ᐅ Underfloor heating with an air-to-water heat pump. House gets too warm when the sun is shining.

Created on: 4 Dec 2019 14:18
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chewbacca123
Hello everyone,

I have a general question.

We moved into our new build four months ago. The living area on the ground floor has three large floor-to-ceiling windows facing south. We have underfloor heating and an air-to-water heat pump.
It provides a really comfortable temperature inside the house, but we have a problem – whenever the sun is shining in winter, even if it’s -2°C (28°F) outside, the temperature suddenly rises to 24°C (75°F) in the living room. It gets uncomfortably warm in here, and the underfloor heating can’t be turned down quickly.
Should we assume that the large floor-to-ceiling windows are responsible for the heat gain? A photo of the south-facing side of the house is attached.
What would you do – always lower all the blinds as soon as sunlight is forecast? That seems quite annoying...
We have motorized blinds controlled by Somfy. Would you consider buying a sensor that automatically lowers the blinds at a certain temperature?

Thanks in advance for your replies.

Neues zweistöckiges Haus auf Baustelle mit weißer Blockfassade, pinker Dämmung und großen Fenstern
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Lumpi_LE
22 Jan 2020 14:11
One cubic meter is about 10 kWh.
With gas, it’s still interesting to consider what the solar thermal system contributes – this is simply not reflected in the displayed consumption, even though it is there.
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boxandroof
22 Jan 2020 14:22
My house without a basement in the frost-free northern region used on average about 40 kWh of heat per day in January, including a 10% share for hot water.

That would correspond approximately to:
- 4 m³ (141 cubic feet) of gas per day at 100% efficiency
- 10 kWh of electricity per day with a coefficient of performance of 4
- 4 liters (1 gallon) of oil at 100% efficiency
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pffreestyler
22 Jan 2020 14:27
Lumpi_LE schrieb:

One cubic meter is about 10 kWh.
With gas, the contribution of the solar thermal system is still interesting – this is simply not shown in the indicated consumption, even though it’s there.
oh yes, I actually didn’t consider that in summer
boxandroof schrieb:

My house without a basement in the frost-free north required on average about 40 kWh heating per day in January, including 10% hot water share.

That would be roughly:
- 4 m³ (140 ft³) gas per day at 100% efficiency
- 10 kWh per day with a coefficient of performance of 4
- 4 liters (1 gallon) oil at 100% efficiency
how many square meters and what indoor temperature?
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boxandroof
22 Jan 2020 14:38
pffreestyler schrieb:

How many square meters and what temperature inside the house?
I actually just wanted to contribute something about the energy sources. These comparisons are not very useful.

The living area is about 150m² (1600 sq ft) with an average indoor temperature of around 21°C (70°F), varying by 1-2°C (2-4°F) depending on the room and usage. On cold days last year, with outdoor temperatures down to -8°C (18°F), the consumption was 70 kWh per day. A very similar house a few kilometers away shows nearly identical monthly consumption according to the database.
tomtom7922 Jan 2020 18:50
blackm88 schrieb:


21.01. Total 23 kWh – of which 13.4 kWh were for our heat pump
Inside the house, from the basement to the upper floor, we have about 22–24°C (72–75°F) in all rooms
Hot water set to 44°C (111°F) with a 3°C (5°F) hysteresis
We still have snow here, outside temperature always below 0°C (32°F) / 940 m (3084 ft) above sea level, 180 m² (1937 sq ft) plus basement

13 kW? For 180 m² (1937 sq ft) plus basement? And almost 1,000 meters altitude? What kind of heat pump is that – horizontal ground collector or brine (ground source)?

Could you please also specify your type of heat pump for comparison?
tomtom7922 Jan 2020 19:02
Read just now from January 17, 2020 at 6:00 PM to January 22, 2020 at 7:00 PM.

122 kWh of electricity recorded on the meter.

So, 25 kWh per day.

And 378 kWh of heat energy.

Room temperature at 22.5°C (72.5°F).

About 240 m² (2,583 ft²) of heated floor area.

Mechanical ventilation with heat recovery (MVHR).

Air-to-water heat pump from Buderus.

480 Nn.

Domestic hot water set to 49°C (120°F) with 6°C (11°F) hysteresis.

Heating curve set to 25.5 / 22 / 0.