I’ve heard that aluminum is toxic. At the same time aluminum frames are said

I’ve heard that aluminum is toxic. At the same time aluminum frames are said to be the healthiest choice for replacement windows, especially for those who are chemically sensitive. Are aluminum windows safe?

—F. Lane, San Diego, CA

Aluminum can be toxic if ingested in large amounts, but there is no evidence that it causes health problems through the kinds of minor skin or airborne exposure one might receive from a window frame. As such, aluminum window frames are certainly healthy alternatives to fiberglass or vinyl, each of which are problematic because they can “off-gas” chemicals like formaldehyde into the indoor environment of your home, which could in turn aggravate chemical sensitivities.

Homeowners should be sure that any aluminum windows they install feature “thermal breaks,” a design that involves fusing two separate frames together so as not to conduct the heat that precipitates mold growth. Millions of people are allergic to mold, which can spread from window frames to the wood structure of a house and cause widespread rot.

On the downside, environmentally conscious consumers should know that the manufacture of aluminum is energy intensive and requires the burning of significant quantities of fossil fuels. Recycling your beer and soda cans can help reduce this problem because it takes far less energy to re-process aluminum than it does to produce it from scratch. Fortunately, a high percentage of aluminum is already being recycled today.

Also, John Bower, founder of the Healthy House Institute and author of several books on eco-friendly design and building, recommends putting triple glazed “low-emission” (“low-E”) coated window glass in aluminum frames to preserve indoor air quality and maximize energy efficiency. “Over their lifetime, houses [with these windows] should save more energy than was consumed to process the aluminum frames in the first place,” he says.

Wood window frames, as long as they are not “pressure-treated” with arsenic-laden pesticides or harvested from endangered “old-growth” forests, are also an attractive, healthy and green-friendly alternative to fiberglass or vinyl frames. But aluminum still provides more bang for the cost-conscious consumer’s buck, often costing less than half of what wood frames would set you back.

CONTACTS: The Healthy House Institute, www.hhinst.com ; Energy Star Anatomy of an Energy Efficient Window, www.energystar.gov/index.cfm?c=windows_doors.pr_anat_window.