I've been preparing U-value calculations for the above floor type in accordance with ISO 6946 and 13370, but this particular building design does not feature the perimeter walls usually associated with this construction. In other words, the void below the floor is completely open and varies in height from 0.7 to about 2.7m. Would I be correct in using the exposed floor method here in lieu of EN 13370 where the floor void height exceeds, say 0.5m and is fully exposed? BR443 does not quote a maximum void height or maximum ventilation opening area for suspended floors, but ISO 13370 states that where the depth of the underfloor space exceeds 0.5m, then the method analogous to that for basements should be used to obtain the thermal transmittance (U-value) of the ground.
At present I am calculating the thermal transmittance of the floor deck (Uf) using RSe = 0.04 and excluding any insulating effect from the ground or void below the floor. Does this sound sensible?