3–5 million installed units have failed insulation on their external pipework.
This typically happens when non-UV-rated nitrile insulation is used; once it breaks down, it absorbs moisture like a sponge.
For each 1% moisture, thermal efficiency is reduced by 7.5%, on site I often find insulation with 10-20% moisture.
AND it gets worse; In A2A refrigeration, we use thin-wall refrigeration-grade copper pipe, A2W generally uses plumbing-type copper pipe.
Copper is an excellent material and one of the most efficient metals for conducting heat.
The second law of thermodynamics states that heat flows spontaneously from warmer to colder bodies, never in reverse. Cold cannot "go" anywhere because it is simply the absence of heat; instead, thermal energy naturally spreads out until both areas reach the same temperature.
Based on a well-dry insulated 35 mm copper pipe at 50°C /4 °C outside air the losses will be circa 11 W/m, for a bare uninsulated pipe, circa 80 W/m, saturated insulation will be circa 150 W/m.
The wet sponge effectively increases the pipework’s surface area.
It is not unusual to have 3 m of external pipework on a commercial building, which would lose almost ½ kW.
This may partly explain why a performance gap is being reported regularly at conferences and in the CIBSE Journal
I believe on a cold, wet winter's day, the losses will be more than the output of a large UK power station.
As for the future of A2A domestic units under the BUS scheme, there are many huddles, as unlike heat pumps, the skills required are different and very costly.
So, I am not convinced people will train to be able to install under the BUS scheme. We have a shortage of people and colleges to train people/
I have 1,000 of pictures showing failed and poor workmanship; there is growing evidence that the same issue can be found in many domestic installations.
It is perfectly feasible in a well-insulated home in the right conditions that a ghost (parasitic) load could be put on the A2W ASHP system if the insulation has failed, as losses will be on both supply and return. This may also explain why people have to operate heat pumps at higher temperatures ( I have been suggesting we start measuring the ΔT from leaving the unit to the terminal unit inside the building.)
I am working with TICA to raise the issue, and hoping to publish a paper later this year and happy to help provide more details for a story.
Finally, when the media and other experts quote performance data, it should be caveated that this is the published data and derived in laboratory conditions and does not include any external losses.
The lack of hot water is a real issue with air to air. My daughter wants to upgrade her heating and desperately needs cooling.
But I am not sure instant water heaters are something she would be happy with given our high levels of limescale. Instant water heaters cannot realistically fill baths.
The simplest and cheapest solution for hot water is the trusty unvented direct cylinder (a tank with immersion heater). Fastest way to fill a bath, better shower pressure than electric shower, and can be heated at off-peak times. Or if you want to spend a little more upfront for lower energy costs, there are now standalone heat pump cylinders.
I always really enjoy your analysis but want to quibble a little with your recent post on AC options.
I’m in East Yorkshire and renting, so a permanent AC installation isn’t an option.
By being sensible:
-opening all windows overnight when outside is cooler than inside
-closing everything (windows/curtains/etc.) at 6am before the temperature rises
-opening the loft hatch
I’ve been able to keep the house at a reasonably comfortable 23-24C even when it was 32C outside today.
My home office however does get slightly warmer and a bit humid so I was considering a portable AC unit for that room only but I’m struggling to understand why a unit that draws back air from outside, as you are advocating, (which would be hotter and more humid than that inside), would be more efficient in my situation?
Air conditioning has two sets of air input and output. The first set draws air in, chills it and blows it back out. At the same time, the second set draws air in, heats it, and blows it out. It can only cool air by heating other air at the same time.
Ideally the hot part is all outdoors. This is how a permanently installed "split" system works. The box outdoors pulls in outdoor air, dumps the heat into it and blows it out hot. Meanwhile the indoor unit pulls in indoor air, chills it, and blows it out cold.
