Keeping your home warm / heating / energy crisis / insulation etc

Looking at options for my kitchen diner that are not the £15,000 it would cost to include wet underfloor. Thinking about plinth mounted fan heaters for the kitchen area and a big, heated rug for the open area. Heating is only on 2-3 month of the year here. New space will be well insulated and buttoned up. Cooking will provide some heat also. Double glazed skylights and windows/doors will provide solar gain.

Just looking to see of the rug heaters heat the space in any way or if it's just warm to the touch.

Floor surface will be cork tiles also.

You could have a small fire of £5 notes, would probably heat the floor just as well.

The large RugBuddy as an example, is 600W. At 25p/kwh, having the rug on 5 hours a day during the week, 10 hours a day at weekends (more than we use any kind of central heating anyway) would be under £7/week or c.£100/year. Which I think is less than £15k

I don't need cost analyses, I asked if anyone had personal experience using them. I'd happily pay £100 per year if it does something.

Don't have experience of the heated rugs but I have (and like) a plinth heater - really effective for heating up a kitchen on cold mornings.

Not going to give you a cost analysis as I don't know how much it costs to run!

However their actual fuel mix will likely be closer to UK Average.

Yep. Depends what your trying to say, but the electrons delivered to anyones house will be close to the regional average for that area. The supplier you chose will have no bearing on what comes through your wires.

This article puts some flesh on my points better. I doubt Tomato are investing in anything given how cheap their rates are - but I'd caution anyone to feel cozy about green tariffs. If you don't have your own renewables, the next best thing you can do to be green is use less, use it when it's cheap and vote for politicians who are pushing grid decarbonisation.

First one I found on Screwfix is 2kw, so 50p per hour. I would see them as something to quickly take the edge off.

Yup - we just put it on for 20min, half an hour first thing when making breakfast. Works well though and I have definitely been happy to have it this last week or so!

As with any resistive electric heating, in the case of the 600W rug thing, it'll be dumping exactly 600W of heat into your room when it's on... more precisely, under a nice insulating rug, and straight down into your floor slab, which will make that 600W feel like fuck all underfoot.

If you really want to go down the route of electric underfloor heating, then laying a cheap leccy mat under your cork floor tiles will work much better. Note: you'd be mad to attempt to actually heat the room with any kind of electric UFH, the cost would be bonkers. This is purely for comfort underfoot.

In any case, if this is a new extension, then make sure the builders install minimum 150mm PIR insulation between the slab and final floor screed, otherwise you'll just be heating up the earth underneath.

Just looking to see of the rug heaters heat the space in any way or if it's just warm to the touch.

If you want the air in the room to be warm you need to do the heat loss calculations and work out whether 600W is enough to compensate. The method of delivery is ultimately unimportant.

I suspect you will be disappointed.

New extension but with suspended timber floor and insulated. I am also looking into the electric matts under floor tiles as well as traditional rads, just exploring lots of options. The original design included wet UFH, but all tenders came back with that being £15k. So I'm trying to remove that without also trying to find wall space for rads as the rest of the layout doesn't accommodate them. The rug would be a thin area rug (likely from ruggable as we have one of those in the living room as they are easily washable) and I would put an insulating/reflective underlay below the heater.

On a similar note, anyone used those heated footpads? This kind of thing:

Thinking of under my desk for WFH as keeping my feet warm when the heating isn't on is difficult. Claims to be ~ 50W so cheap to run but wonder if that's enough to be effective and any other pitfalls.

Is the cost so high because it is a suspended floor?

We are looking at doing an extension or new kitchen and also have a suspended floor, plus limited wall space for rads - I'd worried that underfloor would be difficult but sounds like you've found the same!

but all tenders came back with that being £15k

How big is the space? We've just had a 6 m x 6 m room done for £5k.

I don't really know why it was so high tbh, but three independent tenders came back the same. There's a lot of work involved and manifolds and shit, so I imagine that's a big part of it. YMMV, it could have just been our set up.

Probably 5mx5m

Is there a particular reason why the new extension will have a suspended timber floor, as opposed to insulated concrete slab & screed? When you say it'll be 'insulated', which exact insulation material spec and build-up has been quoted for thus far?

If you're deffo not going for wet UFH, then just install the biggest wet rads that you can fit into the space. As before, if you attempt to heat the space using direct electric emitters of any kind, you're going to have a really bad (expensive/cold/both) time.

That seems really high. We were having an insulated concrete slab done anyway, so specifying wet UFH was £5k extra on top of that, but after two weeks it's already proven to be worth the cost.

Agile prices peak this week, doing about £2/hr just now

Are you not tempted to move to a less volatile tariff like Cosy, or a different supplier?

Kinda, but when comparing them all (inc Cosy just now) they're all more expensive. If it keeps peaking at £1/kWh this winter that'll change but for now seems we're in the right boat. Also need to hold on for £200 referral in March

Have you had any detailed info etc from them then?

Nope, just what the guy told me when he came round to do the survey, nothing in writing yet.

I was too busy repointing to keep warm yesterday, so will chase next week now when it's better sitting at a desk weather...

The original design included wet UFH, but all tenders came back with that being £15k.

I went down a massive UFH wormhole earlier in our project to the extent that I now know more about underfloor than a lot of people working in the 'industry' (that's a slight on them, not me being boasty) and I can tell you now there's no way you need to spend £15k. For comparison, the (very good) plumber we're planning to use has quoted £10k + materials to replumb our entire house, fit UFH everywhere and get us ASHP ready.

What sort of outfits did you send the tender to? Are the quotes you've had for design, supply and install? It's normally much cheaper to buy the bits and get a decent plumber to install than to get a full service quote from big players like Wunda, Nu-Heat, Continal etc. Plus the design service from a lot of specialist UFH places isn't worth the PDFs it's written on, they're often just computer generated based on them ticking a few boxes and entering room sizes, with no consideration of the reality on site because they've never actually visited.

You could use a local UFH specialist who will of course, but that's likely to need even deeper pockets...

Also I agree with @ectoplasmosis and would like to know the construction rationale for a suspended floor in a new extension given it will have much lower thermal mass, be much harder/more expensive to get airtight etc.

Happy to have a look at your quotes and try and work out why they're coming back so high if you like.

And if you want to learn about different UFH types and options I'd recommend Continal's training webinars which are free.
https://www.continal.co.uk/resources/webinars

It sounds to me like @stevo_com ‘s builder quotes just had a ‘UFH - £15K’ line item in them, which makes total sense from a builder’s PoV.

Heating a garage office conversion - wall mounted convector heater or oil filled rad?