LoE 180 vs 272 with and without i89
Hello, I previously wrote asking general questions about window replacement LoE opinions for our passive solar home. We have made progress on researching your ideas and all the major window manufacturers as well as Alpen, and am reposting with a more specific question. As far as our house, the south side has well designed overhangs to let full sun in the winter and none in the summer. West side incoming sun is too hot for a few weeks in summer. Current clear double panes don’t condensate except for bathroom when I don’t turn on fan and it clears quickly. Oberon476 previously confirmed my thoughts for 180 with i89 all around except 272 with i89 on the west side and that is what we are shooting for.
Here’s our dilemma, we’re down to 2 windows manufactures that have the most of what we want. Both have 180 with i89 but only one gives the choice of 272 with i89, whereas we just found out the other can only do 272 with no i89 for those west windows. The price difference is $12k to get the i89 for seemingly similar quality windows otherwise. We hated the LoE 366 sample (too dark and green) we had in the home for a couple weeks so don’t want to go to that. (272 will also take some getting used to as our clear views are paramount.) I’d rather not give up i89 because it’ll take U value from 0.23 up to 0.30 (without argon). That price difference is hard to swallow but we’d get what we think we want. Thoughts?
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Is your goal here to cut down on solar gain (i.e. make the sun "less hot" coming in the windows), or to cut down on energy loss in the winter while still using solar gain to keep some passive solar heating? The biggest impact of those higher numbered low-E coatings is to cut down on solar gain, which will cut down on how much passive solar heating you get.
Personally, like the 180 coating with i89, then step up to full 1-3/8" depth triple pane IGUs (which many manufactures don't offer) if you want better U factor (less overall energy loss in the winter, mainly). I don't like the tint of the higher number coatings just like you've found, but they are needed if your goal is to REDUCE heating from incoming sunlight.
Bill
Thanks for your response. Almost equal goals of cutting down on summer incoming west window heat and to just a slightly lesser degree less heat loss and maintain some solar heating in winter. All with the overarching goal of as bright of light and clear views as possible. It’s a tall order!
I didn’t go toward triple panes due to cost and we thought the 272 would solve the overheating problem with i89 helping the u values pretty well. I know from experience we aren’t diligent enough to close the curtains and don’t like having the views closed in. My inclination is to go with the manufacturer that offered the i89 because this is a long-term purchase and I think we’ll appreciate the better U value in the winter of 272 with i89 rather than without i89.
you can always go the european route and buy exterior motorized aluminum roller shades :p
it won't be too cheap -- several hundred per window, but you could have some exterior applied solar film installed. thats if you go with 272 and find the solar gain to be too uncomfortable
https://llumar.com/content/dam/eastman/performance-films/llumar/nar/documents/english/arch/vista-arch-solar-safety-window-film-specs.pdf
llumar is a pretty big company with nice products. an exterior film would be 100% safe in regards to the IGU, while some interior films are not good.