ᐅ Which type of heating system is recommended for a KfW 55 energy-efficient house?
Created on: 28 Aug 2011 21:12
A
amazingbee
Hello! We are currently planning a house and, since this is not something you do often, we have many questions. Due to the development plan for our plot, we are required to build a KfW 55 energy efficiency house and are now unsure about what type of heating system we need. Builders have given us different advice!
Is it possible to install a standard gas condensing boiler combined with solar water heating, or do we have to use geothermal or air-source heat pumps?
I would appreciate any answers!
Is it possible to install a standard gas condensing boiler combined with solar water heating, or do we have to use geothermal or air-source heat pumps?
I would appreciate any answers!
Ah, okay, great. They drilled at our place on Thursday, and the application was submitted then. Our plumbing contact filled out the application with the details of the planned heating system. It is planned as such and will be listed in the contract with the main contractor, but we haven’t actually "purchased" the heat pump yet; in theory, we could still change the heating system. I’m not quite sure if this means we are eligible for the subsidy or not (since we have technically "purchased" the heating system already at a fixed price with the main contractor).
If I have understood the BAFA requirements correctly, then no, because you awarded the contract for the installation of the heating system with your signature at the construction supervisor, and the application must be submitted before the contract is awarded.
If the contract is awarded separately at a later date, the situation is different...
If the contract is awarded separately at a later date, the situation is different...
I have already asked myself the original question.
In a general contractor’s (GC) quote, the house would be equipped with a gas condensing boiler plus decentralized ventilation (according to the GC’s personal statement, this only applies to the large living area on the ground floor: kitchen, dining room, living room).
To achieve KfW55 standard, we would have the following options:
a) Ventilation system with heat recovery for all rooms – €7,900
b) Air-to-water heat pump, manufacturer Rotex – €4,800
c) Brine-to-water heat pump with ground collectors – €12,500
d) Brine-to-water heat pump with deep boreholes – €19,300
e) Stiebel/Tecalor air-to-water heat pump with ventilation system and heat recovery – €12,400
f) Pellet heating system, manufacturer Wodke vivotec – price on request
g) Hybrid heating system – price on request
From this, I understand that the insulation is already sufficient. I also understand that the prices apply to the basement level (half cellar, half living space due to the sloped site; according to the quote, the cellar is also part of the heated building envelope).
Another GC offered me a controlled mechanical ventilation system with an air-to-water heat pump for an additional €19,000 and was quite surprised that the other GC could offer the same for €12,400. Both offer the Stiebel LWZ 404 model.
However, the final price from the second GC is better; I suspect the first GC included the surcharge for the basement in the shell construction mixed calculation. Very odd, but irrelevant to the main topic.
In summary, KfW55 can be achieved with gas if controlled ventilation is added. The decentralized ventilation as offered does not seem to suffice, probably because it’s not planned for all rooms.
The air-to-water heat pump LWZ 404 has a seasonal performance factor (SPF) of about 3.45, so no BAFA subsidy applies. I could not find the seasonal performance factor for the gas boiler.
From an acquisition cost perspective, here are the options compared to the offered gas system and decentralized ventilation:
1) Controlled mechanical ventilation for €7,900
- Additional gas connection fee from the municipality (€2,500) and chimney sweep costs (20 x €100 = €2,000)
- If the gas boiler achieves an SPF of 1.5, you can get €4,500 back from BAFA
- Immediate bonus from the KfW bank = €5,000
- Interest advantage over 25 years compared to bank interest rates of 1.51% approx. €5,000; at 1.71% approx. €10,000 (I calculated this myself in an Excel amortization plan)
2) Controlled mechanical ventilation and air-to-water heat pump for €12,400
- Gas connection and BAFA subsidy no longer apply
- Same KfW benefits as above
3) Decentralized ventilation and air-to-water heat pump for €4,800
- Same as option 2)
- €3,000 cheaper than gas and lower consumption, but no controlled mechanical ventilation system
The air-to-water heat pump therefore seems to cost about €4,500 more than the gas boiler. It would have to recover this cost through lower operating costs within 20 years. According to co2online:
“As a rule of thumb: the seasonal performance factor must be greater than the electricity price divided by the natural gas or heating oil price, each per kilowatt-hour (kWh).”
