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Xringer · 12-22-09, 02:48 PM

Heating degree day - Wikipedia, the free encyclopedia

"Calculations using HDD have several problems. Heat requirements are not linear with temperature,[2] and heavily insulated buildings have a lower "balance point". The amount of heating and cooling required depends on several factors besides outdoor temperature: How well insulated a particular building is, the amount of solar radiation reaching the interior of a house, the number of electrical appliances running (e.g. computers raise their surrounding temperature) the amount of wind outside, and individuals' opinions about what constitutes a comfortable indoor temperature. Another important factor is the amount of relative humidity indoors; this is important in determining how comfortable an individual will be. Other variables such as wind speed, precipitation, cloud cover, heat index, and snow cover can also alter a buildings thermal response."

I don't have a lot of windows out front, but they are facing south.
And, when you have a day like today, where it's been just above 30 degs
for the last 4 hours with plenty of sun, it gets warm in here..
All that snow in the front yard adds a bit to the solar gain..

I just got back from the movies (Avatar 3D) and my wife had set back
the Sanyo to 68, because it was getting too hot in the living room.

Right now, it's back to 70 in here, and the Sanyo was coasting using 470 watts.
But as the sun is disappearing, the usage is slowing climbing up to 600 W.

Since this is really a Tribrid heating system, I have to look at the solar gain for last year too.
Was it cloudy much last year?

We are seeing a reduction in our power bill right now, and it seems that
running the Sanyo when it's 15 deg outdoors is still cheaper than burning oil.

The oil truck was due here on Dec 21, but I called them to delay the delivery,
because we still have 3/4 of a tank of oil. (Down from 7/8 after the last fill).

12-22-09, 02:48 PM	#5
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	Problems using HDD data Heating degree day - Wikipedia, the free encyclopedia "Calculations using HDD have several problems. Heat requirements are not linear with temperature,[2] and heavily insulated buildings have a lower "balance point". The amount of heating and cooling required depends on several factors besides outdoor temperature: How well insulated a particular building is, the amount of solar radiation reaching the interior of a house, the number of electrical appliances running (e.g. computers raise their surrounding temperature) the amount of wind outside, and individuals' opinions about what constitutes a comfortable indoor temperature. Another important factor is the amount of relative humidity indoors; this is important in determining how comfortable an individual will be. Other variables such as wind speed, precipitation, cloud cover, heat index, and snow cover can also alter a buildings thermal response." I don't have a lot of windows out front, but they are facing south. And, when you have a day like today, where it's been just above 30 degs for the last 4 hours with plenty of sun, it gets warm in here.. All that snow in the front yard adds a bit to the solar gain.. I just got back from the movies (Avatar 3D) and my wife had set back the Sanyo to 68, because it was getting too hot in the living room. Right now, it's back to 70 in here, and the Sanyo was coasting using 470 watts. But as the sun is disappearing, the usage is slowing climbing up to 600 W. Since this is really a Tribrid heating system, I have to look at the solar gain for last year too. Was it cloudy much last year? We are seeing a reduction in our power bill right now, and it seems that running the Sanyo when it's 15 deg outdoors is still cheaper than burning oil. The oil truck was due here on Dec 21, but I called them to delay the delivery, because we still have 3/4 of a tank of oil. (Down from 7/8 after the last fill).