Portable units are a compromise. Ideally the hot part uses outdoor air so as not to waste cool indoor air. But to make the product cheaper and simpler to set up, the hot side can also draw in indoor air, dump heat into it, and blow it out through a single hose. But that means that cool air is being pulled out of the building, working against the efforts of the air conditioner. By bringing in a second hose, you can avoid needing to use indoor air to dump heat into, keeping the building more sealed and using outdoor air instead.
From the US but explains how 2 hose option works! Basically one hose cools the unit mechanics which makes it more efficient while the other extracts the room hot air!
I appreciate the technical descriptions of their systems, now and what could have been, but really what you're talking about is an exponentially, larger facet and belongs in a separate article if not many... Consider France which is mostly nuclear, so should not be an issue.
Ed, I have been looking into this question as I prepare to remodel a house and found a way of using a heat pump based wet underfloor heating system as a cooling solution: https://underfloorheating.info/heat-pump-underfloor-cooling/ Do you have a view on this?
Underfloor is very limited in the effectiveness of cooling it can provide. Firstly it has to be kept above dew point to avoid condensation. This means two things: it can't transfer very much heat (because you can't run it very cold) and it can't remove humidity, which is a big part of how true air conditioning improves comfort. During this heatwave, dew point has been over 20°C, so you wouldn't even be able to keep your floor slab below standard room temperature.
Often underfloor heating is only installed on the ground floor, while it's the bedrooms upstairs most in need of cooling. Also, the cool air will tend to collect at the floor, leaving the rest of the air space warm.
For effective cooling you really need fan coils which can remove moisture and circulate chilled air. One option is to have a ducted fan coil in the loft on its own pipework circuit so you can run that separately for cooling without worrying about condensation. Make sure all the pipes for that circuit are insulated!
Alternatively, just use completely separate split air conditioning for cooling, and hydronic underfloor for heating.
Apologies for the previous truncated post. Such systems don’t seem to exist here, but air heat pumps are very common. I have 2 in a 4 bed 240 sq.m house. They are inexpensive to install and very efficient.
I moved to the UK nine years ago from Cayman, where AC is everywhere (for obvious reasons) and central AC is built into the designs of homes for many decades now. Water heating used to always be done by immersion heaters (typically well insulated and just left on all the time), though after we had a hurricane in 2004 that flooded the ground floor of many homes, a lot of people now have "instant" water heaters. Still electric (so not like the UK combi boilers), but work well when sized correctly.
Anyway, I was a bit shocked when I bought a "new build" home on the southern edge of London to find how hot it gets. As we all know, the UK almost mandates homes to be designed to soak up and retain heat, but in summer, that meant for me that a 26c day and 16c overnight (pretty common) gave me bedrooms that would not cool below about 27c overnight on a still evening.
So, AC was on my mind right away. My house came with (basic) solar already, so that helps a bit, but I invested £10k in total on two air-to-air heat pump solutions (good news is that all domestic AC is already able to heat as well as cool, so that makes the parts and labour zero-rated for VAT when dual use is spec'd, and that means that this is the default for AC installers in the UK already). This was before the £2500 grant, so now each system would be less.
Each system handles three rooms, so de facto the whole house is cooled. In flat out use this week (with temps yesterday at 34c and only dropping to 25c ovenight), it used only about an additional 10kwh over and above the usual daily summer electricity use.
So far so good, but what about the future?
- when my gas boiler dies (useful life around 10 years, so for me that is a couple of years away), I take it out, turn off the gas, then simply use the hot water tank already in the house. For the bathrooms in winter I remove the (hot water) heated towel rails and put in electric ones. That is all I have to do and then I am using an all electric system for heating and cooling
- I will move to an electric car soon enough and will make sure that one has bidirectional charging, so will charge up the car overnight using cheaper electricity and use it as a battery during the day.
- I may upgrade my solar panels for summer AC use, but with the car as a battery, no need for additional battery installation.
All in all, I will be off carbon-based power (gas) soon enough, and with the inexorable transition to renewables, I can see that within a reasonable time I will be heating and cooling my house efficiently (as you note) with air-to-air heat pumps, devices that will use renewable power.
