The short answer, if it is an old house is YES.
According to information I found from Natural Resources Canada on the internet, a rating of 79 on an older house puts it almost on par with an energy-efficient new house (these are rated 80 - 90). My new listing at 4510 Fraserside Drive which was built in 1990 now has an EnerGuide rating of 79 up from 55 before the energy upgrades were made in 2009. A house requiring little or no purchased energy would be rated 91 - 100. A new house with some energy-efficiency improvements would fall into the range of 73-79; a new house built to building code standards is rated 65-72.
Natural Resources Canada explains the system: "An EnerGuide rating shows a standard measure of your home's energy performance. It shows you (and future buyers) exactly how energy efficient your home is. The rating is calculated based on standard operation assumptions so that you can compare the energy performance of one house against another. The home's energy efficiency level is rated on a scale of 0 to 100. A rating of 0 represents a home with major air leakage, no insulation and extremely high energy consumption. A rating of 100 represents a house that is airtight, well insulated, sufficiently ventilated and requires no purchased energy on an annual basis."
4510 Fraserside Drive, Richmond's upgrades have increased its EnerGuide rating from 55 to 79!