ACCA MJ-8 and Window Heat Gain Calculations

Fenestration Cooling Load

There is a big difference between calculating heat gain for generic windows and advanced calculations when windows are rated by the National Fenestration Rating Council

For Generic windows

Tables 3A-1 (vertical glass) and 3C-1 (skylights) are used to locate the HTM.

Looking at Table 3A on page 289 we find all of the needed formulas. Table 3A-1 – Clear Glass is fairly straight forward. To find the HTM, the CTD must be calculated and the exposure known

Just make sure you understand that a Triple Pane window assembly has the same value as a Double Pane Low-e window assembly.

Now let’s look at Table 3D

It’s a whole new ball game, no wonder MJ-8 recommends using software to calculate the window loads. Using this method let’s look at page 303, Table 3D, Default Cooling HTM for NFRC Rated Fenestration Windows, Glass Doors and Skylights. Calculating the fenestration heat gains will require different formulas and more Tables to find formula values such as PSF and CLF (Table 3D).


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The problem with the Bus/Law Exam

The problem is time. 50 questions in 60 minutes requires a steady look-up. Time management and question management is the key, let me explain. In reality, you have a lot more time than you think. You have 60 minutes to get 35 questions right, any grades above 70% does not bring prizes. So you have 15 questions to give away, what next? First, concentrate on the questions that can be answered correct, saving any calculation questions for the end. Your approach to the Bus/Law Exam will determine how much time you have, its your choice. The questions are not that hard, its the time factor that’s tricky. You need to become very familiar with the Bus/Law material which requires some hard work and practice. NCCTI can help!