Under floor heating upstairs

[steady]

What would be the best method in a new build , at the moment we’re doing egg shells and screeding on top ?

[BotusBuild]

There is a train of thought that says in a traditional two storey home (bedrooms upstairs), and depending on levels of insulation applied during the build, that you may not need UFH upstairs.

 

The main question to answer so others can provide improved responses is about the level of insulation and air tightness of the build, and if you have the heat loss figures for the rooms upstairs. Also, what temperatures are you aiming to achieve in those rooms (generally bedrooms are cooler)?

[Kelvin]

We’ve got no heating upstairs apart from electric UFH and heated towel rail in the bathroom. Current temperature in the upstairs  is 18.5°C and the coldest it’s been is around 16°C but that was before we moved in. I cabled for electric wall panel heaters just in case  we felt the upstairs got too cold. Keeping the upstairs cool in the warmer months is a bigger issue and you could use the UFH to help there but there are other ways to do that. 

[JohnMo]

24 minutes ago, steady said:

What would be the best method in a new build , at the moment we’re doing egg shells and screeding on top ?

Then you will add nice carpets and the output of the floor will be killed.

 

Add fan coils for decent cooling in summer and to add heat in winter. Or radiators and run same temp as UFH or just add fixings for electric heaters, just in case you need!

 

Just wouldn't bother with UFH.

 

[steady]

Ok but IF you were doing it ?

[JohnMo]

13 minutes ago, steady said:

Ok but IF you were doing it ?

Egg shells plus screed works. Do 16mm Pert-al-Pert tube.  Insulated below at a higher thermal resistance to what ever is above the floor to ensure heat moves upwards not downwards.

[SBMS]

Probably not answering your question but I spent ages going round in circles on this and decided to go wall mounted fan coils upstairs. Panasonic aquarea system. Means we can do heating and cooling. 2 Temperature zones (natively supported by the system) so can run UFH and fan coils at different temps (low if needed for cooling).
 

I’m not sure the cost of UFH upstairs is justifiable but I do think the cost of proper cooling (AC level cooling) is justified - the way our summers are going. Got Panasonic coming out in a couple of weeks to provide a technical assist on the system design if you had any questions

[steady]

I’m going round in circles also 🤣if we did ufh on first floor what would be the minimum screed depth on top of 15mm castle matts . Think it might be easier with rads (more controllable 

[Nickfromwales]

3 hours ago, steady said:

I’m going round in circles also 🤣if we did ufh on first floor what would be the minimum screed depth on top of 15mm castle matts . Think it might be easier with rads (more controllable 

Why are you wasting room with mats when you can just clip directly to the P5 deck (floorboards)?

[Nickfromwales]

 

 

[steady]

Not sure, why do people use mats ?

[saveasteading]

5 hours ago, Nickfromwales said:

wasting room with mats

Mats look good for upstairs, pinned onto board decking and providing sound insulation.

 

But at £10/m2 it's pointless on the ground floor .. except for discipline on the layout. I've forgotten who posted the other day, the very rough layout.

 

I'm not rating ufh upstairs for cooling.

I notice some suppliers are hyping it while others encourage caution.

Hot air rises, so chilling the floor by 2° isn't going to help much.

 

[Oz07]

On 11/11/2025 at 20:19, Kelvin said:

We’ve got no heating upstairs apart from electric UFH and heated towel rail in the bathroom. Current temperature in the upstairs  is 18.5°C and the coldest it’s been is around 16°C but that was before we moved in. I cabled for electric wall panel heaters just in case  we felt the upstairs got too cold. Keeping the upstairs cool in the warmer months is a bigger issue and you could use the UFH to help there but there are other ways to do that. 

Or an aircon unit in bedrooms that can cool and heat?

[SBMS]

22 hours ago, Oz07 said:

Or an aircon unit in bedrooms that can cool and heat?

We are Doing this but driven by the heat pump instead of a separate air con.  for reference - the cost difference to install fan coil units upstairs (7 units) with fully lagged pipe work (allowing us to run the fan coils at 9degrees when cooling) is around £7k (over first and second floors).  This is only a bit more than quoted price for UFH for those floors. This is much less than price of air con and means our heat pump isn’t sitting idle for half the year. Fan coils are also pretty efficient at running at low temps as well. 
 

I hope the strategy works, but in theory it makes sense??

[Oz07]

Can a normal air to air aircon unit be run by a normal ashp?

[crispy_wafer]

no, but you can fit a fan coil unit which uses the warmed ( or cooled) water from your ASHP CH system.

[Bornagain]

Our 15 yr old self build doesn’t have any heating upstairs.

The walls are ICF with a U value of 0.15, the windows and doors are triple glazed, we have shed loads of insulation under the ground floor and in the loft, we really went to town with the insulation.

Downstairs is heated by an ASHP connected to UFH running on openloop

All the downstairs rooms and the landing are at the same temperature (more or less)

We keep the bedroom doors shut to keep them a couple of degrees cooler than the rest of the house.

During winter we dry washing on clothes maidens, it typically takes a day or so to dry the washing, presumably the MVHR helps.

 

If we were building again, I definitely wouldn’t bother putting heating upstairs.

 

 

 

[SBMS]

3 hours ago, Oz07 said:

Can a normal air to air aircon unit be run by a normal ashp?

No. But there are wall units that are basically the same as the a2a units they just run chilled/warm water as opposed to refrigerant. 
 

https://www.aircon.panasonic.eu/GB_en/product/aquarea-air-smart-fan-coil-wallmounted/