Basement and wall in new construction - experiences

Hello Building Expert,

Pure curiosity; you live and build in my sales area. Recently, I have frequently encountered architects from the Bergisches and further towards Siegerland in similar constellations, and I have always wondered what motivates builders to commission architects who run their offices so far from the construction site.

God forbid. Although we once had contact with an architect from Oberhausen. In the first conversation, however, we were told openly that the construction supervision would be taken over by a local architect. And that we did not want.
We assume that we will build with an architect from Erkelenz. It is important to us that the architect/construction manager and the workers come from the area.

You don't have to “prove” that as a layman either – a good salesman will explain that to you on his own and without being asked.

Actually, one shouldn’t have to, but especially with the salespeople in the model houses, I see little willingness or competence to discuss this topic. And that was always the case on our tour through the various houses. When you said you wanted to build a well-insulated house, absolutely everyone only saw the money in their eyes.

You can assume – if all planners involved in the new construction project do their job right, that you will have operating costs of € 6-800.00 for heating and hot water in a KfW 70 efficiency house (equipped with an air-to-water heat pump and controlled residential ventilation); depending on shower habits. In my opinion, a KfW 55 efficiency house would require about € 500.00, whereas a true passive house may only consume 15% of external energy! Now you can easily calculate for yourself whether and when the extra effort for a solidly constructed KfW 55 or even passive house pays off.

You are specifically referring to an air heat pump here, is there a reason for that?
It is not cheaper in terms of acquisition and ancillary costs than a gas boiler. And an air heat pump in particular has significant disadvantages compared to a ground-source heat pump in these cold winters. Besides, you have to be able to dissipate the excess heat from the solar collectors, and if you can significantly improve the annual performance factor in this way, that is more than fine.
When I roughly calculated the LCC for a ground-source heat pump, I ended up with 50% higher costs over a 15-year period. Even with photovoltaics, a heat pump does not pay off, even with 100% self-consumption (assuming a home battery, which currently costs a fortune). In my opinion, the purchase costs, maintenance, and interest currently make a heat pump (regardless of which one) economically unviable.

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 have to explicitly ask for this! Not to mention that many providers even omit the shutters in the basic house model.

Oh – that is a “Jehovah topic,” and I will be damned if I give a recommendation here. Every material has pros and cons alike; if you ask our builders, two will praise the hollow brick, two the KS (calcium silicate), two lightweight concrete, and two aerated concrete, etc. If you ask here in the forum, the majority will extol the virtues of an ETICS – even within the family, my partner and I debate the sensibility of an ETICS. I don’t like that stuff at all because I wouldn’t want to live in a plastic foil; then I might as well sell prefabricated houses, and that is not my thing for various reasons.

The topic is a point of discussion in every forum. And everyone either tries to stay out of it or to defend their opinion against everyone and everything.
After current considerations, we want to build monolithically with aerated concrete or T7. This way, it is easier to improve the insulation at a later date if necessary. All synthetic insulating materials will not come near our house.

Best regards

Sebastian

Hello Sebastian,

We assume that we will build with an architect from Erkelenz. It is important to us that the architect/site manager and the workers come from the area.

That’s reasonable; nice coincidence: our architect, with whom we have worked for many years, also has his office in Erkelenz

One shouldn’t really do that, but especially with the salespeople in the show houses, I see little willingness or competence to discuss this topic. And that was always the case on our tour through the various houses. When one said they wanted to build a well-insulated house, all of them had euros in their eyes.

I myself have spent some time in W'tal and Hückelhoven in a show house and know what you mean. I was often surprised by the behavior of the so-called “colleagues.” On the other hand, I have to fairly add that many of the potential buyers did not deserve better treatment. Today I am more convinced than ever that comparable characters always find each other ....

You are specifically mentioning an air heat pump here, is there a reason? It is not cheaper in terms of purchase and running costs than a gas boiler.

No, it is a good 4-6 thousand euros more expensive, depending on the house size and habits of the builders. But you must not ignore that you save the gas connection for that; you will never get an air-water heat pump cheaper comparatively.

And especially an air heat pump has clear disadvantages compared to a ground-source heat pump in these cold winters. Also, you have to be able to channel away the excess heat from the solar collectors, and if you can significantly improve the annual performance factor as a result, that is more than fine.

