This project is continued from Part 1.
Note: Please see this newer project for a faster and better way to install a room air vent using Speedi-Boot™, which is available at Home Depot. The remainder of this article explains how to install an air vent using a conventional vent boot.
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
Copyright © 2012 HandymanHowTo.com Reproduction strictly prohibited.
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.
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.
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
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
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?
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.
Thanks so much for this How To guide. I will be tackling the exact same job this weekend and your guide was a great help!
Bob,
Your How to Guide will definitely come in handy with the project I’m about to tackle…which is almost identical to yours.
I’m curious, is there a method to determining the best ceiling location to add the new register? My current register is in the NW corner of the room. The door to the room is in the SW corner…and there is a return air vent just outside of this door. I was thinking of putting the new register in the SE corner of the room (that is, diagonal from the current register).
I take it you have a room over a garage with an A frame roof and dormer windows. The southeast corner would be an good choice. A better choice is the northeast corner because it’s the farthest away from the door & ceiling air return duct in the southwest corner. The idea is to avoid dead spaces and equalize the air circulation. However, if the attic trusswork or low rooflines make it too difficult to install a new ceiling vent in the NE corner, the SE location should do fine.
Do choose a ceiling register with adjustable louvers and vanes to adjust both the volume (balance) and direction of air flow.
Thanks for your response Bob. I appreciate your willingness to respond to questions about such an old project.
When adding the additional register to your daughters room, were you at all concerned about how it would affect the amount of air coming out of other registers in the house? Was there a notable difference in the other rooms?
Your central AC system shouldn’t be running so close to it’s maximum capacity that adding a single register would starve the airflow from other rooms. If you install a ceiling register with adjustable louvers as I recommended, you can adjust (restrict) the airflow to equalize it with the other ceiling register(s). This might be necessary if the new branch line is taken off the main trunk where the air pressure is higher.
As for my home, I have two 3-ton compressors and air handlers which independently serve the upstairs and downstairs living spaces, so overall system capacity wasn’t a concern.
My house suffers from probably what most others do — 2nd floor hotter than the rest of the house in summer and colder in winter. I have a colonial with an integral two car garage with the master suite over the garage. The temperature variance is greatest in that room. I have attempts to adjust this by adjusting the baffles in each distribution line (where I can get to them), and opening/closing the registers each season. Is there a better way without costing a great deal? Would professionally balancing the system help?
Thanks for your reply
You’ve done the basics by adjusting the baffles and registers. I assume the room is too hot or cold even if the door is open, therefore return airflow isn’t an issue. Your options are better air supply and/or better insulation.
Air supply: Short of installing new duct work, an in-line booster fan might help. I have not tried these and your mileage may vary.
Insulation: Better insulation will reduce the overall heating and cooling needs. Is the space between the garage ceiling and the 2nd room floor insulated? Drill a small inspection hole or two in the garage ceiling to find out. There are companies that can install blown insulation inside existing walls.
I am partiioning a large room with two supply ducts and want to move one suply to the new room. It is a first floor bedroom and was hoping to avoid ripping down the drywall ceiling. Do yo know of any tricks/products avaialble to accomplish this? Thanks, jim
If you don’t want the mess and trouble of tearing open the ceiling drywall to reroute the ductwork, then build a new run for the duct extension along the corner of the ceiling with 2×4 framing and drywall as so:
The construction detail for the ductwork extension is:
Key construction elements are:
1) Remove the ceiling register and vent boot from the vent to be moved.
2) Build the box to conceal the new ductwork along the top corner of the room from the old vent through the wall partition to the new room. This technique is not uncommon for remodels and blends in nicely when finished and painted.
3) Run new flexible duct of the same size through the box framing and keep the corner turns wide and gentle for the best airflow.
4) Tie the new ductwork into the old ductwork in the ceiling and seal with HVAC tape. If you can find a rigid duct connector for the two sections, that’d be best.
5) Install a new vent boot and register in the new room partition.
