Look, no rads

[meow2222]

Looks like this reply got lost in the ether...

Do we really have to though? UFH piping is in contact with concrete floor, so peak temps must be limited, concrete is none too elastic after all. But wood is. And here most of the pipe doesnt touch the studs, so 80C water would give a ballpark about 10C stud temp rise over most of the studs. Where the pipe goes thru the studs near top and bottom, I'll cross my fingers and say it probably doesnt really matter if the last 2" of wood is unstable, as it'll result in close to no overall stud movement anyway.

Reason I'm angling for a full temp circuit is cost and simplicity, if it is doable it would be much preferable.

I was thinking that left hanging loose it would have a lot more drillproofness, it'd just move out the way if drilled. Does it have to be supported over an 8' drop at low pressure?

ohhh, yes :)

I suppose 2 strips of wood glued together would make a more stable upright, arranging the growth rings in opposing directions to counter warping, like pineboard does. Thats quite doable. Add a few screws to back up the glue.

And I guess an easy way to set that is to turn down the LSV until it just gives enough heat on the coldest day. Limited flow rate in the pipe will cap the temp for all but the first bit. Microbore itself would limit flow of course.

Have you got the figures behind that? It wouldnt cause discomfort the way over-warm UFH does.

Partly, yes. Theres no easy way to balance the 2 rooms as there is with separate LSVs if you only use the wall rad. What I had in mind was to use it with a room that would have say 2 rads, and instead we have the heated wall plus one rad in each room. Now the wall contributes a lot of the heat, and the individual rads are used for balancing.

It does of course mean you cant switch one room off and have the other on - well you could hang curtains on it, but you cant do that in any easy neat way.

How much of an issue I guess depends on the house and use patterns. It wouldn't be a probem for the app I have in mind.

I guess the main remaining q in my mind now is whether we can get away with full temp circulating water. I suspect so.

NT

[meow2222]

If the wall rad were used as the only room heat, ie no conventional radiators, it could be made as a 2 zone wall by wedging polystyrene sheet in the middle of the wall and having 2 pipe circuits, one each side.

That could open up the range of apps a fair bit.

NT

[The Natural Philosopher]

I think the air in there will get very hot..50C or more..and very hot air is very dry air..its gong to dry the wood like anything...that's the problem. In winter it will shrink massively and in summer it will expand again..

I have already see this in one wall with a lot of pipework going through it..the wall moves +-1 a mm or so summer to winter. And that has but a few insulated flow and return pipes coming from the boiler.

Probably not really..

Using steel framing would be a lot better. Or plywood.

Wood won;t shrink muhj along its lengthe - its pretty stable that way - what will happen is that the wall will get thinner in winter..that leads to problems at the corners with the other walls and the floor.

The floor you can sort with skirting over the floor.. butt watch out for corner cracks - surprisingly big ones.

Just dredged up from the Polylumb docs somewhere. However a typical wall is 2 meters high and maybe 3 meters long - thats a decent enough 600W for a smallish room. these sorts of heating systems are never rapid response..

For the cost of a temp reducing valve I wouldn't risk it. You might experiment with reduced flow and lag the inlet parts of the pipes..

It wont destroy the house structure, but it will bugger up the decoration.

[The Natural Philosopher]

Yup. Better use celotex tho.

It wont be as nice as UFH, but it probably would be nicer than radiators.

[meow2222]

Rough calcs indicated 25C outer skin temp, and something like 5C drop across the PB, that takes us to 30C on the PB inner surface. Air inside will need to be above that, by how much I dont know, but given the figures so far I wouldnt expect to see 50. But I dont actually know.

30-40 is still dry air though, as the air slowly exchanges with room air there will be a net migration of water vapour out of the structure, so I guess we can expect movement regardless of where the pipes are placed, and whether one uses 45C water or 80.

So steel uprights it is.

right.

Latest thinking is now to use 4' loops. Inlet pipe goes across the bottom of the wall, looping up 4' in each cavity, then goes back across the top. Helps the bottom be hotter than the top.

I guess the upgoing bottom loops would be suspended with wire, thus maintaining its ability to move out the way easily if drilled.

Another way to balance heat output across the wall is to use smaller pipe loops at the hot inlet end. At the far wall end we might have 4' loops, reducing to perhaps 2' loops at the inlet end. And really I'm not sure if we need any loops along the top. The hot bottom zone will create convection within the wall, so it might make more sense to have

2 bottom loops than one bottom one top.

If we use steel stud, roughly balancing heat output should be all thats needed, no need to limit water temp for the wood's sake.

Yeah. I think it has to be steel. And that temp limiting the water wouldnt really achieve much. But I'm saying all this without having tried it.

NT

[The Natural Philosopher]

Well that should be OK,..its not so much balancing heat that worries me as peak heat. or rather (as you know) peak *and* continual seasonal dryness.

Well Ive used demounatable steel framed plasterboard stud walls in every office I have fitted out. Its pretty good and cheap to erect. If you get teh wires and pipes in before th second surface is slapped on, its good.

[Doctor Drivel]

Panels are available to go the walls, as are ceiling panels too.

With a stud wall the space between the stud can have a grill at the bottom and one at the top with at the bottom just above the grill, finned copper pipe. Natural convection will circulate heat and the walls will get warm too. Simple cheap and easy, and no rads.

[Doctor Drivel]

Evenly heat all the walls and the Mean Radiant Temperature (MRT) rises. Most heat from UFH is convection.

[Doctor Drivel]

I have seen extensions that end up with cavity wall between the extension and the main house have plastic pipes run in them and filled with sand. Insulation was at the bottom and side to prevent heat loss Worked well. And nice warm wall.

[Doctor Drivel]

Many have in eco houses. One way is have two sheet of steel with plastic pipe between. Inside and out the sandwich have a sand/cement mix. Anyone drilling into the wall will hit the steel. Steel plate is not expensive. Simple to do in renovation or new build.

[meow2222]

Sure, but I dont want those.

Yes it works, but clogs up with dirty fluff in time, and the vents dont look good. What I'm trying to create is something effective, seamless & cheap.

NT

[Doctor Drivel]

Nope. A number of 8mm pipes is better than one 22mm pipe. Much better surface air contact and hot water surface contact too.

[Doctor Drivel]

Stud wall? Foam insulation at the back and to the sides of the stud. MDF inset the same dia of the pipes from the front studs edge. Attach pipes. silicon seal between studs and MDF. Over the lot fix Fermacell pre finished board. High density, so higher mass. The pipes behind touch and heat the Fermacell. See Fermacell makers.