[Greenbuilding] South-facing windows are net energy gains...

[John Straube]

As usual, the challenge is that sunny days are NOT like coin flips, and you cant reach high solar savings fractions using average monthly or even daily data.
Monthly average data can get major savings like 50%., but to get into the 60's and higher is really hard in all cold climates.  Simple back of the envelope calculations are a great start but studying and measuring actual buildings is better.
The highest solar savings fraction that has been documented is now a sola seasonal storage system in Alberta and it is drifting toward 90%
Rather expensive, works only at scale, but neat to see for me.
See www.dlsc.ca and look at the most recent newsletter, or just browse.
All other documented buildings, including highly insulated ones with solar air heating, are much less. Direct Gain systems through windows do about as well as trombe walls, solar heaters, roofs etc.
Norm Saunders probably got some of his homes to 90%+ (100% if you were willing to freeze) but this was never documented.

John

On 2011-01-12, at 8:46 AM, nick pine wrote:

> "Doug Kalmer" <dougkalmer at gmail.com> writes:
> 
>> If you choose the right glazing, your windows can gather more energy than they lose
> 
> Not true, on cloudy days.
> 
> Lawrence Lile <LLile at projsolco.com> writes:
> 
>> Greetings from Missouri, where we are treated to a month of clouds in a typical November.
> 
> NREL says 720 Btu/ft^2 of sun falls on the ground and 1020 falls on a south wall
> on an average 46.2 F November day with a 54.7 high in St. Louis.
> 
> 

Dr John Straube, P.Eng.
Associate Professor
University of Waterloo
Dept of Civil Eng. & School of Architecture
www.buildingscience.com