Hi,
I hope you can help me and that I’m posting in the right category.
We are planning to build a house, and I’m a bit overwhelmed.
I want to keep the additional costs (heating, electricity, etc.) low, but without spending too much money unnecessarily. I also like renewable resources, which is why I have some questions.
Details:
- KfW 55 house with 42.5cm (17 inches) aerated concrete masonry.
- The house is about 133 sqm (1430 sqft) and 126 sqm (1356 sqft) according to living space regulations.
- Four people will live in the house.
- It has a decentralized heat recovery system with a ceramic core.
- The windows are triple-glazed with a U-value of 0.6.
- Underfloor heating throughout the house.
- Plastic roller shutters for all windows.
- 24cm (9.5 inches) roof insulation, thermal conductivity 0.035 W/(m·K).
- 5cm (2 inches) floor slab insulation made of Styrodur C.
Now we have several questions and hope you can help us.
1. We planned a ground-source heat pump (Vaillant flexocompact-exclusive-vwf-118-4) with two boreholes, but would an air-to-water heat pump (Rotex HPSU 508) possibly be sufficient?
2. We are planning a photovoltaic system with battery storage. How many kWp should it have?
3. Is a water-bearing (hydronic) stove for the underfloor heating worthwhile, with or without a chimney?
4. Is solar thermal still worth it?
5. We want to install a small wind turbine with 2 kW output. Is that sensible?
6. The roof pitch is 45°. Should we adjust it to 35° or 40°?
Thank you very much for your help.
Best regards, David
I hope you can help me and that I’m posting in the right category.
We are planning to build a house, and I’m a bit overwhelmed.
I want to keep the additional costs (heating, electricity, etc.) low, but without spending too much money unnecessarily. I also like renewable resources, which is why I have some questions.
Details:
- KfW 55 house with 42.5cm (17 inches) aerated concrete masonry.
- The house is about 133 sqm (1430 sqft) and 126 sqm (1356 sqft) according to living space regulations.
- Four people will live in the house.
- It has a decentralized heat recovery system with a ceramic core.
- The windows are triple-glazed with a U-value of 0.6.
- Underfloor heating throughout the house.
- Plastic roller shutters for all windows.
- 24cm (9.5 inches) roof insulation, thermal conductivity 0.035 W/(m·K).
- 5cm (2 inches) floor slab insulation made of Styrodur C.
Now we have several questions and hope you can help us.
1. We planned a ground-source heat pump (Vaillant flexocompact-exclusive-vwf-118-4) with two boreholes, but would an air-to-water heat pump (Rotex HPSU 508) possibly be sufficient?
2. We are planning a photovoltaic system with battery storage. How many kWp should it have?
3. Is a water-bearing (hydronic) stove for the underfloor heating worthwhile, with or without a chimney?
4. Is solar thermal still worth it?
5. We want to install a small wind turbine with 2 kW output. Is that sensible?
6. The roof pitch is 45°. Should we adjust it to 35° or 40°?
Thank you very much for your help.
Best regards, David
1. We also have the ground-source heat pump; however, the 58-4 model is suitable for 190 m² (2,045 sq ft) of living space. The 118-4 is MUCH too large for 130 m² (1,399 sq ft) – the 58-4 is sufficient (this is my opinion, even though I don’t know your building project in detail). An air-source heat pump is also sufficient – having just one heating appliance inside the house is enough. The question is rather what you prefer. Whether to go for an air-source or ground-source heat pump should depend on the specific offers you receive. For a 130 m² (1,399 sq ft) KFW55 house, the difference in energy costs is usually in the range of 10 to 20 € per month.
2. As much as your budget allows – or none at all. It’s a nice feature, but the return on investment is moderate (if purchased expensively, possibly none at all); however, you usually don’t lose money on it.
3. No.
4. No.
5. No.
6. I would let the house planner decide that, not the renewable energy specialists.
2. As much as your budget allows – or none at all. It’s a nice feature, but the return on investment is moderate (if purchased expensively, possibly none at all); however, you usually don’t lose money on it.
3. No.
4. No.
5. No.
6. I would let the house planner decide that, not the renewable energy specialists.
Just as information: For my KfW55 house project with 141m² (1,518 sq ft), the heating load calculation is now complete: 3.6 kW plus domestic hot water equals 4 kW.
1.6 km (1 mile) of underfloor heating with a supply temperature of 27°C (81°F) at an outside temperature of -12°C (10°F).
Most likely, one deep geothermal borehole.
1.6 km (1 mile) of underfloor heating with a supply temperature of 27°C (81°F) at an outside temperature of -12°C (10°F).
Most likely, one deep geothermal borehole.
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