Hello everyone,
we are planning to build a single-family house with the following specifications:
- one and a half stories
- on a slab foundation
- approximately 125 sqm (1350 sq ft)
- 36cm (14 inches) Ytong blocks (without additional insulation)
- mineral-based exterior plaster
- KfW 70 energy standard
- triple-glazed windows
- heating: gas/solar; underfloor heating throughout the entire house
Regarding a ventilation system, we are unsure about which option would be the most suitable.
Our options are:
- no ventilation system (our builder believes it is not necessary)
- decentralized ventilation system
- decentralized ventilation system with heat recovery
- centralized ventilation system with heat recovery
We have already read a lot on online forums, and the more we read, the more confused and uncertain we become...
Thank you very much in advance for your support!
we are planning to build a single-family house with the following specifications:
- one and a half stories
- on a slab foundation
- approximately 125 sqm (1350 sq ft)
- 36cm (14 inches) Ytong blocks (without additional insulation)
- mineral-based exterior plaster
- KfW 70 energy standard
- triple-glazed windows
- heating: gas/solar; underfloor heating throughout the entire house
Regarding a ventilation system, we are unsure about which option would be the most suitable.
Our options are:
- no ventilation system (our builder believes it is not necessary)
- decentralized ventilation system
- decentralized ventilation system with heat recovery
- centralized ventilation system with heat recovery
We have already read a lot on online forums, and the more we read, the more confused and uncertain we become...
Thank you very much in advance for your support!
B
brokenlink27 Aug 2013 22:26I don’t believe you can achieve KfW 70 standard with gas/solar using 36cm (14 inch) Ytong blocks. I don’t understand why anyone would build with Ytong at all. Are the interior walls at least made of calcium silicate blocks? Before you build your house, take a look at houses built with Ytong blocks; the walls tell the story.
Let me guess—you want to build with TuT, right? With 36cm (14 inch) Ytong, you can barely meet the 2009 Energy Saving Ordinance, and reaching KfW 70 with gas/solar is simply not possible unless you use a heat pump.
Using a controlled residential ventilation system makes it possible, but calculations are necessary. So before you sign, make sure the contract clearly states that you are buying a KfW 70 house, and not something else. By the way, KfW 70 does not say anything about insulation quality.
If you choose a controlled ventilation system with heat recovery, it should be a central system only. Controlled ventilation will never pay for itself but is a nice luxury because you don’t have to ventilate manually anymore. Decentralized ventilation makes sense only if you want it in just one room, for example, a bathroom or utility room, but installing it in every room is not practical.
I would recommend focusing more on insulation and less on technical systems. How about just a gas heating system without solar and instead invest more in insulation under the floor slab, thicker walls, and so on?
Let me guess—you want to build with TuT, right? With 36cm (14 inch) Ytong, you can barely meet the 2009 Energy Saving Ordinance, and reaching KfW 70 with gas/solar is simply not possible unless you use a heat pump.
Using a controlled residential ventilation system makes it possible, but calculations are necessary. So before you sign, make sure the contract clearly states that you are buying a KfW 70 house, and not something else. By the way, KfW 70 does not say anything about insulation quality.
If you choose a controlled ventilation system with heat recovery, it should be a central system only. Controlled ventilation will never pay for itself but is a nice luxury because you don’t have to ventilate manually anymore. Decentralized ventilation makes sense only if you want it in just one room, for example, a bathroom or utility room, but installing it in every room is not practical.
I would recommend focusing more on insulation and less on technical systems. How about just a gas heating system without solar and instead invest more in insulation under the floor slab, thicker walls, and so on?
Hi,
we have just received the documents for the KfW 70 application. We are building with 36.5 cm (14.4 inches) Ytong blocks. They are prefabricated as full-story elements at the factory and delivered in sections about 1.8 m (6 feet) wide. This design eliminates horizontal joints as thermal bridges in the wall.
Combined with a gas condensing boiler, solar panels for domestic hot water, and an insulated ground slab, we are confident to easily meet the KfW 70 standard for our 100 m² (1,076 ft²) bungalow.
What could be worse with a neatly plastered Ytong wall compared to other walls with polystyrene insulation on the outside?
we have just received the documents for the KfW 70 application. We are building with 36.5 cm (14.4 inches) Ytong blocks. They are prefabricated as full-story elements at the factory and delivered in sections about 1.8 m (6 feet) wide. This design eliminates horizontal joints as thermal bridges in the wall.
Combined with a gas condensing boiler, solar panels for domestic hot water, and an insulated ground slab, we are confident to easily meet the KfW 70 standard for our 100 m² (1,076 ft²) bungalow.
What could be worse with a neatly plastered Ytong wall compared to other walls with polystyrene insulation on the outside?
