Hello,
This is about my parents’ house. It was built in the 1960s and is very well maintained. A few years ago, my parents had additional seals installed on the double-glazed windows, and the roller shutter boxes were insulated. For the roof, my father added a layer of mineral wool, I believe with a membrane and then drywall, but I’m not completely sure about the details. The whole house has radiators; there is no underfloor heating. The house is divided into two apartments: the ground floor is rented out, and my parents live on the first floor.
My father has been pestering me for years about the heating system. At the moment, they heat with oil. I estimate the heating system is about 15 years old, maybe a bit older. It works perfectly. My father always says that eventually it will need to be replaced anyway, and he’s not sure if he should start now because he could get good subsidies. If he waits until it breaks down, he’s uncertain whether subsidies will still be available. Would you replace a heating system that’s actually working fine now? I’m skeptical about that. With the current energy crisis, he’s even more eager to act.
The second question is what type of heating to choose now or later. Heat pumps don’t work that well with radiators, right? I have read that it’s possible to retrofit ceiling heating and then cover the ceiling with drywall. Does anyone have experience with this? Gas isn’t connected to the property anyway, and I would hesitate to consider it at the moment. Pellets, well, they are getting more expensive as well. It should also be noted that the orientation is not ideal for solar thermal or photovoltaic systems, and there are large trees casting shadows on the roof. If installing a new heating system, would solar thermal or photovoltaic panels be mandatory?
Many questions, maybe someone can give an assessment.
Best regards,
Tobi
This is about my parents’ house. It was built in the 1960s and is very well maintained. A few years ago, my parents had additional seals installed on the double-glazed windows, and the roller shutter boxes were insulated. For the roof, my father added a layer of mineral wool, I believe with a membrane and then drywall, but I’m not completely sure about the details. The whole house has radiators; there is no underfloor heating. The house is divided into two apartments: the ground floor is rented out, and my parents live on the first floor.
My father has been pestering me for years about the heating system. At the moment, they heat with oil. I estimate the heating system is about 15 years old, maybe a bit older. It works perfectly. My father always says that eventually it will need to be replaced anyway, and he’s not sure if he should start now because he could get good subsidies. If he waits until it breaks down, he’s uncertain whether subsidies will still be available. Would you replace a heating system that’s actually working fine now? I’m skeptical about that. With the current energy crisis, he’s even more eager to act.
The second question is what type of heating to choose now or later. Heat pumps don’t work that well with radiators, right? I have read that it’s possible to retrofit ceiling heating and then cover the ceiling with drywall. Does anyone have experience with this? Gas isn’t connected to the property anyway, and I would hesitate to consider it at the moment. Pellets, well, they are getting more expensive as well. It should also be noted that the orientation is not ideal for solar thermal or photovoltaic systems, and there are large trees casting shadows on the roof. If installing a new heating system, would solar thermal or photovoltaic panels be mandatory?
Many questions, maybe someone can give an assessment.
Best regards,
Tobi
D
Deliverer23 Jul 2022 13:08driver55 schrieb:
The annual performance factor will probably hover around 3.Which would be perfectly acceptable for a poorly insulated house with radiators, don’t you think? If that bothers you, insulation can be improved.W
WilderSueden23 Jul 2022 13:21But let’s be honest… a partially renovated house from the 1960s will hardly get below 200 kWh/m² (20,000 BTU/ft²) energy consumption; many are closer to 300 kWh/m² (30,000 BTU/ft²). If we calculate 150 m² (1,615 ft²) * 200 kWh/m² (20,000 BTU/ft²), that gives us 30,000 kWh of heating demand. Assuming a supply temperature of 55 degrees Celsius (131°F) and an outdoor temperature of 2 degrees Celsius (36°F) — which is already a mild climate — and ignoring that performance drops significantly on colder days without being compensated on warmer days, we get a COP of 2.12. That results in approximately 14,150 kWh of electricity for heating, costing upwards of $5,000.
These assumptions are rather optimistic: the house is only partially renovated, winters are mild, the house isn’t excessively large, and electricity is priced at 35 cents. The reality can be much worse. I don’t need to look at biased reports when I can calculate this myself and conclude that it doesn’t make sense. Such houses simply cannot be converted economically without comprehensive renovation. Period, end of story.
These assumptions are rather optimistic: the house is only partially renovated, winters are mild, the house isn’t excessively large, and electricity is priced at 35 cents. The reality can be much worse. I don’t need to look at biased reports when I can calculate this myself and conclude that it doesn’t make sense. Such houses simply cannot be converted economically without comprehensive renovation. Period, end of story.
D
Deliverer23 Jul 2022 13:37WilderSueden schrieb:
A partially renovated house from the 1960s will hardly achieve less than 200 kWh/m²,So, I don’t think there’s any point in discussing anything over 200 kWh/m², in my opinion. The house has been severely neglected, NOT partially renovated, and needs urgent refurbishment. The major flaw in your calculation is the assumption that 55°C (131°F) is needed at an outdoor temperature of 2°C (36°F). The supply temperature is always specified at the design outdoor temperature (DOT), which is usually between -9°C and -12°C (16°F and 10°F). The 55°C (131°F) supply temperature is therefore only required about 24 hours per year statistically. Average winter temperatures in lowland areas are around 7°C (45°F), and at that point, roughly estimated, a 30°C (86°F) supply temperature is sufficient. This means the difference to a heat pump designed for a 35°C (95°F) supply temperature (at DOT) is only about 6°C (11°F), resulting in an average annual performance difference of just 14%.
Actually, I don’t have to say more—you can read this yourselves. I’ve provided references for the search engines. Disprove the study with your own measurements or calculations, THEN we can continue the discussion.
W
WilderSueden23 Jul 2022 13:49The table does not show NAT, it says "Outdoor Air," meaning outside temperature. And the oil heating system is certainly designed for 55 degrees Celsius or higher, since a high supply temperature doesn’t cost anything in that case. For an average winter temperature of 7°C (45°F), I would like to see an example; even well-known mild winter locations like Konstanz stay significantly below that for three months.
D
Deliverer23 Jul 2022 15:05WilderSueden schrieb:
For an average temperature of 7 degrees during the winter, I would like an example, You are right, I expressed myself incorrectly: It refers to the average temperature during the heating period, not the meteorological winter.
During the heating season, the temperature here in Lower Saxony often ranges between 0 and 4°C (32 and 39°F) outdoor temperature (OT). I have a hydraulic balancing system, large radiators, and have lowered the supply temperature as much as possible. At +7°C (45°F) OT, I cannot achieve a supply temperature of 30°C (86°F). It’s more like 38°C (100°F). This is with 24cm (9.5 inches) of insulation in the upper floor ceiling, insulated windows, and some façade insulation.
At some point, reducing the supply temperature and radiator size simply hits a limit, as this significantly reduces heating output.
At some point, reducing the supply temperature and radiator size simply hits a limit, as this significantly reduces heating output.
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