Since windows vary in size, the calculated thermal performance specifications produced by HOT2000 are likely to vary from the specifications provided on the manufacturers label. Similarly, windows using the same User-Defined Code will have different calculated thermal performance specifications if they vary in size.

The example that follows highlights the variations in HOT2000's calculated thermal performance specifications for windows of different sizes.

Step 1: Create a User-Defined window code by selecting Editors > Code Editor > Window Codes > New User-Defined Code (yellow hat icon in the toolbar) > Overall Window Characteristics.

The fields are then populated with the manufacturer's specifications (which represent results obtained through testing).

In this case, I have created a window code that meets the U-value requirement for a home located in Climate Zone 4 or 5.

Step 2: Add windows to the model and populate the Window Screen with accurate information. The Window Code created in step one should be available from the drop down menu.

In this case, I have created a window with dimensions that match the reference size for this type of window.

Step 3: I will repeat Step 2 and create an additional window, using the same User-Defined Code but varying the size. In the end I will have two windows, one of reference size and one four times larger.

Below is a snapshot of my windows taken from the Summary View. Aside from differences in size, they are identical windows installed in the same location.

Notice the difference in the calculated SHGC. This is due to the performance scaling equation used by HOT2000 to determine the actual performance of each window modeled.