A question we are often asked is, "Do you put argon in your units?" It's an understandable question. Big window manufacturers have strongly pushed the idea that your window units need argon to be efficient. And yes, it is true that argon can increase the efficiency and insulation of your units. But is it worth it?
First, some background. Argon is a noble gas. It is heavier and denser than the air we breathe. When using it in an IGU (insulated glass unit), we first assemble the unit, then poke two holes in the side. Argon is pumped into the lower hole, pushing air out the top hole until the unit is filled, like a balloon. We then seal over those holes, and apply sealant to the entire unit.
Having argon-filled units will impact their insulating properties, but by how much? In an average window unit, argon will increase the R-Value (a measure of insulation) by only 0.5. It will also do nothing to prevent UV radiation coming through the glass. A far more effective barrier system would be to use low-e (low emissivity) glass, which will accomplish both of those tasks.
Further, argon molecules are smaller than those of "room air." This means that, if there is any flaw in the seal, argon is able to leak out of a hole that is too small for air to get back into. This leads to a vacuum inside of the unit, which will draw the two panes together, possibly even breaking them. The next time you are out and about, look at the windows around you. If you see any that are warped and have a reflection that looks like a bubble, that's lost argon! And argon is small enough that it will leak out. Generally, you will lose argon at a rate of approximately 1% per year, which means that all argon units have a lifespan that is not necessarily going to relate to how long their seal lasts.
For those reasons, we tell customers that in the vast majority of cases, having argon in your unit will cause more harm than good. Can we do it? Yes. In fact, in the picture above, those are our argon tanks. We would make money off of pushing argon, at a rate of an additional $2/sq ft. Still, we will nearly always strongly advise against it. It's just not worth it.
~Fanon