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Five step tutorial to calculating the heat load for your radiant heating projectBefore the radiant heating system can be installed one needs to calculate the heat load as different radiant heating system give different BTU output values. Heat load calculation consists of heat loss calculation and the surface heat loss calculation. Both calculations need to be done separately for each room in the house. One can make use of the floor plan as it provides the complete dimensions of the floors, ceiling and walls. Good way to start is to take the dimensions of the doors and the windows.Surface heat loss can be calculated in the following way: Step 1. Calculation of Delta T: Delta T is the difference between the indoor design room temperature (T1) and the outdoor temperature (T2). The indoor design temperature can vary between 68-72F depending on one's preference and the outdoor design temperature is usually low especially during the heating system. One can obtain the indoor design temperature by calling one's local utility company. For example: if T1 is 71 F and t2 is -5F, Delta T = 71F- (-5) = 71F + 5F = 76 F. Step 2. Calculating surface area: If the calculation for outside wall is done including doors and the walls then the calculation for the door and windows heat loss needs to be done separately. Wall area= H (height) *w (width) - DOOR SURFACE -WINDOW SURFACE For example Wall area = 9 ft * 22 ft - 21sq ft - 15 sq ft= 162 sq ft. Step 3. Calculation of U value: In obtaining the wall R value one can use the typical guides to typical R value and typical U value. U value= 1/R - value U- value Step 4. Calculating wall surface heat loss: The surface heat loss can be found out using the formula below: Surface heat loss= U value * wall area *delta T For ex Surface heat loss = .06 *136 sq ft * 77F= 628.32 BTUH Step 5. Calculate total heat loss of wall: One need to follow the following steps from one to four in sequential order to calculate the heat loss separately for doors, windows and ceiling. Calculate Door heat loss, Window heat loss, ceiling heat loss. Total wall heat loss = wall loss + door loss +window loss +ceiling loss Supposing if the wall loss + windows loss + door loss + ceiling loss value is (745 BTUH + 905BTUH + 700 BTUH + 1351BTUH) so the total wall heat loss is (3701BTUH) Air infiltration rate should also be taken into consideration. Following formula can be used for calculating the heat loss owing to air filtration. Air infiltration heat loss = room volume* delta T*Air changes per hour *.018 For actual calculation one may contact the contractor or the system designer. PEX Tubing, Taco Circulator Pumps, Takagi Tankless Water Heaters |