Hello,
we are currently struggling with our heating system. It is warm everywhere in the house—both on the ground floor and in the heated basement room—around 21-22°C (70-72°F). However, the temperature in all rooms in the attic is noticeably lower, usually about 2°C (3.6°F) difference. This is problematic because a) it is too cold and b) it also affects the bathroom.
We have already tried various measures. We adjusted the heating curve, the manufacturer’s service performed a firmware update, and the hydraulic balancing was done again... but the problem remains the same. The attic stays consistently about 2°C (3.6°F) cooler than the other floors. The heating technician said this is normal because of the many windows and that it always tends to be cooler in the attic. He advised us to simply increase the supply water temperature. But that can’t be the solution, right? Although this raises the temperature in the attic, we then have to lower the temperature on the ground floor because otherwise it becomes too hot. The 2°C (3.6°F) difference always stays the same. We have solid ceilings and walls, underfloor heating everywhere, and the room thermostats turned up fully.
Is this really normal, or is the heating technician just trying to sell us that because he has no other ideas? What is your experience? Do you also have such temperature differences?
we are currently struggling with our heating system. It is warm everywhere in the house—both on the ground floor and in the heated basement room—around 21-22°C (70-72°F). However, the temperature in all rooms in the attic is noticeably lower, usually about 2°C (3.6°F) difference. This is problematic because a) it is too cold and b) it also affects the bathroom.
We have already tried various measures. We adjusted the heating curve, the manufacturer’s service performed a firmware update, and the hydraulic balancing was done again... but the problem remains the same. The attic stays consistently about 2°C (3.6°F) cooler than the other floors. The heating technician said this is normal because of the many windows and that it always tends to be cooler in the attic. He advised us to simply increase the supply water temperature. But that can’t be the solution, right? Although this raises the temperature in the attic, we then have to lower the temperature on the ground floor because otherwise it becomes too hot. The 2°C (3.6°F) difference always stays the same. We have solid ceilings and walls, underfloor heating everywhere, and the room thermostats turned up fully.
Is this really normal, or is the heating technician just trying to sell us that because he has no other ideas? What is your experience? Do you also have such temperature differences?
Just took a quick look.
The insulation used is BAUDER PIR FA 160mm (6.3 inches).
There is also mention of an 80x80mm (3x3 inches) PU rigid foam wedge on top.
The insulation is easy to identify. How do I calculate the U-value here? And what should I make of this? A thickness of 16cm (6.3 inches) was installed instead of 20cm (7.9 inches) because otherwise the roof structure would have become too thick. We were assured that this material offers better insulation (thermal conductivity).
@Mycraft: higher heat loss and lower temperatures might be possible. But not a 4-degree difference at the same thermostat setting in every room. That just can’t be true, not in a new build KfW70 house, sorry. Nobody can convince me otherwise. Otherwise, everyone would have that problem. Interestingly, our neighbors don’t...
The insulation used is BAUDER PIR FA 160mm (6.3 inches).
There is also mention of an 80x80mm (3x3 inches) PU rigid foam wedge on top.
The insulation is easy to identify. How do I calculate the U-value here? And what should I make of this? A thickness of 16cm (6.3 inches) was installed instead of 20cm (7.9 inches) because otherwise the roof structure would have become too thick. We were assured that this material offers better insulation (thermal conductivity).
@Mycraft: higher heat loss and lower temperatures might be possible. But not a 4-degree difference at the same thermostat setting in every room. That just can’t be true, not in a new build KfW70 house, sorry. Nobody can convince me otherwise. Otherwise, everyone would have that problem. Interestingly, our neighbors don’t...
Well, I also have a KfW70 house with exactly the same values... it is cooler upstairs than downstairs... which is quite logical, as many have already explained in this thread...
Just a hypothetical example:
On the ground floor, you have an exterior wall area of 10 m² (108 sq ft), which is covered by an intermediate ceiling, so there are no heat losses through it because it is within the heated envelope.
On the upper floor, you have the same 10 m² (108 sq ft) of exterior wall area, plus an additional roof area of another 10 m² (108 sq ft), through which heat losses occur since it is directly exposed to the outside environment.
