ᐅ Prefabricated House Heating: Gas / Air Source Heat Pump / Underfloor Heating
Created on: 11 Sep 2015 01:45
G
Gatho
Hi!
We are currently planning a prefab house and are undecided between Bien-Zenker and Weberhaus. Both strongly promote the Proxon air-to-air heat pump. However, this option is no longer suitable for us. The more we research, the less convincing it seems.
We are now considering an air-to-water heat pump (with underfloor heating) combined with a mechanical ventilation system, or a gas condensing boiler system (also with underfloor heating), likewise combined with mechanical ventilation. Both options should allow for future preparation for a photovoltaic system, which can be installed later. Ground source heat pumps or pellet heating systems are unfortunately not an option due to the high initial investment costs.
The thermal insulation in prefab houses is generally quite good/high. For Bien-Zenker, we would build to KfW 70 standard, and for Weberhaus even to KfW 55.
We are unsure whether it is worth investing the extra cost in an air-to-water heat pump (e.g., LWZ 304 from Stiebel Eltron or THZ 304 from Tecalor), or if a well-established and proven gas condensing boiler might also be a good solution. What about the ongoing costs for maintenance and repairs?
The house will be built in Dortmund, will have no basement, and will have a living area of 130 to 140 m² (1400 to 1500 ft²).
At Weberhaus, the LWZ 304 (with underfloor heating) from Stiebel Eltron currently costs 8555 EUR (including mechanical ventilation) as a "special anniversary offer." We have not yet received an offer for a gas condensing boiler system—only for the air-to-air heat pump from Proxon, which we have already excluded. I have some concerns about the electricity costs in winter and the potential noise from the air-to-water heat pump. Of course, both gas and electricity prices are rising, but modern gas condensing boilers are also very efficient, and with a well-insulated prefab house, gas heating could be a cost-effective solution.
What would you recommend? Is there anything else we should consider? How significant are the maintenance costs in this comparison?
I would greatly appreciate any tips, suggestions, and opinions.
Best regards and thanks!
Gatho
We are currently planning a prefab house and are undecided between Bien-Zenker and Weberhaus. Both strongly promote the Proxon air-to-air heat pump. However, this option is no longer suitable for us. The more we research, the less convincing it seems.
We are now considering an air-to-water heat pump (with underfloor heating) combined with a mechanical ventilation system, or a gas condensing boiler system (also with underfloor heating), likewise combined with mechanical ventilation. Both options should allow for future preparation for a photovoltaic system, which can be installed later. Ground source heat pumps or pellet heating systems are unfortunately not an option due to the high initial investment costs.
The thermal insulation in prefab houses is generally quite good/high. For Bien-Zenker, we would build to KfW 70 standard, and for Weberhaus even to KfW 55.
We are unsure whether it is worth investing the extra cost in an air-to-water heat pump (e.g., LWZ 304 from Stiebel Eltron or THZ 304 from Tecalor), or if a well-established and proven gas condensing boiler might also be a good solution. What about the ongoing costs for maintenance and repairs?
The house will be built in Dortmund, will have no basement, and will have a living area of 130 to 140 m² (1400 to 1500 ft²).
At Weberhaus, the LWZ 304 (with underfloor heating) from Stiebel Eltron currently costs 8555 EUR (including mechanical ventilation) as a "special anniversary offer." We have not yet received an offer for a gas condensing boiler system—only for the air-to-air heat pump from Proxon, which we have already excluded. I have some concerns about the electricity costs in winter and the potential noise from the air-to-water heat pump. Of course, both gas and electricity prices are rising, but modern gas condensing boilers are also very efficient, and with a well-insulated prefab house, gas heating could be a cost-effective solution.
What would you recommend? Is there anything else we should consider? How significant are the maintenance costs in this comparison?
I would greatly appreciate any tips, suggestions, and opinions.
Best regards and thanks!
Gatho
B
Bauexperte11 Sep 2015 11:33Hello,
A user here recently posted their consumption values in euros regarding an air-to-water heat pump; if they read this—Doc, was that you perhaps?—hopefully, they will speak up again. Unfortunately, I’ve forgotten which member it was.
Best regards, Bauexperte
jx7 schrieb:I’m still waiting for users to share their experiences with ground-source heat pumps...
Geothermal energy is expensive, but firstly there is a €4,500 BAFA subsidy, and secondly you save on consumption later, even if the insulation is only standard.
jx7 schrieb:No; if you are referring to the gentleman below, in my opinion, he makes a mistake on his site by grouping air-to-water heat pumps under the general heading of air heat pumps. An air-to-water heat pump requires about 0.2% of the annual operating costs in pure electricity just for defrosting the fan in the outdoor unit.
