One of the biggest takeaways homeowners get from a thorough home energy audit is the sense that they missed the chance to get it right the first time. In order to make right the gaps in insulation and minimize the impact of the thermal bridges created during construction, it's often necessary to undertake a number of projects. Some will be quick and easy, but others may involve removing portions of the roof to get access to compromised insulation, and removing drywall. Without exception, all of these projects are repairative. They should have, and could easily have, been done right the first time, or even on the second chance.
It's not particularly surprising, for example, to learn that an "old" portion of a house isn't properly insulated. It can be distressing, however, to find that a 5-year-old addition is equally weak (like it was in a house I recently worked on). When the addition was being added, it may have been possible to have taken advantage of access to crawl spaces and kneewall cavities to air seal and insulate. Similarly, a roof project could provide the opportunity to properly insulate an attic and remove ineffective insulation. I will guarantee to get the project done right the first time, so you won't be fretting over missed opportunities years down the road.
I realized the first winter that I spent in my new home in Vestal New York that the insulation was insufficient. The house never had a warm comfortable feeling. The bedrooms above the garage were especially cold and the floors freezing to bare feet.