ᐅ Experience with KfW55 solid construction + gas heating + 5 sqm solar panels
Created on: 1 May 2017 20:11
N
Nutshell
Hello everyone,
I wanted to share my experience with my Kfw55 new build from 2013/2014.
We live at just under 300 meters (985 feet) above sea level and built with solid construction.
The house has a rather simple shape.
A standard gable roof without dormers or skylights (upstairs there is one window per room on the gable side).
Styrofoam was not an option for various reasons, so we chose the rather expensive monolithic plan blocks with a lambda value of 0.08.
Size: 111 sqm (1195 sq ft) living space.
Exterior wall: 36.5 cm (14 inches) Ytong blocks // Lambda 0.2 W/m²K
Floor slab insulated with XPS // 0.21 W/m²K
Ceiling on the upper floor has a sloping roof with 24 cm (9.5 inches) // ceiling insulated with 34 cm (13.5 inches) mineral wool // 0.12 W/m²K
Doors and windows are triple-glazed and gas-filled // overall including frames 1.05 W/m²K
Heat generator:
Gas condensing boiler: Viessmann Vitodens 300
System control: Vitotronic 200
Solar thermal system 5 sqm (54 sq ft): Vitosol 200-F
Solar storage tank: Vitocell 100-W 300 liters (79 gallons)
The solar system is used only for domestic hot water (no heating support).
Our gas boiler is switched off from May to September for heating and still consumes about 100 kWh of gas over the summer.
In winter, the solar system barely manages to heat the hot water (2 people), so it usually runs on gas.
Ventilation is handled by decentralized Lunos e² units with 90% heat recovery.
Over 12 months, we had a gas consumption of 8000 kWh.
That currently corresponds to heating costs of about €28 for the house.
We have the temperature set to 23°C (73°F) throughout the house.
(Electricity costs are about €39.)
Overall, we are very satisfied. Of course, the energy certificate shows lower consumption than we actually have.
There is no night setback, and nothing ever switches off or regulates down.
Maybe someone has had similar experiences?
Personally, I’m relaxed about heating costs; even if energy prices rise, paying twice as much would still be less than I used to pay in my smaller 80 sqm (860 sq ft) apartment built in 1990.
I wanted to share my experience with my Kfw55 new build from 2013/2014.
We live at just under 300 meters (985 feet) above sea level and built with solid construction.
The house has a rather simple shape.
A standard gable roof without dormers or skylights (upstairs there is one window per room on the gable side).
Styrofoam was not an option for various reasons, so we chose the rather expensive monolithic plan blocks with a lambda value of 0.08.
Size: 111 sqm (1195 sq ft) living space.
Exterior wall: 36.5 cm (14 inches) Ytong blocks // Lambda 0.2 W/m²K
Floor slab insulated with XPS // 0.21 W/m²K
Ceiling on the upper floor has a sloping roof with 24 cm (9.5 inches) // ceiling insulated with 34 cm (13.5 inches) mineral wool // 0.12 W/m²K
Doors and windows are triple-glazed and gas-filled // overall including frames 1.05 W/m²K
Heat generator:
Gas condensing boiler: Viessmann Vitodens 300
System control: Vitotronic 200
Solar thermal system 5 sqm (54 sq ft): Vitosol 200-F
Solar storage tank: Vitocell 100-W 300 liters (79 gallons)
The solar system is used only for domestic hot water (no heating support).
Our gas boiler is switched off from May to September for heating and still consumes about 100 kWh of gas over the summer.
In winter, the solar system barely manages to heat the hot water (2 people), so it usually runs on gas.
Ventilation is handled by decentralized Lunos e² units with 90% heat recovery.
Over 12 months, we had a gas consumption of 8000 kWh.
That currently corresponds to heating costs of about €28 for the house.
We have the temperature set to 23°C (73°F) throughout the house.
(Electricity costs are about €39.)
Overall, we are very satisfied. Of course, the energy certificate shows lower consumption than we actually have.
There is no night setback, and nothing ever switches off or regulates down.
Maybe someone has had similar experiences?
Personally, I’m relaxed about heating costs; even if energy prices rise, paying twice as much would still be less than I used to pay in my smaller 80 sqm (860 sq ft) apartment built in 1990.
Brief update:
Consumption has settled down a bit again over the past 12 months.
For the next 12 months, I am budgeting 28€/month for heating and hot water costs.
Overall, I am very happy with this, as I continue to heat every room to 22-23°C (71.6-73.4°F) and the bathroom to 23-24°C (73.4-75.2°F). We also do not use any nighttime temperature setback.
Consumption has settled down a bit again over the past 12 months.
For the next 12 months, I am budgeting 28€/month for heating and hot water costs.
Overall, I am very happy with this, as I continue to heat every room to 22-23°C (71.6-73.4°F) and the bathroom to 23-24°C (73.4-75.2°F). We also do not use any nighttime temperature setback.
Small update:
Currently, a monthly gas advance payment of €38.
