Windows play vital roles in our homes: bringing in natural light, connecting us visually with the outdoors, providing fresh air during warm months, helping to slow down heat loss, controlling unwanted temperature increases from sunlight (solar heat gain), and contributing to overall appearance. Balancing these attributes can be complex because some conflict with others; for example, a feature that optimally blocks unwanted summer heat gain may negatively affect views, daylighting, and beneficial solar heat gain in the winter.
But what should be done about existing windows?