1) Solar Heat Gained by the Windows
Please refer the heat load calculations form above.
Firstly, find the direction of all the windows using magnetic compass. In the accompanying heat load calculations form, you will notice six directions of the windows: northeast, east, southeast etc. Separate north direction has not been mentioned since it is assumed that heat absorbed by the windows in north direction is very small. For all the windows in all the directions measure the dimension of windows and fill the details in appropriate column. For instance, if there is a window of 24 sq ft in north east direction, fill the details for North East in the “Item" column the area of 24 in the “Area" column. Similarly, fill the areas for all the windows located in all the directions.
Next, select the proper factor for each of the windows from “Factor" column and round the appropriate factor. For example, for the northeast direction window if there is external awning round off the factor 20 associated with outside awning. Reduce this factor by appropriate margin for glass block windows, storm windows or windows with double glass and find corrected factor. In a similar manner, round off the associated factors for all the windows in all the directions and apply correction factor wherever necessary.
Next, multiply the area of each window with the corrected factor associated with it. These details are filled in the “Area x Factor" column. The maximum value of this column has to be filled in the last column of BTU/HR that indicates the solar heat gained by the windows.
Next, you have to find out the solar heat gained by the windows due to designed dry bulb temperature difference between outside and inside. For this firstly, find the total area of all the windows and fill them in the area column. Find out if the windows are of single glass or double glass and fill the details in the appropriate areas column. Now, round off the proper factor for the designed dry bulb temperature difference. For example, if the desired dry bulb temperature difference between the atmosphere and the room is 17F the associated factor would be 22 for single glass window and 10 for double glass window. Multiply the total area of the window by this rounded factor and fill the result in the last column that indicates the total BTU/HR gained by the windows.