Hi AmyFOD,

Welcome to the forum.

As both Julian and Kev have stated, get more quotes, since £14.5k does seem rather excessive for an ASHP system without radiators.

As far as the need to change your radiators, try to think back to the cold Winter days, how hot did your radiators need to get to keep your home warm? If they were not particularly hot then you may not need to change them.

Your particular problem is living in a Radon gas area. When you had the assessments carried out, did they state the Air Changes per Hour (ACH) rate and the subsequent heat demand due to having to heat the fresh air coming in. It could be quite high in your case.

Dependent upon the number and location of the air vents, in combination with the wind direction and strength, your heat loss due to ventilation requirements could vary quite considerably from one day to the next. This of course makes estimating maximum heat demand all the more difficult.

As somewhat of a solution, you could consider installing Mechanical Ventilation Heat Recover (MVHR), which basically uses the warm air going out to heat the fresh air coming in. The manufacturers claim up to 90% of the heat is recovered, but I don't know how accurate this figure may be. The systems are not particularly cheap, probably several thousands pounds, and require the installation of ducting, but may be cost effective in your case, since it would probably reduce your total heat demand, so a suitably sized ASHP would not need to work as hard and hence could operate at lower temperatures.

 It is also possible to get MVHR systems which incorporate an ASHP, which makes them highly efficient, even in the cold days of Winter. The drawback is they do not produce hot water and are not eligible for RHI payments, but as I understand are considerably cheaper than a full ASHP system.

It may pay you to explore all the various options before your make any decisions.

Hi AmyFOD,

I forgot to ask, do you have solar PV or solar thermal?

@derek-m Hi Derek, currently we don't have solar pv or thermal, but we would consider it.

We only moved in a month ago so we don't have any experience of the depths of winter - it's been pretty chilly but we used to live in a wooden cabin with no central heating so I think we're quite hardy. I don't know what the ACH rate is, they didn't tell us that. I don't know anything about MVHR but it sounds like we ought to think about it. 

We're looking to get a few more quotes and maybe consider a biomass boiler as my partner works in the woods, although there seem to be as many potential issues with that.

@kev-m Thanks for this. The comparison is useful although, as you say, all the different factors at play make it tricky to know how to compare buildings. But I think the more info the better right now!

@julianc Ace, thank you, it does seem high to not include radiators and we also have to pay £250 to get them to come round and do a full assessment. It's non-refundable so it's making getting complete quotes look like an expensive business. Is it expected for us to have to pay for one of these every time we get a quote?

@amyfod I didn’t pay for any assessments. I got a free EPC through Eon who were offering a hybrid system. I decided not to proceed with that. I then got several full ASHP quotes. Most did basic assessments based on the EPC. Lots then said I had to change 10mm pipes to radiators. Nooo!  Several did video walk around for more detailed quotes. Ecobubl, who were my final installers, did a full assessment to MCS standard. I compared this to the other quotes. 
So steps are 1. Get an EPC, but you may have this if recently purchased 2. Seek quotes based on this 3. As questions. Don’t pay £250 or whatever for an assessment until you have finalised your installer and only then if it comes off your final bill

@amyfod, our supplier used the EPC and did a home visit, where they measured the rooms and asked for some details about materials, insulation, etc. They produced quite a detailed quote with a parts and labour list. I then placed the order and paid a fully refundable 25% deposit, after which they did the MCS survey.  There were a couple extra radiators which were covered by a variation notice. Another 25% before they started and the rest on completion. The cost of the MCS survey, calcs and admin was listed as an item on the quote.   

An experienced supplier should be able to quote without doing the full survey. As @julianc says, don't pay for the survey up front, unless it's fully refundable. 

@amyfod just fyi we've had two quotes 14k and 16k for ecodan 14w plus tank plus 300l cylinder, buffer tank and piping etc. No radiators. We already have underfloor heating. MMSP would cost more but you do get it back. Conscious this seems quite pricey - struggling to get others out to quote though.

Have discovered also that the 14kw ecodan is not the same style as the rest of the range which has been redesigned and labelled as 'ultra quiet'. Anyway, contacted our installers and have said want to see this model in action as trying to work out what they are like from quoted decibel range makes hard work of it. All being well going to see one in action tonight.

@kev-m just wondered what your experience of the ecodan 14kw has been like? My neighbours nearest room is about 12 metres away. I know it's a 'find out for yourself and make your own mind up' situation but since you've got the same model was interested?

@rv3 not trying to dissuade you, but have you looked at the Daikin Altherma 3H HT or the 3M?  My 18kW is quiet single fan. Meets planning regs volume <0.63m3

My system £13.7k inc Mixergy 180L & buffer tank. Contact Daikin directly to get local approved installers. 

@RV3 our experience of the Ecodan has been good so far.  Noise certainly isn't a problem in the house.  Outside next to it, well obviously you can hear it.  At the moment, when it's a bit warmer, it's very quiet and I don't think it would carry 12 metres.  When it was colder at the start of April and it was working hard, it was definitely louder.  However, noise nuisance is really subjective and depends on lots of external factors including ambient noise. It's nowhere near the level of the rattly old pub ACs you see; it's more the level of a modern car ticking over.  See what you think when you see one in action but try and get to listen to it when it on full power (not sure how you'd do that though). 

The other point worth making is that when it's cold and the ASHP is working hard, you are less likely to be outside or have windows open.   

@kev-m - that tallies with what we saw - thanks for the perspective.

@julianc - impressive that it's 18kw and so quiet. Think we're probably ok with the ecodan but going to jump onto the Daikin website and do a bit of homework tonight.

As always responses much appreciated thanks. 

@rv3 I keep intending to record the noise level. But weather has warmed up so the ASHP isn’t running 😊

I think the different suppliers much have similarly competing products. My only thought was one fan vs two. The larger two fan boxes need planning permission whereas the Daikin single fan is within permitted development standards.