@editor @tim441 I am thinking along similar lines as an AirCon/MVHR system is beginning to sound very attractive to us too. We have an ASHP and perhaps supplementing this with MVHR might be worth discussing on the forum please. Regards, Toodles.

We took a different approach. All our heating and cooling is done by top end (in efficiency terms) portable air/air units in the rooms that historically had the big fire places with the houses out via the sash windows through two layers of celotex insulation blocks, sheeps wool packing and the like. It's dual hose or in one area a rather cunning use of dual ducted systems to use the cellar as a ground source of sorts.

It's entirely therefore just appliances, none of it is wired in so our conservation people don't care, and we are much happier for not having had to drill holes in 18" thick historic stone walls.

You will need planning and LBC for a fixed install so unless you like being mugged for architect fees, bat surveys and all the rest of it I'd stick to portable stuff. It's got to be a hell of a lot less efficient and used an awful lot before it'll pay off the architects fees!

@etchedpixels i don't  look forward to all the listed nonsense!

But happily bats will not be involved.. no loft or roof space to access. 

I think I can make the application myself - I did for ashp. I envisage the external unit near ashp which is not visible from public areas or impacting the old building.

Internally and drilling will only be in our modern extension.

So overall I'm hoping to benefit from an efficient system to do cooling in summer and heating in shoulder months....and even help with quick boost to heating if cold snap that ashp is slower to react to.

@Tim441, yes, I think A2A heat pumps and air conditioning have now become common enough to justify their own forum section. They overlap with conventional ASHPs, but the questions around cooling, indoor unit placement, refrigerant pipework, condensate, planning and controls are different enough that they probably deserve a proper home.

I’d keep MVHR alongside it only with a clear distinction, because @Toodles’ point is relevant but MVHR is primarily ventilation. It doesn’t normally provide meaningful cooling by itself unless it is combined with additional cooling equipment.

I’ll give it some thought this week.

On your own proposal, my instinct is that you have a reasonably strong case. You already have permission for an ASHP, the new outdoor unit would sit nearby, it wouldn’t be visible from public areas and all the internal work would be confined to the modern extension. Those are probably the main points I’d emphasise in an application.

That said, I wouldn’t assume the modern extension automatically sits outside the listing. My understanding is that later extensions can still form part of the listed building, and fixed air-conditioning work may require listed building consent even where the historic fabric itself is unaffected. Depending on location and jurisdiction, planning permission may also be required. Definitely outside the scope of any authoritative knowledge here though. 

I can see why @EtchedPixels chose portable units, particularly when the alternative involved drilling through 18-inch historic walls. It is a clever solution for that property, but I’m not sure I’d let the prospect of architects, bat surveys and heritage bureaucracy push you towards portable equipment when your proposed fixed installation appears relatively unobtrusive. Again, just an opinion.

Since you successfully handled the ASHP application yourself, I’d probably start by sending the conservation officer a marked-up photograph showing the proposed outdoor unit position, the route of the pipework and condensate, and confirmation that no historic fabric would be penetrated.

I also think your proposed use makes sense. Cooling is becoming harder to dismiss after the summers we are now experiencing, while air-to-air gives you rapid, room-specific heat in the shoulder seasons. I wouldn’t necessarily view it as a remedy for an air-to-water system being “slow”, because those systems generally work best maintaining temperature steadily, but it could be a useful complement where you want a quick boost in one part of the house rather than raising the whole heating system. 

So yes, I’ll look at creating a dedicated section. This is clearly moving beyond the occasional air conditioning question buried inside the main ASHP forum.

@editor msny thanks for comprehensive reply..

I'malmost t certain it will need permission as the ashp did... and the extension itself did.

Sadly these days our local planners and conservation officers will not engage unless I pay for "pre-application' advice. Its costly and very slow. So usually better to simply apply - and tweak the application during the application period.

Actually, I came here today to see if there was already a forum for air to air systems!

We installed an air to water system without really considering air to air.  However, the current heat wave, even here in south Manchester, has made me wonder whether we went for the wrong system.  Air to air systems seem to have lots of advantages:

1. They do cooling as well as heating.
2. They clean and dehumidify the air as well as heating or cooling it.
3. The room (or strictly speaking the air within it) heats up quickly.
4. You don’t have to heat every room, when you’re using only some of them.
5. From what I can gather, high SCOPs are easy to achieve so the installations are less risky than air to water.

