> Flat or float glass plants (NAICS 327211) operate high temperature furnaces that melt siliceous minerals and other materials to produce glass typically used in windows, glazing, and windshields. Glass manufacturing is energy intensive and a significant source of greenhouse gas (GHG) emissions from the industrial sector. Emissions from plants producing flat glass are the largest source of GHG emissions in the manufacturing lifecycle of products made with flat glass. In 2019, 22 flat glass plants reported direct emissions of 2.95 million metric tons of carbon dioxide equivalents (CO2e) to the U.S. Environmental Protection Agency (EPA). Emissions from these plants represent nearly 70% of total direct emissions from flat glass industry.
One advantage of glass is that it's infinitely recyclable.
Wood+epoxy is probably a nightmare to recycle and will just end up in dumps and further contributing to the microplastic problem our world faces. Maybe it's fine. Maybe in 50 years we'll look back on the idea the same way we would if somebody made walls and phone parts of wood mixed with asbestos and lead.
For the recyclability of glass - absolutely. But when we're dealing with windows for houses, while they are recyclable, we're not talking about the glass bottle cycle (wine bottles, beer bottles, soda bottles), but rather windows that tend to be on the 10 year (or longer) length of time.
The recyclability of the house that I currently reside in (different house) has windows that are at least 40 years old (and possibly some that are at least 80). The most recent ones were some done about 20 years ago, and I've got no intention of replacing them (they work quite well).
Glass is recyclable and I wholly advocate its use for bottles and the like.
But how old are the windows in your house? When you replace them - will they be recycled or thrown out with other structural construction waste? When your garage door gets replaced (that's 30 years old), will you separate out the three one foot square windows from that top panel and send that separately to the recycling center? Or will it all get tossed in the large garbage hauler?
I'm not saying that this is good, but rather that the use case for glass (or similar material) for a window in construction tends to have a different life cycle than the wine bottle.
I was replying to wood being a carbon sink being relevant. You are right that the point of comparison should be on the whole process on both sides. Wood being a carbon sink is a component in that, but I doubt that it's hugely relevant.
That quote about absolute emissions doesn't tell me much. The link has a much more useful metric: ~0.55 tons of CO2 per ton of produced flat glass. This is the number that a new process is competing with.
Another consideration is longevity. The rate of amortization acts as a multiplier for carbon footprint. It's hard to compete with glass in this area too.
A biodegradable window in a building wouldn't be much use, you'd have to replace it constantly each time it rotted away. Except maybe in a very dry climate.
I suppose you could paint it, if we also had transparent paint. Well, there are lacquers.
Biodegradation is very much a function of conditions. Wood is biodegradable, but a well built house can avoid biodegradation for hundreds of years. Wood-framed windows are just fine with, in my experience, two caveats:
1. Rainwater needs to drain, even from gnarly little spaces like where the glass meets the wood. If the exterior wood is painted, then the paint needs to be maintained.
2. Interior humidity can and will condense onto the glass if the interior dewpoint is higher than the surface temperature. This can be hard to avoid in cold climates, especially if there are insulating window coverings over the glass. That condensation can drip onto the wood frame. (And, worse, could go through it into the wall cavity. It’s rather rare for the inside of a wall to be waterproofed and flashed like the outside ought to be.)
If I were building in a cold climate, I would stick with moisture-insensitive window frames. (Although aluminum, which can be quite pretty, has terrible thermal performance.)
Yeah, I'm familiar with these issues, living in a 70-year-old hardwood framed and clad house with decaying paint in a wet climate. I'm renovating it gradually.
