Definition Passive House
According to the usual definition (1), a “passive house” is a building that requires less than 15 kW / m² of heat energy per year without taking into account the energy for hot water and electricity. A passive house is therefore a building that requires at least 20 ° C room temperature (assumption: at this temperature, comfort is felt) less than 15 kW / m² of heat energy or 1.5 l / m² of heating oil.
In order to obtain the necessary energy for the building, fossil fuels, energy from renewable raw materials or solar thermal and electrical systems can be used. The main orientation of the building to the south is important for solar heat generation. Due to the high insulation effect of the outer sheath, heat losses are very low. With the help of ventilation systems with heat recovery, fresh cool air is heated with the heat energy from the exhaust air and the exhaust air is cooled in a heat exchanger. Over 90% of the energy is returned to the building in this way. The users themselves transmit heat to the room. Ideally, the heat flows are balanced. In the case of heat differences, stored solar energy is used as a compensation. With this type of building, a conventional heating system can therefore be dispensed with. The production of insulating materials and the necessary technical equipment requires considerable amounts of energy before the building is used. When and how does this affect the amortization? Is more energy saved than consumed by the measures?
Amortization of insulation and technical installations
The Frauenhofer Institute has addressed this issue and has come to the conclusion that the production energy of thermal insulation materials, wind power and photovoltaic plants is amortized relatively quickly. So it is a good idea to isolate the wind and the sun.
From the Research Report of the Frauenhofer Institute (2): “Current Facts on Photovoltaics in Germany” [Status: 14.10.2016]
12. Is the production of PV modules devouring a lot of energy?
The energy recovery time for solar systems depends on the technology and plant location. It is approximately 2 years [EPIA] at 1055 kWh / m² of global horizontal annual irradiation (mean value for Germany). The life span of solar modules is in the range of 20-30 years. This means that a solar system produced today produces at least 10 times more energy during its lifetime than was required for its production. This value will be improved in the future by energy-optimized production processes. Wind power plants have even shorter energy recovery times, usually between 2-7 months.
Experience to date has shown that the use of these techniques is not without problems. On the one hand, moisture is removed from the building by the air exchange, which is partly required inside to avoid drying room air. On the other hand, dusts are passed with humid air through pipelines, filters and heat exchangers, which partly precipitate in the plants. Without maintenance and care, germs can accumulate in the systems.
Use of natural building materials
The use of natural building materials makes it possible to reduce the technical facilities and synthetic building materials. This minimizes maintenance and disposal costs. Ventilation systems with heat recovery are then not necessarily, but rather occasionally required to reduce heat energy. Thus, less electrical energy is needed for pumps and fans, and annual maintenance costs are low. The user behavior is then more decisive for energy consumption. Man is less dependent on technology and can intuitively satisfy his needs for warmth and comfort, which are different in every human being. Since the start of the use of a straw-insulated house with 140m² of living space without a ventilation system with double glazing, the average annual demand for energy for hot water and heating was 240 euros. The building is not airtight.
Reasons for using natural building materials
An explanation for the lower demand for technical apparatus is the properties of natural building materials. The experience with these building materials shows that these odors neutralize, pollute pollutants from the air and dynamically regulate the humidity of the room air (3). On the one hand, the fresh air supply is not necessary for the odors, the pollutants and the moisture to be controlled. This is all the less the more diffuse the wall structure is, and the natural building materials used are altered. Only a tenth of the usual fresh air requirement is then sufficient for humans.
A further explanation is the humidity of the room air. By utilizing the dynamic regulation and storage capacity of natural building materials the humidity is 40 – 60%. Dry room air reduces comfort. An infusion in the sauna shows that the heat by water vapor immediately increases. Conversely, this means that lower air temperatures in humid air are perceived as warmer than in dry conditions. The slightly low internal temperature affects the energy requirements.
When these above-mentioned facts are applied and the outer walls have the pleasant warming of the needlewood, the feeling of cosiness increases. A heavy building material such as a sand-lime brick touched by the hand is felt as cool, even if it is heated to 20 ° C. A piece of conifers is perceived as warm at the same temperature. The reason for this is that, in the case of softwood, the surface becomes as warm as the palping hand in a short time. In the sand-lime sandstone, the feeling of warmth will occur much later, for it is only when it has reached the hand temperature. The temperature difference, the temperature difference between hand and material is the reason for the sensation of on the one hand coolness and on the other hand heat. The re-sending of the heat, the warming up of the building material ensures that this is perceived as warm. As a further example, clothing can be mentioned. Outside temperatures of 20 ° C can be felt as cool when the upper body is free. A shirt made of cotton, leads to cosiness, although the layer of fabric over the skin is very thin. The warming up of clothing is the real reason for this.
The problems of disposal
At some point a building is no longer needed. The use of natural building materials will not lead to a future in the future.
Disposal of insulation materials
The use of synthetic materials can significantly reduce the value of a building. As an example, the currently common heat-bonding system is to be mentioned. Since 1 October 2016, foamed polystyrene insulation panels (EPS) have been designated as hazardous waste. Although the disposal of pure polystyrene is not the real problem, EPS insulation boards produced by 2014 are treated with the chemical “hexabromocyclododecane” (HBCD) (4), which makes them hazardous waste. The separation of the plaster layers from the plates, which also leads to higher disposal costs.The plaster and paint layers contain chemicals which are water-soluble and are washed out during the utilization phase and ultimately land in our waters.
