Hello everyone,
After getting in touch with about half a dozen home builders and having a clear idea of our project (i.e., wishes versus what is feasible), we have now narrowed it down to two builders. Both use different methods to achieve KfW70 energy efficiency standard.
We plan to build a single-family house with approximately 135 m² (1453 sq ft) of living space, including the basement.
Builder A (A* House):
This will be a timber frame construction. They rely on a gas condensing boiler + solar system + controlled ventilation (mechanical supply and exhaust ventilation). The recommendation here was to use gas with an underground gas tank as the solution (which would offer the advantage of being able to choose the supplier). Overall, the conversation seemed the most competent to me, at least judging by my limited knowledge.
Builder B (L* Solid Construction):
Although this is also a prefab manufacturer, they build solid construction (if that term can be used here). According to the representative we spoke with today, the Klimapor walls (which look like a rice cake) are built without membranes, so a mechanical ventilation system is not necessary. To meet the KfW70 standard, they would install an air-to-water heat pump.
In most other aspects, including pricing, both are quite similar. Now we are unsure how to proceed. Builder B told us today that omitting a ventilation system only has advantages. From what I have found so far in my research, the prevailing opinion is different. With a mechanical ventilation system, you supposedly cannot just open the windows whenever you want, or it would affect the costs and performance of the system or limit its purpose. On the other hand, you save on the gas connection costs. Also, since the walls don’t have membranes, the ventilation system would not be necessary anyway. This sounds somewhat... odd to me.
Now we are quite uncertain. We usually sleep with the window open (summer and winter). In the summer, we basically keep the balcony doors open all the time in the living room. We do not want to give that up.
What should we do? Are Builder B’s claims correct or nonsense? Has anyone had experience with this topic or with these builders?
We would be very grateful for any advice!
Best regards, Andi
After getting in touch with about half a dozen home builders and having a clear idea of our project (i.e., wishes versus what is feasible), we have now narrowed it down to two builders. Both use different methods to achieve KfW70 energy efficiency standard.
We plan to build a single-family house with approximately 135 m² (1453 sq ft) of living space, including the basement.
Builder A (A* House):
This will be a timber frame construction. They rely on a gas condensing boiler + solar system + controlled ventilation (mechanical supply and exhaust ventilation). The recommendation here was to use gas with an underground gas tank as the solution (which would offer the advantage of being able to choose the supplier). Overall, the conversation seemed the most competent to me, at least judging by my limited knowledge.
Builder B (L* Solid Construction):
Although this is also a prefab manufacturer, they build solid construction (if that term can be used here). According to the representative we spoke with today, the Klimapor walls (which look like a rice cake) are built without membranes, so a mechanical ventilation system is not necessary. To meet the KfW70 standard, they would install an air-to-water heat pump.
In most other aspects, including pricing, both are quite similar. Now we are unsure how to proceed. Builder B told us today that omitting a ventilation system only has advantages. From what I have found so far in my research, the prevailing opinion is different. With a mechanical ventilation system, you supposedly cannot just open the windows whenever you want, or it would affect the costs and performance of the system or limit its purpose. On the other hand, you save on the gas connection costs. Also, since the walls don’t have membranes, the ventilation system would not be necessary anyway. This sounds somewhat... odd to me.
Now we are quite uncertain. We usually sleep with the window open (summer and winter). In the summer, we basically keep the balcony doors open all the time in the living room. We do not want to give that up.
What should we do? Are Builder B’s claims correct or nonsense? Has anyone had experience with this topic or with these builders?
We would be very grateful for any advice!
Best regards, Andi
B
Bauexperte21 May 2012 00:23Hello,
Further in the building brochure: "The particularly airtight building envelope prevents unwanted heat loss. To ensure controlled fresh air supply, a mechanical ventilation system with heat recovery may be advisable in some cases."
So, which is correct: the salesperson’s statement or the information in the building brochure?
Kind regards
Brisch schrieb:You can already do this today with a "conventional" gas connection. In addition, you have plenty of space in the basement to accommodate the boiler along with all the necessary equipment. What logical reason would there be for you to spend extra money? Perhaps the only exception might be if there is no gas supply near your property and you would have to rely on liquefied petroleum gas.
Builder 1: ... Here, the recommendation was for gas with an "underground" gas tank as a solution (which would have the advantage of being able to choose the supplier)...
Brisch schrieb:Excerpt from the publicly available building brochure: "The solid exterior wall is basically 24 cm (10 inches) thick, made entirely of the solid and healthy natural building material xxx-clay, along with a 12 cm (5 inches) thick full thermal insulation." What exactly is the thermal insulation made of?
Builder B: .. According to the representative we spoke with today, the Klimapor walls (which look like a rice cake) are built without membranes, so a controlled ventilation system is not necessary...
Further in the building brochure: "The particularly airtight building envelope prevents unwanted heat loss. To ensure controlled fresh air supply, a mechanical ventilation system with heat recovery may be advisable in some cases."
So, which is correct: the salesperson’s statement or the information in the building brochure?
Kind regards
Hello,
Best regards
Brisch schrieb:Almost any kind of "creative accounting" seems to be allowed here ;-)
... Both use different methods to achieve KfW70.
Brisch schrieb:Liquid gas and then also solar thermal? That’s quite extreme ;-)
... This one relies on a gas condensing boiler + solar system + controlled ventilation. The recommendation included gas with an underground gas tank as a solution (which would have the advantage of being able to choose the supplier).
Brisch schrieb:Aha, so they think you can skip a blower door test? ;-) What salespeople sometimes come up with is often just disappointing!
... According to the representative we spoke to today, the Klimapor walls (they look like rice cakes) are built without membranes, so a controlled ventilation system is not necessary.
