ᐅ Basement and Wall Construction in New Builds – Experiences
Created on: 14 Feb 2012 12:02
B
Bauender1977
Hello everyone,
I have been reading this forum for a long time since we decided to build a single-family house with an architect. During our initial research phase, many questions arose that resolved themselves through extensive reading. However, there are still some questions left open. I would like to post them here and get your opinions/comments. If this is posted in the wrong forum, please feel free to move it.
- Basement topic:
Since the groundwater on our plot begins at a depth of about 3 meters (10 feet), and considering that the open-pit mine in our region (VIE) had to end groundwater lowering measures sometime around 2016, we need to build a basement with a "white tank" (watertight concrete). According to a quote, a roughly 100 m² (1,076 sq ft) insulated (KFW 55) waterproof prefabricated basement costs about €50,000 plus excavation costs around €20,000. If I want to create several additional rooms (including windows, insulation, and underfloor heating) on the ground floor and/or upper floor, I roughly calculate that I could get about 40 m² (430 sq ft) for the same price, assuming a cost of about €1,400 per m². Could that be correct, or have I missed something in my calculation?
Building plot: 15 m wide x 24 m long (49 ft x 79 ft)
Building envelope: 9 m wide x 15 m long (30 ft x 49 ft)
- Wall construction topic:
As I have read here and elsewhere, there is no perfect solution for wall construction. It depends on many factors. Since we will be building near a railway line (up to 60 dB during the day), we have decided on a calcium silicate block wall construction with a central mechanical ventilation with heat recovery system. Since we want to heat relatively little, we do not want a thin standard wall but rather a bit more insulation. How much more expensive is it to install 240 mm (9.5 inches) of mineral wool insulation instead of 160 mm (6.3 inches) on the house?
Wall construction:
1.5 cm (0.6 inches) gypsum plaster
17.5 or 24 cm (7 or 9.5 inches) calcium silicate blocks (bulk density class 1.2)
24 cm (9.5 inches) mineral wool insulation, thermal conductivity 0.032 W/(m·K)
1.5 cm (0.6 inches) cement plaster
Thank you very much in advance for your answers.
Best regards,
Sebastian
I have been reading this forum for a long time since we decided to build a single-family house with an architect. During our initial research phase, many questions arose that resolved themselves through extensive reading. However, there are still some questions left open. I would like to post them here and get your opinions/comments. If this is posted in the wrong forum, please feel free to move it.
- Basement topic:
Since the groundwater on our plot begins at a depth of about 3 meters (10 feet), and considering that the open-pit mine in our region (VIE) had to end groundwater lowering measures sometime around 2016, we need to build a basement with a "white tank" (watertight concrete). According to a quote, a roughly 100 m² (1,076 sq ft) insulated (KFW 55) waterproof prefabricated basement costs about €50,000 plus excavation costs around €20,000. If I want to create several additional rooms (including windows, insulation, and underfloor heating) on the ground floor and/or upper floor, I roughly calculate that I could get about 40 m² (430 sq ft) for the same price, assuming a cost of about €1,400 per m². Could that be correct, or have I missed something in my calculation?
Building plot: 15 m wide x 24 m long (49 ft x 79 ft)
Building envelope: 9 m wide x 15 m long (30 ft x 49 ft)
- Wall construction topic:
As I have read here and elsewhere, there is no perfect solution for wall construction. It depends on many factors. Since we will be building near a railway line (up to 60 dB during the day), we have decided on a calcium silicate block wall construction with a central mechanical ventilation with heat recovery system. Since we want to heat relatively little, we do not want a thin standard wall but rather a bit more insulation. How much more expensive is it to install 240 mm (9.5 inches) of mineral wool insulation instead of 160 mm (6.3 inches) on the house?
