The energy consumption of buildings and houses comes into discussion at the latest when one is interested in buying or building a new house and an energy certificate is to be issued. Passive house, low-energy house, KfW house and many other terms are used when it comes to energy efficiency, thermal insulation or funding programs. The problem: None of the terms mentioned do not describe a precisely defined standard.
So it is not as if a house is being built according to DIN-X when it is called a passive house or a low-energy house. Despite everything, the terms denote certain standards. Which are and what differences You should be able to, we explain in this article.
How is the energy consumption of a house measured?
Today, houses are usually provided with an energy certificate and thus also sold. In the advertisements, there is often a distinction between requirement and consumption ID. Both types of ID are based on a different calculation of energy consumption. Calculating an energy certificate is for houses and residential buildings By the way, it’s not that simpleas it may appear at first:
- Generally – In principle, the annual consumption of kilowatt hours of energy per square meter of usable area is calculated. A high key figure shows high consumption, a low one low consumption. In addition, houses are now optically divided into efficiency classes based on the banderoles and awards on electrical appliances. However, the usable area of the building is not the living space, but the usable building area as prescribed by the EnEV.
- Energy value – The primary energy requirement and the final energy requirement are stated in each ID. Primary energy describes the total amount of fossil energy used, including losses. This need describes the entire chain – from mining to incineration. Final energy parameters, on the other hand, include any regenerative energy from solar or wood that may be used.
Brand: A requirement certificate determines the values theoretically by means of calculations. A consumption certificate accesses the consumption data.
Anyone who builds a house does not come into contact with these factors at first. An energy certificate will certainly also be issued, but it is preceded by the usual designations relating to the type of house. And if the background is not known, they hardly reveal anything. Who can describe a passive house off the cuff or say what one KfW house 55 is?
What defines a low-energy house?
This house is almost always used in construction projects as a EnEV house or KfW house designated. Other names may exist depending on the region based on local regulations. It is already clear that the term Low energy house is not a protected name, but simply a general name for a house of a certain type. You could compare it with the term ›small car‹. Every buyer can imagine something like this.
Nevertheless, the word low-energy house has a basis:
- Guideline – A low-energy house may have a maximum heating requirement of 70 kilowatt hours per square meter per year. Since the Energy Saving Ordinance in 2009, this has been the minimum basis for all new buildings. An old building can also become a low-energy house after renovation if the requirements are met.
- EnEV house – this is the name for a low-energy house, which purely fulfills the requirements of the ordinance.
- KfW efficiency house – These houses are so named because the promotional loans for the building projects each have their names KfW 55, KfW 70, KfW 40 etc. wear. The number after the abbreviation denotes the percentage of the house’s energy consumption compared to pure EnEV houses. A KfW 55 house therefore only consumes 55 percent of the reference value. The requirement for these houses is thermal insulation, which should keep heat loss as low as possible. Central ventilation systems and the integration of solar systems and alternative heating methods are also part of the implementation. The following applies: the lower the number, the higher the energy savings. Regional rules – there may be other rules depending on the region. So is allowed in Schleswig-Holstein. The new building has to be here be at least 20 percent more economical than the EnEV house.
In principle, prospective builders can therefore trust that their house is already a low-energy house. There is no approval for building another house. Anyone who at the same time relies on alternative concepts, using heat pumps, solar systems and electricity storage, possibly even installing a recovery system for the service water, which can still be reused in the toilet, is very good at it and will receive a high-class, low-energy house.
What defines a passive house?
Are passive houses Low-energy houses per se, of course. But they differ markedly from the usual building type – even if not necessarily visually.
- Optimal construction – A sustainable concept is implemented in the passive house. It has optimal insulation, which is supported by the window fronts, which mostly extend to the west and south. The house should heat itself so that as few other heat sources as possible are required. A ventilation system with heat recovery is also standard. To be accepted as a passive house, a maximum of 15 kilowatt hours of energy per square meter may be required.
- Zero / plus energy house – These houses cover their energy needs completely independently, the plus energy house even generates additional energy.
- Nearest energy house – This term comes from the EU, but in comparison with the houses mentioned above, it describes a weakened energy house: The energy sources should be sustainable, the house should consume a maximum of 40 kilowatt hours per square meter. Thus, the lowest-energy house is much worse than a passive house and is more similar to the KfW-40 house.
Most prospective homeowners take the measures that lead to a passive house or a passive house-like house on their own initiative. Large window fronts usually face south, and insulation is also very important to most people. Solar systems including electricity storage are also nothing new and at the same time offer the possibility of living semi-self-sufficiently. At the same time, many construction options can be combined with one another.
Conclusion: look behind the terms
The term efficiency house is by no means defined. Basically, most people are familiar with the household terms coined by KfW, which initially means loans and subsidies. Passive houses are not absolutely identical either. The most understandable terms that are fixed by the term are Zero or plus energy houses. If zero external energy is used per square meter, it is a zero-energy house; if energy is still generated, it is a plus-energy house. Interested parties should therefore always inquire and check which type of house they are choosing and what exactly the energy certificate of the existing building says.
Photo credits: © Halfpoint – stock.adobe.com, © Gerhard Seybert – stock.adobe.com (sorted chronologically or according to the order of the images used in the buying guide)