Posted By: GarethCSay I installed a top notch A++ rated air conditioning multi split system, thereby reducing my heating related emissions significantly. Am I right that, due to the (almost certainly unused) ability to cool, I wouldn't even get an uplift to my home's EPC?

Why do you think that?

In my own home I installed an A/A ducted system in a large open plan area, ( I had the available space in the loft above), so it made sense to go the extra mile. I accept that not everyone does, but the various wall units are so efficient and some with filtration the A/A option is an excellent choice.
The guts of the systems are simple robust technology with fast response and excellent controls. As for cooling, I've had mine installed for 3 years and it's the best form of CH I've experienced. During that time I've probably run the cooling facility on about 5 or 6 occasions and then only for a few hours, the cooling is TOO efficient to have it on longer. and on the days it's been on, my solar PV has more than powered it.

Posted By: owlmanIn my own home I installed an A/A ducted system in a large open plan area, ( I had the available space in the loft above), so it made sense to go the extra mile. I accept that not everyone does, but the various wall units are so efficient and some with filtration the A/A option is an excellent choice.
The guts of the systems are simple robust technology with fast response and excellent controls. As for cooling, I've had mine installed for 3 years and it's the best form of CH I've experienced. During that time I've probably run the cooling facility on about 5 or 6 occasions and then only for a few hours, the cooling is TOO efficient to have it on longer. and on the days it's been on, my solar PV has more than powered it.

Do you know the answer to my question about how it affects a home's EPC? I've trawled online but drawn a blank.

Hi Gareth,
Sorry I've no idea as my EPC was done before I fitted the A/A system I described. My guess would be that no one has thought about it. If your question pertains to the Summer cooling mode of A/A in my case I'd argue that any cooling is powered by my solar PV and should therefore not considered detrimental.

Just to add that SAP and EPCs are based on calculated heating costs in £, not on energy used/saved.

In SAP 2012 the standard prices per kWh are: 13.19p for electricity and 3.48p for mains gas.

If your heatpump is in the database and is installed with a SPF greater than (13.19/3.48 *0.9) = SPF= 3.4 , then it will improve your EPC rating. Otherwise it will make it worse.

For replacing oil boilers (5.44p) or LPG (7.60p) the breakeven SPF is more reasonable, SPF=2.1 or SPF=1.6 respectively.

I suspect that most people who switch from mains gas to ASHP will be disappointed, because it doesn't improve their EPC. If people use heatpumps that are not in the database and so are assigned a default SPF=1.7, their EPC will get much worse.

This is a big problem for the private and social rented sector where the landlord has to reach a certain EPC before they can let the property.

The Scottish gov are apparently thinking about revising the EPC system to reward energy or carbon savings, instead of rewarding cost savings. Will mean redoing everyone's EPC.

Edit to add: the upcoming next version of SAP10 will have different prices, mains gas users would need to get a heatpump over SPF=4.0 to get a better EPC out of it. Good luck with that...!

Posted By: GarethCtowering absurdity of current policy.
In fact, come to think of it, it's even worse

Yes!

Some A-W heatpumps are available with cooling, and also as similar models with the cooling disabled, I think with a software setting, possibly as a way round the RHI restrictions.

I'm guessing that air-conditioning manufacturers haven't seen any commercial reason why to register their products in databases.


There's a workaround which is: install a coal fired central heating system, declared as your main heating, and use A-A as your 'secondary' system. Coal scores really highly for EPCs, it's very cheap

Posted By: GarethC
Basically, if they recognised the impact on space heating emissions of installing high efficiency A/A heatpumps, they at a stroke introduce a relatively affordable, -relatively- low disruption means of lowering space heating emissions by probably at least as much as A/W heat pumps (taking into account potential use for cooling), so what on earth is not to like?

Maybe Im missing something but as a boiler replacement option, A2A HPs seem a potentially expensive and disruptive option!! As I understand things youve got a choice of a central unit with ducting or individual units per room.

With a ducted system retrofitting ducting means floors up/ceilings down and structural alterations to floor joists where ducts have to pass through them. It maybe possible to work round the occupants but likely they would have to move out while the ducting goes in. .

For individual room heaters theres likely a need for a unit per room or maybe some adjacent rooms can share a unit?? Even so a typical 3 bed house would likely need 5/6 units each needing an isolator/cable installing.

For both systems DHW with point of use heaters cables/isolators need running to all points of use and these could be quite substantial loads for bath/shower heaters. Once the system is in, the redundant boiler, DHW cylinder, pipework, radiators all need stripping out, making good and redecorating.

Assuming Ive understood A2A options correctly, it seems to me that an A2W system is a better fit for retrofit boiler replacements???

Posted By: philedge

Posted By: GarethC
Basically, if they recognised the impact on space heating emissions of installing high efficiency A/A heatpumps, they at a stroke introduce a relatively affordable, -relatively- low disruption means of lowering space heating emissions by probably at least as much as A/W heat pumps (taking into account potential use for cooling), so what on earth is not to like?

Maybe Im missing something but as a boiler replacement option, A2A HPs seem a potentially expensive and disruptive option!! As I understand things youve got a choice of a central unit with ducting or individual units per room.

I think you're missing something.

With a ducted system retrofitting ducting means floors up/ceilings down and structural alterations to floor joists where ducts have to pass through them. It maybe possible to work round the occupants but likely they would have to move out while the ducting goes in.

