Wet UFH

[Josh_DIY]

I'm planning to convert my downstairs to Wet UFH with in between joists and would appreciate your opinions. It's going to be 50mm insulation with pre cut out grooves for 16 mm pipe. Due to different heights in flooring (tiles & engineered floor) could you advise if this would work ok?

 

1. Dining & living room 18mm ply on top of joists with 15mm engineered flooring

 

2. Kitchen/hallway with 22m no more ply and tiles on top.

 

Would this combination work well with these different materials ply & no more ply as good heat conductors. Unfortunately I cannot source 18mm no more ply and would prefer throughout due to better heat conductor? Any further thoughts would be appreciated?

 

Thanks

[ProDave]

I would say the first thing to look at is more insulation. 50mm is not really enough and you will get a lot of wasted heat heating the air under the floor.

 

P.S I moved this the the correct forum section.

[Temp]

I would recommend more insulation. We have 80mm of PIR and would prefer more. 

 

We have 21mm engineered oak boards straight over the UFH no ply. Works ok but I wouldn't go thinner eg not 14mm engineered flooring direct over UFH. 

 

Think about joints in the no more ply. They may need supporting to prevent flexing under tiles. Screw it down well. 

Edited November 13, 2019 by Temp

[ProDave]

We have 300mm of rockwool under ours.

 

In most of the downstairs we have engineered oak flooring. The hall and utility have chipboard then ply then slate tiles.  Both of these work well.

 

In the bathroom we have chipboard, tanking membrane then porcelain tiles.  This does not work as well. I wonder if the tanking membrane is a good insulator? 

[Josh_DIY]

11 minutes ago, Temp said:

I would recommend more insulation. We have 80mm of PIR and would prefer more. 

 

We have 21mm engineered oak boards straight over the UFH no ply. Works ok but I wouldn't go thinner eg not 14mm engineered flooring direct over UFH. 

 

Think about joints in the no more ply. They may need supporting to prevent flexing under tiles. Screw it down well. 

Thanks Temp for your input. Wow 80mm and still no enough why do they offer 50mm 200micron ally which I got from Wunda, shot myself in the foot here, so more insulation under it and no ply just engineered floor on top for better heat conductor.

[Josh_DIY]

27 minutes ago, ProDave said:

We have 300mm of rockwool under ours.

 

In most of the downstairs we have engineered oak flooring. The hall and utility have chipboard then ply then slate tiles.  Both of these work well.

 

In the bathroom we have chipboard, tanking membrane then porcelain tiles.  This does not work as well. I wonder if the tanking membrane is a good insulator? 

Wow 300mm Rockwool it make sense the more insulation the better. How are these companies offering 50mm insulstion between joists and say it's good enough for the job, should of posted earlier before purchase. You mentioned chipboard and ply on top work well, interesting. I hope the 50mm I have will work however I'm not laying engineered floor on top of joists but with increased 18mm ply.

[Onoff]

15 minutes ago, Josh_DIY said:

Wow 300mm Rockwool it make sense the more insulation the better. How are these companies offering 50mm insulstion between joists and say it's good enough for the job, should of posted earlier before purchase. You mentioned chipboard and ply on top work well, interesting. I hope the 50mm I have will work however I'm not laying engineered floor on top of joists but with increased 18mm ply.

 

50mm will "work" but you'll just suffer more heat loss through the floor.

 

I've 150mm of pir on top of 25mm eps. Some have 300mm of eps!

[JFDIY]

Think to 50mm stuff is for a second floor, where you're not mega fussed if some of the heat escapes downward into other heated rooms.

[Josh_DIY]

10 minutes ago, Onoff said:

 

50mm will "work" but you'll just suffer more heat loss through the floor.

 

I've 150mm of pir on top of 25mm eps. Some have 300mm of eps!

It's for downstairs, approx 300mm from the ground so 50mm eps will lose alot of heat underneath. Someone suggested it's good for second floor, really not happy

[Josh_DIY]

5 minutes ago, JFDIY said:

Think to 50mm stuff is for a second floor, where you're not mega fussed if some of the heat escapes downward into other heated rooms.

No its downstairs about 300mm from the ground, shot myself in the foot

[Onoff]

2 minutes ago, Josh_DIY said:

It's for downstairs, approx 300mm from the ground so 50mm eps will lose alot of heat underneath. Someone suggested it's good for second floor, really not happy

 

@Jeremy Harris could probably tell you the heat loss % to ground for different materials. It can be quite sobering and an education.

[Simplysimon]

200mm of kooltherm under the pipes here though not a refurb so easier to install

[Ed Davies]

26 minutes ago, Josh_DIY said:

shot myself in the foot

 

Maybe just nicked a toenail. No reason you can't use the 50mm insulation you've got with more underneath.

 

The tricky bit with insulation between joists is thinking about what moisture will do and how it'll dry out properly, particularly if the insulation goes below the joists. Understand you have 300mm (from top of joists?) do ground level - how deep are your joists?

[Onoff]

I'll be ripping the joists out in my lounge /diner and building back up to finish at a 100mm slab.

 

The dining room is a suspended timber floor. The lounge is some mish mash make up of a concrete slab with joists on top.

 

More digging!

 

I think @oranjeboom dug his whole ground floor down deeper. 

Edited November 13, 2019 by Onoff

[AdamSee]

On 13/11/2019 at 20:16, ProDave said:

We have 300mm of rockwool under ours.

 

In most of the downstairs we have engineered oak flooring. The hall and utility have chipboard then ply then slate tiles.  Both of these work well.

 

In the bathroom we have chipboard, tanking membrane then porcelain tiles.  This does not work as well. I wonder if the tanking membrane is a good insulator? 

 

Yea I've noticed a similar thing in my bathroom. I've don't have a tanking membrane but instead I have a fabric looking uncoupling membrane with marble tiles and it takes an age for the heat to come through. We used LVT in the bedrooms and the heat comes through within 15/20 mins. instead of the hour it takes for the bathroom floor to get warm. I assumed it may have just been down to the density of the tiles but still seems oddly long to me. 

 

It is however a upstairs bathroom but with no insulation underneath as there will be (although not at this present moment in time) a heated room below. 

Edited November 25, 2019 by AdamSee