Kokonaislämmönvastus

Kokonaislämmönvastus, often abbreviated as Rtot, is a key metric used in building physics to quantify the thermal resistance of a composite structure or a building envelope. It represents the total resistance to heat flow through a series of layers, such as walls, roofs, or windows. In essence, it is the sum of the thermal resistances of each individual layer within the structure, as well as the resistances at the internal and external surfaces.

The concept of thermal resistance is inversely related to thermal conductance. A higher Rtot value indicates better insulation and a lower rate of heat transfer. This means that a building with a high kokonaislämmönvastus will lose less heat in winter and gain less heat in summer, contributing to improved energy efficiency and occupant comfort.

Calculating Rtot involves understanding the thermal properties of each material in the construction. Each material has a specific thermal conductivity, which, when combined with its thickness, determines its individual thermal resistance. Surface resistances, which account for heat transfer at the air-material interface, are also included in the Rtot calculation. For a multi-layered structure, the individual resistances are simply added together to arrive at the total thermal resistance. This value is crucial for architects, engineers, and builders when designing and assessing the thermal performance of buildings to meet energy regulations and optimize insulation strategies.