For anyone interested in fine tuning their firewood needs, or just learning more about their wood heating system, what follows may be a methodology that is useful and informative. During the 2nd half of November I logged outside temperature, which has allowed me to calculate Degree Days (based on base temperature of 60F). I also maintained constant my radiant floor temperature at 63-64F, which resulted in inside shop air temperature of 58-64F, and I weighed the wood burned, including kindling. All calculations are based on the assumption that my wood had effective heat value of 6,050 btu/lb (20% MC and 400F flue temp). The shop is 1500 sq ft, R19 nominal walls and R39 nominal ceiling, fairly typical for much newer construction.
During the test period Nov 17pm - Dec 1 am (14.54 days actual):
Degree Days (base 60) = 558
Wood burned = 765 lbs (1,288 lbs burned during the entire month)
Wood heat value = 4,628,250 btu
Btuh = 13,261
Wood/hr = 2.2 lbs (weight a small log to see how small this actually is)
Wood/day = 53 lbs
Btu/Degree Day = 8,294
Wood/Degree Day = 1.37 lbs
Firewood burned during this time was all jack pine, which seasoned (20%) typically weighs 2,670 lbs/cord.
Wood burned for whole month: 0.48 cords
Wood burned during data period: 0.29 cords
Annual normal Degree Days for a reporting station 5 miles from where I live are 9,017 (recalculated to base 60 from base 65). If 1.37 lbs wood/Degree Day, then my annual wood needs are 12,353 lbs, which is, for example:
Aspen: 5.38 cords
Jack Pine: 4.63 cords
Cherry: 3.96 cords
Red Oak: 3.39 cords
White Ash: 3.35 cords
White Oak: 3.08 cords
Hickory: 2.85 cords
Besides Jack Pine, Aspen is the other primary wood I burn, so right now it looks like I will need about 5 cords of firewood per typical year, and my goal is to always burn 2nd year wood, so I will need 10 cords on hand for the start of each heating season.
These numbers, and other data I collected, can be worked to provide other interesting information, but this seemed most useful. Nov - Mar are the normal cold months where I live, and I hope to continue to log data to better understand how btuh changes with differences in the dT between inside and outside temp, and therefore how actual wood usage/needs may vary from this initial calculation.
During the test period Nov 17pm - Dec 1 am (14.54 days actual):
Degree Days (base 60) = 558
Wood burned = 765 lbs (1,288 lbs burned during the entire month)
Wood heat value = 4,628,250 btu
Btuh = 13,261
Wood/hr = 2.2 lbs (weight a small log to see how small this actually is)
Wood/day = 53 lbs
Btu/Degree Day = 8,294
Wood/Degree Day = 1.37 lbs
Firewood burned during this time was all jack pine, which seasoned (20%) typically weighs 2,670 lbs/cord.
Wood burned for whole month: 0.48 cords
Wood burned during data period: 0.29 cords
Annual normal Degree Days for a reporting station 5 miles from where I live are 9,017 (recalculated to base 60 from base 65). If 1.37 lbs wood/Degree Day, then my annual wood needs are 12,353 lbs, which is, for example:
Aspen: 5.38 cords
Jack Pine: 4.63 cords
Cherry: 3.96 cords
Red Oak: 3.39 cords
White Ash: 3.35 cords
White Oak: 3.08 cords
Hickory: 2.85 cords
Besides Jack Pine, Aspen is the other primary wood I burn, so right now it looks like I will need about 5 cords of firewood per typical year, and my goal is to always burn 2nd year wood, so I will need 10 cords on hand for the start of each heating season.
These numbers, and other data I collected, can be worked to provide other interesting information, but this seemed most useful. Nov - Mar are the normal cold months where I live, and I hope to continue to log data to better understand how btuh changes with differences in the dT between inside and outside temp, and therefore how actual wood usage/needs may vary from this initial calculation.