Solar heat load in uninsulated livestock buildings

High environmental temperatures affect animal productivity. Even in northern Europe, especially uninsulated livestock buildings may reach high air temperature levels during warm and sunny days in the summer due to the heat gain by solar irradiation. The objective of this research was to determine the solar heat load, the ratio of solar heat utilization, the absorptance factor, the transmittance-absorptance factor and the overall heat transfer coefficient per m(2) of floor area for an uninsulated building. Two studies were made in the same building but with different roof claddings. In the first study, both the wall cladding and the roof cladding were transparent polycarbonate double web sheets (U-value of 3.0 W m(-2) K-1). In the second study, 85% of the roof cladding was changed to non-transparent black fibre cement sheets. The outside and inside air temperatures, the temperature in the exhaust airflow and the solar irradiation against a horizontal surface were measured continuously. The specific airflow was changed in steps between 0.0017 and 0.027 m(3) m(-2) s(-1). The temperature difference had a maximum about 1-2 h later than the maximum solar irradiation. The ratio of solar heat utilization, defined as the fraction of solar irradiation against the building envelope that is transferred to sensible heat in the air volume, varies due to the ventilated airflow through the building. A higher airflow results in a higher utilization. The transmittance-absorptance factor for the building with transparent polycarbonate roof was 0.36 and the absorptance factor for the building with non-transparent fibre cement roof was 0.20. The overall heat transfer coefficients per m2 of floor area for the same buildings were 11.0 and 12.5 W m(-2) K-1, respectively. (C) 2001 Silsoe Research Institute.