I was given a tour of the heating and ventilation system for a wing of the Minnie Howard School. It was as complicated as a ship’s engine room – and I’ve been in a good few of those.
Outside it was cold, drafty, overcast and damp. Inside there were two boilers but they were never on. The reason was that every calorie of heat was being extracted from the system to be reused again. The battery of solar panels was raising the water temperature to 85F (and I never saw the sun) and then heat exchangers removing the heat from the used room atmosphere were adding to that. The major boost came from the geothermal pipes where the ground is used as a heat producer in the winter, adding about another 15F, or as a heat extractor in the summer, removing about 15F.
Every stage is monitored digitally and every output reacts to the different levels of occupation of each individual room in terms of temperature, lighting and CO2 content.
The total cost was $4.2m which gives a direct payback period of 14 years. But school heating systems are planned to be replaced every 20 years. This has a 40 year plus renewal program. And the system has already saved $5000 in running costs.