Wall construction:
1.5 cm (0.6 inches) gypsum plaster
17.5 or 24 cm (7 or 9.5 inches) calcium silicate blocks (bulk density class 1.2)
24 cm (9.5 inches) mineral wool insulation, thermal conductivity 0.032 W/(m·K)
1.5 cm (0.6 inches) cement plaster
Thank you very much in advance for your answers.
Best regards,
Sebastian
B
Bauender197716 Feb 2012 10:42Hello Building Expert,
God forbid. We had contact once with an architect from Oberhausen. In the first conversation, we were openly told that the construction supervision would be handled by a local architect. And we did not want that.
We assume we will build with an architect from Erkelenz. It is important to us that the architect/site manager and the workers come from the local area.
Ideally, yes, but especially with the salespeople in the model homes, I see little interest or competence in discussing this topic. And that was always the case during our house tours. When we said we wanted to build a well-insulated house, every single one immediately focused on the euros.
You are referring here to an air heat pump; is there a reason for that?
It is neither cheaper to purchase nor in terms of additional costs than a gas boiler. And especially an air heat pump has significant disadvantages compared to a ground-source heat pump during cold winters. Also, you need to be able to dissipate excess heat from the solar collectors, and if you improve the seasonal performance factor this way, that is more than acceptable.
When I roughly calculated the life cycle costs for a ground-source heat pump over 15 years, I came to 50% higher costs. Even with photovoltaics, a heat pump does not pay off economically, even with 100% self-consumption (assuming a home battery, which currently costs a fortune). In my opinion, the purchase price, maintenance, and interest currently make heat pumps (regardless of type) economically unreasonable.
Unfortunately, with large providers, you explicitly have to ask for this! Not to mention that many providers even leave out roller shutters with the basic house.
This topic sparks debate in every forum. Everyone either tries to stay out of it or strongly defends their opinion against everyone and everything.
At present, we intend to build monolithically with aerated concrete or T7 blocks. That way, it is easier to improve insulation later if necessary. All synthetic insulation materials are off our house.
Best regards
Sebastian
Bauexperte schrieb:
Pure curiosity; you live and build in my sales area. Recently, I have often come across architects from the Bergisches Land region and further towards Siegerland in similar situations, and I have always wondered what motivates homeowners to hire architects whose offices are so far away from the construction site.
God forbid. We had contact once with an architect from Oberhausen. In the first conversation, we were openly told that the construction supervision would be handled by a local architect. And we did not want that.
We assume we will build with an architect from Erkelenz. It is important to us that the architect/site manager and the workers come from the local area.
Bauexperte schrieb:
As a layperson, you don’t need to "prove" that – a good salesperson will explain this to you on their own without being asked.
Ideally, yes, but especially with the salespeople in the model homes, I see little interest or competence in discussing this topic. And that was always the case during our house tours. When we said we wanted to build a well-insulated house, every single one immediately focused on the euros.
Bauexperte schrieb:
You can expect that if all planners involved in the new build do their job properly, at a KfW 70 efficiency house (equipped with air-to-water heat pump and controlled residential ventilation), you will have operating costs of €600–800 for heating and hot water, depending on shower habits. A KfW 55 efficiency house should theoretically require about €500, while a true passive house is only allowed to consume 15% of its energy externally! Now you can easily calculate for yourself if and when the extra effort for a solidly built KfW 55 or even a passive house pays off.
You are referring here to an air heat pump; is there a reason for that?
It is neither cheaper to purchase nor in terms of additional costs than a gas boiler. And especially an air heat pump has significant disadvantages compared to a ground-source heat pump during cold winters. Also, you need to be able to dissipate excess heat from the solar collectors, and if you improve the seasonal performance factor this way, that is more than acceptable.
When I roughly calculated the life cycle costs for a ground-source heat pump over 15 years, I came to 50% higher costs. Even with photovoltaics, a heat pump does not pay off economically, even with 100% self-consumption (assuming a home battery, which currently costs a fortune). In my opinion, the purchase price, maintenance, and interest currently make heat pumps (regardless of type) economically unreasonable.
