Window-like building opening, - wherein the building opening comprises an aperture frame , which is connectible with an outer wall of the building , and a casement abutting the aperture frame , these forming a window rebate , - wherein the aperture frame and the casement are sealed relative to one another by means of at least one seal , - wherein the building opening has a ventilation channel by way of which air can flow between the environment of the building and the interior of the building , - wherein an adjustable element by means of which the effective cross-section (Q) of the ventilation channel can be varied between a minimum value and a maximum value is arranged in the ventilation channel , - wherein the building opening has a temperature sensor which sets the effective cross-section (Q) of the ventilation channel in dependence on the temperature (T) detected by means of the temperature sensor , - wherein the temperature sensor comprises a phase change material which changes its phase state, particularly its aggregate state, at a conversion temperature (T0) or in a conversion temperature range (T1), - wherein a setting, which influences the effective cross-section (Q) of the ventilation channel , of the adjustable element depends on the phase state of the phase change material , - wherein the temperature sensor comprises a base body and a work piston , - wherein the base body is arranged in stationary location at or in the aperture frame or at or in the casement , - wherein the work piston is movably mounted in the base body and changes its position in dependence on the phase state of the phase change material by displacement along a piston axis, characterised in that the piston axis extends parallel to that part of the aperture frame or casement at or in which the base body is arranged. - wherein the building opening comprises an aperture frame , which is connectible with an outer wall of the building , and a casement abutting the aperture frame , these forming a window rebate , - wherein the aperture frame and the casement are sealed relative to one another by means of at least one seal , - wherein the building opening has a ventilation channel by way of which air can flow between the environment of the building and the interior of the building , - wherein an adjustable element by means of which the effective cross-section (Q) of the ventilation channel can be varied between a minimum value and a maximum value is arranged in the ventilation channel , - wherein the building opening has a temperature sensor which sets the effective cross-section (Q) of the ventilation channel in dependence on the temperature (T) detected by means of the temperature sensor , - wherein the temperature sensor comprises a phase change material which changes its phase state, particularly its aggregate state, at a conversion temperature (T0) or in a conversion temperature range (T1), - wherein a setting, which influences the effective cross-section (Q) of the ventilation channel , of the adjustable element depends on the phase state of the phase change material , - wherein the temperature sensor comprises a base body and a work piston , - wherein the base body is arranged in stationary location at or in the aperture frame or at or in the casement , - wherein the work piston is movably mounted in the base body and changes its position in dependence on the phase state of the phase change material by displacement along a piston axis, <EOS>