Abstract: Abstract: Heat loss can normally occur from the building envelope (wall, roof, glass) and ventilation system of a piggery in winter, due primarily to the large temperature difference between the inside and outside. A heating system can be widely used to recover the heat loss, inevitably leading to a higher energy demand during large-scale pig farming. Alternatively, it is highly required to meet the specific performance of thermal insulation for the envelope, in order to reduce the energy consumption for the better efficiency of environmental control in the piggery. A large number of pig farms have been built to rapidly resume pig production in China at present. Among them, a newly-developed assembled structure was normally adopted, where the ceiling and upper half wall are mostly made of the composite insulation with the profiled steel plates on both inside and outside, and with the stuffed thermal insulation materials in the middle, whereas, the lower half wall is in brick with the outer insulation board. However, there is little research on the thermal insulation effect of such assembled structure so far. This study aims to clarify the heat preservation, thermal performance, and energy consumption characteristics of an assembled piggery for the breeding and gestation in large-scale pig farms in winter. A field test was also conducted in a pig farm in Chengde City, Hebei Province, China. Some environmental parameters were measured in the piggery, including the inner and outer temperature, relative humidity, carbon dioxide concentration, and ventilation rate. As such, the thermal performance of the envelope was evaluated by the theoretical calculation and in situ test. Meanwhile, the heat transfer coefficients were determined for each part of the building envelope, according to the thermal conductivity of the materials and structure design of assembled piggery. The temperature and heat flux were measured at each measuring point on the inner and outer surfaces of the wall. The measured values were then used to calculate the heat transfer coefficient for each part of the wall. Furthermore, the condensation was estimated for the inner surface of the wall, further to compare the dew point temperature from the enthalpy diagram and the inner surface temperature of each part of the wall at the average outer temperature during the test. The thermal bridge was also be identified to measure the inner surface temperature of the envelope using an infrared thermal imager. The total heat consumption was calculated to balance the sensible heat production of pigs, and the heat loss from the ventilation system and the envelope of the piggery. The result showed that the average temperature and relative humidity were 18.7 ℃ and 65.7%, respectively, inside the piggery under an environmental control system, indicating the comfortable range. By contrast, the average temperature and relative humidity were -9.1 ℃ and 55.8%, respectively, outside the piggery during the test period. The ventilation rates were 0.12 and 0.15 m3/(h·kg) in Units 1 and 2, respectively, and the average carbon dioxide concentration was 5 939 mg/m3 in Unit 1. The measured heat transfer coefficients for the main part of the upper composite insulation half wall and the lower brick half wall with outer insulation board were 0.39 and 0.69 W/(m2·K), respectively, which were 25.8% and 81.6% higher than the theoretically calculated values, respectively. The measured heat transfer coefficient was 0.97 W/(m2·K) for the steel girder part of the upper wall. Moreover, there was no condensation at each part of the wall within the range of temperature and relative humidity inside the piggery under the average temperature outside, indicating better thermal comfort. However, the condensation was easy to occur at the installation joints of doors, windows, fans, cooling pads, and walls, the joints between the upper and lower walls, the joints between the lower chord of the roof frame and the ceiling, as well as the connecting part of the steel columns and the ceiling. In addition, the theoretical total heat consumption of the piggery was 10.73 W/m2 on average, and the average theoretical and measured value was 11.84 W/m2. Correspondingly, the average heat consumption of the envelope was less than 20% of that of the ventilation in this type of piggery. The daily required heating supply was 0.28 kW·h/m2 in theory, where the actual was 0.39 kW·h/m2, according to the use of natural gas. This finding can also provide a strong technical reference for the energy saving and insulation of assembled piggery.