What is a Sustainable house?

A house that’s consumption of natural resources, observing its whole life cycle, is less than the natural resources of the given area, fallen on the house. (Medgyasszay, 2009)

Theoretical Background

sustainable house logoThe “sustainable house” concept uses the concepts of an environmentally friendly, passive and zero emission house. But respective to its definition, sets up two more important criteria:

  • The sustainable house concept does not aim to minimize the energy consumption of the building. But to the cost-effective optimization dependent on geographical conditions.
  • According to the geographical conditions and individual consumption the concept stipulates different regional requirements.

The basic pillar of the definition is that the building stock has strategic importance. The resources currently available and in the near future will be fully utilized for the operation of the building stock. Non-exhaustible renewable energy sources (solar, wind) and renewable energy sources (biomass, geothermal energy) that are used in a sustainable manner can be considered as permanently available energy.

This contradicts the fact that it does not consider many important energy-consuming activities of human activities (eg industry, transport). However, current forms of industry and transport have always been based on non-renewable sources of energy. The scale of consumption is such that it can only be replaced by a new energy source or the use of highly efficient solar energy, even with a radical increase in energy efficiency. However, it is a sensible proposition to address the sustainability issues of the strategic building stock as soon as possible and separate from other consumption.

The energetical criteria of the “Sustainable house” concept (version 4.0):

A “Sustainable house”, defined in Hungary, can only use the natural energy capital of the country in a renewable manner. According to this capacity and the current technical pontential of the country the building’s energy need can be covered by these resources:

  • heating: biomass, geothermal sources (thermal water), solar;
  • hot water: solar, biomass;
  • cooling: electricity gained from renewable resources;
  • cooking: biomass, electricity gained from renewable resources;
  • lighting: electricity gained from renewable resources.

What does sustainable usage of renewable energy resources mean?

Regionally available energy can and should be divided into different segments along energy needs, and energy requirements can be set for each segment. There are no requirements for the sustainable use of building materials in this concept for two reasons.

  • On the one hand, the energy used in the production of building materials in Hungary was 10.6 PJ in 2005, compared to 643 PJ used by the public and the municipal sector. So its role is secondary to the current energy use. [1: KSH, 2005] The primary energy demand of building materials to be built requires further research. However, based on the results of research to date, it can be stated with certainty that natural materials have the property of minimizing the environmental load of building materials production. [2: Medgyasszay, 2008]
  • On the other hand, there is no statistical data on the proportion of the built-in materials produced in Hungary, and we have no comprehensive data on the primary energy demand of the production. Subsequently, the criteria for the energy content of building materials shall be clarified as follows.

In the following, we will only define the requirements for a “sustainable house” for the operation of buildings. Available primary energy can be distributed in a different way than the ones described below, depending on the type of energy we want to use for what purpose.

Heating – hot water production – cooking

The solar energy that arrives to this countries land is much more than the total energy needed. (1800 PJ as the total primary energy demand of Hungary is 1153,2 PJ [1: KSH, 2005]). Its utilization could be free for individual or public purposes. The problems with solar energy utilization are the storage of the solar energy and the initial cost of the production/storage equipment.

The theoretical biomass potential of Hungary for energetic utilization is 203-328 PJ. From which 200 PJ is accessible, according to the calculations of the Hungarian Academy of Science. According to other studies only 67 PJ is accessible [3: Giber, 2005]. Currently, the majority of the utilized biomass in the country is used for industrial electricity production and the efficiency is questionable. Direct thermodynamic usage is advisable for the major part of biomass usage, this means at least 90 PJ could be gained for heating and hot water production.

For larger scale usage, a further possibility is the utilization of our readily available thermal water. According to the Subcommittee of Technologies of Renewable Energetics in the Hungarian Academy of Science, out of the theoretical potential of 63 PJ, 10 PJ could be utilized. [4: Bohoczky, 2008]


In Hungary renewable resourcesthat can produce electrical energy are the following: solar, wind and biomass. The theoretical potentials of the first two are significant (The Hungarian Academy of Sciences estimates that the theoretical potential for solar photovoltaic energy is 1,750 and wind energy 530 PJ / year.) But the really accessible energy is much less. Calculations without biomass resources are approx. 15-25 PJ per year. If, in addition to heating energy use, 21 PJ of biomass can be used to produce electricity, at least an additional 7 PJ can be calculated as renewable energy.

What requirements a “sustainable house” has to comply with?

