Argon vs. Krypton fill in IGUs
We’ve finally had it with all the interior shrink wrap plastic covering our remaining single pane (fixed) windows so i am now looking to re-glaze them with IGUs. (We live in the greater Boston area in a house surrounded by trees filled with walls made from single pane windows occasionally supported by a 2×4 wall, so utility costs and comfort is dominated by heating – ~$1000-1200 p.a vs. no more than $100 p.a. for cooling)
Our existing window frames have relatively limited depth, so optimal IGU thickness is 5/8″ although I can squeeze in 3/4″ thick IGU. The larger windows need thicker glass, limiting me to 3/8″ spacers without alot of work on the window frames
I know Krypton is optimal with the 3/8″ spacer, however, i have not gotten any glass companies to give me a quote on the additional cost of krypton over argon (most have said they have never even seen one outside a trade show, which seems problematic), or the exact U factor performance boost, so i cant calculate if it will be worth the additional cost. So far i’ve gotten:
IGU price of roughly $16-18 / sqft with Solarban 60 and argon fill. (with the Argon fill costing about $2-3 / sqft). -I have lots of tree shading, so very limited to no benefit to going to a higher solar gain coatings, and the solarban 60 will match the smaller movable window sashes i’ve already replaced
Center of window U factor of 0.24 (day) and 0.29 (night) using solarban 60, 1/2″ spacer, argon fill, @0F) – and because the windows are large, the center window U factor is the only one that really matters, and i am not replacing the window frames.
I know going to a 3/8″ spacer will increase the U factor, but as i’ve seen several graphs showing Ufactors by spacer thicknesses, with one showing only a minor loss in argon performance at 3/8″, and another showing substantial loss.
Question 1: How big of a U factor penalty will i face moving an argon fill window to 3/8″ spacers over a 1/2″ spacer at winter temperatures in Boston (which is warmer than 0F on average)?
Question 2: How much lower will the U factor go with a Krypton fill at a 3/8″ spacer at similar temperatures?
Question 3: What exactly is the price difference between argon and krypton? And would there ever be a payback scenario where it would make sense, assuming these windows also last 50 years?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part