With multiple warnings, including here in the forum, that seasonal performance factors are rarely fully achieved (similar to fuel consumption ratings for cars), and assuming current electricity and gas prices of 25 cents and 5 cents per kWh respectively, the air-to-water heat pump would need a seasonal performance factor of at least 5, realistically more like 6 when factoring in some optimism. For the LWZ 404 mentioned above, I would expect closer to 3.
Given these concerns, and assuming the gas boiler easily achieves an SPF of 1.5, I am currently leaning toward gas but against the air-to-water heat pump. However, I am in favor of controlled mechanical ventilation.
If I have any misunderstandings, please feel free to correct or enlighten me.
I understand this is just one GC’s offer — a quick Google search suggests these prices are not entirely unrealistic. I also expect an additional charge for controlled ventilation with regards to the basement, but I don’t think that affects the gas versus air-to-water heat pump comparison.
In a general contractor’s (GC) quote, the house would be equipped with a gas condensing boiler plus decentralized ventilation (according to the GC’s personal statement, this only applies to the large living area on the ground floor: kitchen, dining room, living room).
To achieve KfW55 standard, we would have the following options:
a) Ventilation system with heat recovery for all rooms – €7,900
b) Air-to-water heat pump, manufacturer Rotex – €4,800
c) Brine-to-water heat pump with ground collectors – €12,500
d) Brine-to-water heat pump with deep boreholes – €19,300
e) Stiebel/Tecalor air-to-water heat pump with ventilation system and heat recovery – €12,400
f) Pellet heating system, manufacturer Wodke vivotec – price on request
g) Hybrid heating system – price on request
From this, I understand that the insulation is already sufficient. I also understand that the prices apply to the basement level (half cellar, half living space due to the sloped site; according to the quote, the cellar is also part of the heated building envelope).
Another GC offered me a controlled mechanical ventilation system with an air-to-water heat pump for an additional €19,000 and was quite surprised that the other GC could offer the same for €12,400. Both offer the Stiebel LWZ 404 model.
However, the final price from the second GC is better; I suspect the first GC included the surcharge for the basement in the shell construction mixed calculation. Very odd, but irrelevant to the main topic.
In summary, KfW55 can be achieved with gas if controlled ventilation is added. The decentralized ventilation as offered does not seem to suffice, probably because it’s not planned for all rooms.
The air-to-water heat pump LWZ 404 has a seasonal performance factor (SPF) of about 3.45, so no BAFA subsidy applies. I could not find the seasonal performance factor for the gas boiler.
From an acquisition cost perspective, here are the options compared to the offered gas system and decentralized ventilation:
1) Controlled mechanical ventilation for €7,900
- Additional gas connection fee from the municipality (€2,500) and chimney sweep costs (20 x €100 = €2,000)
- If the gas boiler achieves an SPF of 1.5, you can get €4,500 back from BAFA
- Immediate bonus from the KfW bank = €5,000
- Interest advantage over 25 years compared to bank interest rates of 1.51% approx. €5,000; at 1.71% approx. €10,000 (I calculated this myself in an Excel amortization plan)
2) Controlled mechanical ventilation and air-to-water heat pump for €12,400
- Gas connection and BAFA subsidy no longer apply
- Same KfW benefits as above
3) Decentralized ventilation and air-to-water heat pump for €4,800
- Same as option 2)
- €3,000 cheaper than gas and lower consumption, but no controlled mechanical ventilation system
The air-to-water heat pump therefore seems to cost about €4,500 more than the gas boiler. It would have to recover this cost through lower operating costs within 20 years. According to co2online:
“As a rule of thumb: the seasonal performance factor must be greater than the electricity price divided by the natural gas or heating oil price, each per kilowatt-hour (kWh).”