Possibly, but for suitable properties I imagine ducts could be led without the need for cutting joists. In lofts, with drops to the ground floor where necessary, maybe? Multiple indoor units to serve separate ducts perhaps? Or install as part of a refit. But it would suit some circumstances, I think.

For individual room heaters theres likely a need for a unit per room or maybe some adjacent rooms can share a unit?? Even so a typical 3 bed house would likely need 5/6 units each needing an isolator/cable installing.

I'd think those estimates are the upper limits. But anyway, running a cable, and don't forget the F-gas pipes, isn't the end of the world. A lot of the world has done this for years to install A/C units, so it's not that difficult.

For both systems DHW with point of use heaters cables/isolators need running to all points of use and these could be quite substantial loads for bath/shower heaters. Once the system is in, the redundant boiler, DHW cylinder, pipework, radiators all need stripping out, making good and redecorating.

No, if there is already a DHW cylinder then the obvious thing to do is not strip it out but use its immersion (or fit one) to produce the DHW. And fitting a new DHW cylinder is an obvious alternative to using point-of-use heaters. Yes the boiler and radiators will want removing at some point, though not as a matter of urgency, so undoubtedly it's easier to install a completely new heating system as part of a general refit. But upgrading insulation, airtightness and ventilation also involves disruption; there's nothing unique here.

Assuming Ive understood A2A options correctly, it seems to me that an A2W system is a better fit for retrofit boiler replacements???

I agree that it's just as easy to fit an A/W system in place of a boiler, so perhaps Gareth did overstate the case a bit, but A/A systems are still noticeably cheaper than A/W systems for some reason, despite being more capable in some regards, in that they can do cooling.

A disadvantage of multiple outdoor units would be that they wouldn't be covered by permitted development rights which only allow one heat pump.

If multi split A-A heat pumps are installed can any existing pipework from legacy radiator CH systems be used or would it be a rip out of all the old pipes and install new?

If A-A heat pumps are used for cooling will the pipes need to be insulated to prevent condensation forming on them? If so I presume most would find this a aesthetic problem unless boxed in.

Posted By: WillInAberdeenNew pipes, like microbore plumbing, but with thicker walls and flared connections and insulation of OD perhaps 20-30mm. There's also a comms/power cable, and if it's used for cooling there will be a condensate drain pipe. All run behind linings, or in fat trunking if run on the surface.

Edit AIUI the refrigerant pipes cannot just tee off to different indoor units - instead each indoor units is connected radially from the outdoor unit, or possibly from a manifold unit, so piping will get congested near there.

All of the above would IMO amount to a disincentive to install A-A heat pump if you have an existing radiator based CH system that could take a high(ish) temp. heat pump with little changes to the CH system.

Interesting point I just read. If you convert a gas boiler to hydrogen, you'll need to replace all the radiators with larger ones, just like for a heat pump. The reason is that a hydrogen boiler produces water vapour and that needs to be condensed, just as it is in a gas boiler, in order to achieve high efficiencies. And since the energy density of hydrogen is less, efficiency is important. Unfortunately, to condense all the water vapour you'll need to reduce the flue temperature and hence the radiator temperature. Oops!

Posted By: Peter_in_HungaryAnd heat pump is available now - if the grid can cope with wholesale installation of heat pumps.

Certainly more likely than that the gas grid can supply sufficient truly green hydrogen to sufficient hydrogen boilers now.

The same is actually true of condensing natural gas boilers: they condense more effectively if they run cooler (eg 45⁰C), so really need bigger radiators than non condensing boilers do, and ideally UFH. However most were retrofitted in place of a previous non condensing boiler, so the legacy radiators are often not big enough. Also, many are oversized to provide instant DHW, so they run a few hours a day at high power / high temperature, instead of more hours at lower temperatures, which would require weather compensation controls and better modulation. So in trials, most were found to be running far less efficiently than their manufacturers' claimed.

If this could be fixed easily, it would save ~10% of natural gas consumption, which coincidentally is more than the energy content of the proposal to blend 20% by volume of hydrogen into the gas mains.

In a hydrogen boiler, nearly all of the combustion oxygen goes into making water vapour, versus a natural gas boiler where half the oxygen makes CO2 and only half makes water. So the hydrogen boiler exhaust should contain more water, so condense more easily and have a higher dewpoint than a gas boiler's exhaust - it can run hotter and still condense. They may be doing inefficient things to suppress NOx which might require lower temperatures.

Personally I think it would be a brave politician who approves hydrogen in the gas mains, as energy bills will have to go up as a result and the opponents will point this out. Hydrogen is inevitably going to be more expensive than the natural gas or electricity which are the starting ingredients for making it, so people will find it cheaper to use electric heating, in some form or another.

<blockquote><cite>Posted By: djh</cite>I don't understand why the whole notion seems to have so much traction at present</blockquote>

It represents business as usual for gas extraction and distribution companies, also for boiler manufacturers. It's something that I'm sure they are all lobbying for, and would dearly wish to happen. It's something the public would dearly love to be plausible; replace the gas boiler with something about the same that is "green" and just works with minimal fuss. Everybody is on board wanting it to work!

I think though that where the hydrogen comes from is key to whether the result of all of the above would be greenwashing (CCS of Nat gas given expected methane emissions) or inefficient poor engineering hence expensive (electrolysis of water using renewable electricity) - neither approach seems to make long term sense to me, and will eventually be seen to be a blind alley, effectively another climate delay tactic.