CSK'sMom wrote: ↑I think temp wise, we've been about the same, give or take a few degrees here and there. The windows made and still make a big difference for us. They are top of the line windows that we got a great deal on at the time. We were on a gas contract the yr before the new windows and the yr of so price was the same. The Enbridge weather calculation was that the yr with the new windows was actually 5% colder yet we used 25% less gas. I will say that we purposefully bought the south side for solar gain in the winter as we face east/west. I get full sun more than half way through the house at any given time of the day through the winter months. My kitchen is at the back of the house with an east exposure and my living room is at the front with a west exposure... Now the kicker, we still have the original builders furnace in the house that is 22 yrs old! We certainly can't justify putting a new furnace in at this point until we absolutely have to as we seriously doubt we'll see any real cost savings.
A south facing is definitely nice in the winter. It is amazing how much difference the sun makes (of course the sun has to actually come out once and awhile). For us the south side is pretty much shaded by the neighbours. We get the west side sun in the windows which always warms the place up. We did put the UV film on the windows though this past summer (to protect the new furniture) and I find it blocks some of the heat. Good in the summer but not so nice in the winter.
Temperature in Niagara Falls is about 3C warmer than here on average. That works out to 40-50m3 for us so you are still doing great, especially with an old furnace. Is it high efficiency? Would be hard to justify the expense in your case. I guess at some point you will have to get a new one. It would be interesting to see if there is much difference. We had a mid efficiency at our other house (1100sqft, attached end unit, north side) and used about 3.07m3 per day. This house has a high efficiency (1650sqft, detatched) and we use 3.11m3 per day (year average). So many variables so really difficult to attribute it all to the furnace only.