There are some disadvantages, but they don’t necessarily seem to be show stoppers:

1. The need to install ducting.
2. Disruption and redecoration due to removing radiators.
3. Air to air systems don’t heat the hot water, but presumably there are alternative solutions?
4. Reduced BUS grant.

Am I missing something?

Posted by: @grahamf

↑

Actually, I came here today to see if there was already a forum for air to air systems!

We installed an air to water system without really considering air to air.  However, the current heat wave, even here in south Manchester, has made me wonder whether we went for the wrong system.  Air to air systems seem to have lots of advantages:

1. They do cooling as well as heating.
2. They clean and dehumidify the air as well as heating or cooling it.
3. The room (or strictly speaking the air within it) heats up quickly.
4. You don’t have to heat every room, when you’re using only some of them.
5. From what I can gather, high SCOPs are easy to achieve so the installations are less risky than air to water.

There are some disadvantages, but they don’t necessarily seem to be show stoppers:

1. The need to install ducting.
2. Disruption and redecoration due to removing radiators.
3. Air to air systems don’t heat the hot water, but presumably there are alternative solutions?
4. Reduced BUS grant.

Am I missing something?

I think thats a fair summary.  I would add that

• for a house with many rooms they can work out expensive, particularly if that house already has a built in distribution system (ie the water pipes) 
• many people dont like/the brits arent used to the feel of moving air that is inherent with A2A
• you have to clean the filters regularly
• the units tend to be individually controlled rather than centrally controlled, which can be a faff
• multisplits (where you run multiple IDUs from a single ODU) tend to be more expensive than singles (1 ODU=1 IDU) for reasons I do not understand

For an open plan house or a two up two down they seem to me to be well worth considering, for a house subdivided into lots of rooms with an existing water distribution system less so.

I had A2A fitted to three community centres each with 3 large rooms and several small rooms.  We either didnt bother heating the small rooms at all and relied on spill over from adjacent rooms, or used electric mats.  It worked a treat.  Obviously that's a 'commercial' environment but still domestic in scale and not very different to a medium size open plan house.

My overall feeling is that I'm very happy with air to water. Particularly as we have underfloor heating - I don't think that could be bettered by any alternatives.

But having air to air as well is even better for the advantages of cooling and boost heating etc. At a cost of course.

I guess if starting from scratch i might look at air to water.... adding in cooling via fan coils?

Posted by: @tim441

↑

My overall feeling is that I'm very happy with air to water. Particularly as we have underfloor heating - I don't think that could be bettered by any alternatives.

But having air to air as well is even better for the advantages of cooling and boost heating etc. At a cost of course.

I guess if starting from scratch i might look at air to water.... adding in cooling via fan coils?

In addition to what I posted about A2A I would also agree with the above assessment although we have radiators.

I have one fancoil only and it does work for light (>dew point) cooling, but because its a pitifully small load the heat pump cycles badly, which has the effect of reducing the cooling effect.  With 20:20 hindsight I would have fitted 3-4 fan coils.  As It is Im not sure I have the evidence to say whether fan coils (light cooling mode) plus A2W works well or not.  I am told that UFH with a slab and light cooling works fairly well.  However light cooling does not dehumidify and does not give you US style chill. 

There are units available ('water loop terminals') which are a fancoil with built in W2W small heat pump, thus in principle allowing you to run full aircon on an above dewpoint water feed.  They are expensive and designed for apartments or office blocks, where you supply water at 20C irrespective of whether you want heating or cooling or a mix.  A domestic variant of this concept would be a useful addition to the armoury.  Octopus posted (on facebook) an experiment where they converted a potable aircon unit into such a beast, and hinted that they might turn the idea into a product.

Posted by: @grahamf

↑

Actually, I came here today to see if there was already a forum for air to air systems!

We installed an air to water system without really considering air to air.  However, the current heat wave, even here in south Manchester, has made me wonder whether we went for the wrong system.  Air to air systems seem to have lots of advantages:

1. They do cooling as well as heating.
2. They clean and dehumidify the air as well as heating or cooling it.
3. The room (or strictly speaking the air within it) heats up quickly.
4. You don’t have to heat every room, when you’re using only some of them.
5. From what I can gather, high SCOPs are easy to achieve so the installations are less risky than air to water.