When I write air-water heat pump, I actually mean only a pure air-water heat pump; possibly a combi unit including controlled residential ventilation; a solar thermal system is not needed, apart from the fact that these panels in my opinion are “only” suitable for KfW 70 calculation. If you need hot water, this thing doesn’t really work.

... Especially the acquisition costs, maintenance, and interest currently make the heat pump (regardless of which) economically not sensible in my opinion...

Air/water heat pump

As heat sources, for example, outside air (unrestricted availability), heat recovery from exhaust air or waste heat, as well as absorber systems (e.g., energy fences) can be used.

The installation effort for an air heat pump is limited (e.g., foundations, earthworks, air ducts, channels). Particular attention must be paid to noise and condensate development at the installation site.

Air/water heat pumps are mostly operated as monoenergetic systems for heating residential buildings. The heat pump should cover the heat demand fully up to an outdoor temperature of about –5 degrees (bivalence point). Only at lower temperatures or increased heat demand is an electrically powered heat generator switched on. The average annual outdoor temperature at the site strongly influences the economic viability of an air/water heat pump and must be taken into account during planning.

Proper sizing of the heat pump capacity is important because it influences both the investment costs and the annual heating costs.

In older buildings or heating system renovations, a bivalent – parallel operation with a second heat generator such as oil or gas boiler is also possible. With permanent bivalent system operation, the heat pump can be sized smaller; however, experience shows that later decommissioning of the second heat generator can then cause problems.

It is also possible to combine an air/water heat pump with a ground-source or water/water heat pump. This is mostly practiced with hot water preparation.

The functional principle of a heat pump

The energy transfer in heat pumps takes place as a thermodynamic cycle. The refrigerant, which changes its state (liquid/gas) at low temperatures while absorbing or releasing heat energy, plays an important role. The closed cycle in a compression heat pump is as follows:

In the evaporator, the cold liquid refrigerant absorbs energy from the environmental heat source and evaporates.

The compressor compresses the vaporous refrigerant by consuming mechanical or electrical energy, heating it to so-called hot gas.

The hot gas transfers its thermal energy to the heating system in the condenser and condenses into warm liquid refrigerant.

The warm liquid refrigerant expands at the expansion valve, causing its temperature to drop sharply. The cycle starts again in the evaporator.

Is the heat pump a disguised electric heater?

Every heating system depends on electricity. If the power fails, no wheel turns even with oil boilers and gas boilers. The heat pump uses electricity to drive the compressor that makes the captured environmental heat usable. However, the electricity that drives the compressor and the brine, groundwater pump, or fans for circulating the heat source circuits in efficient heat pumps with an annual performance factor of 4.0 accounts for only a quarter of the heat produced. Thanks to the use of renewable energy sources, electricity is also becoming cleaner. Despite everything, the environmental balance of the heat pump is already significantly better today than that of conventional heat generators.

How much does a heat pump cost?

The different electricity costs depend on the system's annual performance factor. Field tests have shown that the annual performance factor of faultlessly built ground-coupled systems is around 4, for air/water heat pumps generally 3.0 to 3.3.

Once those numbers are determined, the calculation is simple: For example, assuming a heat demand of 15,000 kWh for a new single-family house, you need to buy 15,000/4=3,750 kWh electricity for the ground-source heat pump (annual performance factor e.g. 4.0); for the air/water heat pump (annual performance factor e.g. 3.0), 15,000/3=5,000 kWh electricity. Multiply the calculated kWh by the price per kWh of your electricity contract (about 12 ct/kWh) and you get an electricity cost difference of 150.00 EUR per year. Just as easily, based on the heat consumption and oil and gas prices, you can calculate how much more expensive the annual demand for fossil fuels would be.

Source: Federal Heat Pump Association eV, my homepage

The topic is a discussion point in every forum. And everyone either tries to stay out of it or to assert their opinion against everything and everyone.

As I already wrote: there is no “good” or “bad.” If you followed my suggestion, you should now know that; accordingly, there “can” only be opposing points of view

Currently, we are considering building monolithically with aerated concrete or T7. That way, it is easier to improve the insulation later if necessary. All synthetic insulation materials are out of the question for our house.

Yep. My very personal recommendation (purely subjective and no contest) – build only with Poroton if you have fast-setting cement in the house at all times

Kind regards