For an air-to-water heat pump, I would use very good insulation because otherwise the heating consumes large amounts of expensive electricity.
A user here recently posted their consumption values in euros regarding an air-to-water heat pump; if they read this—Doc, was that you perhaps?—hopefully, they will speak up again. Unfortunately, I’ve forgotten which member it was.
jx7 schrieb:Nowadays, the strict requirement for a purely south-facing roof is being abandoned; a roof area oriented east-west also produces very good yields.
The benefit of a photovoltaic system, as far as I know, depends heavily on whether the roof has a nice south-facing orientation.
jx7 schrieb:I’ve already read that from you twice now. Isn’t that gentleman considered somewhat controversial in the energy sector, or am I confusing something?
A recommended website on the topic “heating comparison” is from the energy consultant Alois Zimmermann, where different heating systems are calculated based on a sample house.
Best regards, Bauexperte
Bauexperte schrieb:
I am always waiting for users to share their experiences with brine-to-water heat pumps ... I will be able to do that starting September 2016.
Bauexperte schrieb:
No; if you are referring to the gentleman mentioned below, in my opinion he makes a mistake on his site by grouping air-to-water heat pumps under the category of air source heat pumps. An air-to-water heat pump requires about 0.2% of the annual operating costs per year as pure electricity costs for defrosting the fan in the outdoor unit. Could you please explain that in more detail? I am interested.
Bauexperte schrieb:
Nowadays, people move away from the pure south-facing orientation as a requirement; roof surfaces oriented east-west can deliver very good yields. Okay, it may be true that very good yields can also be achieved with a west-east orientation, but yields are definitely significantly higher with a south-facing orientation, as it is physically logical that with a south orientation, where the angle between the sunlight and the collector remains closer to a right angle of 90 degrees, more radiation is received than with a west-east orientation, where the collectors are always at an angle and never perpendicular to the sunlight.
Bauexperte schrieb:
Isn’t this gentleman the enfant terrible of the energy sector, or am I confusing something here? I would also be interested in further information on this, preferably in a private message if you do not want to discuss it publicly.
I
Irgendwoabaier11 Sep 2015 12:37jx7 schrieb:
Okay, it may be true that very good yields are possible with an east-west orientation as well, but south-facing setups definitely provide significantly higher yields. This makes physical sense because when the angle between the sunlight and the collector is closer to a right angle of 90 degrees, as with a south-facing installation, more radiation is received compared to an east-west orientation, where the collectors are always at a more oblique angle and never perpendicular to the sunlight. Be careful – what matters is the total solar radiation received throughout the day. In that regard, east and west sides are not necessarily that bad, especially on steeper roofs. Then there is the question of when most energy is needed, which can be affected by how well it can be stored.
B
Bauexperte11 Sep 2015 12:52jx7 schrieb:
I can do that starting in September 2016. That would be great!
jx7 schrieb:
Could you explain that in more detail? I’m interested. Argh – this is what I get for not being a technician... very basic, as much as I can manage as a layperson; okay?
It’s generally agreed that the air-to-water heat pump system is comparable to a reverse refrigerator principle, right?
After the air heated by this reversed principle – using an evaporator and refrigerant – has done its job, it is expelled again to the outside. Since the outside air is directly passed through the evaporator of the air-to-water heat pump, condensation occurs and the resulting water has to be drained away. If it is cold outside, the condensed moisture can cause the evaporator to freeze. Defrosting requires about 0.2% of the annual electricity operating costs.
For a pure air-to-air heat pump, simply put, cold air is warmed using the internal room heat. At low outside temperatures, this logically doesn’t work well – how do you expect to warm 5°C (41°F) cold outside air with, for example, 21°C (70°F) warm indoor air? Therefore, additional electric heating is necessary, and this system is recommended only for houses built to an energy efficiency standard of 40 or better; i.e., single-family homes with minimal heat demand. In such cases, it operates effectively, especially when combined with a photovoltaic system.
Unfortunately, all these systems tend to be grouped under the term “air heat pump,” which leads to confusion and a lack of clear differentiation. I’m sure many homeowners have installed an air-to-water heat pump as their heat source; they would probably be able to give you more detailed feedback than I can, as I rely exclusively on reports from our customers about their consumption. So far, the consensus is that for a household of four people with normal shower usage and a house size of about 150 m² (1,615 sq ft), annual costs for hot water and heating range between approximately €600.00 and €800.00.
jx7 schrieb:
...south-facing locations definitely achieve significantly higher yields, since it makes physical sense that for a south orientation, where the angle between solar radiation and collector is closer to a right angle of 90 degrees, more radiation is received... You probably know this much better than I do; the fact remains that only about a quarter of all available plots are oriented strictly south.
jx7 schrieb:
I would also be interested in more information on this, preferably by private message if you prefer not to share it publicly. There’s no secret here that would require a private message.
