For a fiberglass duct system you will need the following items:
Diffusers, Return and Supply We carry rectangular and round ceiling diffusers for easy installation for flex duct.
Remember that return air diffusers need to be 40% larger than the open space needed because of the blockage area of the grill. For example a 12" x 14" return air grill only has a free open area of 12" x 14" = 168" so 40% or 168 square inches or 100 square inches. Use no more than 6' of Flex duct on any take off if possible because all flex duct has a great tendency to collapse if not properly supported and will crush on tight 90 degree bends. Flex duct collapses very easily so support it well.
If you need to make a turn with flex duct use a metal elbow and pull the flex duct over it. Long radius elbows are better than short elbows. One elbow creates the same resistance as 15' of straight duct so avoid elbows whenever possible. Bull tees and elbows are the type that are made of boxes. Avoid bull tees and elbows as much as possible.
Want to keep your duct system clean? Use return air filter grills. Stop the dirt from entering the duct system altogether. A Hi Media filter is to protect the duct system and equipment from dirt accumulation. None of these devices clean up the environment in your house.
If you're thinking good air filtration will keep pollen, mold, bacteria and other minute airborne particles under control, you're kidding yourself. The minute or second you open your windows or front door billions of them just walked right in your house. Never use a Hi Media filter with return air filters. Never put two filters in the same duct system. This creates too much resistance for the blower.
Know your limits! Don't attempt an installation until you've gained all the information you possibly can. Don't wing it. And don't get too creative. Those creative ideas can cause more problems than you realize.
At the completion of every installation, you need to have a service technician inspect the installation. Please note that if you do the entire installation of your HVAC system without a check out by a licensed authorized technician, you will void the warranty and you will be putting you and your family and your possessions at high risk.
Understanding Furnace or Air Handler positions. In our model design above we used a standard Vertical Mount. The furnace is going to be mounted in the vertical position meaning the furnace will sit on vibration isolator pads and the air will come into the side of our furnace and discharge out the top of the furnace. If we were going to mount the furnace in the Horizontal Mount Position which is typical for an attic mount we then put the furnace down on the attic floor or rafters on vibration isolators and then the air would enter what is normally considered the bottom of the furnace and discharge out the front. If we mounted the furnace in the downflow position we would turn the furnace upside down and place the furnace opposite to the vertical mount and the air would then come in the top of the furnace and discharge out the bottom.