Oh, and given that I am very familiar with AC compressor units outside homes and businesses in Cayman, I was astonished to find that my 10kw exterior unit runs so silently (55dba). At a distance of over about 3m from the unit, the birdsong is louder. Oh, but my neighbour has a portable AC unit running now next door, it is much louder ;)
Thanks! Which make did you get?
Went with the AC company recommendation, Samsung Cebu. Very happy with them. The last few days, at 34c peak, the two exterior units (total of 16.8kwh) and six interior units (total of 17.5kwh) have been going all the time (for about 12 hours per day at least). Incremental electricity usage, astonishingly, only a net 8kwh per day.
I put this down to a few things. First, the rating on the units is peak rating, indoor units cycle on and off based on thermostat. Second, we have a battery of basic solar panels that were installed when the house was a new build. Total rating only 1kwh, but that helps. Third, heat pumps (whether cooling or heating) are pretty efficient these days ;)
The government grant for air-to-air heat pumps, apart from being less generous is entirely wide of the mark. You can only get it if the heat pump entirely replaces your existing heating system. Yet adding an air-to-air unit would provide both air conditioning and a more efficient form of supplementary heating than the existing heating system, allowing reductions in the gas or oil consumed in operating it. Exactly what government policy is intending, yet failing, to do. Associate an air-to-air heat pumps with solar panels to power it, and there is no added load on the grid from the aircon mode because the aircon will mostly be operating in sunny weather.
UK and for that matter all of Europe going “net zero” is a grim joke once you understand that China, India, Africa and the Middle East will *never* embrace the Western obsession with “carbon”. It’s simply not a thing in most of the world, other than participating in fancy conferences and entering into treaties with naive Europeans that confer some advantage. The wealth of a society correlates directly with the availability of cheap, abundant power. The UK will eventually sink below China in per capita wealth, and for what?
All those places are deploying renewables faster than the west, China in particular.
A large part of that is about resiliance though. About reducing vulnerability to an oil shock.
It’s win-win-win-win! Cheaper to install, resilient to oil-price shocks, lower running costs, and lower carbon.
China’s carbon emissions are rising massively at the same time though
They're going from a basic uk medieval level in the 1970s to the leading world superpower in the 2020s, with a population of over a billion. That's not a shock. The average American is ridiculously higher use in every area. What is amazing is how little it has increased per capita in China.
They may have peaked, still need to fall rapidly though. https://www.carbonbrief.org/analysis-chinas-co2-emissions-have-now-been-flat-or-falling-for-21-months/
India is also going solar at an incredible rate. I think you are regurgitating oil company propaganda.
The world is full of oil company shills and bots.
Net zero is cheaper. How have you missed that? It's also generally better against price shocks and less affected by international saber rattling!
China is making and deploying the energy technologies of the 21st century and in doing so decoupling themselves from dependence on fossil fuel imports whilst reducing CO2 emissions. If that’s why they will over take the UK in per capita wealth then we might want to think about emulating their success rather than trying to resist progress. All new electricity generation in countries like India, Pakistan and Namibia comes from renewables. Ethiopia has banned the import of petrol and diesel vehicles. Electrification of heat and transport coupled with cheap electricity from renewables is what we should be going hell for leather on if we want to remain competitive.
You are missing a large part of what China is doing though. They are also bringing on a large number of coal power plants (they have large coal reserves unlike oil) and nuclear plants. They are installing a large amount of renewables but it is by no means their entire energy policy.
Why don’t we have more forward thinking? Every house but every new house should have disabled access and facilities. And downstairs! Even a lift. We all get older! They should have specific pipe runs for electricity and gas. So reading meters should be easier. Not ad-hoc pathways for pipes underground. Basements to should house air to air HVAC systems. Solar panels on roofs and sheds in gardens. Even a windmill at each street corner. If possible ground source heat pumps and air source heat pumps. Back up generators. Car chargers. Great insulation and triple glazing. In fact any modern convenience. Room to park more than two cars comfortably. We have kids who drive! ID card readers at the front door so we know who is knocking on your door. Similar technology to make a phone call so we know who they are! Has anyone got more ideas?
