Principle

If there is a difference between outside and inside temperature in passenger coaches, heat is transmitted through the walls which has to be compensated by air-conditioning and therefore consumes energy. The situation can be improved by the insulation of walls and windows. On the one hand this is a continuous improvement task for the design of new vehicles. On the other hand existing retrofit cycles can be used to improve the heat transition properties of existing stock.

UIC recommendations

The thermal characteristics of railway vehicles (and other confined spaces) are described by the heat transition coefficient (k-value). It measures the heat flow through a certain component (e.g. a wall) in Watts per square meter for an inside/outside temperature difference of one Kelvin (W / m² K).

UIC leaflet 567 gives maximum k-values for passenger coaches at stand-still:

• for the primary passenger area: 1,6 W/m²K
• for the corridors: 2,6 W/m²K

In running trains these values may be exceeded by 0,4 W/m²K

Individual measures

Individual measures to improve the thermal insulation of passenger coaches range from the insulation of walls to the installation of windows with favourable thermal properties. Retrofit experience from SBB show feasibility and profitability of such measures for old stock.