Underfoor heating with air source heat pump

[TomoD]

Hi There

i was hoping someone could share some wisdom! I currently have a uponor minitec underfloor which has been fitted to our hallway, bathroom and front snug. The problem is it was retrospectively fitted and there is no insulation fitted, it has a thin screed of 20mm and has been working well however the cost of running it is eye watering so we haven’t had it on in 2 years! The house is listed, old with sash windows and leaks like a sieve! We have 2 x 30kw boilers connected to a low loss header for CH heating (upstairs and some rooms down stairs ) and water. My question is would it be cheaper to buy an air source heat pump to run the underfloor heating only on a seperate circuit only and let the boilers do the hot water and CH radiators. I believe the air source heat pumps can heat water to a low temp which would be good enough for the underfloor heating ? Any suggestions would be much appreciated thanks   

[Andehh]

If your on mains gas, and a house like that... Stick with gas!!

 

If there is no insulation underneath it then anything you do is just tickling the symptoms. Put a thick rug over the cold floor and leave it until a refurb enables you to insulate the the floor and do it properly. The £3-8k you could spend on the ashp would be better spent doing this!

 

We've got an ashp in a modern build, and I'm happy enough with it... But I would never recommend an ASHP for anyone unless a full refurbish or new build is on the cards.

 

 

Edited October 30, 2023 by Andehh

[JohnMo]

3 hours ago, TomoD said:

My question is would it be cheaper to buy an air source heat pump to run the underfloor heating only on a separate circuit only and let the boilers do the hot water and CH radiators. I believe the air source heat pumps can heat water to a low temp which would be good enough for the underfloor heating ?

Simple answer is no.  UFH without insulation and in a poorly insulated house will have a quite high flow temp, so an ASHP will cost you loads to install and give you no running cost benefits.  Spend your money on radiators in the areas covered by UFH and leave the UFH off.

 

A listed building doesn't always mean you cannot insulate or fix drafts - speak to listed building person, in the local council office, you may get grants to do most things, if you are lucky.

[TomoD]

Thanks for the replies, fortunately insulation cost of the ASHP will be minimal also I may be able to get hold of one at a very reasonable price, I’m more thinking of the monthly running cost as it would be running all the time. 
we had CH before the underfloor was installed but couldn’t get enough output from them due to not enough wall space due to doorways , staircases etc . 
I guess I would like to know what a monthly cost of running a ASHP would be for underfloor heating only? If any one could help it would be much appreciated .cheers 

 

[ProDave]

1 hour ago, TomoD said:

guess I would like to know what a monthly cost of running a ASHP would be for underfloor heating only? If any one could help it would be much appreciated .cheers 

 

A well set up ASHP heating system, will deliver a COP of about 3, which means for every 1kW of electricity consumed, you get 3kW oh heat.  With electricity being about 3 times the cost of gas, that roughly means an ASHP will cost about the same as a gas system.

 

Your problem is a poorly insulated house, with two 30kW boilers that struggle to heat it and cost a fortune.  To replicate that amount of power with an ASHP is impossible, and even if you could, the best you could hope for is similar running costs.  Anyone who says it will be cheaper is an eternal optimist.

[Roger440]

Stick with what you have. Aside from oil, its the cheapest option in your situation.