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

[Lawrence Lile]

> 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.
> 

NREL can say whatever they want, but they haven't bothered to look outside at the coating of lead that substitutes for skies around here.  Weather averages aren't very good at representing extremes that happen rather regularly, but not always on the same date.  "Average" January around here is supposedly 30F because it might literally be 0F or it might be 60F on any given date.   EVERY January the ponds freeze over thick enough to walk on, requiring a couple of weeks below 20F to achieve that.  Maybe they freeze over in the first two weeks, maybe the last two weeks, but they always freeze over. If the temperature was really 30F all the time they would never freeze over. EVERY January we get at least one day dipping below 0F.   EVERY January we also get a few freak 60F days and maybe a week of 45F to raise the average to an unrealistic number.  Anyone who dresses for 30F every day is going to freeze their ass off, on average. Anyone who designs a house for 30F is also going to freeze their ass off.  I am pretty tired of hearing about average weather being anywhere near representative.  It isn't.    On average, year-round, the temperature here is 52F.  Should we design houses for 52F outdoor temperatures?  


Almost every year between Oct 15 and Dec 15  there are 2-3 weeks of solid overcast skies, maybe the first 3 weeks, maybe the last 3 weeks, maybe all in November, maybe not,  and my solar water tank never gets above 65F from a well temperature of 52F for the period.  Average that with a few sunny days or a freak year of great fall weather and you can come up with the BS numbers that NREL is quoting as "averages".  This is a distorted way of looking at weather data.  Real heating systems must cope with peak loads, not averages.