Underfloor heating, is putting in a water system reliable Post Reply

[belinda158]

The underfloor heating in our kitchen has failed and we need to replace. It is currently electric (not ideal) but to put it on our water system digging down a little - not very much. Not sure if it will be worth it. Would love to hear from anyone who has underfloor heating on pipes and if it has been reliable. Don't want to dig down and then find ourselves in a similar place.

[MrsOctober]

Electric underfloor mats should only ever really be used as tile warmers, never the sole source of heat to the room. Wet UFH is a lot more expensive and complicated to install but the running costs are much, much lower. It seems like you’ll already have to take up your floor if your electric matting has failed so it’s absolutely worth the extra hassle of digging down for the wet UFH. Just make sure your builders have done lots before. Once it’s screeded, the UFH has to be turned up by a degree or two each day for a couple of weeks and then down again in order to cure the screed and avoid sudden expansion, BEFORE they even think about tiling. Check that your builder is going to do this before you employ him. Many skip this step because they either don’t know what they’re doing or they don’t care that your tiles will crack or lift in a year or two. Always read the manufacturers recommendations, don’t rely on your builder to do it. Also think about flooring. Porcelain is the best conductor. Wood is an insulator. With the current and future costs of energy we all need to consider efficiency.

[dudette]

We have it and it hasn’t caused any problems. I would say that certain floorings conduct the heat better than others - so hard floors such as ceramic tiles or polished concrete conduct the heat a lot better than wood so you wouldn’t have to crank the temperature up as much.

[OLBC Group]

Hi

Bit of sideline advice here: we don't get involved in small stuff like this but happy to share our experiences.

If you are going to the bother of taking up the floor then definitely lay wet underfloor heatings.

We have fitted nothing but wet underfloor heating for the last 15 years to the extent that we rarely fit radiators except towel rails.

As others have, rightly said, porcelain tiles or natural stone are the best conductors of heat and hardwood floors are not so good - however, it can be made to work by changing the spacing of the pipes to be tighter together (so more loops to the room).

DO use a proper UFH company to design and fit the UFH - designing it isn't a 'builder' job

DO NOT use latex levelling compound anywhere near UFH. Latex (rubber) is an excellent insulator.

DO use a proper screeding company that can lay a level screed so you don't need the levelling compound.

DO make sure that the screed is reinforced with fibres 

DO use a real tiler who won't put the tiles down on dabs (this only support the corners and the middle of the tiles and they break) but for this conversation it also creates an air gap and static air is a decent insulator! Make sure the tiles are laid in a continuous notched trowel bed of adhesive.

DO use tile adhesive with a good plasticiser in it so that as the screen expands and contracts without cracking the tiles.

DO lay a continuous layer of fibreglass mesh in the first layer of tile adhesive. Screed cracks over time and if there is no mesh the cracks propagate through to the tiles.

There is a wrinkle in this: UFH actually makes your EPC worse. EPC's have nothing to do with energy, money or carbon footprint savings or indeed logic or sanity. Contrary to that UFH is the best system to use with a heat pump. Go figure. 

IRL UFH increases your boiler's efficiency as a condensing gas boilers becomes **more** efficient as the return temperature **reduces** and the condensing part of the process becomes more effective. Latent heat of evaporation of water is massive. As UFH works at a much lower flow temperatures, so there is an almost permanent bleed of cooler water into the return system, thus boosting efficiency.

Hope this is helpful.

Best of luck with the project.