Planning permission and air source heat pumps

mumf

It’s a bit rich of councils and government isn’t it. They want to ban petrol,diesel,gas boilers,, coal, and all life in general,and force us to ‘ECO’ alternatives. When you have to pay the eye watering amount to put in heat pumps- an eco- acceptable heating source - you have to have bloody planning permission too! 

What DO they want?

shinytop

mumf said:

It’s a bit rich of councils and government isn’t it. They want to ban petrol,diesel,gas boilers,, coal, and all life in general,and force us to ‘ECO’ alternatives. When you have to pay the eye watering amount to put in heat pumps- an eco- acceptable heating source - you have to have bloody planning permission too! 

What DO they want?

No, you don't.  The vast majority of domestic ASHP installations fall under permitted development.  

gm0

Conversion owner with revoked PD here.  If you have revoked PD rights then the list of things that are allowed without PP (likely a historic list and therefore not listing ASHP most likely) will likely be short.  This should be on the PP for the property in the planning stages for conversion and may now be online if you search depending upon your council. 

Sadly though this means that there is a need for full PP for practically anything not on that list.  Ignoring it can cause issues with nitpickery from conveyancers later.  So up to you.

However there is better news on cost (if not on delay). In this situation councils can and some do (mine did - don't know if this is all) waive planning charges for forced applications that would have fallen within the scope of Permitted Development without the revocation.  

I have used this exemption twice and had to put up with both lengthy delays, correspondence and a level of incompetence bordering on maladministration (they lost material samples at least twice and demanded replacement thereof) and it took nearly a year by the end.  It's a crapshoot - you either get waived through (as you should be after a quick look) or are passed around as deadlines approach as the low priority file nobody wants to spend time on. And  then another contradictory query is raised to "potentially reject" again until you agree to extend - again and again until bored.

gm0

As an aside.  Depending upon the size and construction and age of a barn conversion (BR at timing of conversion and approach taken) they can be among the least ASHP friendly structures. 

A modern blown membrane (sealed box then insulated within) with a MVHR as some recent conversions are with UFH throughout - might be OK for low temperature distribution from ASHP.  But older conversions with radiators and open to the roof beams ceilings, trickle vent/extractor ventilation and 200+ year old walls are a lot less likely to work at all with ASHP.
1990s or earlier stuff I would be sceptical without a very hard look at the design and survey.

A "challenging" project without ripping out and starting again.  Good luck

Reed_Richards

There's nothing magical about ASHPs; they are much like any other sort of boiler BUT the maximum output of a domestic model is typically 15 to 18 kW and one with a larger output capacity would probably be too large in size to qualify as a Permitted Development.  So a large poorly-insulated building would possibly require more output than a domestic ASHP can provide.   

gm0

ASHP (air to water) are much like any other sort of boiler *except* for the claimed and real efficiency over direct electric heating of water for radiators (COP)  2x - 4x+.   This efficiency which is critically dependent upon operating at a low output temperature - say 45C out, 40C back in turn requires large emitters and continuous operation with UFH with a well insulated underlying block providing a heat store.  Trying to turn up the ASHP temperature to approach that of a conventional boiler creates a very inefficient mode of operation and running costs then escalate radically from a level which is already challenging to accept vs the price of gas today (if not tomorrow).  Much fuel poverty politics awaits leavened with the disregard and contempt for science attendant upon westminster decision making.

But the low temperature characteristic of ASHP is why people with radiators need to increase the size of them 2x - 3x - space permitting and to lower the operating temperature if they can't face digging out floors and fitting an insulated pad and UFH where there is none.  But IMHO radiators appear to be a precarious route to take with this sort of project and space limitations will make expanding them in size or number fairly prohibitive for many.  I read a case study (converted farm building) the other day where the achieved ASHP temperature at the radiators was 29C (good flow rads) and 23.5C (poorer flow rads). Somewhere between luke warm and cool.  This was a mixed UFH and Rads example which was working mostly acceptably but the worst conditions and the running costs had been a shock.  What works fairly well <10p kWh works appallingly at 20p kWh.  This is a knotty one for fuel poverty and "how to pay for transition" implications for the politicians who do so love an electricity levy.

