underfloor heating (NLC)

[DJ]

Looking for some comments from anyone who has either put this in their house or has it as their primary form of heating.

From the technical stuff like is there problems zoning this, cost of installation v a traditional radiator system to general user experience like is it as controlable, does it provide adequate heat in winter, cost of running etc.

many thanks

[David]

I converted the ground floor of my house a couple of years ago and it's been a great success. It is an early 90's Cala house with suspended floor so the whole lot was ripped up and I put in 90mm PIR insulation and used copper foil formers for the pipes. I then covered it with standard 18 mm chipboard and 18 mm engineered oak. There are 3 zones with the usual pump and thermostatic mixing valve to reduce water temp.

My only comment is that the zoning wasn't really needed as it seems to work best as a continuous gentle background heat. We did leave some radiators but again this probably wasn't necessary. The improved insulation was probably a major contribution to the success and the cost of running it seems cheaper (again probably due to the extra insulation). Cost - I spent about 10K but this included some other building alterations and if your budget was tight it could be done for less.

But the biggest plus is the 'feel' - it's a very different kind of heat. I couldn't go back to house with radiators.

David

[kerryxeg]

I put UFH in an extension a few years ago, it included circuits in a new concrete floor and some in suspended floors. If your putting it in concrete floors the main cost is labour, so for a newbuild it's a no brainer and very little extra. Same goes for the house insulation, UFH will work best in a very well insulated house with minimal draft, part of the benefit comes from being able to achieve a warm below a cold zone above, but this requires minimal drafts in practice.

In suspended wooden floors you need some good insulation below the pipes, and some means of spreading the heat. This can be done via metal plates, special foil backed insulation or a dry concrete screed (4-1 mix). The other decision with suspended floors is whether to build on top of the existing floor or between the joists. On top is easiest if you've got the head room, and are redoing walls / doors skirtings etc - you need 2" additional height. Going between the joists means cutting the joists to route the piping and setting some battons along the joists to support the insulation / pipes / screed. Structurally you have to consider the additional weight of whatever solution you pick on the joists.

There are many different systems, ultimately it comes down to the weight, the ease of installation and the performance. Performance in UFH terms is the speed of heat up. My system does not use a screed, it is purely insulation with a foil coating, which should not be the best performing, yet I've never found it cold despite the main livingroom having 3 walls of glass. In the worst case scenario you do have some control at the manifold, you should have a mixer valve which sets the temp of the water being circulated and control of the pump speed. Increasing either would improve heat up time.

Most systems recommend a max pipe run of 100m, all manifolds can have a control valve on each circuit, triggered by a room thermostat. But one thermostat can trigger more than one valve ie if you need more than one circuit in a room. I've got standard stats in small rooms and fitted a programmable remote stat in the living room. The remote allows you to turn down the set temp at night or during the day weekdays, but you can also position it where you want ie away from drafts or a fire etc without having to gat a cable to the optimum location. Thermostat location is critical, keep away from drafts or heat sources.

Finally if keeping some radiators, you need to ensure that the flow to the UFH system is balanced ie one system doesn't starve the other. This can be achieved by putting in additional pumps, there will be one on the boiler which provides supply to both systems, then put a pump on each to the UFH manifold supply and one on the radiator supply.

I hope that helps, you'll find many systems which all claim to have benefits over the others, in reality simple is usually the best - lots of insulation, some means of disipating the heat and a well controlled flow system.

Hope that helps, Kerry

[H8OAG]

I had a three circuit system fitted under a new concrete floor in the extension.
Very efficient........compared to the rest of the Edwardian Pile that is Boag Towers.

My Plumber stated it is not wonderful for wooden floors and states that the concrete screed is a must.
Wooden floors irrespective of quality will warp through time. He has re- done his own house to combat this.

Father G should be along in a minute to describe the zillion zone system he has installed in his new Pleasuredome.

Rumour has it that Loch Turret levels dropped by six inches when it was filled.

[David]

Wooden floors irrespective of quality will warp through time. He has re- done his own house to combat this.

Sorry but simply isn't true - there are products out there that are designed for this purpose and, when fitted correctly, will be trouble free. It is two winters since I put my oak floors down and they're as good as the day they were laid.

http://www.chauncey.co.uk/floors/tectonic.php

David

[BiggestNizzy]

The floors with a manufactured body and a timber veneer should be ok, the manufactured board won't warp and you can always resand the veneers

[Northernpar]

I've got normal radiator system in the main house and underfloor in the servants quarters (sorry I mean the in-laws pad) which are joined onto the main house. It's into a concrete floor and if i had the choice I'd plump for it every time. More efficient although not as controllable as radiators but should be used more as a continuous background heat. Got the system zoned in each room and controlled by thermostat except the bathroom which is on all the time. Normally have the system timed but the easiest way would be to install a good quality thermostat in each zone, leave the system on and let the thermo stats do their thing.

Also if the rooms are small it makes a huge difference by freeing up wall space as well which makes the rooms far for useable with respect to furnishings etc. Didn't consider this when putting it in but noticed the difference once it was finshed and furnished. Also have it under wood, tile and carpeted flooring with no problems although the wood is engineered with a 5mm real wood veneer although this is mainly due to it being laid on a concrete base an floating.

[H8OAG]

Dave
Two years is hardly a testament to your theory

I ran it past a friend of mine who is the biggest supplier of wood in all it's forms in Scotland, and he said the following

Wood is an insulator
Therefore your system will have to work harder to heat the room
He recommends concrete or concrete screed every time
The only exception is reclaimed timbers which are generally over 100 yrs old and immune to any warping from dry heat
I will not even repeat what he said about engineered floors, but I guess you would expect that from a timber merchant!

[DJ]

Thanks folks Lots of good info in there to add to what I have already. Just to clarify, it is for a new build with a concrete raft foundation hence why I am thinking about this with the screed on top for the ground floor and normal radiators on the upper floor. Plumber I am thinking of using says it should only be marginally more expensive to install, but trying to put a figure on this. For those that have used terms like 'gentle/continuous background heat' (Northernpar and David) does that mean you think radiators are still required over and above the UFH to obtain a decent room temperature in the middle of winter ?

[Northernpar]

.... For those that have used terms like 'gentle/continuous background heat' (Northernpar and David) does that mean you think radiators are still required over and above the UFH to obtain a decent room temperature in the middle of winter ?

No, the main difference is that traditionally radiators are either on or off with the main reason that the heat transfer from the radiator to the air is fairly quick therefore a room can go from cold to warm/hot in a resonable period of time. The UFH system work differently where you select a room temperature to suit via the thermostat and then let the system maintain that at all times so in summer you'll have the thermostats down and in the winter higher. That's not to say that you can't heat a room reasonably quickly with UFH from cold it's just more controllable to work on a desired room temperature rather than a cyclic heat up/cool down as with a radiator system. Hope that makes sense..........

Also the concrete screed effectively acts as a radiator with even heating throughout the room. The efficiency comes from heating from the bottom up as oppose to a radiator that will heat the air which will rise then cool then decend to the room. Plus the first time you head into the kitchen/bathroom tiled floors with bare feet you'll never go back to a traditional system

[BiggestNizzy]

You could also put a heat exchanger in and get your warm water from a hole in the back garden. or an enormouse trench if you have the space.