ᐅ Underfloor Heating on the Upper Floor – One Room Always Stays Too Cold

Hello everyone!

I'm at my wit’s end. I just can’t get the children's room above 20.5 degrees Celsius (69°F), while all the other rooms on the upper floor reach between 21.5 and 22.0 degrees (71.5 and 72°F) with the same settings. The affected room also feels noticeably cooler.

I have slightly increased the flow rate, but with no success (+0.3 degrees). The valve is now 95% open but the room temperature remains unchanged.

Thermal imaging camera showed nothing unusual, no cold spots. I checked all window seals, also fine. Photos from the installation of the underfloor heating were reviewed, no issues visible. The hydraulic balancing has been done twice to rule out errors.

Two heating circuits of identical length run through the 17 sqm (183 sqft) room. Pipe spacing is 10 cm (4 inches). The supply temperature at 5 degrees Celsius (41°F) outdoor is 27 degrees (81°F). The heating curve is set at 0.35, so at 0 degrees (32°F) outside, the supply temperature is about 28.3 degrees (83°F). We have 22.2 degrees (72°F) on the ground floor, so the supply temperature cannot be the problem.

I turned off the mechanical ventilation for 24 hours, no change. Removed the carpet for 24 hours, no change. There is only a small wardrobe on the floor; the bed is a loft bed and does not affect the underfloor heating.

I don’t understand why this room stays noticeably cooler than the adjacent room (exactly the same conditions).

Do you have any ideas where the problem might be? I don’t want to raise the supply temperature for the 17 sqm if there is no reason to do so for the other 140 sqm.

First, check if the circuits and thermostats have been switched.
This happens more often than you might think.
So close all the other circuits on that floor and then see if it gets properly warm.

After that, perform the thermal balancing instead of the hydraulic balancing.

What is the flow rate in that room?
How does it compare to similar rooms?

Two circuits and a 10cm (5 inch) pipe spacing sounds good at first.

RotorMotor schrieb:
First, check if the circuits and thermostats have not been swapped. This happens more often than one might think. So close all other circuits on the floor and then see if it gets properly warm. Afterwards, instead of a hydraulic balancing, perform a thermal balancing. What is the flow rate in that room? How does it compare to similar rooms? Two circuits and a 10cm (5 inches) pipe spacing sounds great at first.

I was already able to rule out swapped circuits by checking the installation photos. The flow rate is identical (2.8L/min of a maximum of 3L/min) to the other rooms, as I was very careful with the length of each heating circuit during installation. I basically control the temperatures only through the supply temperature. In my opinion, throttling individual valves a lot does not make much sense anyway. In the bathroom, we have an additional heater for extremely low outside temperatures. We have also already carried out the thermal balancing. That’s why I’m running out of ideas. The fact that the system reaches the set temperature throughout the entire house but just won’t work in this one room is driving me crazy.

Allthewayup schrieb:

I was already able to rule out swapped circuits by checking the photos taken during installation.

I would really check that again.

Allthewayup schrieb:

The flow rate is identical (2.8L/min out of max. 3L/min) to the other rooms, as I paid close attention to the length of each heating circuit during installation.

Please post a photo of the manifold.

Allthewayup schrieb:

We have also already completed the hydraulic balancing.

Here I would say: obviously not.
Hydraulic balancing doesn’t mean that the flow rates are the same, but that the temperatures are as desired.

Please upload the floor plan here, meaning the layout of the floor.

Remove the valve and control the flow only using the tacosetter.

Then please provide a picture of the manifold; there might be a bypass installed there that regulates too early.