Questions tagged [ducts]

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Casement Windows: Install Thru Wall A/C Indoors & Exhaust with Ducting

A family member has a business in a century-old building that only has industrial casement, awning, and pivot windows. There's no central A/C & a mini-split can't be hung outside the building. The ...
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2answers
79 views

How do I re-route this wall register to exit a cabinet base?

I am redoing our kitchen, and adding more cabinets. This register ended up behind 2 cabinets. How should I route the duct to 1 or 2 toe kick vents? Do I need duct work under the cabinet, or can I just ...
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1answer
40 views

How to remove slip and drive duct cleat when there is no room on the sides

I need to remove a 2-foot section of ductwork that got flooded so that I can rip out the internal insulation, but I don't see an easy way to remove the drive cleat since there is only about a 3/4"...
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1answer
29 views

How to seal the frayed fiberglass border of internal duct insulation in the middle of a duct

I had to remove the bottom foot of internal duct insulation touching the ground due to sewage backup. Now that there is a frayed edge of internal insulation inside the ductwork with the remaining ...
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38 views

How to replace a supply plenum box with a blower sitting on top of it

I'll probably hire a professional, but I was curious if it's easy to replace a supply plenum box that already has a blower sitting on top of it. How would that be replaced, do you have to keep it ...
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35 views

How to correct an old bathroom ceiling vent fan duct (or lack thereof) in an old 2 story house

I'm fixing up an old home, built in 1930s, renovated in 1980s that has a terrifying fire hazard of a bathroom light/vent fan/heater in the downstairs hall bathroom. When this old unit was removed, not ...
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1answer
68 views

Should a HVAC return be partially closed in proportion to already closed supply branch in basement?

I have damper installed for each supply branch for my basement. There are six supply lines (5" flex duct each) for just basement. It covers 1100 sq ft (includes 1 bed room and 1 bath) for a 3 ...
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3answers
673 views

How should I repair a hole cut into a heating duct?

I found a large hole (~10cm x 10cm) cut into one of the HVAC ducts that supply the bedroom. It was cut between the duct and the joist and is not visible from the ground, I found it attempting to ...
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1answer
45 views

Is there a reason to choose taped fiberglass bats vs fiberglass tubes when insulating heating ducts?

I'm going to insulate the 6" round metal heating ducts in my crawlspace, and I have pretty good access. It's the SF bay area, so it doesn't get very cold. Is there a reason to choose taped ...
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50 views

What is this duct part that was attached to a roof vent?

This plastic part was attached between the flexible duct and a roof vent. The vent was used for a bathroom exhaust fan. What is this part called, and what purpose does it serve? The roof vent was ...
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2answers
140 views

Is there a reason to replace 50 year old metal ducting in the crawlspace with modern insulated flexible ducting?

My concern is heat loss in the chilly crawlspace. No AC here, only forced air gas furnace. The existing metal ducting in the crawl space is over 50 years but is intact. There is a very thin layer of ...
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1answer
57 views

My dryer isn't fully exhausting to the outside?

I recently bought a townhouse which has laundry in the finished basement. I noticed that our clothes took a bit more than an hour to dry in the dryer, so I wondered if there were any lint blockages. I ...
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3answers
52 views

Gas fired Forced-air furnace has a outlet grill in the mechanical room - can I remove it?

I just moved into a house with a gas fired forced-air furnace. Whenever I'm in the basement and the furnace is running I can hear a whistling noise coming from the mechanical room. I traced this sound ...
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1answer
44 views

Should I remove abandoned cold air return trunk?

When the furnace was originally installed, the first floor of my house had four cold air returns, two each on the long walls. When the kitchen was renovated in 2015 (before I purchased the house) some ...
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1answer
107 views

Is this dryer vent installed correctly?

Should I add those vent straps? It seems pretty sturdy, but I want to be certain. Is it even in a good location on the wall? Everyone I spoke with said it looks fine, but still a little strange to me ...
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2answers
121 views

How to fit portable air conditioner hoses through a too small wall vent

Our apartment doesn't have A/C, but we do have wall ports for a portable A/C unit. Unfortunately, I can't really fathom how I'm supposed to hook the hoses up to the wall vents. As you can see, the ...
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1answer
72 views

In Slab Duct Work - Concrete / Cinder Block

I have some weird and what I believe to be abnormal duct under my home. I recently installed a brand new HVAC system and it's not running or performing as desired. I believe I am losing a ton of ...
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1answer
55 views

How can I install ducts on a high place in a building where I can't put nails or screws and where I can't hold ducts to install them?