With multiple warnings, including here in the forum, that seasonal performance factors are rarely fully achieved (similar to fuel consumption ratings for cars), and assuming current electricity and gas prices of 25 cents and 5 cents per kWh respectively, the air-to-water heat pump would need a seasonal performance factor of at least 5, realistically more like 6 when factoring in some optimism. For the LWZ 404 mentioned above, I would expect closer to 3.
Given these concerns, and assuming the gas boiler easily achieves an SPF of 1.5, I am currently leaning toward gas but against the air-to-water heat pump. However, I am in favor of controlled mechanical ventilation.
If I have any misunderstandings, please feel free to correct or enlighten me.
I understand this is just one GC’s offer — a quick Google search suggests these prices are not entirely unrealistic. I also expect an additional charge for controlled ventilation with regards to the basement, but I don’t think that affects the gas versus air-to-water heat pump comparison.
G
Goldi091117 Sep 2016 21:08You probably mean a gas heat pump and not a gas condensing boiler.
Anything else would be new to me.
And with a gas condensing boiler and controlled mechanical ventilation, you don’t automatically achieve KFW 55 standard!
Anything else would be new to me.
And with a gas condensing boiler and controlled mechanical ventilation, you don’t automatically achieve KFW 55 standard!
If the general contractor (GC) includes a gas condensing boiler as standard, then the air-to-water heat pump comes at an extra cost, and if the air-to-water heat pump is standard, then the gas condensing boiler costs extra. Even if it is the same GC and last year the gas condensing boiler was standard and this year it is the air-to-water heat pump...
Actually, the air-to-water heat pump shouldn’t cost more than the gas condensing boiler plus solar, ideally it should be less. But the GC sets the prices...
(Solar was included, it always is – or isn’t it?)
Actually, the air-to-water heat pump shouldn’t cost more than the gas condensing boiler plus solar, ideally it should be less. But the GC sets the prices...
(Solar was included, it always is – or isn’t it?)
I visited the energy consultation today and also followed up with the general contractor. Additionally, I went directly to a construction company.
Yes, it is a gas condensing boiler plus solar, not a gas heat pump.
In summary, here are my notes:
Notes from the construction company:
Costs for a gas heating system (underfloor heating, domestic hot water tank, burner, and solar thermal) approx. 15,000€
Alternatively, pellet heating 16,000€ (without solar)
Alternatively, air-to-water heat pump 22,000€ (without solar, integrated domestic hot water tank)
This means the air-to-water heat pump costs about 7,000€ more.
Notes from general contractor A:
Gas condensing boiler including solar (included in the quote)
Air-to-water heat pump surcharge 4,900€ (Rotex) or 5,900€ (Stiebel Eltron)
Mechanical ventilation surcharge: 7,900€ (basement, ground floor, and top floor)
Mechanical ventilation + air-to-water heat pump surcharge 12,400€ (combined unit LWZ, ventilation in basement, ground floor, and top floor)
Notes from general contractor B:
Gas condensing boiler including solar (included in the quote)
Mechanical ventilation + air-to-water heat pump surcharge 19,000€ (combined unit LWZ, ventilation in basement, ground floor, and top floor)
(overall cheaper than A)
Notes from the consumer advice center’s energy consultation:
Electricity in the heat pump tariff is three times as expensive as gas (15 cents vs. 5 cents).
Assuming an annual performance factor of three, an air-to-water heat pump requires only one-third of the energy.
Overall, gas and air-to-water heat pumps have roughly the same consumption.
Heat pumps cost at least 5,000€ extra.
Gas connection costs about 2,500€.
KfW55 (energy efficiency standard) is also possible with a gas condensing boiler plus solar.
How much the annual performance factor of air-to-water heat pumps is overstated, e.g., only measured at +2°C (36°F), is very difficult to assess and can only be speculated.
Also unclear to me is how much additional energy a preheating coil consumes at subzero temperatures.
According to the consultant, the good annual performance factor of air-to-water heat pumps and others is mainly because the electricity is theoretically generated from renewable energies. He believes the government will likely reverse this in the coming years. Industry associations are reportedly already calling for modifications or reversals. I have not verified these statements.
