If a bath window is glass block glazing with a total area of 15 square feet, what would the net winter heat loss be?

To determine the net winter heat loss through glass block glazing, it's essential to understand the material's thermal properties and how they affect heat transfer. Glass block usually has a higher insulation value compared to standard window glass, but still allows for some heat loss due to conduction.

The net winter heat loss is typically calculated using the formula:

Heat Loss (BTU/hr) = Area (sq ft) × U-value (BTU/hr·sq ft·°F) × Temperature Difference (°F).

For glass block, the U-value can vary, but it is generally in the range of 0.50 to 1.00 BTU/hr·sq ft·°F. In winter calculations, the temperature difference is usually the difference between the indoor temperature (typically around 70°F) and the outdoor temperature (which can fail to drop to 0°F or lower in many regions).

If we consider a U-value of approximately 0.40 BTU/hr·sq ft·°F for glass block (which reflects its insulating properties better than standard glass), and we measure a temperature difference of 40°F (70°F indoors and 30°F outdoors):

Heat Loss = 15 sq ft × 0.40 BTU/hr·sq