Brisch schrieb:Which one?
... But to reach KfW70, he would install an air-to-water heat pump.
Brisch schrieb:Yes, get an independent consultant and planner for heating, domestic hot water, and if needed, ventilation as soon as possible!
... We would be very grateful for any tips!!!
Best regards
Hello.
First of all, thank you for the feedback.
The solution with the buried tank actually came about because we would need to cover about 15 meters (50 feet) from the street to the house. But that was just a suggestion. I would actually prefer a direct connection.
Regarding B: Somehow, the seller's argumentation is starting to make me suspicious.
How is it generally with a KfW70 house like this? Is the statement true that with a ventilation system you can no longer open the windows, or that it doesn’t make sense, for example, to leave terrace doors open for a long time in summer? The decision between options A or B largely depends on the system.
I will still consult an independent advisor...
Reason as above. Whether gas is available at the property is still unclear (it is a subdivided part of a larger plot).
Um... good question...
I tend to believe the building brochure. Which makes me even more unsure.
What do you mean by solar thermal system? What do you mean by "quite a lot"?
See above.
Regards
Andi
First of all, thank you for the feedback.
The solution with the buried tank actually came about because we would need to cover about 15 meters (50 feet) from the street to the house. But that was just a suggestion. I would actually prefer a direct connection.
Regarding B: Somehow, the seller's argumentation is starting to make me suspicious.
How is it generally with a KfW70 house like this? Is the statement true that with a ventilation system you can no longer open the windows, or that it doesn’t make sense, for example, to leave terrace doors open for a long time in summer? The decision between options A or B largely depends on the system.
I will still consult an independent advisor...
Bauexperte schrieb:
Hello,
You can already do that today with a "conventional" gas connection. Also, you have plenty of space in the basement to accommodate the boiler along with all the necessary equipment. What logical reason would there be to spend extra money? The one exception might be that there is no gas supply in the area of your property and you would have to rely on liquid gas?
Reason as above. Whether gas is available at the property is still unclear (it is a subdivided part of a larger plot).
Bauexperte schrieb:
Excerpt from the freely available building brochure: "The solid exterior wall is generally 24 cm (9.5 inches) thick, made entirely from the solid and healthy natural building material xxx-clay, with a 12 cm (5 inches) thick full thermal insulation." What exactly is the thermal insulation made of?
Um... good question...
Bauexperte schrieb:
Furthermore in the building brochure: "The especially airtight building envelope prevents unwanted heat loss. To ensure controlled fresh air supply, a controlled ventilation system with heat recovery may be advisable."
What is true now, the seller’s statement or rather the information from the building brochure?
Best regards
I tend to believe the building brochure. Which makes me even more unsure.
€uro schrieb:
Hello,
Almost all doors are open to "creative accounting." Liquid gas and then also a solar thermal system? That’s quite a lot! ;-)
What do you mean by solar thermal system? What do you mean by "quite a lot"?
€uro schrieb:
Ah, so you can skip a blower door test? ;-) What sellers sometimes say is more than sad! Which ones? Yes, get an external consultant and planner for heating, domestic hot water, and ventilation as soon as possible!
Best regards
See above.
Regards
Andi
Brisch schrieb:
...Regarding point B: Somehow, the seller’s argument is starting to make me suspicious. That is definitely justified. Once you have signed, .... Caution is always the best approach ;-)Brisch schrieb:
..., is the claim true that with a ventilation system you can no longer open the windows, or that it makes no sense, for example, to leave patio doors open for a long time in the summer? That is nonsense. While it does create a temporary, i.e. briefly limited, undefined condition, it does not play a significant role overall.Brisch schrieb:
..I will still consult an independent advisor ... Feel free to send me an email if you need ;-)Brisch schrieb:
..Reason as above. It is still unclear if gas is connected to the property (it is a subdivided part of a larger plot) Natural gas does not require a tank! ;-)Solar thermal systems are often used together with gas condensing boilers to improve the paper balance.
Solar thermal systems are usually not economically viable in single-family homes with typical user behavior!
Best regards
T
Thomas46322 May 2012 17:15Regarding A):
Please ask what exactly the "mechanical ventilation with heat recovery" system is supposed to consist of. There is currently another thread where this is planned to be done only by ventilating through windows — I would advise against this.
Regarding B):
The wall usually consists of expanded polystyrene blocks reinforced with rebar and then filled with concrete. Although this method is quick and inexpensive, it is not really high quality.
Moreover, if you plan to install a heat pump, there still needs to be a circuit "in front of it." The heat pump is typically used only to boost an existing heat source (e.g., geothermal with a ground collector). Without this circuit, the heat pump is completely ineffective. And if you are already investing in a heat pump (which usually costs around 5,000–7,000 euros), you might as well consider the additional costs involved in building a low-energy house or even a classic passive house.
I would definitely recommend consulting a professional here, as also suggested by €uro.
Best regards,
Thomas
Please ask what exactly the "mechanical ventilation with heat recovery" system is supposed to consist of. There is currently another thread where this is planned to be done only by ventilating through windows — I would advise against this.
Regarding B):
The wall usually consists of expanded polystyrene blocks reinforced with rebar and then filled with concrete. Although this method is quick and inexpensive, it is not really high quality.
Moreover, if you plan to install a heat pump, there still needs to be a circuit "in front of it." The heat pump is typically used only to boost an existing heat source (e.g., geothermal with a ground collector). Without this circuit, the heat pump is completely ineffective. And if you are already investing in a heat pump (which usually costs around 5,000–7,000 euros), you might as well consider the additional costs involved in building a low-energy house or even a classic passive house.
I would definitely recommend consulting a professional here, as also suggested by €uro.
Best regards,
Thomas
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