A simple guide to Return Air installation
A duct that returns air is that is carried to the furnace back after dispensing the entire area through the supply duct. The fact is that there is a need for a return air installation, so that the air circulates properly. Normally, the return air duct uses the ceiling joist space as its duct actually and this runs towards the furnace back. With proper tools, installing of return air duct is possible.
Locate the place you want the return air ducts. Make a hole in the drywall to put return air grille. The hole size should be same as the grille size and cut the floor, through the hold. This will give a hole into the joist space of the basement ceiling. Now, repeat this step as you desire to have the return air holes. Ensure to have one per room at least, avoiding the bathroom.
Go and locate the holes in the basement. Start from the farthest hole and install return air duct back towards the furnace. Nail the back panning to the ceiling joists bottom. Ensure the panning is fit in the farthest hole, bend it and attach it up to the floor closing the space. Stop the panning, by the furnace at the same spot in the joists. Now, take it to the floor, by notching this side. Keep it perpendicular to the joists and make holes in the panning. In this way, the air gets into the return air duct from the panning and will reach to run into the furnace.
Cover all the holes in the panning and install the square such that it is perpendicular to the joists. The holes cut in the return air duct top match the panning holes. This allows air to enter the return air duct as this duct is linked with drive cleats and s-slips. The return air duct must be tightly installed to the ceiling joists bottom forming a tight seal. Thus, you may secure the duct with galvanized 1-inch hanger strap to the ceiling joists.
In the return duct, cut a hole close to the furnace and attach another duct to run into the furnace down. Cut a hole to the furnace side matching the filter rack size. Make connections from the bottom and attach to the furnace, so that the duct size perfectly to fit.
Install the filter into the filter rack. Use a high-quality caulk in clear silicone and caulk all the seams and joints of the duct for best energy performance.