A noncalorimetric method for measuring the heat-transfer coefficient (UA) of building thermal envelopes is proposed and applied in an indoor test cell. The UA value measured by this method agrees closely with that measured by a calorimetric method. This method creates a Single input and a Single output data Pair (SSP) from the measured data sets by using digital filters. The filter output and physical criteria are used to determine the correct transfer function, which yields the measured UA value. This method seems to have the following advantages over calorimetric methods: it uses shorter measurement times, uses simpler test equipment, and has minimum thermal intrusion on normal operating conditions.