Idea for cheap ultra low U windows
Interior storm windows are often recommend for energy retrofits:
http://www.aboutsavingheat.com/windows.html
(Scroll down to “Easyslider”)
Next, let’s assume that half the windows in the average house could use obscure glass (most bedrooms, all bathrooms, all basement rooms, hall and stair windows, etc.).
Let’s stuff some attractive white fiberglass between the window and the obscure Easyslider.
Kalwall already does this, but all their fenestration is custom built and expensive.
Condensation is a worry, so I’m wondering if anyone has seen or done this before.
Lowe’s carries white J-M Comfortherm batts, but has anyone seen a source for that stuff that looks like “spun glass”?
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The website you linked to begins "Windows are the eyes to the soul of your house!"
What's the point of windows if they're going to be turned into walls?
Light?
That's a clever idea for obscured glass. In my experience though, home owners rarely want more than 2-3 obscured windows in their homes, and most are lower sash only for privacy. I'm not sure there's much benefit for so little u.i. of glass. I find that the gaps around the sashes and rough opening provide more opportunity.
I am a big fan of interior storms, however, especially in architecturally significant homes. It's the best way to preserve the esthetic and achieve a meaningful thermal upgrade to single strength glass. I find replacement windows rarely have a place in our energy retrofits.
Kevin: Yes light is the answer. How much light comes through obscure glass and a fiberglass batt?
Robert: "thermal upgrade to single strength glass" - you mean single-glazed, single strength is the glass pane thickness (3/32" as opposed to double-strength at 1/8").
Robert,
Kalwall fenestration has about 4" of fiberglass and they claim 20% transmittance. What you wind up with isn't so much of a window as a daylighting source. But you can't work in a kitchen or office that has direct sun either. Daylight is about 20 times brighter than what's needed for human activity.
I realize that some windows are much more than just light sources, but in some rooms, that's all they are.
If the fiberglass insulation is absorbing some of that lost sunlight, then it will heat up and deliver some of that energy to the home just like a radiant heater.
Robert- I stand corrected. What a "pane" to have you criticize the "strength" of my word choice.
You're confusing many elements of lighting.
The outdoor light level is approximately 10,000 lux on a clear day. In a building, in the area closest to windows, the light level may be reduced to approximately 1,000 lux. In the middle area its may be as low as 25 - 50 lux. Additional lighting equipment is often necessary to compensate for those low levels.
The light level required for normal desk activity is in the range 500 - 1000 lux - depending on activity. For precision and detailed work, the light level may need to be 1500 - 2000 lux. Typical indoor residential spaces are in the 20-50 lux range.
Besides the light needed for normal human activity, we often overlook the fact that we evolved in the tropics in very high light conditions and both our bodies and our emotions require regular doses of high-intensity light.
The typical modern American spends as little as 20 minutes per day outdoors, and less in the winter or in very hot climates. Even in the near perfect climate of San Diego (mild weather and 80% more sunshine than other US cities), the typical resident was exposed to a daily average of 350 lux, with most of the day spent in less than 100 lux conditions.
Studies have found that without sufficient daily light exposure, people fall into depression (or what is now called SAD). Treatment for SAD requires at least 30 minutes of 10,000 lux exposure per day or 2 hours of 2500 lux exposure.
Daylighting in our homes not only saves our emotional and psychological health, but also saves energy by requiring less artificial lighting.
And, by the way, if fiberglass between windows absorbed any solar heat it would radiate it outward to the cold side, not inward to the warmer materials and people.
Remember, I'm just brainstorming here, and looking for REAL achilles' heels to my ideas. SAD is still SEASONAL affective disorder, not window light deprivation disorder.
The R16 window I'm proposing could be huge if wanted. Then, depending on the room, another small operable window could be provided. Now you have tons of light, air, low heat loss, and even a view to the outside for a low cost.
This is also what the "aerogel window" developers are hoping for.