Decades ago there was a fairly extensive efforts to help manage solar heat gain and cold weather heat loss through windows around the nation. Since most windows were single glazed and not even thermally improved in any way, these methods resulted in significant changes to energy transfer through windows. Adding a metalized film to the interior side of a sheet of plain glass, using heat reflective blinds, or insulated interior window coverings made a dramatic difference when there was so little resistance to the passage of energy through most windows back then. Of course most of us have plenty of anecdotal experience about how this did or did not work but we may not have the utility bills from when these materials and devices were first installed and how those bills may have gone from sky high to a notably lower high elevation, at least initially.
Today the use of low emissivity, blocking, and reflective factory integrated coatings are the norm as is some thermal improvement through multiple pane, warm edge spacer, and thermal break framing techniques. However, our need to create far more energy efficient building stock than is the norm now means the big changes we have made these many decades do not cover anywhere near enough ground. It really is time to start looking at windows in any form (be they skylight, curtainwall, or punched window) as the open energy doors they are. When we decide to include far more window than we need practically for views, daylighting, and natural ventilation we are most often making a conscious decision to increase energy usage, increase glare, decrease occupant comfort, and accelerate the aging of interior artifacts and furnishings. We then further amplify these troublesome decisions by not designing active window coverings in to our buildings. I suggest that the percentage and design of windows should naturally suit the internal use of a building and that those windows should be managed with active shading systems that control glare, address privacy, and most of all limit, as much as possible, how much unwanted solar radiation heats up our buildings when cooling systems are operating.
We rarely think twice when we manage our doors to prevent loss. We should treat windows the same way as there is so much to lose at this point in history.