Ventilation to combat "stale" air

The Energy Saving Ordinance

The German Energy Saving Ordinance (EnEV) has been in force since 2002, and it requires comprehensive planning and construction measures to significantly reduce the primary energy demand for heating in newly constructed buildings and extensively renovated older buildings. This goal is to be achieved primarily by means of energy-saving heating technology and hot water generation, as well as improved insulation of the building shell.

The exchange of air between indoors and outdoors when windows are closed in buildings which do not comply with the current low-energy house standard occurs at a rate between one half and two times the volume of the room per hour, depending on how tight windows and doors are sealed. In other words the air in the room is renewed between once and twice an hour. The exchange rate of air in buildings built according to the requirements of the Energy Saving Ordinance is sometimes far below one half the room volume per hour. This can give rise to ‘stale’ air.

What exactly is “stale” air?

When the exchange of outdoor and indoor air is low, harmful substances can accumulate inside the home. Building products and interior decoration items such as carpeting, furniture, and wall paints can release many volatile organic compounds (VOCs) and semivolatile organic compounds (SVOC). Human activities may also contribute to deterioration of indoor air quality. With little air circulation an increase in the concentrations of pollutants and water vapour may occur. The effects of these indoor contaminants on health may be diverse, causing for example irritation of the respiratory air ways, allergies, and other health problems.

Excessive water vapour leads to mould infestation, and it is especially formed in places where humidity condenses on cold walls, which can then not dry, because e.g. there is furniture placed in front of them. In such cases, subsequent insulation of exterior walls is recommended to reduce the risk of condensation water formation. However, this measure alone is not enough in buildings with a sealed shell, building residents must also actively ventilate the rooms.

What can be done to combat “stale” air?

Air quality can be improved by using low-emission building products and by frequent ventilation. A mechanical ventilation system that circulates air continuously can be installed, although it must be serviced regularly and checked for growth of microorganisms (e.g. bacteria, mould) inside.

Consumers can easily recognise low-emission products by the Blue Angel eco-label.

In a position paper on energy savings and indoor air quality in buildings (Energiesparen in Gebäuden und gute Raumluftqualität sind möglich) the German Federal Environment Agency ( Umweltbundesamt ) offers hints for a practical solution to the conflict of interest posed between saving energy and preserving good indoor air quality.