Modern windows can negatively impact our health because they block large portions of the light spectrum specifically near-infrared (NIR) and UVA light, both of which play an important role in cellular energy and overall vitality. Sunlight is our primary source of NIR, and when we spend most of our time indoors behind the now standard “low-E” windows, we’re removing key inout signals that our bodies rely on. You can test your windows at home by feeling how much heat passes through the other side or seeing if there is a mark/text for “low-E coating”. Small environmental design changes can have a major impact on how you feel each day, especially if you don’t have the luxury of being able to spend the majority of the day outside (most people). If the weather is warm enough opening windows fully is the best option for better light + more negatively charged “fresh” air. If you live in an extremely hot and sunny environment (ie Arizona)  having low E windows may still make sense. However overall I think energy efficiency standards has come at the cost of our own cellular energy, and is not the tradeoff I want to make.