Dach Sommer

Indoor air quality and a pleasant living environment

Effective airtightness keeps indoor spaces cooler for longer in summer, and prevents excessively dry indoor air and mould formation in winter.

Thermal comfort in summer

Thermal protection in summertime is characterised by the time in hours that it takes for the heat present underneath the roof covering to reach the inside of the structure (phase shift), and by the associated increase in the interior temperature in degrees Celsius (°C) relative to the exterior temperature (amplitude damping).

Cool interiors during hot summer weather

To quantify thermal protection in summer, the phase shift and amplitude damping should be calculated. An airtight thermal insulation structure is assumed here. The heat is conducted to the interior in a relatively sluggish manner (depending on the type and characteristics of the insulation material).

Quick heating up due to air flow

Gaps in the airtightness layer result in air flow from the outside to the inside and thus also in a high exchange of air as a result of the large differential in temperature and pressure between the indoor and outdoor environments. The thermal insulation can then no longer contribute effectively to summer heat insulation and an unpleasant, excessively warm room climate is the result.

Preventing unhealthy indoor environments in winter

The relative humidity in homes should be a comfortable 40–60% during the heating season. A room climate that is too dry is bad for our health.

Dry cold air penetrates through unsealed gaps

The frequently encountered phenomenon of dry indoor air in wintertime is a consequence of the fact that cold outdoor air enters into buildings though gaps. If this cold air is warmed up by heating, its relative humidity content drops. For this reason, buildings with poor airtightness tend to have air that is too dry in winter, and this cannot be rectified to any significant extent by humidification equipment. The consequence is an unpleasant indoor climate. Low relative humidity has a negative effect on our health and comfort levels.

Example: Cold air at 5 °C can hold a maximum of 2 g/m³ of humidity (standard outdoor winter climate as per DIN 4108-3) at a relative humidity of 80%. If this air is heated to 20 °C (standard indoor winter climate), the relative humidity falls to 11.6%.

Mould formation due to condensation

Damage to structures caused by mould formation may occur when humid, warm indoor air enters into the thermal insulation structure in winter – e.g. through gaps in the vapour retarder and airtightness layers – and large amounts of moisture condense. Many mould fungi release poisons – such as MVOCs (microbial volatile organic compounds) – and spores as secondary metabolic products that are harmful to human health. These are a leading cause of allergies. Humans should avoid all contact with mould fungi. It does not make any difference in this regard whether the MVOCs or spores enter into the human body in the stomach through our food or else into the lungs if they are present in the air we breathe.

Systems for reliable building sealing