Which floor do you think requires the heating system to work harder to compensate for the heat losses?
You can find the U-value of your roof in your house documentation... everything should be listed there...
Just a hypothetical example:
On the ground floor, you have an exterior wall area of 10 m² (108 sq ft), which is covered by an intermediate ceiling, so there are no heat losses through it because it is within the heated envelope.
On the upper floor, you have the same 10 m² (108 sq ft) of exterior wall area, plus an additional roof area of another 10 m² (108 sq ft), through which heat losses occur since it is directly exposed to the outside environment.
Which floor do you think requires the heating system to work harder to compensate for the heat losses?
You can find the U-value of your roof in your house documentation... everything should be listed there...
K
Knallkörper23 Mar 2017 10:00The higher heat losses in the attic can be compensated by
a) increased flow rate
b) more closely spaced heating circuits
If this is not sufficient, the supply temperature must be raised; however, the flow rates for the heating circuits on the ground floor and upper floor then need to be reduced.
How does the flow rate compare to the other floors? If the flow rate there is appropriate and possibly even higher than in the other circuits, then there is no air in the system—your heating engineer is correct about that.
a) increased flow rate
b) more closely spaced heating circuits
If this is not sufficient, the supply temperature must be raised; however, the flow rates for the heating circuits on the ground floor and upper floor then need to be reduced.
How does the flow rate compare to the other floors? If the flow rate there is appropriate and possibly even higher than in the other circuits, then there is no air in the system—your heating engineer is correct about that.
Ok, maybe it was a bit unclear before, so here it is again:
Summary: I understand that heat escapes through the attic floor. That it can be cooler there than on the ground floor and basement is accepted. But it is not explainable why, despite all these measures, we never get above 21.2°C (70.2°F) room temperature, EVEN WITH increased flow rate and flow temperature. There is absolutely no change! And that doesn’t make sense to me! There is no temperature difference despite these adjustments.
How can this be explained? Even if the roof is poorly insulated... if I put more energy into a room, more energy must stay somewhere in the room. So there should be a noticeable change. But for us, it’s zero, nothing at all...
- - The flow temperature was increased from 33 to 43°C (91 to 109°F) -> effect on room temperature only 0.2 degrees!
- The flow rate on the ground floor and basement was reduced, while on the upper floor it was increased by 0.5 L/min (0.13 gal/min) -> after 20 hours no change in room temperature. It remains exactly the same as before the increase (21.2°C / 70.2°F).
- All room thermostats on the attic floor are fully open, no more adjustment possible!
- Still, we cannot get above 21.2°C (70.2°F).
- Hydraulic balancing was done but was manually adjusted again yesterday as described (restriction on ground floor and basement, increased flow rate in attic floor).
- Pipe spacing is 10 cm (4 inches).
- Flow rate in all rooms on the attic floor set to 2 L/min (0.53 gal/min).
- Flow rate in rooms on the ground floor/basement is around 1 L/min (0.26 gal/min) or less.
- Room temperatures on ground floor and basement at thermostat setting 3 = 22.5°C (72.5°F).
- Room temperatures on attic floor at setting 6 = 20.9–21.2°C (69.6–70.2°F).
- Thermal imaging camera shows floor temperature at 24.4°C (75.9°F), wall temperature at 21.1°C (69.98°F).
Summary: I understand that heat escapes through the attic floor. That it can be cooler there than on the ground floor and basement is accepted. But it is not explainable why, despite all these measures, we never get above 21.2°C (70.2°F) room temperature, EVEN WITH increased flow rate and flow temperature. There is absolutely no change! And that doesn’t make sense to me! There is no temperature difference despite these adjustments.
How can this be explained? Even if the roof is poorly insulated... if I put more energy into a room, more energy must stay somewhere in the room. So there should be a noticeable change. But for us, it’s zero, nothing at all...
markus270323 Mar 2017 11:50Have you ever closed all the doors for a few hours, turned off the mechanical ventilation system, and then checked if the rooms became different temperatures? If one or more rooms differ significantly, the problem might be found in those areas.
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