Climate Minute #2: Tightening Up Windows
Single-glazed Windows – A Blight on Your Budget and the Planet
Heating and cooling our homes is a major source of greenhouse gas emissions. Windows (especially single-glazed ones) are one of the worst causes of the energy use that creates those emissions.
Single-glazed windows are like thermal holes. They are the source of enormous heat loss in the winter and heat gain in the summer. They have an impact similar to a hole in the wall of your house.
So: get rid of single-glazed windows! But don’t replace them with double-glazed windows - the future is all triple! Triple-glazed windows are no longer much costlier than double-glazed. A recent quote from Marvin windows showed only a 10% difference.
Benefits of Triple-glazed Windows
Triple-glazed windows will:
● Save you money - winter and summer - for as long as you’re in your home
● Increase the resale value of your home
● Be much more comfortable to sit by in the wintertime
● Reduce energy use and related emissions
● Help you be a good steward of precious Lincoln buildings that may last hundreds of years, benefitting both you and future residents
You get a lot for your investment!
MassSave provides 7-year, no-interest loans for approved triple-glazed windows replacing single-glazed, plus rebates of $75 per window. (Note: Neither incentive applies to double-glazed windows replacing single-glazed. The Commonwealth is clearly promoting triple glazing.) IRS tax credits of $600/year (resetting each year) are available for qualifying windows, so spreading work over several years can bring down the cost further.
What’s it likely to cost to replace single-glazed windows with triple-glazed ones? See table.
A single-glazed window replaced with a triple-glazed unit will yield the most energy-efficient result. Another option, for windows that are fixed (very common in mid-century modern homes) or never opened, is to leave the single-glazed window in place and install two interior panes.
Improving Double-glazed Windows
Energy-efficiency experts generally don’t recommend replacement of double-glazed windows because of the high amount of carbon embodied in them. However, such windows should be replaced with triple-glazed units if the seals fail or if exterior walls are being upgraded as part of a renovation or energy retrofit.
Older double-glazed windows with narrow spacing between panes, no inert gas (e.g., argon) and/or no low-E panes are only slightly better than single-glazed windows. For such windows (and even for good double-glazed windows) consider inexpensive ways to improve their efficiency.
The Bottom Line
There are many ways to improve poorly performing windows. They all have good long-term financial benefits, make your home more comfortable, and help you be a good steward of your home.
For more details on improving your windows, see the recording of the February 28, 2023 CFREE Zoom presentation Getting to Zero: Windows.
Michael Moodie,
on behalf of CFREE (Carbon-Free Residential, Everything Electric), a working group of the Lincoln Green Energy Committee.
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