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My heating bills are getting out of control, so I called a company to look at my furnace.
They suggested I buy a new high efficiency furnace.
The price was for the furnace and installation using the existing ducts. For newer ducts the price would be almost double.
Do I need new ducts as well?
You did not reveal how old your existing unit is, but homes with furnaces that are over 20 years old should be inspected for safety and possible replacement.
If your furnace has a metal flue pipe and a standing pilot light, the furnace is not as efficient as the newer condensing furnaces that vent through PVC plastic pipes.
To replace an older 65 percent efficient furnace with a new 95 percent efficient furnace may not be cost-effective unless your utility company has a rebate program. You should also add insulation where possible, air seal the home and seal the ducts at all joints and seams using a metallic tape or a duct mastic. No duct tape.
Installing a new furnace with a new high efficiency fan control without replacing the ducts is not advisable. When a fan tries to force a certain amount of air through the older ducts, the pressures created inside the ducts can damage the fan. I compare it to using a vacuum cleaner when the trash bag is full and the indicator light stays on. No matter how much you vacuum the vacuum motor and fan cannot work against the pressure buildup inside the vacuum bag. Sooner or later the motor will fail.
At a replacement cost for the high efficiency furnace fan, which is close to $1,000, it is not advisable to use the older ducts. There are manuals for the design of the ducts, the fan velocity and the size of both the heating and cooling units that need to be used for every single installation.
Simply guessing at what equipment should be used based on prior installation practices is no longer acceptable. If you experience problems with a new system, there are economical ways to balance the pressures inside the ducts using a barometric pressure bypass valve to relieve the strain on the fan.
Before having a new furnace or a new fan upgrade installed, ask the heating contractor to supply and explain the information they used in designing the system for your home.
can you have it upgraded? If not, then you gonna need both.