Replies

1. Expert Member
   Dana Dorsett|Jul 29, 2021 05:26pm|#1

   Having high SHGC windows is fine for heating-dominated zone 4C, especially when there are 2' overhangs.

   不深思热增量问题。记住that the traditional clear glass single panes & clear glass double panes of the past (which are still installed in most homes in the PNW) have an even higher SHGC than Anderson PassiveSun glass, and most homes in 4C (even those with poor shading factors) do just fine without central air (except at the recent record-setting heat wave.) ANY low-E coating cuts down some of the heat gain, and there is a much longer & deeper heating season than cooling season.

2. 
   Mark Nagel|Jul 29, 2021 05:39pm|#2

   Kevin,

   It's not Summer that's the problem, it's the shoulder months. Early Fall and late Spring bring the sun lower on the horizon during times where the air temperatures are still in the cooling season ranges. The sun drops from overhead to shine under your roof and, depending on their extent (you say 2'), overhangs. This presents possible overheating conditions.

   This is always the tricky part of utilizing solar heat gain.

   For myself (just a bit north of you) I'll have a 6' porch on my south side. It'll catch a lot more of the shoulder-month over-heating problems while allowing the solar gains in the cooler months (I have unobstructed solar as long as there are no clouds- ha ha!). I plan to also deploy external shades from my porch eves should I require even more shading.

   So... don't worry about solar gain in the summer months (other than from East and West exposures- West being the harshest and most problematic). Worry about how to deal with the shoulder months.

   Also, coatings tend to reduce solar heat gain while also tending to retain more heat inside the home. Can you can chicken-and-egg? For myself I'm going to focus more on my "focus," that is, I'm going to measure more (for my southern windows) on visibility quality (more coatings lessen visibility).

3. Expert Member
   Dana Dorsett|Jul 29, 2021 05:53pm|#3

   >"Also, coatings tend to reduce solar heat gain while also tending to retain more heat inside the home. Can you can chicken-and-egg? "

   I say egg! :-)

   Most people in zone 4C already live with much higher SHGC windows than PassiveSun glazing. This is more of a "Princess vs. Pea" sensing issue than a real problem.

4. 
   KevinDowns|Jul 29, 2021 07:30pm|#4

   Dana,

   Thanks for the reply - I think you're right that I might be overthinking things (my wife would also agree). I'm sure the recent heat wave would make us uncomfortable regardless of my window choices.

   Mark,

   I should have specified, my house will be two stories, so the overhang will have less of it's desired impact. Upstairs on the south side will have 8' of overhang on the porch.

   The issue you present about shoulder months is definitely valid but I'm also leaning toward visibility quality, like you, due to the river view. Hoping that ventilation from the bifold and windows can help mitigate extra heat during these problematic months (especially problematic this year).

5. 
   Mark Nagel|Jul 30, 2021 10:42am|#5

   Knowing your/one's requirements, priorities, helps a lot. Then it's a matter of determining how you mitigate those things that fell lower on the list that weren't addressed by the primary solution (such issues will then, later, be sensed as higher-level issues as the original higher level ones were already dealt with).

   Another possible mitigation solution (from a quick internet grab):

   https://h-hmetals.com/products_and_services-item/aluminum-sunshades/

6. 
   KevinDowns|Aug 03, 2021 02:22pm|#6

   Mark,

   A great way to navigate lots of these problems! Thanks for the link - I was considering something along those lines in the future, should additional shading become necessary. The structure is there for attaching, and the design would mesh well.

   Cheers,
   Kevin