The amount that can be pumped around for a given size unit at 40-50C determines what can be done with the emitters available.  Flow volume of how hot water = rate of heat available being transferred.   The 2nd gotcha is cold weather. 
Some ASHP's dial back the possible flow to maintain target temperature when it is cold outside - this to avoid cutting in supplemental heating too early and damaging the spec sheet performance.   But lower flow will mean you are less warm - whatever the spec helpfully says about COP.  Think car gas mileage tests and real world mpg.  The Air heat exchange mechanism also starts to become less efficient. And then it freezes, stops, reverses, or thaws out with direct heating and then sets off again - reducing output over the hours further.  So in the worst UK conditions say circa -15C to 0C are when the ASHP is *least* effective and thus why the sizing and matching and most of all the *insulation* critically matters. 

A fallback being available to pure electric heating or a wood stove or something else seems highly appropriate.  The fact that ASHP have this characteristic doesn't stop them working well at "average temperatures" or indeed for much of the heating season.  So they are a good and inevitable solution - but one which has operational and engineering characteristics which have to be acknowledged and dealt with for new build regs (and enforcement) and in careful retrofit system design.

Other approaches are possible. Each with their own virtues and vices.  For example an electrical heat store would work at higher emitter temperatures just like a conventional boiler so retrofit to existing emitters is fine. Provided there are a block of hours with cheap units where it can be charged up daily cost effectively and the tariffs and metering support that. 

SunAmp did this for home solar input and DHW.  Caldera are trying it for CH (~80kWh daily). It delivers boiler hot water via heat exchanger to existing plumbing.   But in a world with high unit kWh costs or no window in the day with tariffs you can buy where they are cheaper - then it is just an even more inefficient (by ~10%) version of direct electrical heating.  It's key feature is the time shifting of when the units are bought vs when the heat is drawn.  If the tariffs and grid load pattern are around to support its use over a decade then it might be a fine (weather proof) investment in electrical heating.  And if not - not.

shinytop

gm0 said:

ASHP (air to water) are much like any other sort of boiler *except* for the claimed and real efficiency over direct electric heating of water for radiators (COP)  2x - 4x+.   This efficiency which is critically dependent upon operating at a low output temperature - say 45C out, 40C back in turn requires large emitters and continuous operation with UFH with a well insulated underlying block providing a heat store.  Trying to turn up the ASHP temperature to approach that of a conventional boiler creates a very inefficient mode of operation and running costs then escalate radically from a level which is already challenging to accept vs the price of gas today (if not tomorrow).  Much fuel poverty politics awaits leavened with the disregard and contempt for science attendant upon westminster decision making.

But the low temperature characteristic of ASHP is why people with radiators need to increase the size of them 2x - 3x - space permitting and to lower the operating temperature if they can't face digging out floors and fitting an insulated pad and UFH where there is none.  But IMHO radiators appear to be a precarious route to take with this sort of project and space limitations will make expanding them in size or number fairly prohibitive for many.  I read a case study (converted farm building) the other day where the achieved ASHP temperature at the radiators was 29C (good flow rads) and 23.5C (poorer flow rads). Somewhere between luke warm and cool.  This was a mixed UFH and Rads example which was working mostly acceptably but the worst conditions and the running costs had been a shock.  What works fairly well <10p kWh works appallingly at 20p kWh.  This is a knotty one for fuel poverty and "how to pay for transition" implications for the politicians who do so love an electricity levy.

The amount that can be pumped around for a given size unit at 40-50C determines what can be done with the emitters available.  Flow volume of how hot water = rate of heat available being transferred.   The 2nd gotcha is cold weather. 
Some ASHP's dial back the possible flow to maintain target temperature when it is cold outside - this to avoid cutting in supplemental heating too early and damaging the spec sheet performance.   But lower flow will mean you are less warm - whatever the spec helpfully says about COP.  Think car gas mileage tests and real world mpg.  The Air heat exchange mechanism also starts to become less efficient. And then it freezes, stops, reverses, or thaws out with direct heating and then sets off again - reducing output over the hours further.  So in the worst UK conditions say circa -15C to 0C are when the ASHP is *least* effective and thus why the sizing and matching and most of all the *insulation* critically matters. 