Bauexperte schrieb:
This is not a luxury; underfloor heating is now standard, and controlled residential ventilation is, in my opinion, an indispensable must-have!
Unfortunately, with large providers, you explicitly have to ask for this! Not to mention that many providers even leave out roller shutters with the basic house.
Bauexperte schrieb:
Oh – that is a "Jehovah topic," and I will not recommend anything here. Every material has its pros and cons; if you ask our contractors, two will praise hollow bricks, two calcium silicate bricks, two lightweight concrete, and two aerated concrete, and so on. If you ask here in the forum, most will promote the advantages of external thermal insulation composite systems (ETICS) – even within my family, my partner and I discuss the meaningfulness of ETICS. I don’t like this stuff at all because I wouldn’t want to live inside a plastic foil; I might as well sell prefab homes, and for various reasons, that is not my thing.
This topic sparks debate in every forum. Everyone either tries to stay out of it or strongly defends their opinion against everyone and everything.
At present, we intend to build monolithically with aerated concrete or T7 blocks. That way, it is easier to improve insulation later if necessary. All synthetic insulation materials are off our house.
Best regards
Sebastian
B
Bauexperte16 Feb 2012 11:50Hello Sebastian,
That makes sense; nice coincidence: our architect, whom we have worked with for many years, also has an office in Erkelenz.
I myself have spent some time in W'tal and Hückelhoven in show homes and know what you mean. I was often surprised at the behavior of the so-called "colleagues." On the other hand, I have to add fairly that many of the potential clients did not deserve better treatment. Today I am more convinced than ever that people of similar character always find each other...
No, it is roughly EUR 4,000–6,000 more expensive, depending on house size and homeowner habits. But you must not overlook that you save the gas connection; you will hardly ever get an air-to-water heat pump for such a reasonable price again.
When I write about air-to-water heat pumps, I mean strictly the pure air-to-water heat pump; possibly a combined unit including mechanical ventilation with heat recovery; a solar thermal system is not necessary, apart from the fact that in my opinion, these panels are only suitable for calculating KfW 70 standard. If you need hot water, this kind of system doesn’t really work.
Air-to-water heat pump
Heat sources can include, for example, outside air (unlimited availability), heat recovery from exhaust air or waste heat, as well as absorber systems (e.g., energy fences).
The installation effort for an air-source heat pump is limited (e.g., foundations, earthworks, air ducts). When selecting the installation location, noise and condensate development must be particularly considered.
Air-to-water heat pumps are predominantly operated as monoenergetic systems for heating residential buildings. The heat pump should cover the heating demand fully down to an outdoor temperature of about –5°C (23°F) (bivalence point). Only at lower temperatures or increased heating demand is an electrically powered heat generator activated. The average annual outdoor temperature at the installation site strongly affects the economic efficiency of an air-to-water heat pump and must be considered during planning.
Correct sizing of the heat pump capacity is essential, as it influences both investment costs and annual heating expenses.
In older buildings or heating system renovations, bivalent operation—parallel running with a second heat source, for example, an oil or gas boiler—is possible. In continuous bivalent operation, the heat pump can be designed smaller; however, later decommissioning of the second heat generator can cause problems.
It is also possible to combine an air-to-water heat pump with a ground-source or water-source heat pump. Most often, this is done to provide domestic hot water.
How a heat pump works
The energy transfer in heat pumps occurs as a thermodynamic cycle. The working fluid is especially important, as it changes state (liquid/gaseous) at low temperatures by absorbing or releasing heat energy. The closed cycle in a compression heat pump is as follows:
In the evaporator, the cold liquid working fluid absorbs energy from the ambient heat source and evaporates.
The compressor compresses the gaseous working fluid, consuming mechanical or electrical energy, heating it to so-called hot gas.
The hot gas releases its thermal energy to the heating system in the condenser and condenses into warm liquid working fluid.
