Experience of / Advice about : Retrofit underfloor heating

[Sideways]

I need to update and redecorate a small bedroom in a late 70's house.
It's on the ground floor and one of the colder corners of the house.
Being a small space and as I plan to improve the insulation of the room, this could be a good opportunity to DIY install a wet underfloor heating.

I'd love to learn from anyone who has experience of this.

I don't want to raise the floor level massively.
I'm interested in something like foam slab down onto the existing concrete, something precut for holding the plastic pipes in place, a cover board like high pressure laminate to take and spread the load, engineered wood strip flooring to finish.

It's a bedroom, so not high traffic. I prefer to avoid a poured floor as that makes it much harder to repair if anything fails in years to come.

Thanks

 

[Doug B]

Did just this a good few years ago I’m sure I’ve some photos somewhere, put down insulation then into the grooves in the insulation fitted aluminium heat spreading plates & finally put the pipe into the plates, this I then laid an engineered oak floor on.

 

[Spectric]

These panels for pipe layout are good and makes getting the leveling compound level Self-Adhesive Profix Panels - UK Underfloor Heating

Complete systems for a single zone Profix Low Profile Retrofit Underfloor Heating Kit - 10 SQ/M





Before covering pipes you want to pressurise with a pressure tester and leave under pressure whilst covering and it has set.

 

[baldkev]

Grant do a system where you fit pipes into a board with the pipe grooves, then cover with thin ply.
Ive recently had a Grant low pro ufh system fitted on a house I'm doing for a customer. We had glendinnings excelio pumped in ( flow screed )

Their tech department are very helpful and will recommend suitable products

 

[MikeJhn]

A ground floor room needs as much insulation as you can fit below the heating elements/pipework, big mistake not to do this, the heat will just disappear into the floor mass otherwise.

 

[pgrbff]

As MikeJhn says, unless you insulate well under the pipes, or the slab has insulation under it, which I guess is very unlikely, you are going to lose a lot of the heat. The flooring you put on top is also important because wood will tend to insulate and stop the heat coming through. I have installed UFH in UK type buildings and here in Italy. For it to work well in my opinion it really needs to be in a slab that is insulated below. The slab heats up and acts as a store for the heat, giving it off slowly. When I installed in Ireland, between joists with aluminium spreader plates and wooden floorboards, it wasn't very effective at all and squeaked and creaked as it warmed up.

 

[Doug B]

I’m guessing after almost 2 years Sideways has finished his re-decoration

 

[deema]

I’m guessing after almost 2 years Sideways has finished his re-decoration

All I’m going to say is the Mrs Sideways is the most understanding person I have ever met.

 

[deema]

I would drill the concrete with a hole saw to see what beneath the concrete. With it being a 1970’s house there may be minimal to no insulation under the slab; I think it only became mandatory under building regs in the 1990’s. If tgere is no insulation, I would dig u0 the base and redo the floor. It sounds daunting, but, I did it in a room in my house that’s just a little smaller than the room you’re doing. Without proper insulation under the slab adding UFH IMO is pointless.

 

[deema]

I have had just about every form of UFH added to my house. Having seen how it’s done I would now not hesitate to do it myself. It’s very easy!
If you’re going to add UFH over time over the entire downstairs I would probably go for the routed out polystyrene panels with reflector. It’s quick and easy to install and reduces headroom under doors by about 25mm. It also increases floor height compared to other rooms that haven’t been done by 25mm. The other approach is to rout out the concrete floor with a special grinder. For the size of room this will be done in a day, and the hire of the machine is very cheap, far cheaper than the panels. I did most of the routing in one of my rooms. Horrible job! But, the greater thermal mass and zero increase in floor height / door height reduction is in my opinion worth it.

The big advantage of the polystyrene boards I have found is that its almost like having radiators, I can heat up the rooms that it’s in very quickly, unlike the UFH buried in screed / concrete where you have to heat up the thermal mass. The downside is that unlike concrete, when the heating is off, the floor cools down quickly and isn’t as nice to walk on. I have the boards on the upstairs, so not an issue as it’s all bedrooms.

Special grinder - hire the dedicated extractor too!

Ground out concrete floor

Routed out floor panels

Laid floor

 

[pgrbff]

I’m guessing after almost 2 years Sideways has finished his re-decoration

I'm sure you're right. I didn't read the date.

 

[deema]

On the UFH under floor boards on suspended floors I had battens added under the joists, membrane, kingsman insulation then another membrain, pipes and then levelled up using screed before the floor boards went on top. It sounds worse than it us to do. It’s very effective.

 

[Sideways]

Just for completeness, this room still hasn't been redecorated. Lots of stuff got in the way but it is now near the top of the list...
I can't justify ripping up the concrete slab in one small room to insulate and replace it - so I've decided to just put down some xps (?) insulating foam + laminate floor, and upgrade the radiator after a complete replaster.

All this does bring home how standards have moved on. It's so much easier to incorporate a decent level of insulation when you build a house than to retrofit it afterwards.

 

[Doug B]

Just for completeness, this room still hasn't been redecorated.

& you’re still married you’re a lucky lad