Underfloor heating the underside of the first floor..

[cjard]

So I'm thinking about underfloor heating on the ground floor; simple enough: put pipes down and pour screed. Done.

But then arose the query of what to do in the upstairs. I've seen and been told of a technique where one installs the loops to the underside of the floorboards, just leaving along loop hanging down, fit it to metal spreaders, and screw the spreaders to the underside of the floor deck (22mm chipboard)
-- but it seems to me that using this technique, one must drill every joist and then the entire roll of pipe must pass through every joist.. i.e. the very first hole that is drilled in joist number 1, ends up having nearly the entire length of pipe loop passed through it, hole in joist #2 has slightly less pipe (the distance of the loop size in between joist 1 and 2)

Thus it strikes me that this process could well end up a massive pain in the arse, and risk damaging the pipe quite a lot. The only way to avoid it seems to be to cut the pipe into loops twice the length of the joist span, run it there and back, and then joint it at the point where the joists are drilled. Are such joints reliable? They should probably be engineered out wherever possible, right?

So perhaps the most sensible way for the upstairs is to get some of those thin boards with a pre cut groove, and suffer the loss of 16mm or so of room height?

-

In a related vein, all this messing around with the floor problem got me wondering, given that I'm going to cover the floor in thick carpet, killing the UFH effectiveness, why don't I just put the UFH pipes in the walls instead? The walls have a service void built into them of 25 mm and a reflective membrane on one side of the void, plasterboard the other - is it possible to effectively heat a room by heating up the walls instead of the floor? Heck, why not just get those grooved boards that are intended for the floor and fit them instead of plasterboard, fit the pipes, then plaster over the pipes? And don't hang any pictures, of course

 

[muggles]

Some systems allow you to notch the ends of the joists rather than having to drill through, but you do need to lay the UFH before the floorboards go down

 

[cjard]

In these engineered joists, a 35 mm hole can go anywhere on the centreline of the web but most of them are on hangers and the hanger design means that it would damage any pipe fed through the a half moon 35mm hole at the end of the joist.. So fitting ufh ahead of time probably wouldn't have worked out either, alas..

Of course, one could have taken a risk in putting a groove in the flange, above the hanger bearing (as arguably the top face is doing little)..

..then the system would probably be more at risk of the apprentice's nail gun than collapse of the joist!

 

[cjard]

It's been rightly pointed out that fitting the ufh pipes on the underside requires the pipe to be fed through all joists. Has anyone a practical solution to this tedious and damage prone operation?

 

[muggles]

It's much easier with two people, and easier still with three - one to hold the coil of pipe and unreel it as required, and one or two feeding it through the holes

 

[Agile]

There was a nice system at the Ecohomes exhibition.

Its a square corrugated metal section about 1 mm thick which takes the pipes above it which are then buried in cement.

You them end up with a cement floor which you finish as you like.

The metal transmits the heat so its quite efficient at spreading it.

About £20 per m² but then you do have to add the cement. But probably not much more than wooden floorboards.

I might use it in my extension upstairs.

Tony