ᐅ Achieving KfW 70 standard without solar panels? Alternative ways to meet KfW 70 requirements?
Created on: 24 Feb 2011 10:01
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DiinHello everyone,
As I mentioned in another thread, we are planning to build a KfW 70 house.
The current plan to achieve these standards includes:
- Insulation: 8 cm (3 inches) on the base, 14 cm (6 inches) in the walls, 24 cm (9.5 inches) in the roof
- Mechanical ventilation with heat recovery
- Underfloor heating
- Gas condensing boiler
- Plus solar thermal system
However, I now think that the solar thermal system is not very cost-effective at 4,300 EUR since it really only heats the water.
If we wanted heating support as well, it would cost 7,500 EUR and require over 9 square meters (97 square feet) of unattractive collectors on the roof.
… I don’t like any of that! And I also question its real benefit.
BUT when I asked the provider (who only performs an energy demand calculation during the architect consultation, after signing the contract :mad ), he just said that we need the solar system to meet the KfW 70 standard.
So my questions are:
- Isn’t it possible to achieve this by adding more insulation, shutters, triple glazing, or something else?
- I could also accept removing gas altogether, but geothermal is beyond our budget and I have no knowledge about air-to-water heat pumps…
Do you have any ideas how we could avoid solar thermal? The renewable energy in the mechanical ventilation system should already count, right?
Thanks so much for your help!
By the way… I’m also trying to get an appointment with the consumer advice center at the same time, which is not so easy.
As I mentioned in another thread, we are planning to build a KfW 70 house.
The current plan to achieve these standards includes:
- Insulation: 8 cm (3 inches) on the base, 14 cm (6 inches) in the walls, 24 cm (9.5 inches) in the roof
- Mechanical ventilation with heat recovery
- Underfloor heating
- Gas condensing boiler
- Plus solar thermal system
However, I now think that the solar thermal system is not very cost-effective at 4,300 EUR since it really only heats the water.
If we wanted heating support as well, it would cost 7,500 EUR and require over 9 square meters (97 square feet) of unattractive collectors on the roof.
… I don’t like any of that! And I also question its real benefit.
BUT when I asked the provider (who only performs an energy demand calculation during the architect consultation, after signing the contract :mad ), he just said that we need the solar system to meet the KfW 70 standard.
So my questions are:
- Isn’t it possible to achieve this by adding more insulation, shutters, triple glazing, or something else?
- I could also accept removing gas altogether, but geothermal is beyond our budget and I have no knowledge about air-to-water heat pumps…
Do you have any ideas how we could avoid solar thermal? The renewable energy in the mechanical ventilation system should already count, right?
Thanks so much for your help!
By the way… I’m also trying to get an appointment with the consumer advice center at the same time, which is not so easy.
Hmm, KfW 70 without triple glazing? (rare)
Shutters usually cause energy losses! (undamped boxes, etc.)
But with a heat pump, you can achieve KfW 70 without solar panels; you just need to calculate it. An air-to-water heat pump or ground-source heat pump with mats or trench collectors, including installation and underfloor heating, costs around €18,000–22,000 (for a single-family house of about 125m² (1,345 ft²)).
If you add up your gas heating with connection, chimney, radiators, chimney sweep, and solar panels, it won’t cost much less either.
If you build turnkey with a contractor, the mark-ups are usually quite high!
Shutters usually cause energy losses! (undamped boxes, etc.)
But with a heat pump, you can achieve KfW 70 without solar panels; you just need to calculate it. An air-to-water heat pump or ground-source heat pump with mats or trench collectors, including installation and underfloor heating, costs around €18,000–22,000 (for a single-family house of about 125m² (1,345 ft²)).
If you add up your gas heating with connection, chimney, radiators, chimney sweep, and solar panels, it won’t cost much less either.
If you build turnkey with a contractor, the mark-ups are usually quite high!
