Wet underfloor heating advice for extension and existing area

[dave2612]

I would appreciate some advice about the best way to install UFH for our extension and existing area.

The areas marked on the picture are as follows…

 

Yellow – existing timber floor with approx. 1.2m void
Green – existing solid concrete floor
Blue – new extension

 

I assume the extension and existing concrete floor will be simple enough, though I’m assuming the concrete will have to be dug out to a certain depth.

 

With regards to the yellow section, I think I have 2 options, backfill the void or batten and insulate running the pipes along the existing joists?

 

Bearing in mind that the yellow section will have a kitchen and large island on it which won’t require the pipes to be run under.

 

Or - we make things easy and get an overlay system like NuHeat LoProMax so we can have a single zone instead of two zones which we would have to have if we used the 2 different methods of UFH mentioned above?

Thanks in advance for any advice!

[JohnMo]

Main thing I can think of is make sure the loops are confined to a different floor buildup. So kitchen has loops that stay in the kitchen and don't overlap into green or blue area. Reason, the heating properties will be different, so you can fine tune each area with adjusting the flow to those loops.

 

The other thing is insulation - more is better, you need a finished U value of 0.15 or better. If not running costs will be high and you would be better sticking with radiators, if you want something smaller than a normal radiator fan assisted are pretty small with a good output.

[Redbeard]

I'd say get rid of the suspended floor and replace with insulated concrete, or glaspor or whatever you fancy. Reason for this is that I suspect your under-floor cross-ventilation will be sub-optimal and (UFH loops notwithstanding) I would not be certain of the long-term 'health' of your floor. Also what would you do where the pipes must cross joists? I have seen a tendency towards 'over-notching', though it does tend to depend a bit on the age/joist depth.

[dave2612]

6 hours ago, JohnMo said:

Main thing I can think of is make sure the loops are confined to a different floor buildup. So kitchen has loops that stay in the kitchen and don't overlap into green or blue area. Reason, the heating properties will be different, so you can fine tune each area with adjusting the flow to those loops.

 

The other thing is insulation - more is better, you need a finished U value of 0.15 or better. If not running costs will be high and you would be better sticking with radiators, if you want something smaller than a normal radiator fan assisted are pretty small with a good output.

Thanks John, the area is all open plan, so are you suggesting that different zones will be better ? With regards to the insulation it's not a problem insulating the wooden floor or the extension, what might be an issue is the concrete floor, we'd have to dig the existing floor out to do this. Nu Heat reckon with the overlay system it's doesnt need the insulation?

 

Thanks!

Dave

[dave2612]

4 hours ago, Redbeard said:

I'd say get rid of the suspended floor and replace with insulated concrete, or glaspor or whatever you fancy. Reason for this is that I suspect your under-floor cross-ventilation will be sub-optimal and (UFH loops notwithstanding) I would not be certain of the long-term 'health' of your floor. Also what would you do where the pipes must cross joists? I have seen a tendency towards 'over-notching', though it does tend to depend a bit on the age/joist depth.

Thanks Redbeard,

 

I think the issue is there is a lot to backfill!

[JohnMo]

3 minutes ago, dave2612 said:

so are you suggesting that different zones will be better

Not really, just that you have separate loops confined to each area. Not much a fan of zones.

 

4 minutes ago, dave2612 said:

Nu Heat reckon with the overlay system it's doesnt need the insulation?

That's them wanting to sell product, not what's correct for your wallet. Physics doesn't change, conduction heat flow will always try to move from a warm area to one at lower temperature. So unless you restrict that with insulation, the heat will flow downwards more than upwards.

 

The issue is with different U values, due to different amounts of heat flow downwards, you can need very different flow temperatures to heat the different areas to similar temperatures.

 

[dave2612]

33 minutes ago, JohnMo said:

Not really, just that you have separate loops confined to each area. Not much a fan of zones.

 

That's them wanting to sell product, not what's correct for your wallet. Physics doesn't change, conduction heat flow will always try to move from a warm area to one at lower temperature. So unless you restrict that with insulation, the heat will flow downwards more than upwards.

 

The issue is with different U values, due to different amounts of heat flow downwards, you can need very different flow temperatures to heat the different areas to similar temperatures.

 

Thanks again John.

 

So the issue is probably going to be the concrete floor and having to get it all dug out to get some insulation in. 

[dave2612]

What if we keep 'proper' UFH for the extension (blue area) and put a radiator in the green area, most of the floor will be covered by kitchen in the yellow area, so maybe we just insulate that really well under the existing floor? As the finished floor would be either vinyl or laminate a warm floor doesn't matter too much for us.

[Gus Potter]

On 10/10/2023 at 15:25, Redbeard said:

Reason for this is that I suspect your under-floor cross-ventilation will be sub-optimal

Good pointer.

 

To expand. I think you are jumping the gun here. Before you get into the nitty gritty of loops, zones etc you need to understand how the wall fit on the floors, the solum structure and the founds below.

 

You are introducing insulation so changing the dew point location. To be brief you could have a house with masonry walls, the internal leaf may have booby traps as it could sit on a built in timberwall plate. You may have a timber frame and indavetantly cause it to rot at the main structural supports.. that will result in disaster.. I kid you not.

 

Post what you know about the floor zone.. if you know little.. stop what you are doing and find out!

 

I like what you are doing have experimented myself on different houses with my own designed UF systems.. in all sort of floors, suspended  etc  so have been there and worn the shirt.. but the protection of the structure comes first then we get to play with the fun bit.... manifolds, pipe sizes etc.

 

Play safe an get stuck into investigating the underbuilding. Also if you can post a floor plan of the whole house this would help.. you can have a mixture of solid and suspended floors. I have and got round this on ocasion by ducting while appreciating the prevailing wind and what is round about. It may sound like hard work but.. best to put effort in early as if you get it wrong it can be very expensive.

 

 

 

 

[dave2612]

Sounds like the option of just installing UFH in the new extension would be the simplest. Another thought would be that as we want Aircon in the room anyway we could just use the Aircon to heat the room as well? Not sure how much this would cost to run Vs ufh?

[JohnMo]

Heat pump of various kinds are on here, including A2A.

 

https://www.eurovent-certification.com/en/

 

I stated looking into it, see attached

 

 

MoreDetailPerformance2.xlsx