well, you could use a rule of thumb such as: 1.5 cfm per every square foot of office space. this will not only take care of your heatload, but will address your fresh air requirements. now convert this to 400 cfm per ton. then, for each ton, figure about 25000 btu. this converted to baseboard @500 btu per foot using 180 degree water will require 50 feet of baseboard. this formula sucks so dont use it in real life, just do a load calc!