The Appraisal Institute of Canada offers an online guide which helps homeowners calculate the average return on their investment in a renovation project. Choose “bathroom renovation” and plug in an outlay of, for example, $30,000 into the calculator and RENOVA niftily tallies a 75- to 100-per-cent return, which translates to an added $22,500 to $30,000 on the resale value of your home. Kitchens also rank well up the list with a similar 75 to 100 per cent payback. Swimming pools, home theatre rooms and interlocking brick driveways yield only 25 to 50 per cent. The payback for installing central air…