A fallback being available to pure electric heating or a wood stove or something else seems highly appropriate.  The fact that ASHP have this characteristic doesn't stop them working well at "average temperatures" or indeed for much of the heating season.  So they are a good and inevitable solution - but one which has operational and engineering characteristics which have to be acknowledged and dealt with for new build regs (and enforcement) and in careful retrofit system design.

Other approaches are possible. Each with their own virtues and vices.  For example an electrical heat store would work at higher emitter temperatures just like a conventional boiler so retrofit to existing emitters is fine. Provided there are a block of hours with cheap units where it can be charged up daily cost effectively and the tariffs and metering support that. 

SunAmp did this for home solar input and DHW.  Caldera are trying it for CH (~80kWh daily). It delivers boiler hot water via heat exchanger to existing plumbing.   But in a world with high unit kWh costs or no window in the day with tariffs you can buy where they are cheaper - then it is just an even more inefficient (by ~10%) version of direct electrical heating.  It's key feature is the time shifting of when the units are bought vs when the heat is drawn.  If the tariffs and grid load pattern are around to support its use over a decade then it might be a fine (weather proof) investment in electrical heating.  And if not - not.

@gm0, you make some valid points. I don't think anyone will disagree that a poorly designed heating system won't work as well and will be more expensive to run than a well designed one. If an ASHP can only heat radiators to 29 degrees and is working flat out to do so then it is undersized or there is something else wrong with the system. The 40-50 degrees you mention will be easily achievable by a correctly sized ASHP, except maybe when it's really, really cold.  Whether that will heat the house in question is a different matter but if the system is designed well, it will. 

Have you seen a modern K2/K3 radiator? To say you need radiators 2-3 times the size is a bit misleading; they are 2-3 times the emitting area.  We have radiators sized for an ASHP and they are not especially big looking.  

The problem is that gas is so cheap that wasting it doesn't cost much money.  To continue your car analogy, nobody in the USA cared that their cars did 15 mpg because gasoline was almost free.  We did here and in Europe though, where petrol was much more expensive so our cars were much more efficient but no less effective.  People have got used to shorts and T-shirt temperatures in their houses all year round and installers have got used to installing whatever gas boiler and system design they feel like. That doesn't work with ASHPs, where we need properly designed systems and to be a bit more willing to wear a jumper occasionally.  

I don't think ASHPs are a panacea but used appropriately, they have their place.  Coverted barns and farmhouses may not be it though, but I'm not really concerned about the small and relatively affluent group whose problem that is!  But however it's done, heating our homes is going to cost more in the future.  Whether that's paid for by tax, subsidy or people just sucking it up is a hot (!) topic.


  

    

Reed_Richards

I have an an ASHP with radiators.  It operates at 50 C flow 45 C return although an optional weather compensation feature will dial this down when it is relatively warm outside.  It is rated to achieve SCoP of a little over 3.  I had new radiators installed but these replaced two-panel radiators from 1980 with finned radiators so many of them are physically smaller than the ones they replaced.  It was installed last December and kept us warm through the winter, in fact a little too warm initially until I got the thermostat settings right.  Last winter was long and cold although without any extremes of cold weather.  It hasn't been in place for a year yet but seems on track to use about a third of the kWh that the oil boiler it replaced used.  My heat pump is rated to perform down to -15 C although at that sort of outside temperature I suspect it would be no more efficient than a fan heater.  But fortunately such extremes of cold weather are rare where I live.

gm0

The reasonable implication of all this is to be *very* careful about the installer and their incentives and competence - customer references for similar installations already in use etc.

Let's just agree they need to be bigger and triples to achieve a goal of distributing the same overall quantity of heat at the lower temperature over the longer run time in moving from gas/oil to ASHP. 

The point of comparison for K3 sizing - as small singles or as an alternative my finned 1990s doubles will vary with the site.  Some will be a lot bigger and some won't.  Pragmatic guidance would address both possibilities