It's a building like that and we need to install ducts at where the red line is. There is no near balconies or windows to help me put the screws in the wall. The ladder can reach up to the blue line ...
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31 views

How do I shorten pre-installed ducts without cutting into the ceiling?

Upgrading a bathroom fan and I need room to convert a 3" duct to a 4" flapper on the fan (about 7" of length overall). The ductwork is rigid sheet metal and ran directly to the old fan. ...
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1answer
73 views

What is this sealing material inside a duct collar?

Most of the duct dampers don't provide 100% seal from air flow. The below picture might be. I have collar with damper, But its just not enough to stop/bypass the air flow. what is this called in the ...
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2answers
83 views

One branch of my HVAC receives zero airflow, is there a design flaw with this layout?

Question: Why would the 6" duct (represented by the red X) produce almost zero airflow? I have a small piece of tissue attached to it to see that it's barely blowing anything. However, the blue ...
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1answer
54 views

Does a vent register boot always has to be installed parallel to wall for a better air flow all around?

In my basement, I have a gas pipe (1" diameter) running between the joists. There is a reason why I have choose this cavity to run a supply line from where. But I am end up using a end boot ...
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2answers
1k views

How can I offset 6" ducting by just a few inches?

I am installing a range hood and due to a ceiling joist in the way, I have to offset the ducting going through the ceiling by about 3" from the center of the hood. I have to do this within about ...
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1answer
82 views

Do I need to seal the rotating seams of a duct elbow?

Kitchen range hood installation questions: Do I need to seal the points indicated by the arrows? Any opinions on mastic over foil tape? I have some 3M 3340 laying around. Can mastic be used inside ...
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1answer
96 views

How can I insulate a duct running through an unconditioned kneewall space?

Unfortunately, I have to run an 8 inch HVAC duct through an unconditioned kneewall attic in southern Ontario (climate zone 6). I am trying to decide between two options: Encapsulate duct with spray ...
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1answer
39 views

What material should I use to hide a duct running just above the floor in a closet?

I have an 8-inch HVAC duct running along the back corner of a closet (4 feet wide) at ground level. I assume a good way to hide it would be to build a frame of 2x4s. However, while drywall would work ...
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1answer
27 views

Size of a return duct

because I have a large bedroom, I’m adding another return duct which I will put on the ceiling against the wall. It's a 15’ ceiling and I want to get the trapped hot air out. Now, I was thinking of ...
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45 views

In long run, Which is the best way to connect a flex duct to a Take Off Start Collar?

Please, Please vote up to a right answer. I found in the internet, Connecting a flex duct to take off start collar/ connect still a debatable, I need an answer from people of this community. Thanks! ...
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3answers
554 views

How can I reattach an HVAC duct that came loose below the floor?

I just moved into a new house and found that couple of floor ducts have fallen off in the space below. They were screwed from below to keep it in place and I am not sure how to fix it back again to my ...
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2answers
49 views

Can I Take off from top and side of a trunk line under same bay?

Could you please help me. There is an article about 2 foot rule of take off. https://hvactoday.com/0719-two-foot-rule/ In my case, There is already an existing take off from the top , can i directly ...
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30 views

Is 4in pipe OK for range hood with 7in vent?

We bought a 350 CFM range hood with a 7in vent. Our installer ran a 4in diameter flexible aluminum foil air duct horizontally through the floor joists to outside. We are now told the 4in pipe is too ...
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40 views

which is better placement of flex duct in this case?

In the below picture. I have two options to run 1st flex duct. I am running 5 inch flex duct. Option 1 : Between joists where gas pipe is running, Here I would be able to use End Boot only. does the ...
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2answers
97 views

How can I bend 180 degrees over a duct trunk with height restriction?

I have to run a flex duct from opposite side of main trunk, as other side of the trunk in the direction flex duct is running is not accessible. This is in basement, I am using start collar with damper ...
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1answer
309 views

Is there a minimum for spacing between take-offs from an HVAC trunk line?