Hot water energy demand

The largest item in the energy consumption of buildings is currently the heating energy demand. However, when defining the requirements for a “sustainable house”, the first criterion is the domestic hot water production. We do this because the amount of hot water cannot be reduced for hygienic reasons. Only by increasing the efficiency of mechanical systems can the amount of renewable energy required be rationalized.

In Hungary, the average consumption of hot water is 40-50 l / day / person, and approx. 0-10 l / day / person communal use. Domestic hot water from renewable energy sources can be provided by 60% solar, 40% biomass or thermal water. For the country’s total population, taking into account 10,000,000 “unit consumers”, a net 12.5 PJ, assuming 85% mechanical efficiency, would generate a gross 14.5 PJ of energy to produce the required domestic hot water.

It can be stated that according to the “sustainable house concept” the energy demand for domestic hot water can be solved in Hungary. With the usual use of solar energy, so that the use of biomass or thermal water is not more than 1.45 GJ or 400 kWh per year. Based on the typical domestic hot water demand of residental and public buildings (4: 1) and the area ratio of residental and public buildings (2: 1) and assuming a mechanical efficiency of 85%, for residental buildings gross 10 kWh / m2a, for public puldings gross 5 kWh / m2a, biomass or thermal water is needed.

Heating energy demand

Previously, 90 PJ of biomass, 10 PJ of geothermal energy and unlimited amounts of wind and solar energy are potentially available in Hungary. Since 14.5 PJ of energy is to be used for domestic hot water production, the renewable energy for heating is 86.5 PJ of biomass and geothermal. The use of solar and wind energy for direct thermal heating purposes is currently not economically viable and scientific advice.

The heating energy demand can thus be calculated under two assumptions:

  • a) Based on the amount of energy per capita as follows. The available energy is divided into 10,000,000 parts, the amount of energy per capita is 8.6 GJ, or 2,400 kWh / year / person, which is approx. 5 q means firewood per person per year. As this amount must cover the heating requirements of both the home and the workplace, the amount of firewood used for heating the dwelling house is 3.5 q / year / person.
    b) Based on the energy demand per square meter as follows: The domestic building stock is approx. 480,000,000 m2 (4,000,000 apartments with an average of 80 m2 and about half as many offices and public buildings.). Based on the heating energy demand of this area, the gross primary energy demand of the “sustainable house” in Hungary is 43 kWh / m2a biomass or thermal water. The requirement value can be determined in relation to the energy quality of the building, assuming 85% mechanical systems, as a net heating energy requirement of 36 kWh / m2a.
Additional note to heateing energy demand

When determining the heating energy requirement, the following additions should be made:

  • 1) The determination of the requirement value is recommended according to method b). When designing buildings, it is not possible to determine how many people occupy the building, which would result in different requirements for the designer according to method a).
    2) The requirement value is an average value. It will be necessary to specify later what requirements can be set for new buildings, for existing buildings which can be upgraded energetically or for existing buildings which are not energetically upgraded (monuments).

Cooling energy demand

The cooling energy demandhas to be reduced radically in the case of residential buildings. In the case of self-contained houses, adequate architectural and structural design features can completely eliminate this demand.

In case of office and multi-storey buildings, instead of the conventional air conditioning, with the usage of heat exchanged airing, structure-cooling or geothermal heat-pumps, the energy demand of cooling can be significantly reduced.

Other electricity consumption (lighting, appliances)

In case in the “sustainable house” concept the electricity requirements of other consumtions (cooking, lighting, etc.) has to cover with only regionally produced water, wind and solar energy, 25 PJ is available. Based on the typical use of electric energy of residential and of public buildings (1: 1) and area ratio for residential and communal buildings (2: 1) the cooling, lighting and other electric energy needs has to cover with 14 kWh/m2a for residental buildings and 28 kWh/m2a for public buildings. (It should be noted that the energy demand for lighting and household appliances will also need to be further reduced, as the average annual energy consumption of an unheated residential building in Hungary is 1,500 kWh, which is 20 kWh / m2a in terms of an average home size.)

Longer articels


1: KSH, 2005
KSH: Magyar statisztikai évkönyv 2005.
2: Medgyasszay, 2008
[Medgyasszay, P “A földépítészet optimalizált alkalmazási lehetőségei Magyarországon – különös tekintettel az építésökológia és az energiatudatos épülettervezés szempontjaira” (PhD disszertáció), 2008. BME
3: Giber, 2005
Giber János (et. al.): A megújuló energiaforrások szerepe az energiaellátásban, GKM. Budapest, 2005.
4: Bohoczky, 2008
Bohoczky Ferenc: Megújuló energiaforrások jövője Magyarországon. Konferencia előadás, 2008.