Date: Fri, 15 Apr 2011 12:41:22 -0400
From: Dr John R Dykers
Subject: window energy loss – Vogler post 14 April 2011
Single pane glass prevents convection (air movement carrying heat) loss, but feel the inside of a single glass pane on a cold day outside and you can feel how cool it is – glass conducts heat. Glass also transmits radiant energy from the sun which then strikes whatever inside your house and is converted into heat energy; feel the top of the table next to a window that sunlight is streaming in – you can feel the warmth – good in winter, bad in summer.
A double glass pane has a layer of air trapped between the two panes and conducts less heat in or out but still transmits the radiant energy as above. A shutter ON THE OUTSIDE prevents this heating effect, the “greenhouse effect” that keeps a greenhouse warmer in winter. (see shutters on The Dykers Building 401-A N. Ivy Ave in Siler City – when used properly – Dr. Walker has them open now – they reduced the electric bill for cooling in Sumer by $100 a month)
Blinds on the inside trap the heat near the window but are not nearly as effective as outside shutter, just easier to open and close. Maybe Vogler has a system for opening and closing the outside shutter electrically that is easier than my office setup which requires opening the window and reaching out to close or open the shutters, a requirement on the second story in back, or walk outside and open or close and hook.
Storm windows also are great for reducing heat loss by radiation/convection back out, but still transmit radiant energy in from the sun, great in the winter. But they are a hassel to open when you want to allow a cool breeze in the summer.
I don’t know Vogler Blinds folks, but their post is reasonable and scientifically sound.
John Dykers