Retrofit wet UFH

[NoNameNoNumber]

We have a ~2000 build, EPC says solid concrete floor assumed, no insulation.
We’re looking to change from oil to ASHP and part of that will be pretty drastic plumbing changes. Perhaps wet UFH is the way to go. Dig up ground floor slab, insulate and add UFH. Then I saw on TikTok a company chasing the floor out to fit the tubes. Does this rely on a well insulated slab already or it it not particularly relevant?


Alternatively, we stick with no floor insulation and chase the walls/ceilings out to remove all the microbore.

Anyone dealt with a similar dilemma?

 

[b0rn2sk8]

If you don’t mind loosing a few cm of height, you can retrofit UFH on top of a slab with no chasing.

I think there are systems than can get it down to 17mm.

You don’t want to chase into an un-insulated slab, the heat loss to the ground will be massive. I’d check it’s actually I insulated, I’d expect it would be at that age. Grab a drill have do a little exploring, the screed on top of insulation will not be particularly thick, just watch out for hidden pipes buried in it.

If it’s un-insulated I’d consider going above, it will be far cheaper and less messy than digging down, insulating and re-screeding.

If you do go ahead, make sure you choose a fairly narrow pipe spacing so you can run the flow temps as low as possible which is better for heat pumps (and uses less gas/oil).

 

[NoNameNoNumber]

Thank you for the info, that would make life much less messy, the mrs wants to replace all the skirting anyway, Id need to trim all my new doors down :/
~17mm I could deal with, we only have 8’ ceilings so would certainly want as minimal as possible.

 

[Hyburnate]

Thank you for the info, that would make life much less messy, the mrs wants to replace all the skirting anyway, Id need to trim all my new doors down :/
~17mm I could deal with, we only have 8’ ceilings so would certainly want as minimal as possible.

Just check how much of a lip you have left at the bottom of your doors

 

[kai]

Have a look at my active thread at the moment in this forum. The latest pictures show my retrofit with the manifold. It's not installed yet functioning but has just been pressure tested.

I had the same issue as yourself. Rather than digging up old screed etc we retrofitted 16mm using this product.

https://www.theunderfloorheatingstore.com/products/prowarm-loflo-lite-dual-purpose-panel-16mm

The rooms we didn't install UFH; we put osb board down to bring the level up - before putting new flooring / skirting so it all run level. However this is just mainly down it being so open plan and not necessarily required.

 

[Doughnut007]

Is retrofit UFH on an insulated slab effective?
Or do you loose a lot to the ground?

 

[Coran]

@NoNameNoNumber if you send an email to the supplier Kai linked to above with a copy of your floor plan and an explanation of what you want, they’ll spec the underfloor heating for you and give you a cost for all the materials you need (incl manifolds, pumps, adhesives etc). You’ll then need to find suitable labour to install it.

Is retrofit UFH on an insulated slab effective?
Or do you loose a lot to the ground?

The boards Kai linked to have a bit of insulation underneath and foil on top so should dissipate most heat upwards.

 

[NoNameNoNumber]

Have a look at my active thread at the moment in this forum. The latest pictures show my retrofit with the manifold. It's not installed yet functioning but has just been pressure tested.

I had the same issue as yourself. Rather than digging up old screed etc we retrofitted 16mm using this product.

https://www.theunderfloorheatingstore.com/products/prowarm-loflo-lite-dual-purpose-panel-16mm

The rooms we didn't install UFH; we put osb board down to bring the level up - before putting new flooring / skirting so it all run level. However this is just mainly down it being so open plan and not necessarily required.

Thanks for the info, looks like a suitable way for us to go-despite the upheaval. But to replace all of the microbore downstairs would require butchering the walls, coving anyway. and pulling floors upstairs.
Either way-it won't be pretty.

Are you on a heat pump?

 

[Coran]

Thanks for the info, looks like a suitable way for us to go-despite the upheaval. But to replace all of the microbore downstairs would require butchering the walls, coving anyway. and pulling floors upstairs.
Either way-it won't be pretty.

Are you on a heat pump?

He’s just installed a brand new boiler (from his extension thread). Sounds like he wasn’t in a position to consider a heat pump time-wise.

I have the same UFH setup with a heat pump and it works well.

 

[NoNameNoNumber]

Done a little digging
We have 25mm of polystyrene then 50mm of screed on our floors.

How bad an idea is it to just rip all that out, lay new insulation (something better than polystyrene) and screed over wet UFH
VS trying to overlay a retrofit kit.

 

[b0rn2sk8]

I’m not sure I’d bother, it would make a right old mess and you’d still probably end up raising the floor height a similar amount anyway.

 

[NoNameNoNumber]

Fair point… the full picture.

Oil boiler is nearing EOL. Boiler service + parts, breakdowns etc in the last 2.5 years is costing £300 a year just to keep it going and we’re told it was rubbish when new, now it’s old and rubbish I should keep a £5k pot ready for its replacement…
Next issue, 3/5 houses built have needed new oil tanks, mine is on a boundary right next to an open water source and ~2m from the house… so we’re told another 3-5k to fit a new compliant tank in the next couple of years, and I’ve gotta find somewhere else to put it…

Ergo the chats around ASHP since we have had 6.7kW PV installed on the roof.

We’re going to be having an extension to the kitchen and diner, making around 40m sq of tiled social space we just can’t run on electric UFH so this is where the real desire for wet comes in.

So if we were to leave the floor and replace all the microbore/upsize the rads, then yes we’re ASHP ready but we really would prefer some kind of heating to the porcelain floor.

 

[964rs]

The low profile retrofit UFH stuff is literally made to do the job you want to do.

If you dig out what you have and replace it your more than likely going to put down 100mm insulation with at least 50mm screed on top.
So you are still worse off for head room than putting the best retrofit system in.

 

[NoNameNoNumber]

What is the best retrofit system?

Would it still require screed over the top?

 

[Coran]

What is the best retrofit system?

Would it still require screed over the top?

I don’t know if it’s the best but the one Kai and I linked to above works well. You can get the slightly deeper one which allows for 15mm pipes. No screed required and includes some insulation below.

 

[b0rn2sk8]

I’d 100% retrofit. Digging that all out is a move out job, it will take weeks to do it properly.

 

[964rs]

By the best ones i just mean ones that have thicker insulation and maybe bigger pipes.These will add to the final floor height. Some do have screed over top some don't.
Having a recommendation from somebody who has fitted that system (IE coran above) is probably a good way to go.
In your specific case i would also 100% retrofit.

 

[Dr House]

You know you can mill into the existing screed floor and lay your pipes into that?

https://x.com/retrorouteufh?s=21&t=D1v3GK9gMSn4AYpUgmuhNw

Or use something like Thermoskirt

 

[NoNameNoNumber]

You know you can mill into the existing screed floor and lay your pipes into that?

https://x.com/retrorouteufh?s=21&t=D1v3GK9gMSn4AYpUgmuhNw

Or use something like Thermoskirt

We don't have enough insulation under our screed for that AFAIK.

 

[NoNameNoNumber]

I guess the fireplace has to come out?
Rebed the hearth higher up, move the mantle too?
Also new front door in first too?

Spoiler: Pics