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

By: Mike

Mike — Fri, 20 Jan 2012 14:04:30 +0000

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.

By: Bob Jackson

Bob Jackson — Thu, 19 Jan 2012 20:53:28 +0000

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.

By: Mike

Mike — Thu, 19 Jan 2012 12:57:04 +0000

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.

By: Bob Jackson

Bob Jackson — Thu, 07 Jul 2011 22:24:50 +0000

> 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.

By: Jessica

Jessica — Thu, 07 Jul 2011 14:17:58 +0000

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?

By: Bob Jackson

Bob Jackson — Sun, 26 Jun 2011 23:51:09 +0000

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.

By: Alan

Alan — Sun, 26 Jun 2011 21:27:50 +0000

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!!

By: Bob Jackson

Bob Jackson — Sun, 26 Jun 2011 21:07:11 +0000

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.

By: Alan

Alan — Sun, 26 Jun 2011 19:00:44 +0000

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…

By: Bob Jackson

Bob Jackson — Sun, 26 Jun 2011 13:41:43 +0000

> 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.