“Layton Consulting Fenestration Nerds” By Anton Van Dyk: Triple Glazing and Your Carbon Footprint.
There is a relatively new conversation occurring in the fenestration industry and that is around EPDs, otherwise known as Environmental Product Declarations. These are the documents that identify the amount of carbon used to manufacture and transport the product. It seems that at every conference I have attended lately, was a speaker on this topic. So, the big question everyone is asking is “How much embodied carbon is in your product?”.
What I find interesting is that about a decade ago, I toured my first glass float plant and one of the first things that I noticed was the size of the “smokestack” that was coming out of the roof of the building. It resembled a coal-fired plant from 100 years ago. To this day I remember my first question -“How much natural gas do you burn a month?” At that time, it was 1 million dollars worth. Not that it means much today, but it was a lot for that time. Enough for me to realize something way before EPDs were a thing, it takes a lot of carbon to produce float glass.
If you have never seen how glass is made, just consider what it takes to melt sand and then float it on a bed of molten tin to make it smooth and clear. You heard that - molten tin. Glass floats on molten tin just like oil floats on water. It's how we can achieve very clear glass surfaces.
At this time, energy codes in my region were starting to be codified for the first time and awareness of higher-performance windows was starting to take shape. The City of Vancouver passed one of the first building codes in North America that limited the use of a window to U1.44 which started to create a unique conversation. What does it take to achieve U1.44 and what new features should I consider in a window?
Some early assumptions from designers were that this would take triple glazing, but LowE technology at that time created opportunities that allowed double glazing to still thrive so the upgrade cost was not as significant as some assumed it would be. But what did happen was a new conversation started to take hold and that was: "What would it take to achieve higher performance windows and what technology would we need to consider to meet new codes?" The reality was that we knew codes would tighten and triple glazing would be in our future for more and more homes. Now keep in mind, I’m from Vancouver which has a fairly mild climate so triple glazing was never really a big topic for discussion as it never seemed to be needed to meet expected comfort levels.
As a result of this, I started to think and ask an interesting question which was “How much embodied energy does it take to manufacture a triple-glazed window versus how much energy would a triple-glazed window save in a mild climate like Vancouver? I asked this question as often as I could, in my lunch and learns, on Twitter, LinkedIn, etc. No one had an answer. Well, fast forward a decade and we are starting to have answers to this question. I was close at the time using the term embodied energy, and now we use the term embodied carbon. I could relate more to the term energy than carbon as I cannot picture a KG of CO2 but I get a hydro and gas bill in the mail so using energy as a metric made more sense to me as a homeowner.
To this day I still have not had a single person in this field be able to answer this question which kind of worries me. The reason why is too often I see prescriptive building designs ask for triple glazing in conjunction with a performance range of U1.20. The issue with this is that with LowE technology today you can achieve U1.20 ranges in double glazing for mild climates that have lower condensation risks on the inside surface of the glass.
So what do we do with all this info? Well, we can simplify it down to some core factors. These are:
Double glazing can achieve U1.20 range performance using surface 2 and 4 LowE. This does increase condensation risk but it is ideal for mild winter climates such as Vancouver. Condensation can still occur, but usually on those few extremely cold days that happen only a few times a year.
Triple glazing consumes more carbon than double glazing.
Hydroelectricity in regions like Vancouver is a low-carbon energy source.
When you package all this into one decision tree, you can start to see that the general assumption that triple glazing is better, may not be.
As the requirements become more and more technical, the need for a comprehensive submittal package that you can send to an architect for project approval will become the most important document that you will have in your organization. So if you have not considered this, it is now time. Let me know if you need some help. I’ve been down this path a few times.