Underfloor heating

We had elec under floor heating in one of our homes .It was left on for approx ten years while the house was empty (no one at home)for most of the time. The house etc was kept dry and warm (orchids flourished in some rooms).Plants (outside)near the outer walls flowered longer than when it was not on!! When we were at home with the doors opened often and other movement of air the heat soon dispersed and other heating was needed. We thought it was cheap and safe but cost is relative and the many hundreds per year would put some people off.

It is efficient, provided it is done properly with the correct insulation sequence. If you are getting a new boiler, get a condensing type. They will particularly benefit from the low output temperature required and will condense like anything, particularly if you have no radiators, or can arrange mixing valves, to get a return temp of 30C or thereabouts.

Christian.

I'm afraid that every time I have visited someone whose house had underfloor, I have been very glad to get out of it! I find it a horrible, very uncomfortable way of heating. I wouldn't worrk about the children playing on the floor, use clothes or carpets.

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There are two common forms of underfloor heating, electric and hot water. Electric systems tend to be found in older properties (apart from single room floor warmers) and are generally not liked. They were often fitted in council properties, badly designed and installed and arranged to come on at night to use cheap rate electricity so rooms were always too hot during the day.

Hot water systems are now the most common and are normally cheaper to run than conventional systems by about 10% because the temperatures they run at suit condensing boilers well and because room temperatures can be set a degree or so cooler than with conventional systems for the same level of comfort.

As far as room comfort is concerned having now had underfloor heating for 10 years I would be most reluctant to return to any other form of heating. Whenever surveys of user liking of heating systems are carried out underfloor heating invariably scores the highest of all systems.

One thing you will need to bear in mind is that the underfloor heated area will need its own controls, both to mix water to maintain the effectiveness of the older parts of the system as others have explained and to compensate for its thermal mass. The underfloor heating will need to start heating earlier than the rest of the house but can be turned down earlier as well. To maintain a pleasant temperature in our house in the winter between 18:00 and 22:00 the heating effectively comes on at about 15:00 but goes off at about

Any figures to back up this article of faith? Rads systems can be designed to get the best from a condensing boiler as well.

If a house is near permanently occupied then underfloor "can", not always, work out cheaper to run. But the problem is that they require long heatup and cool down time, so are left on 24/7 wit a night temperature setback. If your house occupancy is erratic, you require a fast heatup system, which underfloor is not.

Comfort depends on the design and controls used. A floor that is designed to have even heat and expensive controls will perform far, far better than a cheap system with basic controls.

Link please?

Because of this lag, I know some people who are well pissed off with underfloor hearting having a gas fire to fill-in in the warm up gaps.

Underfloor can be fine, but you have to know what you are getting into.

Look at

Make sure the floor you install it in has thick high performing insulation underneath as you don't want to heat the earth under. The insulation should be like a tray, coming up at the sides. The tray is filled in with a cement screed with the side exposed to the same level as the screed, then the final floor finish is over.

It will work fine from a combi.

Thanks for that Peter

This may be a dumb question but can you use all types of floor coverings with underfloor heating, carpets etc. Surely underfelt would act like an insulator?

Suzanne

It is a bit complex to add on, because you need to use somewhat cooler water for it than for teh rest of teh CH, AND to do it properly iut needs to be timed a little in advance of normal heating, so you end up with things like 3 way controllers, (UF/CH/HW) extra valves or pumps and some form of temp. reduction valve.

On the other hand, if you ar a bit cavalier, you can just lay some flexible butyl pipe in the screed, and pretend its a huge radiator. Its a lot bettr than nothing especially if you have other heating n teh kitchen.

See

I have to say I entirely disagree. The warmth is just simply all pervasive: There are no cold spots and its a delight to walk on with bare feet.

The scret is to have a lot of pipework in there, and not to run it too hot.

Cheaper than rads as a lot less heat loss due to convection - and no convection draughts.

Freedom to put furniture anywhere, no hot spots - even warmth.

Very much a DIY install - Nu-Heat for example make an add-on pack for adding underfloor heating to a conservatory, by tapping off existing rad circuit.

Control is different - not on/off, but set back temp, i.e. you set it to go to for example 10 deg lower when unoccupied rather than off - that way it only has to bring up from a background temp rather than from cold. This helps negate the slow response time.

Anybody who has had UFH .... will never go back to rads.

Rick

That's if its designed well, installed so no cold spots on the floor and well controlled. If not then they can be very uncomfortable and nighmare to live with. Having weather compensation helps to alleviate the warm and cold periods, due to the slow response, when the weather suddenly changes.

Yes, you can BUT unless you insulate DOWNWARDS as well, you will lose more heat downwards than upwards if you see what I mean. and also in order to get THROUGH the carpet etc you have to run at a higher floor temperature than e.g. slates or tiles - or even laminate. This reduces the efficiency a fair bit and needs to be thought about in the design.

