Well I did what I thought was the right thing....1680 square foot bungalow with a full, finished, walkout basement. ICF basement walls, SIP main floor walls, R50 blown attic insulation, HRV and 98% efficient propane furnace. I topped up the tank after 30 days and to my disappointment 467 litres consumed @ .63 / litre for a total of $337.64 including taxes. Based on research and testimonials from others who have built this way, I thought that I would be able to heat this place with a candle! Anything that you could contribute to make me feel better and ease my fear of the cold weather to come would be appreciated.

check for a propane leak

TL,
OK here goes. Math 3.8 L per gallon so 467/3.8=122 gallons per month or about 11 million btu’s per month. You have 3300 ft^2 of conditioned space. That is what we know.
 
Now for some questions. We don’t know your climate or Heating degree days this month, I assume you are Canadian since you gave quantities in liters? What is your zip code? Do you also heat domestic hot water with propane? Lots of people taking long showers, Cooking with gas? Keep the thermostat set to 80°F? How big is the furnace in btu’s? Did you have any blower door testing and duct testing done?
 
If you can hear the furnace when it is firing, you can figure out what its consumption is if it is not modulating. A furnace burns about 1 Liters per hour for every 23,000 btu of rated capacity so if it is a 60,000 btu furnace it would Have to be firing 6 hours per day to consume that much propane.
 
This usage rate does not make sense in a sips/icf house. I can think of several possibilities, one that is already mentioned and that is a propane leak. The other possibility is that they initially filled your tank say 80% full and the second time around they filled it to say 90% capacity because it is cold and they don’t need to account for the thermal expansion that they do in warmer months. My propane delivery guy won’t fill an above ground tank more than 80% but will fill a buried tank to 95% if requested. The third possibility is that the builders were idiots. Are the ducts for the hot air run up in the attic? Are they exposed ? Maybe a large hole in one of them. Did they forget to put in one of the windows? Did you have any blower door testing and duct testing done?

You need to give us more to work with.
Eric

ha, ya, are you missing a window somewhere?  Were all panels installed or did you leave one off?  jk 

As I said in your other thread, check for a leak.  I am not sure what else it could be (outside of the options eric offered)

Do you have 3 teenagers taking endless showers in this house? (I've known some who could burn through 2-3 MBTU of hot water heating in a month just showering, and that's no exaggeration.)

What are your ICF & SIP R-values? (R18 ICF or SIPs don't save you a whole lot over conventional code-min stick framed in cold & very-cold climates with a real heating load. R25-ish & up is usually a measurable improvement.)

What is % of the total wall area is windows & doors?

Tested the air leakage rates on this place?

How many heating-degree-days (C or F) did you go through for that amount of fuel use?