This tutorial explains how to add a room air duct for heating & cooling.
Room Heat & Cooling Problem
My daughter’s bedroom was too warm in the summer and too cold in the winter because it had just a single air duct from the central heating and air system. By comparison, my son’s bedroom is about the same square footage and has two supply air ducts that keeps it comfortable year round. I therefore decided to install a second air vent to the ductwork for my daughter’s bedroom.
Room Heating and Cooling Factors
The bedroom is located in the front wing of the house and I found access to that part of the attic is difficult. The attic insulated with blown fiberglass – white fluffy stuff that looks like cotton. I found that the attic over my daughter’s bedroom had little or no insulation in large areas because of the limited access; instead the workers just piled the insulation near the entrance to this part of the attic – correctly assuming that no one would see the sloppy work… until now. Proper insulation is critical for climate control.
Speedi-Boot™ – A Faster and Better Way
The remainder of this article explains how to install an air vent using a conventional vent boot.
Air Duct Installation Materials
The materials for the six inch diameter branch line cost about $60 at Home Depot:
- Starting Collar – 6 inch diameter
- Insulated Flexible Duct – 6 inch diameter, 25 feet length
- Register Box – 6 in by 10 in
- Register Grille – 6 in by 10 in
- Metal Foil Tape – one roll
- Nylon Zip Ties – 36 inch
The tools needed for this project are:
- Carpenter’s square
- Tape Measure
- Step Ladder
- Cordless Drill/Driver
- 3 inch Wood Screws
- 1/2 inch self-tapping sheet metal screws
- Cordless Fluorescent Light (very helpful)
- Sabre Saw (or Jigsaw)
- 15 amp Heavy Extension Cord
- Small Finishing Nail – 4d (penny) size
Duct Work Installation Guide and Tips
GAF Materials Corp. has several helpful duct work Installation Guides, Tips and FAQs. I recommend reviewing these references to customize the duct work layout to fit your particular situation.
Ceiling HVAC Vent Installation
The first task is to locate the new register vent on the ceiling. I measured the existing ceiling register and plotted the new register in an identical position on the right side of the room. A carpenters square is used to draw a perfect 6″ by 10″ outline on the ceiling where the new hole will be cut for the air vent.
I relied on the regular spacing of the ceiling joists such that the register box would be in the gap between the ceiling joists. Before cutting the drywall, I drove a finishing nail into the ceiling to verify there were no joists, making a series of small holes as shown below. If I made a mistake in the position of the register box, it’s easy to patch the small hole made by a finishing nail. A stud finder could be used.
A Rotozip spiral saw is used to cut the drywall for the ceiling register. Tip: Have a helper hold a vacuum cleaner hose up to the saw to catch most of the dust.
I left the drywall panel in place to prevent the attic insulation from falling into the room. I’ll remove the panel after the insulation is cleared away in the attic.
Now it’s time to go into the attic.
Attic Access for Ductwork
Be extremely careful while working in the attic. Step only on the joists because the drywall under the insulation will not support your body weight – you can fall through the ceiling – resulting in injury or at least a messy drywall repair.
The attic gets very hot in the summer and you can quickly over heat. It’s best to work very early in the morning before it gets hot.
I needed to go into the attic to install the register box and flexible air duct. But I found there was a problem – I couldn’t get to the attic above the bedroom because the roof deck over the main house didn’t leave enough room to squeeze my 215 lb frame through the low gap. Crawling wasn’t an option due to the risk of falling through the ceiling.
To solve the problem, I cut the roof deck with a handsaw and sabre saw as shown in the photo below. This allowed me to crouch and slide through with ample handholds while walking on the ceiling joists.
View of the roof deck cutout looking back to the main house from inside the L wing.
Here’s the insulation problem I found – mounds of it were on the left, but little or no insulation was over the rear areas of the attic above the bedroom. I redistributed the insulation evenly over the attic.
This project is continued in Part 2.
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