Maybe you are thinking of investing in a new 90% efficient furnace to save some energy dollars. Maybe you’ve already made the switch. Great idea! But there are few things you should consider when investing in expensive new heating or cooling equipment.
The efficiency of a furnace or air conditioner is determined in a laboratory under ideal conditions. In the real world, the delivered efficiency of a system is largely dependent on how efficiently your duct system conducts conditioned air to your home.
Unfortunately, the typical heating or cooling system delivers only 57% of the rated capacity of the equipment to the home it is conditioning. In other words, about 36% of all energy consumed is wasted overcoming deficiencies in the duct system. Below are some of the commonly encountered problems that rob energy bucks.
- Return duct too small. Air flowing back to the air handler must equal the amount of air being delivered to the building. If the return duct is too small or obstructed, there will be insufficient air, causing the equipment to work harder than necessary and burn fuel when it doesn’t have to. Sometimes, upsizing the return duct can be the most cost-effective measure you can make to save energy. While we are on the subject, avoid furnace filters that are too restrictive and change or clean them at least once a month during the heating or cooling season.
- Just like water, air is a fluid. If there are obstructions to air flow – kinked ducts, for instance or the dreaded pressure drop boxes pictured below, air will tend to eddy at the obstruction, cooling in the process; the desired amount of air will unlikely reach the room you are trying to condition.
- Duct Leakage: It’s estimated that about 20% of all conditioned air ends up in crawl spaces and attics because of leaks in duct system. Below is a photo of an obvious and all too common duct leakage site – holes at duct connections.