Are the duct sizing requirements the same for both heating and cooling?
Sometimes, but not often.
Most of the time, the airflow requirements for cooling are greater than they are for heating.
If cooling needs more air, it stands to reason that the ductwork that carries the air must be larger.
If the designer wanted your duct system to handle just heating, chances are that it won't be large enough to meet the airflow requirements for cooling.
If he designed the system for heating, but also thought about adding air conditioning to the system at some point, your duct work may be adequate to meet your cooling needs.
How can I tell if the ductwork on my existing warm/hot air heating system is large enough to handle the cooling for my home?
The only REAL way to know is to perform a heat-gain/loss calculation on the structure.
Sometimes a SWAG is taken, or a rule-of-thumb is applied, but your home may be different from what is "normal".
A common rule-of-thumb is to provide 80 square inches of supply per ton, plus 10% for return.
Will I have to change my duct system if I add air conditioning (cooling) to my warm/hot air heating system?
It depends.
If your heating system was installed with no thought given to the future possibility of adding cooling, you will most likely have to alter the air-distribution system.
These alterations will probably involve installing larger ducts.
If, when the heating system was designed, the designer sized the ducts for cooling, it is likely that the air-distribution system will not need much changing.
In general, airflow requirements for cooling are greater than the requirements for heating.
The only way to know for sure is to have a heat gain/loss calculation done in the structure.
There are situations where the airflow requirements for heating are greater than those for cooling. An example of this would bea basement area that is located below grade.
The cooling requirements would be much less than the airflow requirements to heat the space.
Do I need to have my air ducts cleaned regularly?
Contrary to what others may say, the answer is no.
You need to have your duct system cleaned only if there is excessive dirt accumulation.
Dirt can get into your duct system if you operate the system without air filters, or if there are leaks in the return side of the duct system.
By using a high-quality filter, you will prevent most dust and dirt from entering the duct system.
In addition, the filter must be properly sized so that there are no air leaks around the filter.
If there are leaks in the return duct, unfiltered air from the structure can enter the system.
This dust and dirt can accumulate within the ductsystem.
If it turns out your ductwork does need cleaning, find out where the dirt is coming from and fix that situation first.
That will keep you from having to have your ducts cleaned regularly afterwards.
I have strange smells coming from the air ducts
Often, strange smells from the air ducts originate in the basement.
If the ductwork is not properly sealed, the blower will pull air into the appliance from the surrounding space.
If there is a litter box near the furnace, for instance, the odor from the box might enter the ducts along with the air.
The air will be heated (or cooled) and then distributed to the entire structure.
The air distribution system takes air from the occupied space, heats or cools it, and then returns it to the space.
As long as the duct system is tight, and properly sealed, there should be no infiltration of odors from the surrounding air (from either the basement or the attic).
A heat exchanger separates the air flowing to and from the building from the gases produced during the combustion process.
If the heat exchanger is in good shape, the byproducts of combustion should not intermingle with the air from the space.
If there is damage to the heat exchanger,the fumes from the combustion process can seep into the air in the space.
If you suspect this, inspect the system and the integrity of the heat exchanger promptly.