Your correct Nigel. That’s why we all need a leveller to ensure that if he gets such money he has to spend it back. We can’t allow money to keep going one way. The rules need to be changed. And that’s why I’m trying to tell those interested that money flow back by spending is key. In fact it’s the only way to perpetuate a monetary exchange of payment for work.
Ah, that's only for the super rich, and those with expense accounts and fat pensions (MPs) don't care about the running costs of their homes!
What that should tell us Nigel is that we are underfunded and underpaid!
There is apparently £19 trillion pounds out there in the aether.
If all that were to be SPENT in just one rotation. Once, not millions of times a day but once in one whole year, we should be able to supply £3.8 trillion pounds to our government from vat alone! One tax only, no other taxes, just one on one spending rotation in one whole year.
Our government gets £1.1 trillion pounds from all taxation from all spending now.
So we could have a surplus each month instead of a deficit. We could have four times our tax take four times!
Now that’s not just our government, it’s also us!
The revenue could increase our incomes by four times easily.
We have had a cash flow problem since the war. Money isn’t the problem we should have sufficient based on population and need. So the key is SPENDING money.
We have had so much money outside our daily economy that we have been underfunded. And the flow is small because the vast sums are unspent! Unused and idle.
What could have been? What could we have now. We just need those holding money to spend it continuously. Earn as much as we can. But spend it is the key to growth.
Well, actually... It should tell us that the UK money is getting pumped away to other countries very rapidly, and the majority of the wealth left behind isn't liquid, but rent seeking.
Cashflow is the issue in the UK.
Spot on Nigel.
Thatcher took away exchange control regulations and allowed money to move abroad.
So yes our daily productive economic pot is devoid of freely spent money. Instead it’s full of money resupplied by debt. Loaned by those holding that money here and abroad.
So the sort of change we need is to reinstate exchange controls. Reintroduce a new currency. You have to swap all sterling here and abroad for a new uk only digital currency.
Then when all money is in the uk we put a spend by date on that new currency.
This would mend our economy overnight.
The tsunami of spending would give that cash flow we all need. Higher wages and so no need to borrow on a daily basis for necessities.
But our politicians don’t have that sort of vision!
Not sure I love the idea of money expiring with regularity! Inflation is bad enough as it is.
Inflation grows when money is short. When those needing it want more from the meagre pot. When taxes are high and costs are high.
When plenty of money is around profits are guaranteed. No need to profiteer. If they have to spend it they begin to realise they don’t need it all! How many shirts can a man need? If there is an abundance of goods prices fall. Inflation is reversed.
It’s counterintuitive I know. But reason should prevail.
How can we sustain a position in a democracy that allows the few to hold all the money? That’s undemocratic. The money has to be valueless ti be a token of fair and full exchange?
Is David Beckham worth 10000 nurse? Of course not. Is it fair he earns his best? Yes if course but we need a leveller. And forcing spending ensures that. Ensures the constant return of money to the pot or to the government pot. One way you get a fair exchange. The other? The return of money that’s always needed.
Be rich off the stuff we buy! Not money itself. Every successful business does it! And nearly every family in the uk do it, spend all their money each month. So where is the problem? Rainy day money is for a drought. But if money is ensured to revolve in higher amounts then it’s a flood every month!
You can buy Midea portable split air con units for £1k. They give proper aircon performance because the heat exchanger is outside. Very popular in Germany - good for renters including apartments with balconies. https://www.midea.com/uk/air-treatment/porta-split
They were about £850 before the hot spell. We got one for our office - which just about kept us alive, and I’m going to get one later in the year when prices have gone back to normal!
to be fair regarding the name, they’re essentially always pumping heat, it’s just whether you want to pump the heat into the house or out of the house
I thought Material World (your book) was absolutely fabulous.