B
Bauexperte25 Feb 2011 10:14Hello,
As a rule, architectural services and the preparation of the offer up to the building contract are free of charge for interested parties; at least with reputable providers. It is different with energy efficiency calculations, as these usually require external expertise, which naturally costs money. Therefore, it is understandable that the provider does not want to take on these costs before having planning security. Would you invest in people if you were not sure that the paid service is not wasted?
However, you can ask your provider to commission the calculation (provided by the structural engineer) before signing the contract if you cover the costs; expenses are around €600.00 plus VAT - these costs will be credited in case of awarding the contract, provided the structural engineering is included in the fixed price.
With these questions, I seriously wonder what kind of salespeople you are dealing with.
You can waive solar on the condition that the building envelope is constructed to KfW 70 standard and you purchase either a ground source heat pump – whether borehole or surface – or an air-to-water heat pump as the energy source. In both systems, the heat pump also handles domestic hot water heating. A ventilation system is always worth considering for various reasons, mainly due to the high airtightness of modern houses; however, on its own, it is not sufficient to achieve the KfW 70 status.
Conventional option: the building envelope built to KfW 70 standard, gas condensing boiler with solar panels on the roof, and a ventilation system. In the latter case, your personal needs and financial budget determine the type of system.
One more note: lately, I have often noticed in the prefab house market that the KfW 70 rating is nicely calculated. Especially when a wall assembly with a very good U-value is emphasized, it is worth asking for the U-values of the other building components!
For various reasons, I think this is not a good idea given the options available; look for the nearest energy agency office in your area and arrange a consultation there. Alternatively, search online for a building services technician / energy consultant / engineer who really knows their subject.
Best regards
Diin schrieb:
BUT after asking the provider (who only does an energy demand calculation during the architect consultation, after signing the contract) he just said that we need the solar system to meet KfW 70.
As a rule, architectural services and the preparation of the offer up to the building contract are free of charge for interested parties; at least with reputable providers. It is different with energy efficiency calculations, as these usually require external expertise, which naturally costs money. Therefore, it is understandable that the provider does not want to take on these costs before having planning security. Would you invest in people if you were not sure that the paid service is not wasted?
However, you can ask your provider to commission the calculation (provided by the structural engineer) before signing the contract if you cover the costs; expenses are around €600.00 plus VAT - these costs will be credited in case of awarding the contract, provided the structural engineering is included in the fixed price.
Diin schrieb:
Do you have any ideas on how we can avoid solar? Renewable energy is already provided by the controlled ventilation system, right?
With these questions, I seriously wonder what kind of salespeople you are dealing with.
You can waive solar on the condition that the building envelope is constructed to KfW 70 standard and you purchase either a ground source heat pump – whether borehole or surface – or an air-to-water heat pump as the energy source. In both systems, the heat pump also handles domestic hot water heating. A ventilation system is always worth considering for various reasons, mainly due to the high airtightness of modern houses; however, on its own, it is not sufficient to achieve the KfW 70 status.
Conventional option: the building envelope built to KfW 70 standard, gas condensing boiler with solar panels on the roof, and a ventilation system. In the latter case, your personal needs and financial budget determine the type of system.
One more note: lately, I have often noticed in the prefab house market that the KfW 70 rating is nicely calculated. Especially when a wall assembly with a very good U-value is emphasized, it is worth asking for the U-values of the other building components!
Diin schrieb:
By the way ... I’m also trying to get an appointment with the consumer advice center, which is not so easy.
For various reasons, I think this is not a good idea given the options available; look for the nearest energy agency office in your area and arrange a consultation there. Alternatively, search online for a building services technician / energy consultant / engineer who really knows their subject.
Best regards
Diin schrieb:
.......I don’t like any of this! And I also question the actual benefit. That is entirely justified!
Diin schrieb:
....BUT when asked, the provider (who only performs an energy demand calculation during the architect consultation, after contract signing :mad) said we need the solar system to achieve KfW 70. Are you sure this is a suitable contractor????????????? Here, they want to sell a standard in-house solution, completely independent of what would actually make sense for the client!
I don’t always agree with Bauexperte, but when using a heat pump as a heat generator, massive internal walls and ceilings are always a clear advantage!
Regards
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