The warm liquid working fluid expands at the expansion valve, causing its temperature to drop abruptly. The cycle then repeats in the evaporator.
Is the heat pump just a disguised electric heater?
Every heating system depends on electricity. When the power fails, oil boilers and gas boilers stop working too. The heat pump uses electricity to drive the compressor, which makes the environmental heat usable. However, the electricity powering the compressor, brine or groundwater pump, or fans to circulate the heat source circuits accounts for only about one-quarter of the heat produced in efficient heat pumps with a seasonal performance factor of 4.0. Moreover, the electricity becomes increasingly cleaner thanks to the use of renewable energy sources. Even today, the environmental footprint of heat pumps is significantly better than conventional heat generators.
How much does a heat pump cost?
Electricity costs depend on the system’s seasonal performance factor. Field tests have shown that the seasonal performance factor of properly installed ground-source systems is around 4, while air-to-water heat pumps typically range between 3.0 and 3.3.
Once these numbers are known, calculating costs is straightforward: assume a heating demand of 15,000 kWh for a new single-family home. For a ground-source heat pump (seasonal performance factor 4.0), you would purchase 15,000/4 = 3,750 kWh of electricity; for an air-source heat pump (seasonal performance factor 3.0), 15,000/3 = 5,000 kWh of electricity. Multiply the calculated kWh by your electricity rate (approximately 12 cents per kWh) to find a difference in electricity costs of about EUR 150 per year. Similarly, you can compare heat consumption and oil or gas prices to calculate how much more expensive fossil fuel demand would be annually.
Source: Bundesverband Wärmepumpe eV, my website
As I already wrote: there is no "good" or "bad." If you followed my suggestion, you should know that now; therefore, there “can” only be opposing viewpoints.
Yep. My very personal recommendation (purely subjective and unofficial) – only build with Poroton if you always have rapid-setting cement in the house.
Best regards
Bauender1977 schrieb:
We assume we will be building with an architect from Erkelenz. It is important to us that the architect / site manager and the workers come from the local area.
That makes sense; nice coincidence: our architect, whom we have worked with for many years, also has an office in Erkelenz.
Bauender1977 schrieb:
Ideally, you shouldn’t have to, but especially with the salespeople in the show homes, I see little willingness or competence to discuss this topic. And that was always the case during our tour of the various houses. When it was said that we wanted to build a well-insulated house, every single one had dollar signs in their eyes.
I myself have spent some time in W'tal and Hückelhoven in show homes and know what you mean. I was often surprised at the behavior of the so-called "colleagues." On the other hand, I have to add fairly that many of the potential clients did not deserve better treatment. Today I am more convinced than ever that people of similar character always find each other...
Bauender1977 schrieb:
You’re referring to an air-source heat pump here, is there a specific reason? It is neither cheaper to purchase nor in running costs compared to a gas boiler.
No, it is roughly EUR 4,000–6,000 more expensive, depending on house size and homeowner habits. But you must not overlook that you save the gas connection; you will hardly ever get an air-to-water heat pump for such a reasonable price again.
Bauender1977 schrieb:
And especially an air-source heat pump has significant disadvantages compared to a ground-source heat pump in these cold winters. Also, you need to be able to dissipate excess heat from the solar collectors, and if that improves the seasonal performance factor considerably, that is more than acceptable.
When I write about air-to-water heat pumps, I mean strictly the pure air-to-water heat pump; possibly a combined unit including mechanical ventilation with heat recovery; a solar thermal system is not necessary, apart from the fact that in my opinion, these panels are only suitable for calculating KfW 70 standard. If you need hot water, this kind of system doesn’t really work.
Bauender1977 schrieb:
… Especially the purchase cost, maintenance, and interest make heat pumps (regardless of type) economically unviable in my opinion at present...
