The insulation in our ceiling was old: weathered bats and lots of uncovered areas. I put in new ceiling bats to keep the house warmer in winter- it was freezing inside! Well, not really freezing, but cold..
Last night I measured the temperature and came up with the following graphs. Please note that the fireplace was petering out around 7:30 PM and relit at 7:00 AM.
The left graph shows the inside temperature (blue), outside temperature (red) and the difference (yellow).
The right graph shows the loss of temperature per hour – between 0.2 and 0.4 degrees per hour.
Subjectively, it is refreshing to wake up to a house that doesn’t feel cold. Objectively, the temperature loss before insulation was at least 0.5 degrees per hour, and that was on nights when the temperature stayed above 7 degrees and was mostly around 11.
I have as of yet been unable to find a benchmark from other houses to know whether this is as good as expected or not.
Anyway, these preliminary results show that $1100 and twenty hours creeping through small spaces (and a bit of itchy skin) were worth it.