There are some disadvantages, but they don’t necessarily seem to be show stoppers:

1. The need to install ducting.
2. Disruption and redecoration due to removing radiators.
3. Air to air systems don’t heat the hot water, but presumably there are alternative solutions?
4. Reduced BUS grant.

Am I missing something?

On the disadvantages

1. Depends on the system. Ducted is one approach but not the only one. For some buildings ducting is great as it goes in the loft for the upper floor or does a whole bungalow easily.

2. You don't need to remove them, you can keep both systems or leave them in place decoratively until you want to redo that room. It's common to fit the air/air first, then later remove gas, because with no real grant holding you hostage to do it all at once you can do it in a rational, low risk, normal human kind of fashion.

3. There are air/air systems that also do water, however currently heating the water overnight on an EV tariff via an immersion often is cheaper all in unless you use a lot of water. Or you keep the gas for it

4. No grant in reality. The equipment is far cheaper and whilst the grant theoretically exists nobody in the industry seems to think it's useful as it'll cost them more per install in being registered with yet another makework body, doing lots of pointless paperwork and courses and being required to rip out the gas at the same time and often massively overinstall. The aircon industry is many decades old, they don't need a (failing) regulator for fly by night grant chasers.

One of the problems with trying to split things as advantages and disadvantages is that a lot of them can be either and differing things matter to different people or in different places. So for example if you've got some garbage newbuild box that wasn't designed to cool properly then cooling is really important. If you've got a properly built older house with an actual loft then you probably only need to fit a load of extra vents, a cotton barrier and maybe some cowls or similar chimney effect venting even though it was never designed for this climate.

Same is true of a lot of other bits. Being able to heat rooms independently is great for some people, disliked by others. The air cleaning effect is loved by people with things like asthma, but other people hate it for the fact filters need cleaning etc.

On other points.

- You don't need lots of units if your building was designed to be heated from central spots at least just less big ones. Many installers though will insist that you need exactly the maximum number of units that the outside part of the kit can support and they like to upsell sometimes 8)

- A small terrace you can indeed heat/cool with one up and one down and a few door openings.

- One real big value for air/air is that it's not constrained by the weak heat transfer through water that air/water has. That means it can heat spaces that an air/water system would struggle with or require fantastically expensive radiator upgrades. That's particularly useful in things like listed buildings where you can't fix the insulation, or solid wall buildings where it's very hard to fix the insulation properly without turning it into a mould farm.

And all of it has to be looked at in the full building context sometimes. For example if you've got nice radiators and the air/water grant covers it beautifully but your house cooks in summer it might be that what you need isn't aircon but more basic stuff - screening windows from high sun, solar on the roof to act as a parasol, a proper cooling and circulating loft space and so on.

We have lots of tools from around the world, and many of them are actually vastly more cost effective than simply tackling either heating or cooling head on as a "meet the existing watts in/watts out" problem.

Posted by: @tim441

↑

@editor msny thanks for comprehensive reply..

I'malmost t certain it will need permission as the ashp did... and the extension itself did.

Sadly these days our local planners and conservation officers will not engage unless I pay for "pre-application' advice. Its costly and very slow. So usually better to simply apply - and tweak the application during the application period.

The conservation policies in place via CADW and EH are very clear that buildlings need to be sustainable. There are clear policies on how and where to do solar and the like. The underlying argument is that an unsustainable building becomes unused and unused buildings decay and are lost. Not all conservation officers (when the council even really has one) seem to get this, and it's not helped that austerity has meant many councils CO is one of something like four jobs they do and their actual qualification might well be in things like urban planning.

We've recently applied for 11kW of solar on the garage/coachhouse roof and had no trouble at all because it's not harming the underlying building, especially as we specified a mounting system designed to avoid drilling slates.

Pretty much anything involving planning within the curtilage of a listed building requires planning permission and listed building consent.

Some listed building and especially conservation zone people fit the "through the wall" type units where the unit is internal but has two 15cm or so vents to outside. That's more holes in the building fabric but means that the external view is basically unchanged except for two fairly easy to hide fan grilles. That can be useful but presumably if you already have air/water you already figured out where to stick an external unit unobtrusively.