Consumption from 2019 to 2020 was 6,400 kWh.
Temperature constantly at 22-23 degrees Celsius (72-73°F) in all rooms except the bathroom, where it is 24-25 degrees Celsius (75-77°F).
(No nighttime setback)
I am satisfied.
Our house has so far withstood weather and other conditions well, as we have been living here for 7 years now.
The only defect is fine cracks in the walls, most likely due to unprofessional workmanship. For example, no reinforcing mesh was applied.
The exterior plaster shows no cracks, so I believe the movements in the masonry are of a normal nature.
At some point, we will renovate... once the loan is paid off.
Speaking of the loan, we are currently working on some optimizations.
Immediate loan (0.61%, €44,000 (approximately $48,000))
Forward loan 07/2023 (0.84%, €43,000 (approximately $47,000))
Forward loan 01/2026 (1.45%)
Currently, a monthly gas advance payment of €38.
Consumption from 2019 to 2020 was 6,400 kWh.
Temperature constantly at 22-23 degrees Celsius (72-73°F) in all rooms except the bathroom, where it is 24-25 degrees Celsius (75-77°F).
(No nighttime setback)
I am satisfied.
Our house has so far withstood weather and other conditions well, as we have been living here for 7 years now.
The only defect is fine cracks in the walls, most likely due to unprofessional workmanship. For example, no reinforcing mesh was applied.
The exterior plaster shows no cracks, so I believe the movements in the masonry are of a normal nature.
At some point, we will renovate... once the loan is paid off.
Speaking of the loan, we are currently working on some optimizations.
Immediate loan (0.61%, €44,000 (approximately $48,000))
Forward loan 07/2023 (0.84%, €43,000 (approximately $47,000))
Forward loan 01/2026 (1.45%)
There is news!
Over 12 months, we consume an average of 8,000 kWh of gas.
In the coldest February, daily consumption ranges between 45-75 kWh, depending on the temperature.
The attic often becomes unbearably warm, so we plan to install split-system air conditioning in the bedroom, children’s room, and office. We also want to install an indoor unit in the open-plan living room and kitchen on the ground floor.
Outdoor unit
CU-4Z68TBE
Master bedroom (12 m² (129 sq ft) east-southeast)
CS-Z20XKEW
Children’s room (12 m² (129 sq ft) west-northwest)
CS-Z25XKEW
Office (12 m² (129 sq ft) southwest)
CS-Z35XKEW
Living room (35 m² + 15 m² kitchen (377 + 161 sq ft))
CS-Z35XKEW
I would also like to use these units for heating, not just cooling. Now that gas has become very expensive, investing in a high-quality modern air conditioning system makes sense. Of course, it’s not practical when it’s -10°C (14°F) outside. But if, as a private household, our gas supply were suddenly cut off, I would have a working fallback—even if the usual 23°C (73°F) cannot be reached everywhere with only one unit on the ground floor. Still, it should be suitable for emergency operation.
What do you think of these expansion plans?
Over 12 months, we consume an average of 8,000 kWh of gas.
In the coldest February, daily consumption ranges between 45-75 kWh, depending on the temperature.
The attic often becomes unbearably warm, so we plan to install split-system air conditioning in the bedroom, children’s room, and office. We also want to install an indoor unit in the open-plan living room and kitchen on the ground floor.
Outdoor unit
CU-4Z68TBE
Master bedroom (12 m² (129 sq ft) east-southeast)
CS-Z20XKEW
Children’s room (12 m² (129 sq ft) west-northwest)
CS-Z25XKEW
Office (12 m² (129 sq ft) southwest)
CS-Z35XKEW
Living room (35 m² + 15 m² kitchen (377 + 161 sq ft))
CS-Z35XKEW
I would also like to use these units for heating, not just cooling. Now that gas has become very expensive, investing in a high-quality modern air conditioning system makes sense. Of course, it’s not practical when it’s -10°C (14°F) outside. But if, as a private household, our gas supply were suddenly cut off, I would have a working fallback—even if the usual 23°C (73°F) cannot be reached everywhere with only one unit on the ground floor. Still, it should be suitable for emergency operation.
What do you think of these expansion plans?
D
Deliverer23 May 2022 17:38The idea itself is good, but the units chosen are too large.
I would go with 2 kW everywhere (if those are already available; often 2.5 kW is the minimum), and if you want to be on the safe side, use 2.5 kW in the living room.
By the way, single-split systems are cheaper (shorter pipe runs, less expensive units), more comfortable (because they cycle less frequently), and more redundant than multi-split systems. You just have to find space for all the indoor units... Maybe consider a mix?
I would go with 2 kW everywhere (if those are already available; often 2.5 kW is the minimum), and if you want to be on the safe side, use 2.5 kW in the living room.
By the way, single-split systems are cheaper (shorter pipe runs, less expensive units), more comfortable (because they cycle less frequently), and more redundant than multi-split systems. You just have to find space for all the indoor units... Maybe consider a mix?
Similar topics