Air Source Heat Pumps

[DaveCrampton]

Does anyone have an Air Source Heat Pump? Our 7 yo gas boiler is failing and I am considering buying an Air Source Heat Pump instead of just paying a plumber to swap the old for new boiler.

My other half is sceptical as someone she knows at work says she saw a TV programme which suggested air source heat pumps are not great at heating if your house is not brand new with lots of insulation.

We have a 70s timber frame bungalow (timber frame supporting the roof), with brick walls which are not structural. The loft has sufficient insulation but our walls are not well insulated and we can't have cavity wall insulation as this could spill into the rooms if we remove an electrical socket or make a hole in the plasterboard. We live in Scotland and the outer brick has rough cast with stones embedded. One option could be to remove the old rough cast and add insulation in the form of polystyrene blocks, which have rough cast applied over them.

Does anyone long term experience of an air source heat pump in an older house? Did you have to add lots of insulation or has you found the heat pumps not great at heating?

 

[shropschris]

I think you would need to ad insulation which ever road you head down ,ASHP work better in a well insulated building, so do gas boilers to be fair.

 

[True Romance]

Been watching a few videos recently on these and it's very marmite. Search EV man. He had one installed recently and without solar and battery back up the running cost seemed pretty much the sane as a gas boiler.

 

[paddy26]

You'll definitely need to insulate. Airtightness is also important. For efficiency heat pumps work better at lower water temps than oil/gas. This suits underfloor heating and not rads. To offset this you may need to oversize your rads or go with aluminum rads.
We bought a bungalow that was at 1st fix stage. Floors were poured so we didn't do underfloor heating. Instead we went x1.5 on the rad sizes. Walls are pumped + 2" insulated slab(internal) on external walls. We also did airtightness. Chimney was removed.
Heatpump is 9.2kw. 1st one lasted 10years. Compressor(expensive) had to be replaced and system regased twice. I used a refrigeration guy as there was nobody local trained to work on them.
We installed a new one last year. No issues so far.
We're happy with it but I wouldn't recommend one unless you have very good insulation and airtightness.

 

[Bav]

If this government are pushing ASHPs, that's good enough for me... to run the hell in the opposite direction!!!!!

 

[DXX]

My neighbour has an air source heat pump installation on an old poorly insulated house. My observation is that it runs in the summer but I haven’t seen it running much in the winter. That’s an indication that the recoverable energy in low ambient temperature isn’t cost effective.
I spoke with the installers as I was interested that they were installing on a stone built, solid walled / floored house. One said he just did what the other one told him to do and the other said I just do what the office tells me. I think there are some companies offering very poor advice to house owners.
I studied thermodynamics, fluid mechanics and heat transfer among other modules for many years in my formal training. While equipment and materials have improved the basic principals and engineering laws haven’t.
What seems to be overlooked is this lump of machinery that is sitting outside, if it lasted forever maintenance free it might be a more tempting offer.

Here’s a few links, I find the SkilBuilder site seem to offer some practical and impartial advice.

 

[boxelder]

We're on our second house with ASHP. The first was a '50's semi that we extended and added the system to. Last 5 years, we've been in a detached house, my wife designed (architect). In a nutshell:
1. You need insulation. They are best run constantly at lower temps, over bigger surfaces, so large radiators or underfloor.
2. The result is a house that is almost always at about the right temperature - you don't notice the temp much as it's always about right - no "Ooh, isn't it warm with the heating on" or "Brrrrr, time to turn on the heating".
3. With current electricity prices, the economic argument for them has been torpedo'd, especially as decent servicing is as hard to source and costly as for a T6.
4. They run on electricity, which will always be readily available and can be produced renewably.

It doesn't sound like a great option for your situation.

 

[jimc91]

Aren’t they noisy as well, neighbours might not be happy

 

[boxelder]

Aren’t they noisy as well, neighbours might not be happy

Not really. Nowhere near as loud as a T6 starting up at 6.30am......

 

[Bav]

Aren’t they noisy as well, neighbours might not be happy

Good point - just need to determine under which SWOT heading that should be listed.

 

[Rioja John]

I worked for an housing association before retirement and they fitted some of these systems and were anundated with complaints, not warm enough, costly to run and noisy.

John.

 

[Mule]

It's an interesting question and probably one that ASHP installers are best placed to advise you on following a visit to your property.

I live in the south east so can only comment on my own experience with an ASHP, which aligns with @boxelder and @paddy26 comments above....

ASHPs like all heat pumps emit a lower heat output than conventional central heating so need to run longer and with more efficient heating sytems, such as Type 22 radiators or underfloor heating. However, in the right situation they are more efficient and more cost effective than oil and gas.