I have to add 3 take offs from my main HVAC supply/trunk. Is there a minimum amount of distance I should maintain between each of the take offs? What should I do if I don't have the minimum distance ...
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2answers
197 views

What is the purpose of these ducts in HVAC/laundry room ceiling?

Attached picture (1st pic) is ceiling of 2nd floor condominium laundry room, there is HVAC and water heater also in the room. Due to recent water damage ceiling was removed. I have question about ...
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1answer
38 views

Can I go with higher CFM for bathroom ventilation fan?

I need to replace my bathroom ventilation fan. I am in 2nd floor condominium. My bathroom dimensions are 60 square feet and ceiling height is 8'2". As per formula I found for CFM (height × length ...
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2answers
78 views

How to add insulation to ducts in hot uninsulated attic?

I have central air with ducts running through the hot, uninsulated attic (there is blown-in insulation between the joists to insulate the rooms below). Fortunately it's only about 25 feet of ductwork, ...
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1answer
87 views

Using a bathroom fan with a smaller duct - is there a minimum size?

I am looking for information on how to properly replace a bathroom fan which is not working well enough (probably insufficient CFM). The bathroom fan I need to replace is a 90mm fan rated for 65m3/h (...
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0answers
34 views

Extending a forced air heat register

Adding a small room. Want to extend HVAC to the new room. HVAC guy warned me very expensive for such a small job and told me (wink wink nudge nudge) easy to do it myself. Attic above: Question: The ...
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1answer
59 views

Can I move air return higher?

I need to install some open shelving but the brackets they use are at a height that would interfere with the air return pictured. Would it be okay to relocate the return 4” higher or is there a reason ...
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1answer
55 views

Would a ducted heat pump lose a lot of effeciency if the ducts are installed in an open crawlspace?

Currently I use a woodstove to heat my place (no ducts). I am thinking about installing an air-to-air ducted heat pump to heat my place. I am trying to figure out what are the important factors (in ...
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1answer
60 views

How do i reduce and split hvac duct from 8" round into two rooms

Hi i have small minisplit with 350 cf/m i attached a plenum with 8 inch ridgit round duct attached to it now i need to run it into a bulkhead where one register goes into a small room aprox 12x12 ...
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1answer
32 views

Best way to insulate supply duct with minimal clearance

I wanted to wrap the supply side ductwork, but the return is mounted so close to it, in some spots barely 3/4 of an inch of space between them. What is the best way to insulate in this case? Supplies ...
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65 views

Duct work 'pushed' drywall from ceiling, can I jack it up?

Edited original question: Horizontal heating supply stack (4X15) runs between 2x8 joists under bathroom. The take off for the above bathroom register is located 4" from a rectangle to round ...
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1answer
72 views

Will this ductwork for my range hood work?

I installed a new exterior wall vent and ran 6" round galvanized steel duct work through my ceiling joists to the spot where our new range hood will be. There was a significant amount of PEX ...
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0answers
23 views

cold air return using resilient channel

I'm using resilient channel on a metal stud wall for sound reduction. The cold air return is in a wall that is not panned. The plan was drywall would enclose the area making it tight with airflow ...
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3answers
109 views

What type of duct should I use for a clothes dryer exhaust?

I am planning to relocate my gas dryer to the center of my basement. The closest vent is in one of the walls 16ft/5m away. To reach it I would need to run an exhaust pipe horizontally, enclosed in the ...
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1answer
37 views

How to fit a damper in duct?

I've seen some videos on how to fit a damper in a duct but his damper had only one spindle, requiring a single hole. The dampers in my local store, however, have two spindles, at 180 degrees, meaning ...
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1answer
31 views

How can I inspect 6" horizontal ducts to locate a rattle?

Something is rattling somewhere in a 6" round metal ceiling HVAC duct network, not near any vents. Maybe it's a loose damper. The ducts are now behind finished wallboard and since the airflow ...
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0answers
72 views

Ceiling Register Box Insulation and Airtightness - Is this correct?

I'm in the process of making all the ceiling punctures into my attic air tight and better insulated with caulk and spray foam to reduce moisture and my energy costs. However, the HVAC ceiling register ...

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