A great article and lots of things to digest here, I’d like to make a few points.
Both A2A and A2W system work by increasing pressure of a refrigerant gas, the pressure increases is generated a compressor driven by an electric motor driving, the compressor accounts for 95% of the energy used.
Motor technology and efficiency have improved, but the main gains have come from speed-controlled compressors and fans. Historically, compressors were driven by AC motors that needed separate speed-control devices, many of which delivered little energy saving at reduced speeds.
AC motors had a limited minimum operating speed because they relied on airflow over the motor for cooling.
EC and DC motors have built-in speed control and remain highly efficient at reduced speeds. With the latest IE4 and IE5 motors already around 95% efficient, future gains are likely to be minimal.
Commercially, A2A systems are widely installed, and the UK market is mature, with around 750,000 units sold each year.
These include single-split, multi-split, and VRV/VRF systems, all of which provide both heating and cooling.
The problem is that around 99% of the estimated 3–5 million installed units have failed insulation on their external pipework.
This typically happens when non-UV-rated nitrile insulation is used; once it breaks down, it absorbs moisture like a sponge.
For each 1% moisture, thermal efficiency is reduced by 7.5%, on site I often find insulation with 10-20% moisture.
AND it gets worse; In A2A refrigeration, we use thin-wall refrigeration-grade copper pipe, A2W generally uses plumbing-type copper pipe.
Copper is an excellent material and one of the most efficient metals for conducting heat.
The second law of thermodynamics states that heat flows spontaneously from warmer to colder bodies, never in reverse. Cold cannot "go" anywhere because it is simply the absence of heat; instead, thermal energy naturally spreads out until both areas reach the same temperature.
Based on a well-dry insulated 35 mm copper pipe at 50°C /4 °C outside air the losses will be circa 11 W/m, for a bare uninsulated pipe, circa 80 W/m, saturated insulation will be circa 150 W/m.
The wet sponge effectively increases the pipework’s surface area.
It is not unusual to have 3 m of external pipework on a commercial building, which would lose almost ½ kW.
This may partly explain why a performance gap is being reported regularly at conferences and in the CIBSE Journal
I believe on a cold, wet winter's day, the losses will be more than the output of a large UK power station.
As for the future of A2A domestic units under the BUS scheme, there are many huddles, as unlike heat pumps, the skills required are different and very costly.
So, I am not convinced people will train to be able to install under the BUS scheme. We have a shortage of people and colleges to train people/
I have 1,000 of pictures showing failed and poor workmanship; there is growing evidence that the same issue can be found in many domestic installations.
It is perfectly feasible in a well-insulated home in the right conditions that a ghost (parasitic) load could be put on the A2W ASHP system if the insulation has failed, as losses will be on both supply and return. This may also explain why people have to operate heat pumps at higher temperatures ( I have been suggesting we start measuring the ΔT from leaving the unit to the terminal unit inside the building.)
I am working with TICA to raise the issue, and hoping to publish a paper later this year and happy to help provide more details for a story.
Finally, when the media and other experts quote performance data, it should be caveated that this is the published data and derived in laboratory conditions and does not include any external losses.
Just shows if you write some decent content that it does not get read.
The lack of hot water is a real issue with air to air. My daughter wants to upgrade her heating and desperately needs cooling.
But I am not sure instant water heaters are something she would be happy with given our high levels of limescale. Instant water heaters cannot realistically fill baths.
The simplest and cheapest solution for hot water is the trusty unvented direct cylinder (a tank with immersion heater). Fastest way to fill a bath, better shower pressure than electric shower, and can be heated at off-peak times. Or if you want to spend a little more upfront for lower energy costs, there are now standalone heat pump cylinders.
You can get VRV with heat recovery, Daikin have a good range, see lots of them commercially as TM44 Air Conditioning Inspector
Hi Ed
I always really enjoy your analysis but want to quibble a little with your recent post on AC options.
I’m in East Yorkshire and renting, so a permanent AC installation isn’t an option.