Yes they run on electricity (which is not particularly cheap at the moment) but they're still efficient. My ASHP produces 4kW of heat per 1kW of electricity consumed in the summer but this coefficient drops to 2kW per 1kW of electricity in the winter when the air temperature is lower. This is great for providing our domestic hot water all year round but less efficient in the winter when we need the heating.

Hence the insulation come into play. Although this applies to all houses regardless of what heating system you have. (The better insulated a house is, the less heat it loses and the less money you spend replacing the lost heat.)

I have a 1970s built house with approx 400mm of insulation in the roof, cavity wall insulation (the blown fibre stuff that was retrospectively added 10 years ago) and no insulation in the concrete floor. However, I did find a company who retrofitted under floor heating and this has proved to be a game changer and one that the Wife is most impressed with.

Linking this back to your question, I doubt from the information you have provided that an ASHP is the right solution for you based on the single skin walls, but I'd still recommend you explore the idea with professional installers in your area and try 3 or 4 to get a consensus on the viability. Maybe with upgraded radiators, UFH and decent loft insulation the numbers will work for you.

 

[Pauly]

I think the key factor of ASHP is flow temperatures
As mentioned above boilers are designed to put out water at a much higher temp then ASHP and are designed for conventional rads etc, ashp flow temps are much lower and better suited to underfloor heating

We have done loads of ashp (wired up as we are sparkies) and in my opinion if its new build with good insulation, underfloor heating and solar PV then its a great option, if its an existing house with rads then its not

We worked for LA/housing associations and the powers that be decided xx% of their properties should be green and decided ashp were the way to do it and also decided the best place for these was in houses that didnt have piped gas so we were involved in dozens and dozens of heat pump installs in mostly out of town houses that ran on oil or lpg tanks and for the most part when fitted the householders were not pleased, systems had to run for days to get heat back into the properties and often radiators had to be replaced with forced air myson heaters to try and extract the most heat from the systems

I have been out of the loop the last couple years as we have moved away from LA work but i would look up the difference between low temp and high temp systems
High temp systems pass through the heat exchanger twice and can put out much higher flow temps so are less reliant on forced rads and also less reliant on booster (immersion) heaters to top up the water to a satisfactory temperature, but of course these systems are a different price range !!

Bottom line for me, if your property is not suitable and you dont have PV get a gas boiler

 

[Fluff34567]

I bought a house with a heat pump but it has underfloor heating , the house is from 1995. Its extremely quiet and the unit is inside. Will get more pics later though the European systems are different to what the UK would have.

 

[La paix]

Hi, I work in partnership with a company that have been installing ashp, gshp and water source for over 10years.

There is one word that is key, design. Flow temperature and differential is critical to efficiency. Get these wrong, and lots of installers potentially are, things get expensive quickly!

We thermally model every house on a room by room basis prior to quoting for anything and are more than happy to tell people not to do it!

 

[Gavinda]

As has been said insulation, airtightness and system design (heat emitters, distribution pipework, flow rates etc.) are key to a satisfactory install. Are you able to ensure you can cover all these bases? If not and honestly you're unlikely to find someone who will. I'd go with another gas boiler for now until the heat pump sector in the UK matures.

 

[david173]

looks like its mostly been covered here so ill keep it sweet (ish).
I would only ever bother in a new self build (not the mass produced developer minimum building standard homes) where you can get super airtight and super insulated or a very extreme renovation. By extreme im talking new concrete insulated floor slabs, external insulation and reduction of cold bridges, new windows etc etc. almost a passive standard. Underfloor heating for me is a must for it to have the thermal comfort you want.

you have to ask yourself why??? you can mostly likely get several gas boilers for the price of the unit let alone the upgrades needed. Its not going to save much money is you don't have your own means of electricity generation.

It extracts heat from the air,( very simplified) how much heat in the air do you think there is in the winter when its - 5 outside and thats when you need the most heat? Ground source heat pump would be much more effective as the ground is a constant approximate 11 Celsius all year round.

 

[La paix]

Interestingly as per David above new builds now have no real choice, as we can see no way of getting through the new building regs and sap10 with a gas boiler!

Gshp only viable on much larger houses due to installation costs

 

[Sackmycook]

Hi, I work in partnership with a company that have been installing ashp, gshp and water source for over 10years.

There is one word that is key, design. Flow temperature and differential is critical to efficiency. Get these wrong, and lots of installers potentially are, things get expensive quickly!

We thermally model every house on a room by room basis prior to quoting for anything and are more than happy to tell people not to do it!

What is the company name?

 

[La paix]

Xpert Energy, although currently not operating up north! Please feel free to message if you had any queries, hadn't planned on "selling" on here but rude not to answer the question!