Retrofitting underfloor heating in older property

[Dave4290]

I am looking for advice about moving from Oil heating to an air source heat pump. I was contacted by a company to say that we quality for the latest government grant (ECo4 - Flex) to replace our 10 year old oil boiler. They are suggesting to move to an air source heat pump with solar PV system and the maximum contribution I would need to make would be £3K. As part of this retrofit they would need to upgrade the radiators and pipework to be bigger, however, they said this may mean some pipework being in sight.


The property is a dormer bungalow built in 1970 with solid brick walls with cavity (already insulated, but needs to be be replaced). The footprint is 130sq mt and the floor is a concrete slab but has a strange very small timber floating floor (1/2 foot max height) where the current heating pipes run - this has no insulation or ventilation and is something I was considering changing to be honest. Half the house has older wooden double glazing half has been replaced last year with PVC (the other wad due to get finished this year/next year.

On the face of it it seems to be a good deal, but I am unsure if this would be wise move beyond economics so have a few questions:

1. Will the proposed heat pump and radiators be sufficient for the age and size of property? I've heard mixed opinions about air source heat pumps efficiency and running costs in older properties
2. Would replacement pipework likely be copper? I am surrounded by fields so have the joys of mice who love plastic
3. I really don't like the idea of pipework on show. I assume this is why the previous owners built this diy timber floor. The company didn't mention it, but would wet underfloor heating be a better long term solution? Could I convert the pipes they put in to UFH later when budget permits? Online quotes suggest about £85 sq meter I that about right
4. If I went for UF, how long would the screed take to set before flooring and furniture can be put down

 

[oldbutnotdead]

Not an expert in the field but nearly always with grant installations you get what you're given which will be the cheapest hardware installed in the quickest way with little or no consideration for aesthetics (see council house rewires where it's surface trunking everywhere instead of using the original conduit or chasing in and making good). Most likely placcie pipe if that's the cheapest way to do the job.
You need some heat loss figures for your house (IE how many kWh does it take to keep the place comfortable) and compare them with the output on their proposed ashp.
UFH can work well with ashp (low continuous temperature delivery), yes you should be able to retrofit that on - again I'm no expert. Screed- 1 day per 10mm I think is the guidance

 

[Dave4290]

@oldbutnotdead many thanks for the reply. Was tempted by the offer given my oil went from up £450 > £1350 per tank (3 required per annum), but the earache from the wife might offset the cost saving lol

Plastic pipes are asking for trouble unless the cat steps up her game lol

Will look into UFH to see if I could retrofit this afterwards, but suspect it is going to be out of my budget

 

[Loofah]

3k contribution sounds very low for all that kit and installation. Get everything in writing! You should be able to specify copper pipes etc but it will likely affect the contribution cost.

Screed types vary. You can walk on them very quickly but to put a floor covering on you're looking at quite a while
"According to industry guidelines a 75mm traditional screed would require up to 110 days to dry at 20˚C and 50%RH at the rate of 1mm per day for the first 40mm and 0.5 mm thereafter." -https://www.screedscientist.com/what-affects-screed-drying-time/

 

[Dave4290]

@Loofah I am ever the skeptic, and I know you shouldn't judge a book by the cover, but the first guy who came to the door looked less than professional. So much so, I phoned SCARF to see if they had heard of the company. They confirmed they had worked with them before, but I still will make sure to get everything in writing.

We could vacate the house for few weeks, but not 110 days. It sounds like if we retrofitted UFH afterwards we might have to live with no floor coverings for a few months (is that even allowed under H&S)

 

[Loofah]

Probably be less time with the CH on but you have to figure out how to fit the UFH first. Ours, not retrofitted, was block and beam floor, 100mm insulation (I think), piping for UFH then 75mm screed.

 

[Dave4290]

Probably be less time with the CH on but you have to figure out how to fit the UFH first. Ours, not retrofitted, was block and beam floor, 100mm insulation (I think), piping for UFH then 75mm screed.

My thinking was removing the weird floating floor and taking it back to the concrete slab so i'd have plenty of room to play with. Then insulation, piping and screed

 

[Loofah]

Check if you need a separate moisture barrier before the insulation too

 

[Dave4290]

I imagine the concrete base would have a damp proof membrane in but perhaps adding another would be the way to go. I assume if I add a moisture barrier on top of the concrete base before the insulation, it wont cause an issue having two moisture barriers i.e. moistire wont get trapped between them