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
I agree with this argument:
The other argument
I doubt that. I would claim: the steeper a roof is, the more important a south-facing orientation becomes.
A photovoltaic calculator online showed in a sample calculation that for a 25° roof, a west-east roof receives 14% less solar radiation compared to a south-facing roof, and for a 38° roof, a west-east roof receives 24% less solar radiation compared to a south-facing roof.
Irgendwoabaier schrieb:
The question then is, when is most of the energy generated here needed? How well can it be stored?
The other argument
Irgendwoabaier schrieb:
Careful – what matters is the total solar radiation over the day. East and west sides are not so bad, especially with steeper roofs.
I doubt that. I would claim: the steeper a roof is, the more important a south-facing orientation becomes.
A photovoltaic calculator online showed in a sample calculation that for a 25° roof, a west-east roof receives 14% less solar radiation compared to a south-facing roof, and for a 38° roof, a west-east roof receives 24% less solar radiation compared to a south-facing roof.
Bauexperte schrieb:
The fact is that only one quarter of all available plots have a purely southern orientation.Purely northern orientations work as well, just use the other side of the roof...
(At least when we’re talking about a gable roof...)
There are also intermediate variations, for example, southwest or northeast orientation of the two roof sides.
I still believe that a south/north orientation of the two roof sides is best, and west/east orientation is the least favorable. Whether it’s still profitable in the end, I cannot assess, and it probably depends on the individual case.
To my knowledge, larger solar systems used for heating support sometimes have the panels installed at a steeper angle and on the west side. The reason is that during the heating season, the sun is lower in the sky, while in summer, the small amount of hot water needed can easily be produced with the steeper panels.
I am not sure if this approach makes similar sense for photovoltaic systems.
I am not sure if this approach makes similar sense for photovoltaic systems.
Bauexperte schrieb:
In my opinion, he makes a mistake on his website by grouping the air-to-water heat pump under the category of air-source heat pumps.Mr. Zimmermann does distinguish on his website between air-to-water heat pumps and air-to-air heat pumps, but he uses unusual terms for them: air-source heat pump and ventilation heat pump. The air-to-air heat pump is portrayed even less favorably than the air-to-water heat pump, although the sample house used is a KFW-100 house. For passive houses or KfW-40 houses, air-to-air heat pumps can definitely be a very cost-effective solution.
There are indeed some odd posts on his site, but his example calculations are unique on the internet and seem quite reasonable, even though it’s clear that changing the conditions (living area, basement yes/no, insulation, climate zone, different contractor pricing, assumptions about future increases in electricity, gas prices, etc.) can easily lead to different results.
However, by studying the tables, it is possible to get a rough idea of the approximate costs of the various systems and the relationship between operating costs and investment costs.
Musketier schrieb:
To my knowledge, larger solar thermal systems for heating support sometimes have the panels installed at steeper angles and facing west. The reasoning is that during heating periods the sun is lower in the sky, while in summer the small amount of hot water needed can easily be generated with the steeper panels.
Whether this makes similar sense for photovoltaic systems, I don’t know.Yes, for solar thermal systems, a west/east orientation can be beneficial because people typically shower in the mornings and evenings. Steeper roof pitches are advantageous then since the sun is low on the horizon during those times. The system works best when the panels are perpendicular to the sun’s rays.
For photovoltaic panels, where electricity is generated and fed into the grid throughout the day, a south-facing orientation is better. In our latitudes, a roof pitch of about 30 degrees is optimal, but the performance does not decline significantly if the angle is 20 or 40 degrees.
I
Irgendwoabaier11 Sep 2015 14:13jx7 schrieb:
For photovoltaic systems that generate and feed electricity into the grid throughout the day, a south-facing orientation is better. In our latitude, a roof pitch of 30 degrees is optimal for this, but the difference isn’t much worse if the pitch is 20 or 40 degrees. With the addition: ‘when feeding electricity into the grid’ – you then have to calculate when and how much is fed in, and what the overall balance looks like over the year. This mainly depends on individual consumption patterns. Only when a large part of the energy is stored for personal use can you generalize again and consider the 30° south-facing orientation as the best possible alignment.
But that leads somewhat off-topic.
Air-to-water heat pump / geothermal energy (borehole or surface system?) / gas is always a location-dependent question.
For us: the plot is too small for surface geothermal, boreholes aren’t permitted (would not be approved), and the distance to the nearest gas line is about 35m (115 feet). All this is in the mildest region of Bavaria... Therefore, the air-to-water heat pump was the more economical solution. Photovoltaics would be possible (30° south orientation), but currently not cost-effective due to a low share of self-consumption.
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