Reflective window films pros and cons
A reader asks if adding a reflective window film will affect heat transmission in winter.
I live in an apartment with large northwest facing glass doors leading to a balcony and central atrium. Even though we are good friends with our neighbours across the atrium, it would be nice to have a little more privacy than we currently do. I don’t like having our blinds (made with “Ecoview” fabric) down all day and I was thinking of getting a window treatment that makes the glass reflective so you can’t see in. Would this adversely affect heat transmission in the winter? Would it also reduce the amount of light entering the living area? We also have a retractable awning that helps keep the sun off the windows in summer.
Reflective window films that reflect light and thus provide privacy will indeed reduce solar gain in winter. The external awnings are the best way of regulating solar gain, day by day, regardless of what the seasonal averages suggest. The other characteristic of reflective films is that they rely on a particular imbalance of light, in that they will reflect to the brightest side. This is outwards during the day, but at night it is the reverse, thus making your blinds essential for privacy in any case.
The “Ecoview” blinds you already have are probably the best option for privacy while still getting some of the view, although when down they too will block some winter solar heat gain.
— Dick Clarke