The use of buried pipes reduces the energy consumption for heating of agricultural greenhouses by increasing the air temperature and also improves indoor conditions by reducing temperature fluctuations during the day. A parametric analysis has been performed for a typical glass greenhouse to illustrate overall system performance. The greenhouse-air temperature increases during the winter with increasing pipe length, decreasing pipe diameter, increasing depth up to 4 m, and decreasing air velocity inside the pipes. Measured data from a 1000-m(2) fibreglass greenhouse with four buried pipes are found to be in good agreement with calculated values.