Air-to-water heat pump
Heat sources can include, for example, outside air (unlimited availability), heat recovery from exhaust air or waste heat, as well as absorber systems (e.g., energy fences).
The installation effort for an air-source heat pump is limited (e.g., foundations, earthworks, air ducts). When selecting the installation location, noise and condensate development must be particularly considered.
Air-to-water heat pumps are predominantly operated as monoenergetic systems for heating residential buildings. The heat pump should cover the heating demand fully down to an outdoor temperature of about –5°C (23°F) (bivalence point). Only at lower temperatures or increased heating demand is an electrically powered heat generator activated. The average annual outdoor temperature at the installation site strongly affects the economic efficiency of an air-to-water heat pump and must be considered during planning.
Correct sizing of the heat pump capacity is essential, as it influences both investment costs and annual heating expenses.
In older buildings or heating system renovations, bivalent operation—parallel running with a second heat source, for example, an oil or gas boiler—is possible. In continuous bivalent operation, the heat pump can be designed smaller; however, later decommissioning of the second heat generator can cause problems.
It is also possible to combine an air-to-water heat pump with a ground-source or water-source heat pump. Most often, this is done to provide domestic hot water.
How a heat pump works
The energy transfer in heat pumps occurs as a thermodynamic cycle. The working fluid is especially important, as it changes state (liquid/gaseous) at low temperatures by absorbing or releasing heat energy. The closed cycle in a compression heat pump is as follows:
In the evaporator, the cold liquid working fluid absorbs energy from the ambient heat source and evaporates.
The compressor compresses the gaseous working fluid, consuming mechanical or electrical energy, heating it to so-called hot gas.
The hot gas releases its thermal energy to the heating system in the condenser and condenses into warm liquid working fluid.
The warm liquid working fluid expands at the expansion valve, causing its temperature to drop abruptly. The cycle then repeats in the evaporator.
Is the heat pump just a disguised electric heater?
Every heating system depends on electricity. When the power fails, oil boilers and gas boilers stop working too. The heat pump uses electricity to drive the compressor, which makes the environmental heat usable. However, the electricity powering the compressor, brine or groundwater pump, or fans to circulate the heat source circuits accounts for only about one-quarter of the heat produced in efficient heat pumps with a seasonal performance factor of 4.0. Moreover, the electricity becomes increasingly cleaner thanks to the use of renewable energy sources. Even today, the environmental footprint of heat pumps is significantly better than conventional heat generators.
How much does a heat pump cost?
Electricity costs depend on the system’s seasonal performance factor. Field tests have shown that the seasonal performance factor of properly installed ground-source systems is around 4, while air-to-water heat pumps typically range between 3.0 and 3.3.
Once these numbers are known, calculating costs is straightforward: assume a heating demand of 15,000 kWh for a new single-family home. For a ground-source heat pump (seasonal performance factor 4.0), you would purchase 15,000/4 = 3,750 kWh of electricity; for an air-source heat pump (seasonal performance factor 3.0), 15,000/3 = 5,000 kWh of electricity. Multiply the calculated kWh by your electricity rate (approximately 12 cents per kWh) to find a difference in electricity costs of about EUR 150 per year. Similarly, you can compare heat consumption and oil or gas prices to calculate how much more expensive fossil fuel demand would be annually.
Source: Bundesverband Wärmepumpe eV, my website
Bauender1977 schrieb:
This topic is a discussion point in every forum. Everyone either tries to stay out of it or defend their opinion against everyone and everything.
As I already wrote: there is no "good" or "bad." If you followed my suggestion, you should know that now; therefore, there “can” only be opposing viewpoints.
Bauender1977 schrieb:
Currently, we plan to build monolithically with aerated concrete or T7. This way, it is easier to improve the insulation later if necessary. We want nothing synthetic as insulation materials in our house.
Yep. My very personal recommendation (purely subjective and unofficial) – only build with Poroton if you always have rapid-setting cement in the house.
Best regards
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