The insulation was brushed away from the ceiling cutout for the new vent boot and air register.

Register Cutout - Attic

Here’s the same view from inside the bedroom.

Register Cutout - Bedroom View

A 2×4 frame is made to mount the vent boot and register box. I used 3 inch wood screws to fasten the frame to the joists. Notice the vent boot at the left side of the photo to check the fit with the wood box frame.

Framing for Vent Boot and Air Register

The insulation jacked it pulled back to reveal the inner duct. The inner duct is slipped over the vent boot.

Inner Core of Flexible Duct Slipped over the Vent Boot

The inner duct is secured to register boot with metal foil tape for an air-tight seal.

Flexible Duct Taped to the Vent Boot

The outer insulation jacket is pulled down and fastened with a large zip tie.

Flexible Duct Zip Tied to the Vent Boot

The register box is attached to the wood frame with 1/2 inch self-tapping sheet metal screws. The screws are attached from the inside as shown here.

Vent Boot Mounted in Ceiling

The branch line is connected to the main ductwork with a starting collar. An outline is traced in the trunk rigid air duct and cut out with a utility knife. Here’s the starting collar and take-off hole in the main air duct are shown here.

Starting Collar and Take-Off Hole in the Trunk Ductwork

The starting collar is placed into the rigid air duct as shown. Notice the rectangular “fingers” are inside the ductwork. The fingers are bent outward against the rigid air duct to hold the starting collar.

Starting Collar in the Ductwork

The starting collar fingers are folded out and the adapter sealed to the rigid ductwork with metal foil tape.

Starting Collar Sealed with Metal Foil Tape

The inner duct is pulled over the duct adapter and fastened with two layers of metal foil tape as was done at the vent boot.

Inner Duct Pulled over the Duct Adapter

The outer insulation jacket is pulled over the duct adapter and zip tied in place. Notice the gentle bend in the flexible duct – it is very important to avoid kinks and pinches that will restrict the air flow.

New Ductwork Branch Line

This is the newly installed branch line into the attic above the bedroom.

Flexible Duct Branch Line

The register is attached to the ceiling with the two screws provided with the unit.

Ceiling Air Register

I turned on the furnace and checked the air flow from the new register. I was pleased to have a strong air flow that matched the other ceiling register – which is expected since both branch lines are attached to the same central duct. My daughter reports her room is much warmer now.

Fiberglass Insulation

The blown-in white insulation did a poor job of covering the attic above the bedroom. Months later, after I installed the Solatube Skylight, I put down two bags of Owens Corning R-30 insulation in 24inch by 48inch batts. Two bags of 88 square feet each covered the attic. Cost of each bag is about $65. The R-30 insulation is quite thick as you can see by the section in the center of the photo. This made a noticeable improvement in the comfort of the bedroom. The batts were laid over the white blown-in insulation.

R-30 Fiberglass Insulation Batts

Take care,

Bob Jackson

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Update: For a faster and better way to install an air vent, see these projects:
* How to Add a Room Air Duct with Speedi-Boot™
* How to Install an Air Vent in a Suspended Drywall Ceiling

The 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.

Air Duct Branch Line

Other 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.

Materials

Air Duct Branch Line Materials

The materials for the six inch diameter branch line cost about $60 at Home Depot:

1. Starting Collar – 6 inch diameter
2. Insulated Flexible Duct – 6 inch diameter, 25 feet length
3. Register Box – 6 in by 10 in
4. Register Grille – 6 in by 10 in
5. Metal Foil Tape – one roll
6. Nylon Zip Ties – 36 inch

Tools

The tools needed for this project are:

• Handsaw
• Carpenter’s square
• Tape Measure
• Step Ladder
• Cordless Drill/Driver
• 3 inch Wood Screws
• 1/2 inch self-tapping sheet metal screws
• Flashlight
• Cordless Fluorescent Light (very helpful)
• Rotozip
• Sabre Saw (or Jigsaw)
• 15 amp Heavy Extension Cord
• Hammer
• Small Finishing Nail – 4d (penny) size
• Pencil

Duct Work Installation Guide and Tips

GAF Materials Corp. has several helpful duct work Installation Guides, Tips and FAQs. I recommend you review these references to customize the duct work layout to fit your particular situation.

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.

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.

Register Grill Outline 6

A Rotozip spiral saw is used to cut the drywall for the register grill. Tip: Have a helper hold a vacuum cleaner hose up to the saw to catch most of the dust.

Cutting the Register Box Hole

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.

Register Cutout

Now it’s time to go into the attic.

Attic Work

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.

Attic Wing above the Bedroom

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.

Roof Deck Cutout

View of the roof deck cutout looking back to the main house from inside the L wing.

Roof Deck Cutout - L Wing Side

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.

Mounded Insulation

This project is continued in Part 2.

Take care,

Bob Jackson

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