Heating a cold utility room: water or electric in the floor?

Joined
9 Aug 2006
Messages
1,727
Reaction score
121
Location
Lancashire
Country
United Kingdom
OK, please bear with me on this.

Our utility room is 2650mm x 2650mm, so 7m2. It's unheated and since we had the new condensing boiler fitted it is freezing as there's no big lump of cast iron giving off heat like there was with the old boiler. It's also outside the main mass of the house so gets very cold.

Floor is about 3" of concrete on top of bison beams and blocks over a void. When we fitted the new boiler we removed the tiles and tidied the floor up with a few mm of a water-based self-leveller. This has brought the floor to the same level as in the adjacent kitchen where instead of concrete screed, polystyrene slabs were laid down with t&g chipboard on top, a creaky and flexy but very warm floor covering.

Running right across the middle of the floor and through the kitchen door are the gas pipe and the F&R pipes for the downstairs heating circuit, hidden in a conduit.

Once kitchen units, washing machine etc. are installed the remaining open area to be heated will be around 4 m2.

Now, the first option is electric: lay insulation board then cable or cable mat then fill with a latex levelling compound, cost about £450 for materials. There's a fused spur handy for this.

The problem: this would add another 10 - 20mm to the floor bringing it well above the adjacent kitchen. Also Mrs RR would run it all the time, probably also with the window open for ventilation because she uses the utility to dry clothes, so the electric bill would be massive.

Second option is hot water. This would mean excavating all the concrete right down to the blocks, laying some kind of insulation, plastic pipes on top and connecting to the CH circuit. It would need isolators so this connection would need to be outside the floor (it would end up hidden inside the kitchen units). Then fill around the pipes with concrete or a flexible self-leveller.

The benefit: the mass of the floor becomes a big storage radiator and once warmed up, won't add much to the thermal load on the boiler. With TRVs on all the house radiators it can even warm the room when the rest of the rads are partially shut down. We have a heated warehouse at work for viscous raw materials and I am really impressed with the efficiency of the warm concrete floor.

Question: would it be worth bringing the pipework out of the floor somewhere ouside the kitchen units in order to include a TRV in the circuit?

Question: what do you think of the relative merits of both systems? I'm not so worried about the installation cost, I'm more concerned about the long term operating costs and the reliability of the system.
 
Sponsored Links
So it's safe to assume that there's no room for a radiator anywhere then, which could be tee'd into the pipework just as it leaves the boiler manifold (is the boiler floor or wall mounted?)

If you are going for underfloor heating, I think I'd lean towards a wet system, which would be connected via an independent pump, manifold and controller, which would be useful in the warmer months should you wish to keep this utility area as a drying room when the rest of the building is turned off.

In my limited experiences with electric u/f heating, this only ever seems to get the floor warm and isn't really sufficient for heating the room. But I don't know to be honest.

Whatever you go for, sufficient insulation is necessary, and a covering of 60mm screed over pipework will add to your woes.

Are you sure there's nowhere to stick a radiator? This could, like underfloor heating, have an independent control system via a 2-port valve and controller/room stat.
 
  • Thanks
Reactions: r_c
Sponsored Links
If you are going to do it properly - and according to regs - it gets quite complicated as regs require that the floor surface ( I assume this means at any point ) not exceed 30 C.

Unless your new boiler has different circuits with different temps available, then you would need to mix your input which is presumably around 60/70 C ( ? ) for rads down to about 40C with cold water and thus another feed to the manifold.

The reason for these regs is that when they first tried UFH ( not the Romans ! ) in the 60's or so, they input about 80C with very wide pipe-spacing and this cause major medical problems with" heavy-leg syndrome " ( phlebitis) if people were above a hot-spot for extended periods.

Having said that, this is a utility -room and unless it is also used for ironing, nobody is going to be there for very long.

I don't know if you are going to do a heat-loss calc, but pipe cos quote an output of 80-100 W ( they disagree on this ) per lm of 16 mm PEX pipe with input of 40 C.

In contrast, a friend of mine, just laid a few loops off a 60 C rad-circuit without any mixing etc to warm his bathroom-floor and is very pleased with the low-cost results.
 
Thanks. The area not to be occupied by units has three doors (garage, kitchen and out) so there's very little room to put a rad, it would have to be vertical and the pipework would need chasing into the floor.

The wet solution is beginning to look quite costly, especially as the gas and CH pipe conduit divides the floor into two separate areas to heat. This would also leave a band about 1 ft wide right across the floor that wasn't heated.

Somebody has suggested a Myson Kickspace 500 fan radiator, which runs off both water and electric. These are around £200 on Eblag and this would be the easiest solution, combined with a felt of some sort for extra insulation under the flooring.

Good idea?
 
Could be a good compromise. Surprised they can get up to 1.4 kW out of 150 cc water-content thoughl
 
Nothing to stop you making your own of course - small rad or coil of microbore copper and a fan to push the air out.
 
You never answered my question aobut whether the boiler was floor or wall mounted :cry:
 
So, it should be easy to tee into the flow and return, and run these pipes up and over doorways and/or along the back of cupboards then? If you're feeling particularly keen, could you not put insulation up and overboard at least some of the area too (possibly hiding some of the wall- clipped pipes)?
 
Ah! The boiler and all the pipework are on the wall opposite the kitchen door so the whole lot will be hidden behind units and panels. This will make it very easy to fit a Myson kickspace fan radiator, which is the option that seems to be looking the easiest and the least costly.

Today I saw the three electric heaters, which supply 14 kw to the water runing through the thick slab of concrete in our heated warehouse floor. Super little things, which have given 5 years of continuous service so far without complaint, keeping the warehouse at a steady 30 degrees C. A bit too good for my 7m2 utility room though!
 
Ah! The boiler and all the pipework are on the wall opposite the kitchen door so the whole lot will be hidden behind units and panels. This will make it very easy to fit a Myson kickspace fan radiator, which is the option that seems to be looking the easiest and the least costly.

Today I saw the three electric heaters, which supply 14 kw to the water runing through the thick slab of concrete in our heated warehouse floor. Super little things, which have given 5 years of continuous service so far without complaint, keeping the warehouse at a steady 30 degrees C. A bit too good for my 7m2 utility room though!
Can you not steal them :idea:

While you are piping up for one kickspace, it may be worth putting another set of tails in as well should you decide that a second becomes necessary :idea:
 

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Sponsored Links
Back
Top