In the book "Modern hydronic heating for residential and commercial buildings" by john seigenthaler...during heat load calculation, "exposed ceilings" are only considered. what does this term mean?? does this mean that it is single storied building and is it okay to overlook the heat loss from the floor and what about the ceilings common to two rooms which are anyway going to be heated?? please help me remove this confusion.

Only surfaces that are actually “exposed” to the outdoor temp are “considered” when performing a heat gain/loss analysis. “Exposed” means that the surface is at the outdoor temp on one side. “Considered” means that the surface area is included in the analysis. Surfaces that have BOTH sides at the same indoor design temp are NOT considered.

Thank you so much sailawayrb!!!

What about considering the heat loss from the ground floor since it is in contact with the soil beneath?? should it be dealt as if it is exposed??

Yes, floor heat loss should be considered too. Floor exposed perimeter is normally used in the heat loss analysis in lieu of exposed surface area like as is normally used for ceilings and walls. Perhaps try our free DIY heat loss software after first reading the associated software instructions:

Borst Heat Loss Analysis Software