Interstitial condensation is a condensation phenomenon that occurs inside a material due to a sudden drop in temperature between one of its sides and the other. This phenomenon is typical in most thermal insulators.

The amount of water vapor that the air can support varies significantly depending on the temperature. For example, at 25°C, saturation (100% relative humidity) is reached with 20g of water, at 25°C to 14°C, about half of the vapor will condense as water.

Air is a very good thermal insulator, so most insulating materials are obtained through structures that trap air or sometimes gas. When interstitial condensations occur, this air is replaced by water, which, unlike air, is a good conductor of heat. For this reason, when insulating materials get wet, they lose their properties.

To avoid this, vapor barriers are placed in the enclosures, which make it difficult and slow down the passage of vapor through the wall, and allow the insulation to remain dry. Vapor barriers are placed in combination with air chambers, which allow adequate ventilation of the insulation.

• - Thermal bridge.

• - Dew point.

• - dew point calculator.