The problems of disposal are always shifted to the future. For young people, this is certainly not a motivating prospect, on the occasion of the multitude of problems which are expected of them. The now young people will ask themselves whether they should be grateful to the elderly for their achievements. From their responses the corresponding interpersonal behavior will develop.
Maintenance of modern ventilation systems
A very unpleasant topic of the trailers of the passive house is the maintenance of modern ventilation systems (5) with heat recovery. There are installations with long pipelines, which run to a central heat exchanger, which takes in the outside air and preheats it with the heat energy of the extracted air. At this point, the systems compensate for heat losses with heating energy or heat pumps. Warm air is again distributed in the rooms. For noise-free design the noise is transmitted over the cables.
As already mentioned, the germination of the plants is threatened if not high-quality filters, which clean the incoming and outgoing air of dusts, and the pipelines are maintained as required. Already these circumstances are the cause of illness and exhaustion.
In another method, decentralized fans with heat exchangers are installed in the outer walls. These fans blow the indoor air for a while to the outside. A perforated rotating metal plate is heated. Then a change of direction takes place. The outside air is sucked in, passes through the preheated metal plate and reaches the interiors. Also with this variant regular maintenance and green cleaning of the plants are essential. The decentralized fans have problems with the noise protection. Outside noise can occur almost unhindered. Even the quiet noises of the fans intensify in the case of soiled equipment and are particularly annoying at night.
Condensates and dusts are generated in both systems. This combination is a good foundation for the formation of molds and germs. It is therefore absolutely necessary to clean the air filters, air passages and heat exchangers at least once a year. 100% cleaning is not possible (6). As a result, molds and other decomposition products form over the course of time. There are also positive experiences with ventilation systems, which have been germ-free for a long time. But since the heating and ventilation systems are the most important components in the passive house currently used, construction defects have a particularly disadvantageous effect. The resulting consequences are a major problem.
Can a building really be passive?
A building is only perceived as really passive when the heat, the consumed electrical and the production energy of all building materials, their dismantling, including transport, machine and human use are taken into account. The designation zero or plus energy house therefore corresponds more to the concept of the passive house. This is achieved by the dimensioning of the solar systems. The larger the systems, the higher the energy gain is. In essence, it does not matter whether the energy is produced on the house roof or in an energy factory. In the first case, the owner himself is the manufacturer, in the second the current is paid directly at the manufacturer’s stream. Ultimately, only energy is consumed when it is also solar energy. The term “plus energy house” ultimately means that the energy supply is covered by solar energy.
It should be noted that the term “passive house” basically obscures how much energy and is required for the production, maintenance and disposal of ventilation systems, solar photovoltaics, electronic control, synthetic insulation materials and the maintenance and care of insulated plaster façades.
From a financial point of view, the support systems of a photovoltaic system, a thermal solar system and corresponding heating boilers or geothermal heat are also required by other people in the form of electricity. These funds are also generated with energy.
Knowledge gaps in natural building materials
Taking into account the described problems, the natural construction shows that natural building materials are superior to the currently customary building materials. The frequent use of artificial building materials and plants is probably due to the belief in progress in technology. This blinded us to a sober assessment of the possibilities of natural building materials available so far. In the same process, the knowledge and experience of dealing with natural materials are declining. The purely technical, physical method of observation in the building industry has led to a sum of regulations which paralyze the freeman from developing something new from the old. All building materials must be tested and certified. While a good craftsman was familiar with the necessary recipes of mortar mixes, it is dependent on special finished products from large manufacturers. With his own mixes he is forced to prove his credibility with regard to his knowledge and experience. At the same time, it is at the same time in competition with the manufacturers, the regulations, experts and jurisdiction behind them. Besides the easy availability of conventional building materials, these are reasons which hinder developments and new applications with natural building materials. Developers and artisans, who are versatile and who do not have enough time and capital to implement their ideas, are particularly affected. An elaborate bureaucracy and the licensing system hinder the realization. In the meantime, more confidence in the written version of a product description exists than in the actual material knowledge of experienced craftsmen and developers.
Pioneers and friends of building biology
The pioneers and friends of building biology are an exception. Thanks to their long-term efforts, natural building materials are no foreign words. Many projects prove the future viability and importance of building biology. Passive houses made of natural building materials certainly belong to the future. If only at the edge, the wood and clay building is still perceived as existent. However, its possibilities are by no means exhausted. The predominant use of natural building materials is not based on the technical equipment of buildings. Rather, the technique is to support the living where it is really necessary. The greatest possible independence from technology is an increase in the sense of freedom and self-responsibility. This is possible, has already been proved by pioneers and friends of building biology.
Sources (german language):
1. Prof. Dr. Wolfgang Feist (Passive House Institute) – Quality requirements for passive houses
2. Frauenhofer Institut – “Current Facts on Photovoltaics in Germany” Version dated 14.10.2016
3. Rainer Nowotny (Hanffaser Uckermark) – Diffusion in hydrophilic fiber formations
4. Architects & Engineers EnEV – Energy efficient planning and building according to EnEV 2016 New practical handbook
5. VDI Association of German Engineers, Düsseldorf: VDI-Directive-6022