What is the net heat gain on the north wall as per the calculations?

The net heat gain on a wall, such as the north wall in this scenario, is determined through calculations that typically involve factors such as solar gain, heat transfer due to temperature differences, and any heat generated by interior sources.

If the answer provided is 245 btuh, it suggests that the evaluation took into account all relevant factors influencing heat gain uniquely experienced by the north wall. This could involve aspects like the orientation of the wall, shading from surrounding structures or trees, insulation quality, and specific material properties that affect thermal conductivity.

In calculating heat gain for a wall, solar radiation and its angle can significantly influence heat absorption, especially in different seasons or times of the day.

The other choices represent different calculated values that might have stemmed from varied assumptions or inaccuracies related to the wall's exposure, the materials used, or miscalculations in the area of solar gain. Therefore, 245 btuh is the correct assessment based on the calculated parameters and configurations specific to the north wall, while the other options did not align with the correct set of variables or calculations performed.