Hello,
We are starting to get really frustrated... every builder tells us something different...
We want to build a 130sqm (1,399 sq ft) KfW 70 house with the living room facing south, and we are unsure whether to choose gas or an air source heat pump. Some providers, at almost the same price level, offer us air source heat pumps and claim that the annual costs are significantly (30%) lower compared to gas, while others doubt this.
We understand that insulation with gas/solar systems is usually better because an air source heat pump boosts efficiency more towards KfW 70 standards compared to gas/solar, which might argue in favor of gas. An air source heat pump might fail somewhat sooner, and in case of problems, you can usually get quick and competent local support with gas. With air source heat pumps, there could be more difficulties. Additionally, the noise of air source heat pumps (in our case about 3 meters (10 feet) from the neighbor) is not insignificant. Some say that sooner or later, everyone ends up having issues with neighbors for this reason.
We are interested in air source heat pumps with storage tanks from these providers: Vaillant, Mitsubishi Zubadan, and Rotex.
What we are really curious about is the annual cost for heating and hot water with both systems.
We live near Kassel.
What should we choose, and what would be cost-effective TODAY? What is your opinion on Vaillant?
Regards
Gigi
We are starting to get really frustrated... every builder tells us something different...
We want to build a 130sqm (1,399 sq ft) KfW 70 house with the living room facing south, and we are unsure whether to choose gas or an air source heat pump. Some providers, at almost the same price level, offer us air source heat pumps and claim that the annual costs are significantly (30%) lower compared to gas, while others doubt this.
We understand that insulation with gas/solar systems is usually better because an air source heat pump boosts efficiency more towards KfW 70 standards compared to gas/solar, which might argue in favor of gas. An air source heat pump might fail somewhat sooner, and in case of problems, you can usually get quick and competent local support with gas. With air source heat pumps, there could be more difficulties. Additionally, the noise of air source heat pumps (in our case about 3 meters (10 feet) from the neighbor) is not insignificant. Some say that sooner or later, everyone ends up having issues with neighbors for this reason.
We are interested in air source heat pumps with storage tanks from these providers: Vaillant, Mitsubishi Zubadan, and Rotex.
What we are really curious about is the annual cost for heating and hot water with both systems.
We live near Kassel.
What should we choose, and what would be cost-effective TODAY? What is your opinion on Vaillant?
Regards
Gigi
This was the case here. Before construction started, I received this along with the structural engineering documents. I also remember the requirement to comply with the energy saving regulations when submitting the building permit / planning permission application.
However, we did not make any changes at all to the detailed construction plans created after the building permit was issued. No windows were moved, no walls altered.
And I’m very glad we proceeded this way. Because in this neighborhood, there are at least two individuals who immediately report any alleged irregularity or supposed violation of the development plan to the building authority, resulting in work stoppages. No chance for us.
Since we are talking about a solar system Hotzenplotz here, I’d like to add that it does matter to me whether this system complies with the rules or not. It costs money. I have to use it, but it’s not free. So I want it to do what it is supposed to do, namely provide hot water. As much as possible. I’ll say it again: since mid-March, our solar system, which faces south-southwest and is tilted at 30cm (12 inches), has been able to supply almost all our hot water requirements on its own, the daylight is sufficient. It manages this until mid-September—so about half a year. Even in January, on clear days, it supplied hot water.
Why not angle the roof by 15 degrees to improve performance? So that it works effectively! The argument about storms is nonsense. Then the builder should attend some training on how to securely fasten things on a roof to withstand storms. It’s possible. Karsten
However, we did not make any changes at all to the detailed construction plans created after the building permit was issued. No windows were moved, no walls altered.
And I’m very glad we proceeded this way. Because in this neighborhood, there are at least two individuals who immediately report any alleged irregularity or supposed violation of the development plan to the building authority, resulting in work stoppages. No chance for us.
Since we are talking about a solar system Hotzenplotz here, I’d like to add that it does matter to me whether this system complies with the rules or not. It costs money. I have to use it, but it’s not free. So I want it to do what it is supposed to do, namely provide hot water. As much as possible. I’ll say it again: since mid-March, our solar system, which faces south-southwest and is tilted at 30cm (12 inches), has been able to supply almost all our hot water requirements on its own, the daylight is sufficient. It manages this until mid-September—so about half a year. Even in January, on clear days, it supplied hot water.
Why not angle the roof by 15 degrees to improve performance? So that it works effectively! The argument about storms is nonsense. Then the builder should attend some training on how to securely fasten things on a roof to withstand storms. It’s possible. Karsten
R
R.Hotzenplotz30 Mar 2018 22:15Nordlys schrieb:
Why not angle the 15-degree roof a bit?Because it looks bad. In that case, we would rather choose a brine heat pump. Building a 15° roof and then angling the solar collectors more steeply cannot be an aesthetic solution.
Since it’s just about a 100 kWh difference per year (15 or 30°), I didn’t care.