An air return duct will be needed in the new room. You could build a return duct the same way as the supply duct extension, or if noise won’t be a problem, install a pass-through grill in the wall partition.
Suppose the old vent is a few feet from the wall and building a duct extension 90 degrees out from the wall would look silly. Just cut a hole in the ceiling next to the wall between the floor joists (make sure it’s the same joists where the air duct is located!) and with long arms, reroute/extended the old air duct to the wall and into the new corner box you’re building to the new room. You’ll have a small amount of ceiling drywall repair to cover up the old vent hole.
Hello Bob,
Great solution as it involves new construction rather than the mess of tearing up the ceiling.
Thanks for the advice. Jim
I live in a 3 story townhouse, with the lower-level being the basement, the main level consisting of the living room, kitchen and 1/2 bathroom and the 2nd level having the master bedroom/bathroom, 2 smaller bedrooms and a full bathroom in the hall. Each level is approximately 800 sq feet (20 ft wide X 40 ft deep. The attic has the trunk line (from the basement) that has (6) 6″ flexible duct lines going to all the rooms upstairs, with 2 going to the master bedroom.
My problem is that the 2 smaller bedrooms never get comfortable in the winter or summer unless the thermostat is set to an extreme temperature while the master bedroom becomes excessively warm or cold. I went into the attic and tried moving the flexible ducts to make them straighter and also added at damper to one of the ducts (at the trunk)going to the master bathroom. I plan on adding more dampers to the other two ducts going to the master bedroom to see if this improves airflow to the smaller bedrooms.
I should also add that there are 2 electronic dampers in the basement on the trunk line that supplies the heat/AC to the basement and main level. I was told I have a 2-Zone system (not 100% sure). The thermostat in the hallway upstairs turns the system on/off, along with being able to switch the Heat/AC on/off, and the thermostat on the main floor can do everything except turn the system on/off.
The air return is at the top of the second level near the ceiling.
I am looking for possible ideas to correct the situation, including adding second ducts to the smaller bedroom (directly frim the trunk), adding more dampers, etc… I need ideas and/or solutions..
Thanks in advance..
-Alan
> The air return is at the top of the second level near the ceiling.
So there’s just the central air return in the 2nd floor hallway and no air return ducts in the two smaller bedrooms?
Step 1:
How strong is the air flow to the two smaller bedrooms on the 2nd level? Is it about the same as coming from the ducts in the master bedroom?
Step 2:
Does the air flow to the smaller bedrooms change noticeably when the door is closed? Are the smaller bedrooms uncomfortable all the time or only when the door is closed?
Recommendations:
A) If the airflow to the smaller bedroom(s) with the door open is significantly weaker than the master bedroom, balancing the air flow with dampers could be a solution.
B) If the airflow drops significantly with the door closed, then a new return vent and duct would be appropriate, but may only be a marginal improvement.
C) Since you have attic access to the trunk line and six existing 6″ supply duct lines, the ideal solution would be to install a new 6″ duct line from the trunk to each bedroom with a new 6″ return air duct line to each room. Install the new supply vents on the opposite side of the room away from the existing vents and doorway. Place the return duct near the door. Use an adjustable register on the new vents to adjust (balance) the air flow; simpler than dampers inside the ductwork and easier to tweak.
The advantage of new duct lines is it not only increases the airflow, but diversifies the airflow to equalize the room.
Thanks for the prompt reply Bob…
> The air return is at the top of the second level near the ceiling.
So there’s just the central air return in the 2nd floor hallway and no air return ducts in the two smaller bedrooms? <<
Yes, there is only one central air return. Nothing any of the bedrooms.
The existing 6" air duct line in each of the smaller bedrooms is in the center of the ceiling and you're advising me to put a new 6" air duct line (from the trunk)at the opposite end… I don't really want to move the exisiting one(s) unless I have to so i am wondering if I should put the new ducts close to wall that has the windows, which is opposite the wall that has the door??
As for putting in the new 6″ return air duct lines; can I use flexible duct or do I have to use rigid??
