Fitting wet UFH under bathroom floor

[vetinry]

We're cracking on with the renovation of our house and I now want to tackle the upstairs bathroom.

Currently there is a radiator in there, which works off the DHW system.

We'd like to tile the floor and therefore to avoid cold feet, I'd like to install wet underfloor heating for colder weather, whilst keeping the existing circuit for a towel radiator.

The floor is 18mm plywood sitting across 600mm centre joists (8x2's). I really don't want to raise the floor height if possible and so I'm wonder if it's possible to install a wet system below the plywood and then tile onto the ply.

Most of the spreader plate systems appear to be designed for much closer joists (350 to 450mm) and so i'm wondering if I could install insulation on batons between the joists, just low enough to clip in pipe and then either leave an air gap, or fill with dry screed up to the level of the joists and then replace the plywood floor and tile over.

Or, another possibility was to use the Overlay lite panels between the joists with a 12mm pipe clippped in, again level with the top of joists and plywood and tiles above.

Will any heat actually get through the plywood.

Since my system is oil boiler currently, what temperature could I run the system at? Rather than using a seperate manifold and pump, would it be ok to just run this off the main system, with or without a temperature mixer valve.

Any help would be much appreciated.

And I'm still also looking for an experienced heating engineer / plumber because some of my system needs upgrading (new water cylinder in new position / system changing from Y plan to S-plan to incorporate 2 or 3 zones including UFH in kitchen)

Am struggling to find anyone in Oxfordshire

Many thanks

Steve

 

[Barry98]

if your looking at doing just this one room id be tempted to fit electric IMHO

 

[vetinry]

I guess that might be an easier install option, but will it be cheaper to run?

 

[Barry98]

its also thinner as well and you can put tile adhesive straight on it for tilling i think its cheaper but that depends oon cost of your oil i would suppose

 

[SimonG]

Depends on size. But I would be tempted to go electric, not a fan but for a small bathroom ok, I would lay the insulation board on top of the plywood, then the mat and then tile with flexible adhesive and grout, using a plasticiser in the grout. Run the mat to an external, to the bathroom, timer/stat.

I wouldn't advise using the wet with oil for such a small area, if you did go this route you would still need manifold, mixing valve, thermostat and pump. It would be mounted below the ply, would prefer to see 3/4" at least and then tile with flexi adhesive and grout with plasticiser. May find doing it this way you get a lot of cycling of the oil boiler.

 

[dontknowitall]

I'd go for electric as well. I think it costs around a 120W light bulb per session (obviously depending on how long it's on, how hot, etc).

 

[tackleburger]

You can't do wet underfloor heating in that manor it would heat up and get too hot for a start. You would have to fit a zone valve, pump, mixing valve & manifold kit. Not worth it. Get a decent electric one with a redundant circuit built in just in case.

 

[vetinry]

Thanks for all the responses
Clearly, electric appears to be the preferred option here.

Just to add another dimension, I am also contemplating moving away from a oil based system to perhaps using an ASHP.

Would this change anyone's opinions as to what I should do?

And any takers for probably quite a bit of heating work in the South Oxfordshire area?

Cheers

Steve

 

[SimonG]

The ASHP wouldn't change my thoughts on the UF htg.

Too far for me, used to live near Chipping Norton as a kid! Somebody on here will be close.

 

[dontknowitall]

I used to live in Hook Norton ('64 - about '84).