We lived in the house for 5 years before doing the reno. The house was built in '76 and was all original when we moved in. It's tough for us to gauge the difference in temperature retention, because there were a number of other changes that could affect the difference:
- We didn't have the heat loss measured to start with and we haven't measured it since the reno.
- The entire house was all carpet except for main entrance and we had it all replaced with hardwood throughout.
- We replaced the 7' sliding door to the backyard with a 16' sliding door with additional peaked windows.
- We enlarged and replaced every other window in the house (circa 1976 & 2003), with high quality modern windows.
- We replaced the wood burning fireplace with a gas fireplace and we also removed the entire chimney stack.
- We removed all the interior walls, so we lost the the HVAC vents in the middle of the house and now all the vents are along the perimeter.
- We had to have the HVAC rerouted to the perimeter vents, adding resistance and more 90deg bends, affecting overall air flow.
- We had siding added to the entire exterior of the house, over the existing brick and wood siding, so provides great wind protection.
In general I think the house now holds heat very well, except one bedroom, which happens to be on top of the uninsulated garage. I don't know much about insulation, but I recall reading somewhere that it fibregalss sags and maybe degrades over time, so it stands to reason that our 40yr old insulation doesn't compare to either the current R value of the spray foam, or the tightness and quality of the fill.
If you can afford it and will stay there for a while, then it might be worthwhile. Any questions - just ask