Riverside cottage 6

[Tim Lamb]

Foundation trenches underway...

Most people I have asked seem to think underfloor heating for the second floor a bit unusual but, at our age, 24 hour occupation is common. Also, swmbo is against wall hung radiators in living areas.

Anyway I am now having a closer look at the specification provided by JG Speedfit. The aluminium spreader plates they supply are intended to fit between joists spaced at 400mm. For the new dormers area this is OK except where doubling has occurred for additional strength. The old part is basically 600mm but there is so much doubling, this is a rare event.

We discussed issues with returning plastic pipes over joist tops rather than through slots or holes and also the possibility of using the eaves space for this purpose.

One suggestion has been to cross batten the whole of the second floor. Apart from the loss of head space (25mm) this seems the answer to a maiden's prayer: solving the return loop issue and varying joist spaces.

Does anyone have experience of 22mm flooring chip in these circumstances? Mid joist, a 25x50mm batten will not provide much support for any floor joints.

[Capitol]

Put the piping under the joists? Plasterboard does not need much support, fewer battens.

[Tim Lamb]

Hmm.. for second floor wet underfloor you need insulation below the pipes. Also best if the spreader plates are in close contact with the floor material.

[Capitol]

Hot air rises. The radiation effects will be almost zero with low water temperatures. Why more insulation than plasterboard below? the pipes can be resting in a chickenwire mesh support on a few screwed up battens which will give good circulation, How are you planning to support the plastic pipes with a top down installation? I have no experience of spreader plates, but designing heat sinks for semi conductor cooling shows that vertical expamet works quite well. when the hot air gets to the flooring, I doubt that spreader plates will have much effect. Just a few thoughts.

[tabbypurr]

I didn't expect that, with it being expanded steel. It could be useful, do you have any figures?

NT

[The Natural Philosopher]

One of the most effective bits of UFH upstairs I have ever encountered was pure accident. A builder ran hot water pipes to the CH un-insulated under the bathroom floor. IN addition the hot water supply to the bath also ran there. A hot bath in winter left a very warm floor.

I'll expand on some issue :

1/. Insulation. Barely worth it. To prevent a hot ceiling downstairs? It will already be hot wont it with ground floor heating. Why not let it add to upstairs heat? In the case of upstairs bedrooms run a few degrees cooler you can often get away with little or no upstairs heating at all. OK if you want a roaring hot bathroom it may make sense to pack some celotex in there.

2/. Spreader plates. More bunk. Natural convection will do the job. These 'quick install' kits makes sense when you are paying contractors to do the job, but a D-I-Y install is a lot cheaper if you just e,g. find something to tie wrap the pipes to, or locate them in some other way. All you have to do is get hot pipes in there. tthe heat has to go somewhere.

3/. use of chip. That's fine. It will insulate more than screed, but that just means you want be sucking as much heat out of the pipes, so use more pipes!

I'd lay pipes at no more than 4" centres for a toasty bathroom.

************************************

IN essence the problem boils down to packing in pipe at 4" centres under the floor somewhere & locating it securely. And maybe a bit of insulation underneath.

The rest is 'marketing'...

[Mark Allread]

Thinking of Tim's comments about using the bedrooms 24 hours/day at times

- would it also make sense just to run the heating pipes around the outside of the rooms rather than heating unnecessary areas under beds?

That way the walked upon and exposed area are always warm but nothing is wasted under beds. I accept that bed positiions *may* change but that, generally, is only when a new occupier moves in. Unless Tim wants to future proof for that.

[The Natural Philosopher]

depends on whether you like a warm bed!

The only real effect of UFH under furniture is that the underside of the furniture and the floor below gets hotter. That simply means less heat lost from those bits of pipe.

As long as you have *enough* pipe it doesn't really matter.

I assume will be zoning with valves and stats on a per room basis?

[Capitol]

Sorry, no figures as the work was done years ago. I used aluminium expamet. I used it again for the open gas fire heat exchanger I built 30 years ago as layers between a steel cone to get the correct extraction for the flue gases and the outer brass decorative flared chimney shroud. It worked quite well in producing a stream of hot air coming out of the top outlet gap, which would otherwise have been much less. As this was a modern inglenook design, the fireplace ceiling level hot air then moves at low speed through a perforated steel lintel, then up through wide vertical vents into the room. It was a bit of a pig to build. I did consider fanning the hot air through the lintel, but it worked just about OK on the few occasions it is used and I didn't want to upset the air flow around the fireplace throat. It was designed as a decorative feature rather than a functional heating system to meet her desires!

[Capitol]

Yes, our bathroom floor has accidental under floor heating as the uninsulated 28mm hot water pipes to the gravity fed system run under it. Even the cold tap is warm!

[Mark Allread]

Not even in winter! I much prefer a cold bed and even colder room - except on a morning when I get up.

Hmm - holes in the bottom of the wardrobe and drawers to allow air circulation will give warm clothes to put on - that I do like the sound of.

[Tim Lamb]

In message , Mark Allread writes

er.. The 24 hour occupation was an indication of age rather than

*hot-bedding* migrant lodgers:-)

I think the pipe layout needs some care but unless bed linen drapes to the floor, I don't see it as an area to avoid.

[Tim Lamb]

Yes. Two manifolds and lots of stats.

[Tim Lamb]

I think the recommendation is a layer of rockwool. A bit of noise insulation would be nice (creaky floor experience) but I guess low mass insulation not much help.

I suppose they might reduce response times and hence thermostat overswings.

I was more concerned about relatively unsupported floor joints. The bathroom floor here (new 21 years back) creaks like a tall ship in a gale. Glueing joints has been mentioned here but I don't recall the context.

Yes. My merchant has offered 35% discount on list!