Results from the Junkers solar simulator:
15° tilt:
Collector: 6.65 + 6.65 m² Junkers VK230-1
Characteristic curve: eta0 = 0.745 a1 = 2.007 W/(m²·K) a2 = 0.0050 W/(m²·K²)
Tilt: 15.0/15.0° South deviation: -45.0/45.0°
System type: Domestic hot water
Storage tank: SK 300-5 solar (290 liters (77 gallons))
Temperature: Max. 85°C (185°F)
Min. 52°C (126°F)
Heat demand: 15.70 kWh/day = 300 liters/day (79 gallons) from 10°C (50°F) to 55°C (131°F)
Month | Solar yield | Radiation | External energy | Coverage rate | Efficiency
[kWh] | [kWh] | [kWh] | [%] | [%]
January: 123 | 382 | 374 | 25 | 32
February: 201 | 610 | 270 | 43 | 33
March: 397 | 1274 | 113 | 78 | 31
April: 449 | 1668 | 48 | 90 | 27
May: 490 | 2218 | 28 | 95 | 22
June: 473 | 2158 | 28 | 95 | 22
July: 504 | 2447 | 12 | 98 | 21
August: 499 | 2210 | 11 | 97 | 23
September: 441 | 1418 | 56 | 89 | 31
October: 328 | 942 | 171 | 65 | 35
November: 151 | 433 | 330 | 31 | 35
December: 84 | 258 | 394 | 17 | 32
Total: 4139 | 16018 | 1834 | 69 | 26
Specific collector annual yield: 311 kWh/m²
30° tilt:
Area: 6.65 + 6.65 m² Junkers VK230-1
Tilt: 30.0/30.0° South deviation: -45.0/45.0°
System type: Domestic hot water
Heat demand: 15.70 kWh/day = 300 liters/day (79 gallons) from 10°C (50°F) to 55°C (131°F)
Conventional energy: Natural gas condensing boiler
Efficiency: 103% / 85% / 70% during operation in winter / spring, autumn / summer
Month | Solar yield | Energy saving | CO2 saving
[kWh] | [kWh] | [m³ gas] | [kg]
January: 146 | 141 | 0 | 0
February: 225 | 219 | 0 | 0
March: 406 | 444 | 0 | 0
April: 448 | 527 | 0 | 0
May: 488 | 587 | 0 | 0
June: 471 | 673 | 0 | 0
July: 503 | 719 | 0 | 0
August: 498 | 712 | 0 | 0
September: 445 | 552 | 0 | 0
October: 356 | 419 | 0 | 0
November: 177 | 196 | 0 | 0
December:101 | 98 | 0 | 0
Total: 4264 | 5285 | 1 | 2
In this simple setup, adjusting from 15 degrees to 30 degrees provides about 100 kWh more solar yield with 10 collectors—5 on each side.
Independent of the economically negligible difference, it is absolutely important to me that everything complies with legal regulations.
Nordlys schrieb:
And I’m really glad I proceeded that way. Because here in the neighborhood there are at least two people who immediately report any supposed irregularity or alleged breach of the zoning plan to the building authority, getting construction stops enforced. No chance with us. I can only agree with that. Better to invest a bit more money and obtain a building permit instead of relying on permit exemptions. For the reasons mentioned. The same happened on the neighboring property, but that was a justified case. He thought he could build however he wanted and that setback requirements, parking regulations, etc., were just recommendations. One call to the building authority in September and an immediate construction stop followed. Since then, the construction site has been idle. If he had applied for a building permit, at least he wouldn’t have started building and now be stuck financing a half-finished construction...
Solar panels would not be an option for us at 7°C (45°F), and mounting them raised on a pitched roof looks, in my opinion, like something forced and poorly done. The experts then place racks on the facade [emoji849]. Either mount them raised on a flat roof (which I would find aesthetically acceptable), or as Karsten does, on the roof surface itself (which would be my preference), or with a low-pitched roof consider something without solar thermal…
R.Hotzenplotz schrieb:
Because that looks terrible. We would rather choose a ground-source heat pump. Building a roof with a 15° (15°) pitch and then mounting solar collectors at a steeper angle can’t be the aesthetic solution.Good man [emoji1303][emoji4]
R
R.Hotzenplotz30 Mar 2018 22:32Nordlys schrieb:
So? Will it be calculated?The general planner has now proposed it this way and is asking for confirmation. Previously, the contracted installer assured me after our phone call that angling is not an option. Therefore, I assume everything is fine.
I can request the thermal insulation verification and inform them that I want to review it before I commit to a specific heating system.
Nordlys schrieb:
Okay, convinced. Angling hardly makes any difference.Neither 300 kWh nor 400 kWh really helps. It’s just a joke. It’s only done to make it look good. The yield will be even lower since the initially planned 10 m² (108 sq ft) of collectors is now reduced to three elements because more don’t fit due to the chimney. The 10 m² were four collectors.
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