Ideal is stone, tiles or laminate with thin rugs. Or wood boards. But beware warping! Parquet is probably as good as it gets!

The key is to have the downwards insulation ten timje or more better than teh upwards, so that you only lose 10% downwards. Well thtas a very simplistic view, but serves to illustrate the point.

More or less, some types of flooring don't like the raised temperature but any modern flooring material will state if its suitable for UF heating.

Yes it does - but it isn't a very good one and in practice makes no noticeable difference. We have carpets, tiles and wood on various floors in the house and all work. All have been tested and approved for heat by the cats.

Forced air and underfloor can mean the stat can be turned down a few degrees. Both about the same. Forced air is highly responsive, unlike underfloor heating.

Ever heard of Mean Radiant Temperature?

Forced air and underfloor about the same. Insulation levels? In the building fabric?

It is. Install perimeter skirting heating. Room temps can be lowered too.

Only for all day occupation. The erratic lifestyles of modern people means underfloor is unsuitable for many in running costs and warm up.

In today's instant society, of instant communication and next day deliveries, underfloor will not suit most people.

It suits your lifestyle. That is the prime point.

You haven't a clue.

I have. Electric. The control naff on-off stats and made it uncomfortable. Yet is did have an even heated floor.

No a pro in the game sonny boy. Listen and learn!

Not so. The reason why Santoprene pipe was invented in Canada was that running a spiral of plastic pipe caused uneven floor temps. The floor would be far hotter on the flow side and at time very cool on the return after it released its heat to the floor.

It can be greatly minimised. You know little of control. Even our snotty uni man mentioned the cold spots in on-off stat switching.

I have access to most HVAC mags and browse them all.

"Build IT". Ever browsed that mag? Full of UFH adds. They are pandering to their advertisers. The best system is forced air ventilation, which can humidify very easily and give constant fresh air. No wet heating system can do that. It can de-humidify, but a small chiller has to be installed.

Forget it mate.

You have "never" lived in properly designed and installed up to date forced air and vent system. Fresh air all the time and silent. Yu experiences are limited.

That is the problem!!!

Wheeled calor gas. Are you mad? You spend a fortune on a heating system and you have to wheel in a box to heat the place. Juts put in a heating sytem that doesn't have the response of the Queen Mary's steering. Then all is fine.

Except an even longer war up period.

No. Don't confuse insulation with thermal inertia. Get an education i instead.

On the contrary, to quote from

"Good Thermal Design Tips (extract)

Use hydronic radiant floors

Heat people, not air"

Richard Kadulski wrote the following on MRT in the Renewable Energy Policy Project :-

"A simple formula has been developed that allows normal comfort level of a room to be calculated by adding the two primary heating components: air temperature and mean radiant temperature (average room surface temperature).

The formula is: air temperature ( F) + mean radiant temperature ( F) = 140 ( F).

For example, with a conventional forced warm air heating system we can maintain comfortable conditions at an air temperature of about 72 deg F (22 C) with a mean radiant temperature of 68 F (72 + 68 =

With a radiant heating system, comfort is achieved at 68 F air temperature if the mean radiant temperature is 72 F (68 + 72 = 140)".

With blown air systems the radiant temperature of all surfaces must always be equal to or below the air temperature and for equivalent levels of comfort higher, not lower, temperatures are required.

I would have thought you would have known that was the subject of the references I quoted.

It still doesn't give you the large radiant surface.

I don't know of many people whose "erratic lifestyle" means they have in advance no idea whatsoever of the time of day they will be in or out. Equally I don't know of many who have remotely controlled heating controls or only switch the heating on when they get in.

For those few who don't know whether they will be in or out at any time at all and who habitually leave the house unheated until they get in and then want a very rapid response then underfloor heating has little attraction. The running costs as I am sure you are aware will still not differ markedly.

I hadn't thought about the influence of next day deliveries on heating systems I must admit.

Ah.

Plumber?

One waits. I have a feeling it will be a long wait however.

For some reason that doesn't happen in mine or any other I have seen. Might possibly have something to do with the way the pipe runs were planned.

Could you explain the physics behind this assertion please?

You will be able to read the articles then.

Possibly because it is popular with people more concerned about quality than price?

Are you suggesting the results were falsified?

Possibly, but certainly greater than yours.

As has been explained to you before I have had some experience of a very modern system near here with all the bells and whistles. It has now been removed at considerable expense because the owner found it to be far too uncomfortable.

As usual you rather missed the point.

Exactly the same amount of blood, body parts and general combat detritus can be found on the kitchen (tiled) and lounge (carpeted) floors so I doubt this is the case.

I have one of his books. He attempts to simply explain MRT ina few paras and fails and gives that formula you posted. He is a green architect and attempts to be an expert on HVAC, but he does highlight pros and cons of UFH, exactly as I have.