By being sensible:
-opening all windows overnight when outside is cooler than inside
-closing everything (windows/curtains/etc.) at 6am before the temperature rises
-opening the loft hatch
I’ve been able to keep the house at a reasonably comfortable 23-24C even when it was 32C outside today.
My home office however does get slightly warmer and a bit humid so I was considering a portable AC unit for that room only but I’m struggling to understand why a unit that draws back air from outside, as you are advocating, (which would be hotter and more humid than that inside), would be more efficient in my situation?
Air conditioning has two sets of air input and output. The first set draws air in, chills it and blows it back out. At the same time, the second set draws air in, heats it, and blows it out. It can only cool air by heating other air at the same time.
Ideally the hot part is all outdoors. This is how a permanently installed "split" system works. The box outdoors pulls in outdoor air, dumps the heat into it and blows it out hot. Meanwhile the indoor unit pulls in indoor air, chills it, and blows it out cold.
Portable units are a compromise. Ideally the hot part uses outdoor air so as not to waste cool indoor air. But to make the product cheaper and simpler to set up, the hot side can also draw in indoor air, dump heat into it, and blow it out through a single hose. But that means that cool air is being pulled out of the building, working against the efforts of the air conditioner. By bringing in a second hose, you can avoid needing to use indoor air to dump heat into, keeping the building more sealed and using outdoor air instead.
Thank you: perfect explanation! Shame there’s no portable unit with this capability available in the UK…
Portable not very efficient
From the US but explains how 2 hose option works! Basically one hose cools the unit mechanics which makes it more efficient while the other extracts the room hot air!
https://www.forbes.com/sites/forbes-personal-shopper/article/dual-hose-vs-single-hose-portable-ac/
Or this which has very easy to understand diagrams:
https://www.woolie.co.uk/article/convert-ac-from-single-hose-to-dual-hose/
I moved from Scotland to NZ over 20 years ago. Left a house with full gas central heating
And the Meaco is out of stock. Same as most everything else around the country. I can’t wrap my head around the opportunity to
Print money that’s been passed by so often.
Environmental concerns, perhaps?
Why not mention that?
I appreciate the technical descriptions of their systems, now and what could have been, but really what you're talking about is an exponentially, larger facet and belongs in a separate article if not many... Consider France which is mostly nuclear, so should not be an issue.
Ed, I have been looking into this question as I prepare to remodel a house and found a way of using a heat pump based wet underfloor heating system as a cooling solution: https://underfloorheating.info/heat-pump-underfloor-cooling/ Do you have a view on this?
Big fan of Material World.
Simon
Underfloor is very limited in the effectiveness of cooling it can provide. Firstly it has to be kept above dew point to avoid condensation. This means two things: it can't transfer very much heat (because you can't run it very cold) and it can't remove humidity, which is a big part of how true air conditioning improves comfort. During this heatwave, dew point has been over 20°C, so you wouldn't even be able to keep your floor slab below standard room temperature.
Often underfloor heating is only installed on the ground floor, while it's the bedrooms upstairs most in need of cooling. Also, the cool air will tend to collect at the floor, leaving the rest of the air space warm.
For effective cooling you really need fan coils which can remove moisture and circulate chilled air. One option is to have a ducted fan coil in the loft on its own pipework circuit so you can run that separately for cooling without worrying about condensation. Make sure all the pipes for that circuit are insulated!
Alternatively, just use completely separate split air conditioning for cooling, and hydronic underfloor for heating.
really helpful, many thanks
Apologies for the previous truncated post. Such systems don’t seem to exist here, but air heat pumps are very common. I have 2 in a 4 bed 240 sq.m house. They are inexpensive to install and very efficient.
i want air-to-water heat pump to heat my radiators in the winter and i want air-to-air to cool my rooms in summer
Oh..and i want the external boxes to be of a more aesthetic design so that my house doesn't resemble a chip shop
if you can arrange that please, thanks Ed