When you make changes to one part of a house, you may create problems elsewhere. Rising energy costs and federal subsidies have encouraged homeowners to swap conventional furnaces for high-efficiency, direct-vent models. Unfortunately, the atmospherically vented water heater is often left behind. These orphaned water heaters are now venting into an oversize flue that was once shared by two appliances. Half of these orphaned heaters won’t have enough draft to get flue gases outside the house.
One solution is to install a chimney liner. These flexible liners, which are fished down the existing chimney, reduce the size of the chimney for better draft. Another solution is to install a power-vented water heater, which has a built-in fan that forces gases outside the home. Both of these solutions cost hundreds of dollars though. Another possible solution is to seal all the air leaks between where the water heater is located and the attic. Sealing these holes often improves draft because it means the water heater’s flue pipe is no longer providing the makeup air that the stack effect is moving into the attic.
Overall, a house is a system. This is just one example of a system in a home that needs to be cared for. It is important to keep in mind the unseen systems in a house to prevent issues that building sciences can fix.