- Dec 15, 2015
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Just moved into a new place in Oct (owned by the in-laws), and got our first post-initial fill bill for our Propane (so normalized usage throughout the month) 453 gallons for $1,300 or so. I've been running some numbers and I'm not quite sure if this is supposed to be reasonable or not, hoping someone in here can shed some light for me.
House is ~3100 sq ft, most is single floor with an upstairs area (outside entrance) consisting of about 1100 sq ft. We kept the heat off up there (baseboard radiant heating). Downstairs uses radiant in-floor heating (not in-slab I don't think, it seems to be one of the misc 'concrete-on-joists' configurations... could be wrong). 3 zones, the one we spend the least amount of time in was set to 60, other two zones to 65. Outside temps were generally in the 10's-30's all month, giving me an average delta of around 45F.
Boiler is a Weil-McLane Ultra 105, rated at 105k BTUs, at 92% efficiency.
If I've done my math right:
435/30=14.5 gal/day...
14.5*91,000 BTUs=1,319,500 BTUs/day...
/24=~55,000 BTUs/hr...
*92% efficiency=50,580 BTUs output...
/3300 sq ft = 15.3 BTUs/sq ft. average.
/2000 sq ft = 25.3 BTUs/sq ft average
I have no idea if that is considered to be efficient for either number, the closest I could find is this page stating that .1 BTUs/hr/sqft/degreeF is great, .3 is good, .6 is fair, and 2 is bad.
https://www.radiantec.com/wp-conten...diant_Heat_Design_and_Construction_Manual.pdf (page 3)
Per the above values, with an average delta of 45F, I have the following rough numbers:
.34 BTUs/HR/sqft/degree delta for 3300sq ft
.56 BTUs/HR/sqft/degree delta for 2000sq ft
Note that the above is a bit higher than reality due to us having a hot water heater eating a little gas, as well as incidentals from a gas stove, and dryer. I'm assuming that the vast percentage (>90%) of the fuel is being used by the boiler however.
The reason I keep separating out the sq footage is that although we have the heat off in the upstairs 'apartment', there's a few air pass-throughs (presumably for heating assistance and cooling upstairs) so I'm assuming I'm heating that space as much as I am downstairs. Place also has very high ceilings in the living/kitchen area, so there's a lot of cubic footage of air to heat. Energy company confirmed there's no leaks in the system.
Note that since the above sticker shock, I turned the radiant heating down to 50 on all zones and we've started leaning very heavily on our pellet stove instead (I assumed it would be less efficient, it's apparently far more for what we're trying to accomplish).
Does this all seem out of bounds? Should I be looking at upgrading insulation/doors and windows to improve efficiency? Or am I just stuck with a second mortgage now? Thanks!
House is ~3100 sq ft, most is single floor with an upstairs area (outside entrance) consisting of about 1100 sq ft. We kept the heat off up there (baseboard radiant heating). Downstairs uses radiant in-floor heating (not in-slab I don't think, it seems to be one of the misc 'concrete-on-joists' configurations... could be wrong). 3 zones, the one we spend the least amount of time in was set to 60, other two zones to 65. Outside temps were generally in the 10's-30's all month, giving me an average delta of around 45F.
Boiler is a Weil-McLane Ultra 105, rated at 105k BTUs, at 92% efficiency.
If I've done my math right:
435/30=14.5 gal/day...
14.5*91,000 BTUs=1,319,500 BTUs/day...
/24=~55,000 BTUs/hr...
*92% efficiency=50,580 BTUs output...
/3300 sq ft = 15.3 BTUs/sq ft. average.
/2000 sq ft = 25.3 BTUs/sq ft average
I have no idea if that is considered to be efficient for either number, the closest I could find is this page stating that .1 BTUs/hr/sqft/degreeF is great, .3 is good, .6 is fair, and 2 is bad.
https://www.radiantec.com/wp-conten...diant_Heat_Design_and_Construction_Manual.pdf (page 3)
Per the above values, with an average delta of 45F, I have the following rough numbers:
.34 BTUs/HR/sqft/degree delta for 3300sq ft
.56 BTUs/HR/sqft/degree delta for 2000sq ft
Note that the above is a bit higher than reality due to us having a hot water heater eating a little gas, as well as incidentals from a gas stove, and dryer. I'm assuming that the vast percentage (>90%) of the fuel is being used by the boiler however.
The reason I keep separating out the sq footage is that although we have the heat off in the upstairs 'apartment', there's a few air pass-throughs (presumably for heating assistance and cooling upstairs) so I'm assuming I'm heating that space as much as I am downstairs. Place also has very high ceilings in the living/kitchen area, so there's a lot of cubic footage of air to heat. Energy company confirmed there's no leaks in the system.
Note that since the above sticker shock, I turned the radiant heating down to 50 on all zones and we've started leaning very heavily on our pellet stove instead (I assumed it would be less efficient, it's apparently far more for what we're trying to accomplish).
Does this all seem out of bounds? Should I be looking at upgrading insulation/doors and windows to improve efficiency? Or am I just stuck with a second mortgage now? Thanks!