ASHP retro fit

[Johnnym]

I currently live in a house that’s around 25 years old, which still has the original gas boiler and although we have it serviced regularly, it’s been giving us some trouble recently. We’ve ran the system through a power flush twice in the last 4 years and have had to replace a few parts while it’s failed on us a few times. I’ve been putting off getting a new boiler but it’s looking more and more likely that we’ll need to do so. 

 

So, I’ve been wondering is it worth replacing it with an ASHP. The house is a 5 bed David Wilson type build over two floors, has double glazing, the loft is well insulated and has cavity wall insulation. So it’s reasonably well insulated. With the £5k ‘green home’ grant available it makes sense to take a look at an ASHP. 

 

However, with most houses of this type, it only has radiators and not underfloor heating (which seems to work best with the lower temperatures of the heat pumps). So I guess the questions I have around this are. 

 

 

Is it worth looking at retrofitting a low profile underfloor heating system rather than using radiators. 

 

Can you run underfloor heating off the existing rad feeds (bearing in mind this will be a lower temperature with an ASHP compared to gas). I’ve only seen one system that seems to offer this as a solution (running new pipework on an existing build seems like a real pain/mess/expensive). 

 

Some rooms will still need to run off radiators so does anyone have any recommendations on using aluminium or fan assisted radiators as I will probably need to replace some (although the fan assisted ones seem expensive and there aren’t too many on the market). 

 

Has anyone (or is it even possible) cool the house in the summer months using the radiators with an ASHP to ‘cool’ the water down? I think this is probably a no! 

 

How reliable are ASHP’s and is it easy to find someone to fix it when they do go wrong. 

 

 

Other points worth a mention, I’m working from home most of the time now so there will be someone in the house nearly 24 x 7, so a more constant temperature in the house is desirable. I’ll probably look to install solar panels at some point soon as well which may help with the running costs of an ASHP. 

 

 

I’m just a little worried that that the time isn’t quite right to make the jump just yet as not too many people seem to be using this (vs gas), so would I be better in staying put with gas and a new boiler for another 8 – 10 years? 

 

 

Sorry for such a long post!! 

 

[gavztheouch]

https://trystanlea.org.uk
 

the above is a nice blog from a chap who installed a heat pump in a less than ideal house using just normal screw fix double panel rads. He is managing a cop of 4 and uses low flow temps.

 

you don’t need underfloor. You can use a larger size of a normal double panel rad. You can also use fan coil rads which are much smaller and can releases a lot more heat. Fan coils are rads with a very small fan built inside to increase heat transfer.

 

Your house sounds ideal for heat pump. However it might not save money vs mains gas especially if you need to change a lot of radiators. 

Edited January 4, 2021 by gavztheouch

[TonyT]

I think it’s a personal situation and how you heat the home currently and to what temperature you are comfortable with.

 

i have a Victorian property and heat it with a condensing combi boiler, year on year making more and more improvements as time, funds and willingness for disruption allows.

 

Second boiler in this home now fitted after 14 years use, boiler modulates to lower output and weather compensation controls etc, I’ve tried running boiler output  temps lots lower and the room temp difference is noticeable, SWMBO noticed the drop in temp and has medical issues so need to maintain temps that’s acceptable to us.

 

good luck with whatever you decide 

 

 

 

[Johnnym]

Thanks, I should add to those comments that I appreciate that a) it will be more expensive to do this than just put in a new boiler even with the grant and b) the running costs might be a little higher as gas is so much cheaper even if it consumes less energy although hopefully long term solar will pay its way towards it. 
 

We do like the house relatively warm at between 20 - 22 C. 
 

I’ll have a read of that blog as well. 
 

if anyone has any comments on the cooling side I’d appreciate it. It was a real pain this summer with the heat at home. 

[TonyT]

The chap in the link has a house with 77m2 floor area so remember that!

im enjoying reading his posts.

 

you also get triple panel convectors, so even better heat output.

[gavztheouch]

another good resource from the same guy is this video.