Hello,
For an economic assessment, the Energy Saving Ordinance/KfW certification is completely unsuitable because it requires knowledge of the actual demand (capacity, energy) for heating and hot water under the specific conditions of the individual building project.
What is directly relevant for a homeowner is not theoretical primary energy under standardized boundary conditions (assessment procedures) but the actual energy consumption considering the particularities of the individual building project.
Anyone who is satisfied with just a "best case calculation" should verify afterwards, for example by measuring the actual yield of the solar thermal system with a heat meter. Then consider what the additional investment was really worth!
A monolithic wall construction is a compromise between competing requirements. For a DIY builder, this may be a viable approach since different priorities apply here.
In a contract build, one should be less willing to accept compromises. Although all functional requirements may be met overall, the details often look less favorable: (load-bearing capacity (thickness of the structural envelope), point load transfer and distribution, sound insulation, thermal insulation in relation to insulation thickness, summer heat protection, etc.).
In other words: it somehow works, but it is not optimal!
Best regards.
Explosiv schrieb:However, this results in continuous butt joints.
... Prefabricated as full-height elements in the factory and delivered as approximately 1.8 m (6 feet) wide panels. This eliminates horizontal joints as thermal bridges in the wall. ...
Explosiv schrieb:
... Combined with gas condensing boilers, solar thermal for domestic hot water, and insulated ground slabs, we easily meet KFW 70 standards for our 100 m² (1,076 sq ft) bungalow. ...
For an economic assessment, the Energy Saving Ordinance/KfW certification is completely unsuitable because it requires knowledge of the actual demand (capacity, energy) for heating and hot water under the specific conditions of the individual building project.
What is directly relevant for a homeowner is not theoretical primary energy under standardized boundary conditions (assessment procedures) but the actual energy consumption considering the particularities of the individual building project.
Anyone who is satisfied with just a "best case calculation" should verify afterwards, for example by measuring the actual yield of the solar thermal system with a heat meter. Then consider what the additional investment was really worth!
Explosiv schrieb:There are not only this manufacturer for aerated concrete but also significantly cheaper ones.
... What worse outcome can be expected from a neatly plastered Ytong wall than from other walls with polystyrene insulation on them?
A monolithic wall construction is a compromise between competing requirements. For a DIY builder, this may be a viable approach since different priorities apply here.
In a contract build, one should be less willing to accept compromises. Although all functional requirements may be met overall, the details often look less favorable: (load-bearing capacity (thickness of the structural envelope), point load transfer and distribution, sound insulation, thermal insulation in relation to insulation thickness, summer heat protection, etc.).
In other words: it somehow works, but it is not optimal!
Best regards.
Hi
There are certainly construction joints, approximately every 1.8 meters (6 feet). Is that more joint than with conventional bricks? Probably not.
Whether the solar system will be cost-effective in practice remains to be seen. However, for the KfW assessment, several specific details of the building project are likely important. The assessor only started work after the exact location and orientation of the house, as well as the position and size of windows and roof surfaces, were finalized. It is clear that the standardized calculations do not accurately reflect reality, but they are necessary for applying for a subsidized loan.
In my opinion, the potential disadvantages of aerated concrete do not outweigh those of a wall clad with polystyrene. With a single-story construction, load transfer through the wall is not necessarily an issue. Thermal insulation relative to the insulation thickness is only one factor if space is limited.
Of course, there are specialized building materials for every aspect, but how many layers do you really want to build into your exterior walls? Load-bearing layer, thermal insulation layer, soundproofing layer, weatherproofing layer?
There are certainly construction joints, approximately every 1.8 meters (6 feet). Is that more joint than with conventional bricks? Probably not.
Whether the solar system will be cost-effective in practice remains to be seen. However, for the KfW assessment, several specific details of the building project are likely important. The assessor only started work after the exact location and orientation of the house, as well as the position and size of windows and roof surfaces, were finalized. It is clear that the standardized calculations do not accurately reflect reality, but they are necessary for applying for a subsidized loan.
In my opinion, the potential disadvantages of aerated concrete do not outweigh those of a wall clad with polystyrene. With a single-story construction, load transfer through the wall is not necessarily an issue. Thermal insulation relative to the insulation thickness is only one factor if space is limited.
Of course, there are specialized building materials for every aspect, but how many layers do you really want to build into your exterior walls? Load-bearing layer, thermal insulation layer, soundproofing layer, weatherproofing layer?
Explosiv schrieb:
...In my opinion, the potential disadvantages of aerated concrete do not outweigh those of a wall clad with polystyrene.... If, for whatever reason, you don’t like this insulation material, there are alternatives! Explosiv schrieb:
....Sure, there are specialized building materials for every aspect, but how many layers do you really want to build your exterior walls from? Structural layer, thermal insulation layer, soundproofing layer, weather protection layer? Ideally: three!Best regards.
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