By James Pan
1) Interior unit with no solar panels or insulation (25°F)
2) Interior unit with solar panels and no attic insulation (32°F)
3) End unit with solar panels and insulation (49°F)
Based on this one-time measurement of three homes, it appears that attic insulation makes a noticeable difference in attic temperatures. The warmer the attic, the less heat is lost from inside the house through the ceiling. Another survey will be conducted in mid-summer to see if insulation has a similar effect on cooling.
A web search should reveal whether the saving in energy costs is worth getting insulation. There is no question that lowering the probability of having liquid freeze in the attic in an extended cold spell is beneficial.
If anyone has installed attic insulation and has cost figures for energy usage before and after, please let James Pan know at firstname.lastname@example.org.