Ducts are a critical part of making your home energy efficient. If they're leaking air--which they almost always do--or if they're losing heat because they're uninsulated, they're contributing as much to global warming as they are to keeping you warm.
What You Should Know
- A typical American home has 180 feet of ducts.
- When the first air that comes out ofthe vent after you turn on the heater is chilly, and stays chilly for a long time, you know your ducts are uninsulated and you're wasting energy.
- If you seal your leaky ducts, your furnace will heat your house more quickly and distribute the warm or cool air more evenly, and you'll greatly reduce the chances of dust, humidity, or gas fumes entering our heating system.
- A leaky duct system not only wastes energy but also can worsen the quality of your indoor air. For instance, a leaky duct system can cause harmful gases from gas appliances (such as a furnace, stove, or water heater) to be circulated to the rest of your house. A leaky duct system can also cause the air pressure in your home to decrease, sucking unwanted hot or cold air from the outside in.
- You can save up to 10% of your heating or cooling costs by insulating and tightening up ducts.
- Even if the air isn't actually escaping from an uninsulated duct, you lose a lot of heat through its thin metal walls.
Easy Things You Can Do
Check your ducts for leaks. Hop into that crawl space or attic, or bring a flashlight to your heating vents, and start looking for disconnected, kinked, or crushed ducts as well as any gaping holes. If there's a room in your house that never gets warm or cold enough, lift off the vents inthat room and use a flashlight to look for a disconnected duct.
To detect small leaks, turn your furnace on and run your hand along the duct to feel for escaping air. Also, look for dirt streaks near the ducts' seams or on the insulation covering the ducts. Dirt indicates an air leak where dusty air has been escaping for years. You may also find peeling duct tape, exposed metal, or ripped outer covers, all of which could indicate a leak. Last, the most important place to check for leaks is where your ducts connect to your furnace.
Test your ducts. Although disconnected ducts are easy to spot on your own, it's best to locate small duct leaks using professional testing equipment. Consider having a heating contractor or energy auditor conduct a duct blaster test, which pressurizes your duct system to tell you exactly which ducts are leaking and by how much.
Seal your leaky ducts. You can get a contractor to seal your leaky ducts or you can try doing it on your own, as long as you know how to use the sealing materials safely (read all directions!) and are aware of your local building codes (which tell you what kind of sealant ou can use, et cetera). First, rejoin any disconnected ducts using duct ties, drawbands, or mechanical fasteners. Then seal any leaks or seams with water-soluble mastic caulking only.
If your ducts aren't insulated: Turn on your furnace and feel for air escaping around the duct joints. If you feel any (and you probably will), clean around the joint, then seal with mastic or approved tape.
- Insulate the ducts with 2-inch thick fiberglass; seal the seams with tape or mastic sealant approved by Underwriters Laboratories. If ducts are hard to get at, call a heating contractor.
If your ducts are already insulated: It's harder to find out if your ducts leak. You can expose the joints (where the ducts bend, for instance) to check. Or leave it ot an expert.
- Before you start any work, check to make sure the insulation isn't asbestos (looks like off-white, stiff, heavy cloth). If it is, stay away! If you're not sure, check it with your local buildign department.
Don't use duct tape! Believe it or not, regular old duct tape should not be used to seal ducts, since its adhesive will dry out over time, causing it to peel or fall off. Een UL-181 (approved by Underwriters Laboratories, Inc.) or foil-faced duct tape is just a temporary fix. Also, simply insulating your ducts will not fix air leaks since insulation stops only heat flow, not airflow.
Go high-tech. There is a new, high-tech way to seal your ducts called Aeroseal, which is applied by a professional contractor. They clos all your vents and then blows adhesive particles, called Aeroseal, into your duct system. The particles stick to and fill up your leaks and is faster and more effective than sealing with mastic caulking or tape, and costs about the same as having a professional seal your ducts with mastic caulking.
Sources: 51 Easy Ways You Can Prevent Global Warming and Save Money, by Jeffrey Langholz, PhD, and Kelly Turner, and 30 Simple Energy Things You Can Do To Save the Earth, by PG&E