Notes based on other forums and a simple Google search regarding various users’ consumption:
- Annual heating costs for air-to-water heat pump approx. 750€ - 1,200€
- Heating costs for gas approx. 200-500€ higher per year
- Over 10 years (best before), maximum savings around 2,000-5,000€
- So far, no real winters have occurred where the disadvantages of an air-to-water heat pump become apparent; last such winter was probably 2010
- With an extra cost of at least 5,000€ for the air-to-water heat pump, it only becomes cost-effective over a longer period
My current personal opinion:
An air-to-water heat pump does not currently make sense.
However, this depends on the final cost of the gas connection.
In the end, the process will probably be:
- Plan the house without heating (initially considering gas)
- Have a heating load calculation carried out
- Obtain concrete offers for specific heating systems and final costs
- Sleep on it for a night
- If there is no clear opinion in favor of the air-to-water heat pump, stick with gas
Yes, it is a gas condensing boiler plus solar, not a gas heat pump.
In summary, here are my notes:
Notes from the construction company:
Costs for a gas heating system (underfloor heating, domestic hot water tank, burner, and solar thermal) approx. 15,000€
Alternatively, pellet heating 16,000€ (without solar)
Alternatively, air-to-water heat pump 22,000€ (without solar, integrated domestic hot water tank)
This means the air-to-water heat pump costs about 7,000€ more.
Notes from general contractor A:
Gas condensing boiler including solar (included in the quote)
Air-to-water heat pump surcharge 4,900€ (Rotex) or 5,900€ (Stiebel Eltron)
Mechanical ventilation surcharge: 7,900€ (basement, ground floor, and top floor)
Mechanical ventilation + air-to-water heat pump surcharge 12,400€ (combined unit LWZ, ventilation in basement, ground floor, and top floor)
Notes from general contractor B:
Gas condensing boiler including solar (included in the quote)
Mechanical ventilation + air-to-water heat pump surcharge 19,000€ (combined unit LWZ, ventilation in basement, ground floor, and top floor)
(overall cheaper than A)
Notes from the consumer advice center’s energy consultation:
Electricity in the heat pump tariff is three times as expensive as gas (15 cents vs. 5 cents).
Assuming an annual performance factor of three, an air-to-water heat pump requires only one-third of the energy.
Overall, gas and air-to-water heat pumps have roughly the same consumption.
Heat pumps cost at least 5,000€ extra.
Gas connection costs about 2,500€.
KfW55 (energy efficiency standard) is also possible with a gas condensing boiler plus solar.
How much the annual performance factor of air-to-water heat pumps is overstated, e.g., only measured at +2°C (36°F), is very difficult to assess and can only be speculated.
Also unclear to me is how much additional energy a preheating coil consumes at subzero temperatures.
According to the consultant, the good annual performance factor of air-to-water heat pumps and others is mainly because the electricity is theoretically generated from renewable energies. He believes the government will likely reverse this in the coming years. Industry associations are reportedly already calling for modifications or reversals. I have not verified these statements.
Notes based on other forums and a simple Google search regarding various users’ consumption:
- Annual heating costs for air-to-water heat pump approx. 750€ - 1,200€
- Heating costs for gas approx. 200-500€ higher per year
- Over 10 years (best before), maximum savings around 2,000-5,000€
- So far, no real winters have occurred where the disadvantages of an air-to-water heat pump become apparent; last such winter was probably 2010
- With an extra cost of at least 5,000€ for the air-to-water heat pump, it only becomes cost-effective over a longer period
My current personal opinion:
An air-to-water heat pump does not currently make sense.
However, this depends on the final cost of the gas connection.
In the end, the process will probably be:
- Plan the house without heating (initially considering gas)
- Have a heating load calculation carried out
- Obtain concrete offers for specific heating systems and final costs
- Sleep on it for a night
- If there is no clear opinion in favor of the air-to-water heat pump, stick with gas
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