A method for determining the heat loss coefficient K of a premises, characterized in that it comprises steps in which: - in the unoccupied premises, a campaign of measurements of at least one temperature inside the premises T ik at closely-spaced time intervals is performed over at least two successive time periods D k corresponding to distinct heating powers P tot k of the premises; - the temperature of the outside air T ek at said same closely-spaced times is determined; - for each time period D k, on the basis of the evolution T ik ( t) of the quantity T ik as a function of time: ∘ either, if there exists a time interval Δ t k for which the evolution T ik ( t) is substantially linear, the slope α k of the tangent to the curve T ik ( t) is determined over this time interval Δ t k and the value of the heat loss coefficient K of the premises is deduced on the basis of the slopes α k; ∘ or, if there does not exist any time interval for which the evolution T ik ( t) is substantially linear, a time interval Δ t k ' is selected over which the evolution T ik ( t) is substantially exponential of type exp( -t / τ), with τ the thermal time constant of the premises, and the value of the heat loss coefficient K of the premises is deduced, which is the value such that the curve Ln θ k t − P tot k K / θ k 0 − P tot k K is a straight line, with θ k ( t) = T ik ( t)- T ekm ' where T ekm ' is the average of the temperature measurements of the outside air T ek over the time interval Δ t k '. - in the unoccupied premises, a campaign of measurements of at least one temperature inside the premises T ik at closely-spaced time intervals is performed over at least two successive time periods D k corresponding to distinct heating powers P tot k of the premises; - the temperature of the outside air T ek at said same closely-spaced times is determined; - for each time period D k, on the basis of the evolution T ik ( t) of the quantity T ik as a function of time: ∘ either, if there exists a time interval Δ t k for which the evolution T ik ( t) is substantially linear, the slope α k of the tangent to the curve T ik ( t) is determined over this time interval Δ t k and the value of the heat loss coefficient K of the premises is deduced on the basis of the slopes α k; ∘ or, if there does not exist any time interval for which the evolution T ik ( t) is substantially linear, a time interval Δ t k ' is selected over which the evolution T ik ( t) is substantially exponential of type exp( -t / τ), with τ the thermal time constant of the premises, and the value of the heat loss coefficient K of the premises is deduced, which is the value such that the curve Ln θ k t − P tot k K / θ k 0 − P tot k K is a straight line, with θ k ( t) = T ik ( t)- T ekm ' where T ekm ' is the average of the temperature measurements of the outside air T ek over the time interval Δ t k '. ∘ either, if there exists a time interval Δ t k for which the evolution T ik ( t) is substantially linear, the slope α k of the tangent to the curve T ik ( t) is determined over this time interval Δ t k and the value of the heat loss coefficient K of the premises is deduced on the basis of the slopes α k; ∘ or, if there does not exist any time interval for which the evolution T ik ( t) is substantially linear, a time interval Δ t k ' is selected over which the evolution T ik ( t) is substantially exponential of type exp( -t / τ), with τ the thermal time constant of the premises, and the value of the heat loss coefficient K of the premises is deduced, which is the value such that the curve Ln θ k t − P tot k K / θ k 0 − P tot k K is a straight line, with θ k ( t) = T ik ( t)- T ekm ' where T ekm ' is the average of the temperature measurements of the outside air T ek over the time interval Δ t k '.