For calculating the heating surfaces of radiators and pipes for schools, greenhouses, etc., the following notes are useful: - For brick buildings, for a temperature of 50° F., use 7sq. ft. of heating surface for every 1,000 cub. ft. of space; for 55° F., use 9 sq. ft.; for 60 F., use 12 sq. ft.; for 65° F., use 15sq. ft.; for 70° F., use 19 sq.ft. For lean-to glasshouses, for a temperature of 45 F., use 37ft. of 4-in. pipe for every 1,000 cub. ft. of space; for 50° F., use 40 ft. of 4-in. pipe; for 55° F., use 45 ft. of 4-in. pipe; for 60° F., use 50ft. of 4-in. pipe; for 65°F., use 55ft.of 4-in. pipe; and for 70°F., use 60ft. of 4-in. pipe. For spau houses, add one-fifth.