Questions from Client Regarding Healthy Window Replacement Materials
Question: "Can you suggest the least expensive and environmentally safe window replacement materials for the chemically sensitive? I currently have large old casement windows. They are rusting and have cranks that get stuck. Although the look is delicate and clean-lined, I must replace them. Most high end, energy-saving brands may have toxins that outgas."
-- a.r., Long Island, New York
Answer: "Thanks for your question on replacement windows. Here are my thoughts:
"Regardless of materials, it is also extremely important that the installation and flashing be done properly so that rainwater does not seep into the wall cavity. Also, builders whom I know here in Minnesota say that you want to avoid any window assembly that combines metal and wood, because they do not bond properly. (This information is all on pages 73-74 in my book, 'Breathing Walls'.)
"Local experts here in Minnesota recommend fiberglass, as it flexes and will not separate at the caulk if it gets dinged or hit by large hail, as metal window cladding does. They say fiberglass is more flexible and forgiving, allowing the caulk to remain undisturbed if the frame is disturbed.
"Polyurethane caulk lasts longer and will bond to glass much better with glass than silicone caulk, but I know there are MCS sensitivity issues. I know of an aquarium-grade non-toxic silicone caulk by GE, but I don't know how that would hold up in outdoor weather over time. As long as it was reapplied every two years or so, you might be okay.
"Experts say sealants behind metal window frames fail over time and need to be replaced every 12 years. They also recommend leaving a gap at the bottom of windows to let rainwater escape.
"Local experts use wood-frame windows and repaint and recaulk them regularly. Then they last the longest. Old solid wood windows from 100 years ago, made with rot-resistant oak, were the best. All finishes for you need to be non-toxic, but perhaps that would be your best bet, installing custom-made wood windows that you have maintained regularly."