UFH and radiators

[Whyisitsodifficult]

We’re in the process of building a single storey rear extension. We’re having UFH but one plumber has suggested having one radiator as a back up/extra source of heat. I’m torn as to whether a) we need one and b) do I want one! The extension is approximately 36m2 anyone got experience of this?

We’ve got electric underfloor heating to make it nice underfoot but radiators to heat the space. I’d think that the need for radiators probably depends on the amount of glazing, aspect, region etc.

What kind of UFH, if it's water - then a water filled radiator is pretty pointless as a back up - except that it does work more quickly. Water UFH is fab but you do need to think ahead and it's better with a fairly stable temperature 24/7 as it takes ages to warm up from cold.

If it's electric, then this works much faster.

Whichever you have you need lots and lots of underfloor insulation if the hearing is to be effective and economical.

I'm in a new build with water UFH downstairs which is brilliant (slow and steady as above - I'm retired so frequently in all day).

I have electric in my bathroom, which is great but I also have an oil filled towel radiator and for much of the year it's enough (and cheaper) on its own.

Have a look online for a BTU calculator. Find out how much heat the space needs and how much your heating will kick out. Better to do 3 calculators and go for the highest.

We've just done a 45m2 lounge/kitchen/diner heated by 3 of these:

www.radiatoroutlet.co.uk/1780-x-354mm-anthracite-double-oval-tube-vertical-radiator

They kick out loads of heat (3rd one is bigger) and look fab.

The front of the house is Edwardian with original sash windows, the new part has a lot of glass in it. The UFH will be water, we tend to leave our thermostat on 19c so the boiler kicks in if it drops below that. I guess we’ll do the same with the UFH so shouldn’t drop too cold. I’m just worried that UFH won’t heat the space up enough but I have no experience of using it. As lovely as it sounds walking on a warm floor will the space around it feel warm? I’ll check out the BTU calculator thanks.

We have exactly the same although larger. Loads of glass but well insulated. We don't have a radiator, just the UFH. The UFH is fine and we don't need a radiator but what you do have to cater for is that the UFH takes a lot longer to heat the room up, like hours. However, it switches off a lot earlier on a night so by 7pm it switches off and the room still sits at 23plus degrees at 10

The only advantage then if the radiator is fast heating up but it won't be as efficient as the UFH and then you also have a radiator on the wall collecting dust etc and I love not having rads on the wall at all

I would leave it to be honest. You will find the new part will be so well insulated, if the UFH breaks a electric heater will suffice until you get it fixed and really will a sole system it is really only the pump that is likely to fail.

Be aware though that the UFH won't be covered in any central heating maintenance insurance such as British Gas

If you are having wet ufh laid in concrete, and it ever goes wrong, it might be so difficult and expensive to repair that you just cut it off, so a radiator point will be useful.

Also if you want to heat the room quickly.

We have had wet under floor heating leak and you really do need to repair it. Our house insurance paid for new floor and redecoration as well. Cutting it off is just ridiculous.

If you are having a radiator because ufh might fail, you might as well not have the ufh in the first place. You have to opt for one or the other because if ufh goes wrong, and you don’t use it, you really won’t heat up that space with a tiny “back up” radiator.

Your space is nearly the size of my kitchen which is totally glass on two sides. No wall space for a huge radiator or two. So ufh heats it all. If you want to heat it conventionally, then have radiators of the correct btu, and forget ufh, but ufh is effective with the right flooring. Heat rises!

You can use a flow screed for surrounding the pipes and this allows for a much quicker heat up time.Should be less than 1 hour. Laying in concrete isn’t great and uses more fuel to heat up the concrete! Try and avoid this.

North facing or south facing? Will the new glazing all be double glazed? Good insulation? What kind of floor?

If it’s N facing, wood floor, or single glazed/badly insulated I’d say get a back up rad.

From cold it can take a while to warm up UFH 1-3 hours depending in a number of thing size of boiler depth of pipes size of the room . once it is its great . if its a big house the boilers could struggle power everything . work out the BTUs of all the radiators & boiler and see what's left . if you have plenty having another radiator would allow the room to have a quick blast of heat or a top up when required .

Hmm lots to think about, I need a chat with my plumber! It’s a north facing extension, lots of glass but hopefully it’ll be highly insulated! As I’ve said before I leave our thermostat on 19c all the time so the boiler just kicks in when it needs to. Will the UFH run on the same system so should just kick in with the rads? @BubblesBuddy how do you know if you’ve got a leak? What do they do, rip your whole floor up? 🤔

We have it and I wish I'd put a rad in.

If the place is cold and you want heat NOW then UFH takes hours to heat up. A decent rad takes minutes. Put one in if you can.