UFH - concrete slab above or below?

[pilsbury]

On my extension I was planning a MOT sub base, sand blinding, DPM, 150mm concrete slab, 100mm celotex, slip membrane, UFH pipes and 50mm screed....... in that order.

I've been reading a host of info with some suggesting insulation and UFH under the slab which takes longer to warm up but then maintains temp better and for longer

Thoughts on how it's done best?

 

[PullerGas]

Yes

 

[pilsbury]

That clears a lot up. Thanks......

 

[bernardgreen]

but then maintains temp better and for longer

and longer after everyone has left the room and heating is no longer needed in the room.

 

[pilsbury]

and longer after everyone has left the room and heating is no longer needed in the room.

And takes longer to heat up when you want it on. Thanks for confirming my suspicions

 

[Madrab]

Depends on the space heating design requirements. UFH heating and large thermal masses aren't point of use, they are designed to warmed up and then maintained to keep a constant mean temp throughout the larger main traffic spaces. Generally they are not really designed like rads to be put on when the room is to be warmed then switched off when not.

If that's what the design and user requires then UFH is not really suitable.

 

[Agile]

On my extension I was planning a MOT sub base, sand blinding, DPM, 150mm concrete slab, 100mm celotex, slip membrane, UFH pipes and 50mm screed....... in that order.

Thoughts on how it's done best?

What you have described is what I would consider as ideal.

The worst aspect of UFH is the long thermal time delay and that arrangement minimizes it.

Tony

 

[pilsbury]

Thanks for clarifying

 

[PullerGas]

UFH is the BEST way to heat any home, it's the most comfortable & a delight to live in a house with it.

Simple, it runs at a lower temperature & ideal for condensing boilers. This makes it very, very efficient.
It mostly provides a radiant heat, it minimises the radiant heat the human body loses. Humans sit around a fire & enjoy the radiant heat it provides, so we feel far more comfortable with UFH.

 

[PullerGas]

and longer after everyone has left the room and heating is no longer needed in the room.

BG you're clueless & completely ignorant about UFH.

 

[Doggit]

As it's an extension, that implies that you have radiators in the rest of the house, which means that you want the extension to run in tandem with it. On that basis, your method is the best option, but a 50mm screed will take time to heat up and cool down; this'll mean that you have to switch the boiler on earlier to get the slab up to temp by the time that the rads come on. You may want to look at a more low profile system, and then tiles or engineered wood on top, to keep the extension more in sync with the rest of the house.

 

[PullerGas]

As it's an extension, that implies that you have radiators in the rest of the house, which means that you want the extension to run in tandem with it. On that basis, your method is the best option, but a 50mm screed will take time to heat up and cool down; this'll mean that you have to switch the boiler on earlier to get the slab up to temp by the time that the rads come on. You may want to look at a more low profile system, and then tiles or engineered wood on top, to keep the extension more in sync with the rest of the house.

Rubbish, the UFH can be controlled as a separate zone on the house Central Heating system. Completely independent of any other part of the house. With a preferred temperature & set-back, very easy to control.

 

[Doggit]

If you reread what I posted - and prefereably without the attitude - I never said it couldn't. What I did say was that the boiler would have to come on earlier. I anticipated that the OP was well aware of everything else that you were kind enough to elaborate on.

 

[PullerGas]

If you reread what I posted - and prefereably without the attitude - I never said it couldn't. What I did say was that the boiler would have to come on earlier. I anticipated that the OP was well aware of everything else that you were kind enough to elaborate on.

Attitude??!!...mate, I don't have an attitude. You're clueless, I'm experienced, sorry but I can't sugar coat it. Back peddle all you like, you're still talking drivel.

 

[bernardgreen]

For what it is worth the experience of a friend who installed UFH

When the children were young and [their mother] was at home most of the day UFH was ideal but still had to be supplemented when the wather was cold. When the children were older and [their mother] went back to work the house was empty most of the day. Getting the start time correct in order to have a warm house in time for [mum] and the children coming home was difficult. A fast response heating source was needed and to achieve this we have installed radiators.

To be fair that house is a converted old building and not well insulated. A well insulated and air tight box of a house might be well served by UFH as the only heat source with floor temperatures warm enough to keep the house warm while still being cool enough to walk on in comfort.

A calculation involving heat loss, effective floor area and required floor temperature will give an idea of whether UFH alone is going to be sufficient while still being comfortable to stand on