ACTIVE HOUSES TAKE SUSTAINABLE CONSTRUCTION AND SOURCING INTO CONSIDERATION
When designing an Active House, it is important to evaluate recycled or reused content and sourcing. It is preferable to include building components or elements that have already been used (re-use), or materials reclaimed from old buildings or processes (recycle), to reduce the environmental load of the building materials.
A distinction is made between recycled content (that has already been used) and virgin material that could be recycled or reused at the end-of-life stage of the building. The recycled content includes pre-consumer, internal and post-consumer recycling. Recyclable content is aimed at materials or elements that can be reclaimed post-consumer. Both are evaluated by weight and shall take into consideration 80% of the weight of the building.
Responsible sourcing includes the requirement to use certified sourcing either directly, like PEFC and FSC for sourcing of wood, and EPD (environmental product declaration) for other materials.
The process of constructing a new building causes various emissions to air, soil and water, which have different impacts on the environment. When constructing an Active House and conducting a Life Cycle Assessment, it is important to know and consider the different impact categories of these emissions, which may have serious environmental effects. They are explained in the following:
GLOBAL WARMING POTENTIAL (GWP)
The accumulation of so-called greenhouse gases in the troposphere causes increased reflection of infrared radiation from the earth’s surface. Consequently, the temperature on the earth’s surface rises. This phenomenon is referred to as the ‘greenhouse effect’, affecting human health, ecosystems and society in general. The global warming potential groups together gases in relation to the impact of carbon dioxide (CO2).
OZONE DEPLETION POTENTIAL (ODP)
Ozone (O3) occurs as a trace gas in the stratosphere (10-50 km altitude) and absorbs solar UV radiation. However, human emissions induce the thinning of the stratospheric ozone layer since certain gases, such as halocarbons, work as catalysts degrading ozone to oxygen. Thus the transmission of UV-B radiation is increased, with potentially harmful impacts on human health, terrestrial and aquatic ecosystems, causing for example DNA-damage, cancer (especially skin cancer) and eye irritation, crop failures and the decrease of planktons. The ozone depletion potential groups together the impact of various ozone depleting gases. The reference variable used is R11 (trichlorofluoromethane CCl3F).
PHOTOCHEMICAL OZONE CREATION POTENTIAL (POCP)
A higher concentration of ozone in the troposphere (0-15 km altitude), the so-called summer smog, is toxic to humans and may also cause damage to vegetation and materials. When exposed to solar radiation, nitrogen oxide and hydrocarbons form round level (tropospheric) ozone in a complex chemical. This process is called photochemical oxidant creation. Nitrogen oxides and hydrocarbons are produced during partial combustion. The latter is also created by using petrol or solvents. The ozone formation potential is related to the impact of ethylene (C2H4).
ACIDIFICATION POTENTIAL (AP)
Acidification of soil and water results from the conversion of airborne pollutants into acids. The major acidifying pollutants are sulphur dioxide (SO2), nitrogen oxides (NOx) and their acids (H2SO4 and HNO3). These gases are generated during combustion processes in power stations and industrial buildings, in homes, by cars and small consumers. Acidification has a wide range of impacts on vegetation, soil, groundwater, surface waters, biological organisms, ecosystems and building materials, e.g. forest decline and acid rain. The acidification potential groups together all the substances contributing to acidification in relation to the impact of sulphur dioxide (SO2).
Eutrophication means excessive fertilisation of soil or water and describes the concentration of nutrients and nutrient enrichment in an ecosystem, which may cause an undesirable shift in species composition and elevated biomass production. The major nutrients are nitrogen (N) and phosphorus (P). These substances are contained in fertilisers, nitrogen oxides from combustion engines, domestic wastewater, industrial waste and wastewater. Plants in excessively fertilised soils exhibit weakening of their tissue and lower resistance to environmental influences. In aquatic ecosystems, increased biomass production may lead to depressed oxygen levels, because of the additional consumption of oxygen in biomass decomposition. This may result in fish death and the biological death of water. Furthermore, a high concentration of nitrate can render groundwater and surface waters unusable as drinking water since nitrate reacts and becomes nitrite, which is toxic for human beings. The eutrophication potential groups together the substances in comparison to the impact of phosphate (PO4).