Underfloor heating - how do you use it?

[PumpingRSI]

We're having underfloor hearing put in our new extension with 3 zones areas - kitchen, utility and office. I know it's a low gentle sort of heat but do you keep it on at night? In the office it will only be used 3 times a week or so, does it make sense to time those areas to switch off more?

Also does it vastly increase your heating bills?

Realistically I know it's the only way to hear such an open big space but just trying to prep myself.

We only had ours in the bathroom so didn't see a massive increase in electricity bills.

The system should come with it's individual thermostat and we'd set a timer for it to come on 15 minutes before our alarm went off in the mornings and then again at around 10pm on Monday to Friday. Weekends just turned it on as we wanted.

Is your UFH electric or water? This determines how fast it takes to come to required temperature and also impact how long you want to have it on.

We have water UFH in our hallway and reception room. These rooms have no other heat source - not planned by me, but the house came that way. The hallway is on a different zone than the reception room with separate timers. After much tinkering, the best thing is to keep the UFH on all the time, albeit at a lowish temperature O/n and when not planned to be in use as it takes many hours for it to go from cold to desired temperature. To run it in this manner, the heating adds about £2/day to the heating cost of the house (which is a draft victorian one).

Hi,
It's water UFH we are planning on.

and a concrete floor?

We are thinking of this for new extension but I'm a bit concerned whether it will get warm anough and also the cost. £60 a month extra seems high, not sure I want it that badly!

presumably that would just be for those days that it is on? So not summer.

It's very worthwhile in a room that is used during the day, since it gives a constant comfortable warmth. In a new floor, with insulating slab beneath the concrete and well-insulated walls, I would hope it will be more economical than in a draughty old house.

Hi, yes would be in new extension with concrete sub base and well insulated walls. £600+ a year extra seems ghastly!

I don’t think it costs more than radiators. We have a wet system and it’s brilliant as it frees up walls and is an all-over heat gentle heat. You would have to pay something for heat, so what would another form cost you? It’s the difference, if any, you need to think about I don’t think underfloor is that much of an extra, if at all.

Is there a particular type of floor insulation you should use with wet ufh? Does it vary if you have wood or tiles? I'm wary of having a large tiled area as i presume it would mean having to have the ufh on more to take the chill off?

You do have to have it on all the time which means we live in our kitchen now as it’s warm the whole time. We turn it off when we go away and it can take two days to reheat to a decent temperature again.

I had our whole house, upstairs and downstairs, built with UFH and it was both fantastic and very cheap to run. Wet UFH runs at a lower temperature than the water in your radiators (obviously) so gives a gentle warmth to the concrete base; once it’s warm it holds the heat so the temperature is pretty stable and there is no need for a blast of heating time. We had a timer and thermostat for every zone to make sure each was warm enough at the right time and the bathrooms were warmer than the bedrooms. Cannot recommend it highly enough, and miss it more than anything else (including XDH) now I no longer have it. Can’t recommend it highly enough.

Added bonus: wet towels thrown on floor by teenagers get dry and warm.

We have just had a three zone water based system put in. I didn't want it initially, we did it to save wall space but I love it! We just leave ours at a comfortable temperature all the time. I was told it is more efficient to do it this way rather than let the slab cool and then reheat it all the time.

We carpeted one of the zones, wooden floor in the others. Kept the underlay/carpet under the recommended 2.5 tog and am just as happy with its performance under carpet asI am with the wooden floor.

We've only had it working for a couple of months so don't know what effect it has had on bills (in all honesty I am rubbish at keeping check on them anyway!).

Floor insulation:. Most often, wet systems have the pipes embedded in the concrete when a new building or extension is built. Under the heated layer is rigid foam insulation board, then the concrete subfloor, dpm, and base which might be crushed stone.

If you have a suspended wooden floor, especially in an existing house, you lay the pipes between the joists, with a spreader, then insulation beneath, then floorboards beneath. This does not take so long to warm up because you are not heating a slab of concrete.

Foam is used because it is rigid and weight-bearing, it will support a slab of concrete, and because it has about twice the insulating power as a layer of mineral wool of the same thickness. You might use mineral wool if you were adding to an existing house with a wooden floor, because it can be packed tightly between the joists without needing precision cutting, you have adequate joist depth for a thick layer, and it is cheaper than foam.

Floorboards on top, I meant, not "floorboards beneath"