If I remember again, I will gladly let you know. At the moment, I only have a vague memory that this person – if it is that gentleman – is not well regarded in the energy consulting industry because he apparently promotes conspiracy theories about intentional misinformation concerning fuel cells.
Regards, Bauexperte
D
Doc.Schnaggls11 Sep 2015 13:08Hello,
that’s right, we installed a Tecalor THZ (equivalent to Stiebel Eltron) in our Weberhaus, but specifically the 403 SOL model.
We chose the 403 model because our heated area is slightly larger. This system also allows for solar collectors to be connected for domestic hot water production. We had the necessary piping installed from the utility room up to the attic, although so far no collectors have been connected.
You don’t need to worry at all about the noise from the air-to-water heat pump. Ours is located in the basement utility room behind a standard interior door. When that door is closed, the heat pump is no longer audible in the ground floor or in the adjacent guest room, even though the stairwell is open.
The electricity costs are moderate—the electric backup heater has only been used once, on the day the heating system was started at -22°C (-8°F). However, it switched off again after less than an hour and has not been used since.
We also installed a 4.25 kWp photovoltaic system on the roof right from the start. On our best day so far, this system generated 32.4 kWh. Currently, the grid operator credits us around EUR 36.00 per month for excess energy fed back to the grid, but we expect this to increase after the first annual billing.
If you have the option, I would recommend investing around EUR 10,000.00 in a photovoltaic system during construction. As for battery storage, in my personal opinion, I would wait a bit longer, as prices will most likely become more affordable.
We are more than satisfied with our air-to-water heat pump.
Best regards,
Dirk
that’s right, we installed a Tecalor THZ (equivalent to Stiebel Eltron) in our Weberhaus, but specifically the 403 SOL model.
We chose the 403 model because our heated area is slightly larger. This system also allows for solar collectors to be connected for domestic hot water production. We had the necessary piping installed from the utility room up to the attic, although so far no collectors have been connected.
You don’t need to worry at all about the noise from the air-to-water heat pump. Ours is located in the basement utility room behind a standard interior door. When that door is closed, the heat pump is no longer audible in the ground floor or in the adjacent guest room, even though the stairwell is open.
The electricity costs are moderate—the electric backup heater has only been used once, on the day the heating system was started at -22°C (-8°F). However, it switched off again after less than an hour and has not been used since.
We also installed a 4.25 kWp photovoltaic system on the roof right from the start. On our best day so far, this system generated 32.4 kWh. Currently, the grid operator credits us around EUR 36.00 per month for excess energy fed back to the grid, but we expect this to increase after the first annual billing.
If you have the option, I would recommend investing around EUR 10,000.00 in a photovoltaic system during construction. As for battery storage, in my personal opinion, I would wait a bit longer, as prices will most likely become more affordable.
We are more than satisfied with our air-to-water heat pump.
Best regards,
Dirk
Hi!
First of all, thank you for all the responses!
@Wastl
Which air-to-water heat pump system do you have installed in your house? How loud is it? Since we don’t have a basement, the air-to-water heat pump would be placed in the utility room, and I’m still a bit unsure how much noise from the heating system can be heard in the adjoining rooms.
@SirSydom
You’re right, a gas boiler does mean additional costs for the gas connection and a chimney… and solar panels also have to go on the roof, otherwise you won’t meet the requirements.
@Computersyvlia
Thanks, I’ll contact DocSchnagels.
EDIT: Oh, he already replied at the same time – thanks!
Best regards
Gatho
First of all, thank you for all the responses!
@Wastl
Which air-to-water heat pump system do you have installed in your house? How loud is it? Since we don’t have a basement, the air-to-water heat pump would be placed in the utility room, and I’m still a bit unsure how much noise from the heating system can be heard in the adjoining rooms.
@SirSydom
You’re right, a gas boiler does mean additional costs for the gas connection and a chimney… and solar panels also have to go on the roof, otherwise you won’t meet the requirements.
@Computersyvlia
Thanks, I’ll contact DocSchnagels.
EDIT: Oh, he already replied at the same time – thanks!
Best regards
Gatho
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