I haven’t had a chance to check about air flow changes as of now.
Thanks again…
Right – don’t move the existing air ducts. It’s best to install the new air ducts above the windows at the opposite wall from the door. Windows are a source for the heat & cold from the outdoors even when closed, so putting the new vents in the ceiling above the window helps to mediate the hot/cold spot here. Since the window is at the far side of the room opposite the door, that’s even better so the air will travel the full length of the room to reach the new return vent above the door.
> As for putting in the new 6″ return air duct lines; can I use flexible duct or do I have to use rigid??
Flexible duct is fine for a single return branch line. Flexible duct is internally supported by a wire coil and the negative return air pressure is not much, so the flexible duct won’t collapse. All the individual room returns in my home (built in 2002) are flexible duct lines back to the rigid trunk line.
Thanks for the information on placement of the new returns/supply ducts. Before I make that move I am going to reinstall the existing lines from the trunk, eliminating the bends coming off the trunk – I was reading that the bend/angles should occur 1 or 2 feet from the trunk. I will use the proper strapping to hang them if necessary and use just the length needed.
When I can I will take some before and after pictures. I am learning that houses, condos, & townhouses built in masses tend to use inferior parts, or not at all – none of the existing supply ducts have dampers in place, just the one that I put in… They are also lazy when doing things the right way, so I am going to “MAKE IT RIGHT!” –> stolen from Mike Holmes!!
Before and after photos would be welcome; I’ll post them here with your permission.
> They are also lazy when doing things the right way, so I am going to “MAKE IT RIGHT!” –> stolen from Mike Holmes!!
Quality and workmanship are often problems on any home. I once converted a covered porch into a new room on former house in Florida. The blueprint had to be signed off by a certified Civil Engineer for wind loading (hurricane country) to obtain the building permit. The Civil Engineer I hired was mostly working on expensive mansions and condos as a independent inspector for the homeowner. He showed me notebooks of photos with building code violations, shoddy work and botched jobs. He said quality is often a problem no matter what the house’s price range. Enter “goober” in the search bar at the top right corner of HandymanHowTo.com for examples of poor workmanship I’ve found and corrected on my home.
We are going to add another vent to our son’s bedroom because it gets very hot during summer and cold in winter. The room has 2 1/2 outside walls and one large window. The one wall that is entirely an inside wall has a bathroom door and a closet, so that wall is pretty full already. The only vent into the room now is under the large window. Is it correct that we should place the other floor vent on the other outside wall? I want to make sure that we get good air circulation in the room. Due to the design of the room, the other place we are thinking about adding it due to ease of install is in front of one of the sliding closet doors. The intake vent is above the bedroom door which is the wall opposite of the one we are thinking of placing the new vent on. Any resources/information for vent placement?
> Is it correct that we should place the other floor vent on the other outside wall?
That would be the best choice. Supply vents should be located by windows (as you already have) or as far away from the entry door as possible to maximize the distance the air travels to the return vent for equalization.
Bob – The home we recently purchased has a “bonus” room upstairs above the great room that was added after the home was built. It’s approx 20 x 9 and has a spiral staircase going up. It appears reasonably well insulated (examined from attic). We have 2 ac units and there are 2 vents from each going to the attic room, but there is no return up there. The only way for air to get out is to be pull down through the spiral stair entrance by the main returns in the great room. The air always seems stale and it’s uncomfortably hot in the summer – even with both ac units feeding the room. Would it make sense to add a return (or returns) up there? Thanks.
How does air in the room feel when the door is open for an hour or two? An open door is the same as a return vent. If the room is comfortable when the door’s open, then add sufficiently sized return duct. If not, then a larger air supply is needed to keep up with the summer heat.
See my advice dated December 14, 2011 at 11:00AM in this post for duct sizing calculations.
Bob – Thanks for the reply. There is not a door in the traditional sense. The sprial staircase goes up from the great room but the opening at the top is probably the same square footage as a door. I’ll check out the link you provided. Thanks again.