Excavations Part Two: The cool duct & cellar
In the low energy future that we face we will need to be able to store food in cool places without using the huge quantities of energy that freezers and fridges currently consume. I was inspired by the cool cupboard design that David Holmgren and Su Dennet used at 'Mellidora'. The idea is that cool air is drawn from a cool space (in their case, under the house), up through a cupboard and out a metal flue pipe in the ceiling. Fruit, most vegetables, cheese, butter and eggs can be stored in the cool cupboard for reasonable lengths of time at temperatures of around 10-15 degrees centigrade. While it does not replace the job of a fridge, it does reduce the need for a large fridge, reducing electricity consumption considerably.
The cellar will be used to store preserved and bulk foods, where more room is needed. The idea of integrating the cellar and cool cupboard makes sense to me, drawing cool air from a cool space - but comes at a price. Warm air will be drawn into the cellar constantly. After much discussion I believe that this will not have a big effect on the effectiveness of the cellar, as the space is surrounded by cool thermal mass which will help to regulate the temperature.
The cellar will sit about 1350mm underground, the roof of the cellar will be 1m above ground level and a 5000 litre watertank will sit on top. This will give a small head for the water (allowing gravity feed) and provide thermal mass above the cellar. I am considering siting a header tank for the house on a stand above the cellar/water tank.