If the floor was lying on the wet ground, a vapour pressure gradient (Fig. 15.4) will cause the water steam, rising to a vapor barrier. Given the temperature of soil in 10C in the UK, the bottom plate can be as cold as 0C after many months of work of shop, and any moisture condenses under floor insulation freeze, and, in the cold and expand. During the " lens " ice plates of the floor, unable to expand down, raise the floor (frost heaving).
Frost heave prevents the supply of low-intensity heat to the lower insulation to keep it above the freezing point. This can take several forms:
Low-voltage electric resistance heater cables fixed structural slabs of the floor, and then protected within 50 mm of a thickness of cement and sand to give a suitable surface on which floor of a vapour barrier can be pledged. Heating with thermostat, and usually include distance read or write thermometer to give a visual indication of the temperature of the floor in several places below isolation.
Pipes buried in the structural slabs.
They are connected with the delivery and return headers, and glycol is circulated. In this heated by the waste heat from the refrigeration plant. MDPE (medium density polyethylene) is a normal pipes under the floor glycol heater mats. Steel pipe should not be used under the floor, if not protected from corrosion.
The vent pipe to allow the current ambient air through the soil under the base slab. It is not very suitable in cold climates.
At the very damp earth or where the finished floor level shall be in accordance with deck vehicles, cold store floor can be raised above the existing ground level. This is done by creating a dwarf wall or increase of the length of piles, if they are to support suspended floor
at the correct height. This leaves a void air about 1 m under the cold store, through which air can circulate naturally, though, forced ventilation may be necessary to reduce condensation.
Cold storage