How to Add a Room Air Duct for Heating & Cooling – Part 2

This project is continued from Part 1.

The insulation was brushed away from the ceiling cutout for the new register.

Register Cutout

Register Cutout - Attic

Here’s the same view from inside the bedroom.

Register Cutout - Bedroom View

Register Cutout - Bedroom View

A 2×4 frame is made for the register box and fastened with 3 inch wood screws. Notice the register box to the far left to check the fit.

Framing for Register Box

Framing for Register Box

The insulation jacked it pulled back to reveal the inner duct pipe and slid over the register box.

Flexible Duct Attached to Register Box

Flexible Duct Attached to Register Box

The inner duct is attached to the register box with two layers of metal foil tape.

Register Box and Duct Taped Together

Register Box and Duct Taped Together

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

Flexible Duct Zip Tied to Register Box

Flexible Duct Zip Tied to Register Box

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.

Register Box Mounted in Ceiling

Register Box Mounted in Ceiling

The branch line is connected to the main air duct using a round duct adapter. An outline is traced in the main rigid air duct and cut out with a utility knife. The duct adapter and hole in the main air duct are shown here.

Duct Adapter

Duct Adapter

The duct adapter is placed into the rigid air duct as shown. Notice the rectangular “fingers” inside the duct adapter. These are folded out to help hold the duct adapter in place.

Duct Adapter

Duct Adapter

The duct adapter fingers are folded back and the adapter is fastened and sealed with lengths of metal foil tape.

Duct Adapter Taped In Place

Duct Adapter Taped In Place

The inner duct is pulled over the duct adapter. It will be fastened with two layers of metal foil tape.

Inner Duct Pulled over the Duct Adapter

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.

Duct Taped and Zip Tied

Duct Taped and Zip Tied

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

Branch Line

Branch Line

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

Ceiling Register

Ceiling 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

R-30 Fiberglass Insulation Batts

Take care,

Bob Jackson

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7 Responses to “How to Add a Room Air Duct for Heating & Cooling – Part 2”

  1. Frank Says:

    How did you deal with the fiberglass in your clothes and skin? I have an attic and would like to work in there, but with the white insulation it is very messy and gets over everything.

  2. Bob Jackson Says:

    Working with fiberglass for an hour or two on a small job – a couple of rolls of insulation – doesn’t bother me. I do wear long pants and long sleeves. A dust mask and gloves are recommended, but I’ve not been bothered handling the glass with my bare hands. It probably depends a lot on your skin sensitivity. Take a shower afterwards and run your work clothes through laundry in the normal way. You will see a lot of very short fibers and dust floating in the beam of the flashlight when working in the attic, so a dust mask a good choice.

  3. john Says:

    Before you touch any insulation please note that if it was laid before 1995 it may contain asbestos. If so do not touch it get the removers in a dust mask is not enough and 20 to 40 years down the line a slow and painfully death is a possibility. Look up HSE asbestos as a general guide

  4. Bob Jackson Says:

    My home was built in 2000 and this isn’t an issue with the fiberglass duct board as shown in the project.

    As best I can tell, asbestos was banned in the United States in 1977 where it was used to cover metal air ducts. The situation in Great Britain may well be different as discussed at the “Health and Safety Exclusive (HSE)” – see following links.

    Links further reading:
    * Asbestos in Your Home by the United States Environmental Protection Agency (EPA).

    * Indoor Air Quality – Environmental Protection Agency (EPA) – See the “What to Expect From an Air Duct Cleaning Service Provider” statement about asbestos.

    * Asbestos health and safety by Health & Safety Exclusive (HSE) of Great Britain

    Thanks,
    Bob Jackson

  5. Alan Says:

    I have just converted my 2 car garage into a game room and was going to branch 2 lines into it off my central system. Do I need to put a return air vent into the main house where the air handler gets its return air for the main house?

  6. Bob Jackson Says:

    Yes, you need a return air vent from the converted garage back to the main house. It’s best to locate the supply air vents near the windows (if possible) and install the return vents on the opposite side of the room to mix the air.

    Also think about replacing the garage entry door with a standard interior door as the original door would have a weather seal to prevent drafts from the unheated garage. The gap between the bottom of an interior door and the floor is a significant contributor to the return air flow pathway.


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