DIY Underfloor heating?

The system we have in the conservatory is embedded in the screed, but could have been used as you mention.

Our add-on system runs off the normal central heating, via a motorised valve and unvalved return (like a radiator), but that is far too hot, so there is a blending valve and a separate pump.

Water is circulated by the dedicated pump, from the floor, through the blending valve and back to the floor. If the water is too cool, the blending valve mixes it with some from the main central heating and the excess naturally exits to the main system.

It works well, but there is about 4" of screed, so warm-up and cool down are slow. You need to have the heating on well before you need the room and off well before you finish using it.

Cats love it though!

SteveW

yes and yes.

First though is te floora groud floor. 1" of insulation is not enough for a ground floor. 6" minimumum

It is a ground floor, is that right? That would be disappointing, though I can see the danger of heating the space under the house.

We had a conservatory put up about 5 years ago. Floating floor with concrete beams and breeze block, covered with screed and 75 or 100 mm of Celotex (I can't remember the actual thickness). Then laminate.

The UF heating was by electric film - 1.8kW. At the time, we considered hot water - either UFH or radiators, but connecting it up to the current HW system required approval, and the boiler was running pretty near to capacity anyway. But we find the UFH is not sufficient to keep the conservatory warm in winter, and is very expensive to run. Really, there aren't enough decent days in winter to merit using the conservatory anyway, and when it is sunny that will supply a useful amount of heat, and it can be supplemented with a fan heater. I'm not sure that any type of UFH in a conservatory is justified unless the conservatory is triple or quadruple glazed.

Jeff, I have yet to find any justification for a conservatory.

When you have a house with a hall, kitchen (small and only for cooking, not eating) and a through living room, plus three children, you want another downstairs space! Self-building a conservatory was the cheapest option and, at the time, the only financially practical one. Insulated cavity walls, partial solid roof, double glazing, triple-wall roofing, blinds all round and under-floor heating, make it practical to use for almost all the year - hot summer days are the only problem.

As the rules have changed, we may change the roof to keep some of the sun out.

SteveW

Ah. You didn't mention it was a suspended floor.

Lift it, and put 6" celotex between the joists, tape over, and then lay your pipes on top

No need for poly ,poulding. Just use big plastic staples to located them to the celotex If the joists are stable you can screed/tile or else overboard with ply and engineered wood.

Aim for a spacing of around 4" between pipes to get best output.

I've often wondered why, given that its being heated and cooled, does this not result in either creaking noises or if in a rigid material eventually concrete cracking or leaky pipes? Brian

No not in the uk really. Its a slightly less cold version of outside where it does not rain. Brian

Umm.. you have to slot the joists for the pipe return. An alternative is to use the pre-formed 22mm slotted flooring chip plus your choice of overboard. If you fancy ceramic floor tiles there are cement based boards for this.

Have a look in here or one of their many competitors

The pipes are plastic and able to cope with a little flexing and do it silently, even with minor misalignment at a slight crack. The screed as a whole sits on insulation and stops just short (25mm or so) of the walls due to insulation being placed around the edges before laying the screed. That gives some space to expand and contract slightly without significant forces being generated.

As to how likely things are to fail. It has been done that way for decades and there doesn't seem to be big fuss about failures, so it must work. Certainly ours does.

As for the type that is laid within insulation panels, perhaps with spreader plates to distribute the heat. I would assume that the insulation flex stops creaking noises and the floor on top is a floating floor, so that can freely move too and is little different to the expansion and contraction of a laminate floor.

SteveW

I'm an avid plant grower, so it's more of a greenhouse attached to the house than a conservatory! And, having one side of it as a house wall, means it's a bit cheaper to heat than a greenhouse, and it keeps one wall of the house a little warmer.

But it's somewhat true what you say. As a "room" it is usually too cold in winter and too hot in summer. Nice in spring and autumn, though.

What about 'I need the floor and inch higher' did you not get? simply add 1" batten to the joists after the pipes ate laid in between the pipes.

An alternative is

Those laternatives only make sene if yuopu have a team of three on 200 a day each and te labour saving is worth the cost of the special board.

I put a 3mm foam underlay between the spreader plates and the 12mm plywood floor. No creaks or noise you assume are copper pipes moving with expansion in a radiator set up.

I laid the pipe and Angela managed the pipe reel. Which is now redundant and available for a few beer tokens.

If you can only raise the level by 1", your options are very limited. There's nowhere near enough room for a wet system, so it would have to be electrical - which would be very expensive to run. Even then, there's insufficient headroom for a decent amount of insulation.

When we converted an integral garage into a kitchen, we needed to raise the floor level by 6". We installed a wet system but even 6" was tight and only allowed for about 3" of insulation in order to make space for a couple of inches of screed on top of the pipes.

You don't have to use screed. There are systems that use thin, grooved insulation on top of the existing floor, with the pipes in it and metal spreader plates to spread the heat. With a few mm of laminate floor underlay on top and then laminate. 1" might be more than a bit tight though. Further insulation can be put between the floor joists.

SteveW

Ther is more than enough room for a wet system

The pipes are less than an inch diamter. Insulation goes below between te joists.

I was assuming it was a solid floor. If it's a suspended floor, there's more chance - but still too tight in my view.