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Questions tagged [ducts]

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Air return proximity to furnance

We are refinishing our basement that wasn't original conditioned. New supplies and zoning were added by a contractor. We want to add an air return in the living space by tapping into the main return ...
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2answers
31 views

How do you remove and re-install Register Duct Boot?

Is it possible to remove and replace this register duct boot without screwing up the dry wall around it? Large Images: https://imgur.com/a/lh9HIt2
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2answers
36 views

How to calculate CFM/pressure needed to move water vapor through duct?

I made a cheap, high capacity humidifier from a mist maker, storage crate, and 120mm fan (the fan blows into the crate, which pushes the mist out). This 4" flex pipe works fine to exhaust the mist ...
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1answer
50 views

Move floor vent into the wall

Currently right by the toilet in my bath there is a heating register on the floor. I want to build a small wall at the same location and have the heat exit out of the base of that wall. Is there a ...
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1answer
25 views

Material for stud cavity cold air return

I'm totally aware of the arguments for and against stud cavity air returns so I don't need opinions on that, but I do need an idea of the best material for lining the outside of the stud cavity with. ...
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1answer
48 views

Dropped item in furnace duct

While trying to stop the ticking noise coning from my furnace ducts, I accidentally dropped a small piece of fire retardant foam (as you can see in the below photos) in one of the vertical furnace ...
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0answers
43 views

How do I stop the ticking noise coming from my furnace duct? [duplicate]

I've had some HVAC people here to look at the ticking noise coming from our furnace duct. One of them installed a brace on the piece in question. This seemed to make the ticking less frequent, ...
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2answers
22 views

Forced-air heater for old floor registers

I have an older home which used to be centrally heated by a furnace in the crawlspace, but has since been retrofitted with forced-air wall heaters: Some of the wall heaters are in inconvenient ...
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24 views

Best way to connect to short dryer duct inside wall

What is the best way to connect my dryer securely to this outgoing dryer vent? Should I find a small connector piece, place the crimped end inside the vent, and secure the inside of the joint with ...
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1answer
32 views

Crack in wall over heating duct

thanks in advance for any advice. We bought our 100-year-old house last summer, so this is our first winter in it. The walls are not insulated, so we can tell where the heat ducts run not only because ...
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32 views

Concerns with installing 4“ Dryer Booster Fan into 7” duct

Our new-to-us home was built in 1850, so there's been a lot of oddball things done to it's guts over time. One of these is the dryer vent duct work that looks to have been installed sometime in the ...
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1answer
51 views

How can I prevent makeup air vents from exhausting conditioned air?

The utility room has two 8-10 inch ducts running to it from the exterior of the home. There are also three fireplaces in the home, and we have noticed that occasionally the house smells like smoke, ...
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2answers
120 views

How do I install flex duct to existing duct including registers

When my home was built in 2016 the HVAC runs from the furnace in the basement up through the house uses 7" R4.2 insulated flex duct. I am in the process of finishing my basement and I would like to ...
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3answers
50 views

How to seal joints in ductwork when tape is not an option

The duct-work in the basement for my forced air heating system has been modified at various points over its long history and as a result had quite a few leaks when I moved in recently. I used foil ...
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2answers
59 views

Why is this airduct twitching and making a noise?

I have an air duct in my basement. It leads from my furnace (I think?) to the outside world. However, as you can see from this video, it is "twitching". Every second or so it jerks slightly and ...
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2answers
57 views

Is 4“ Ducting Used for a 4” Bath Fan?

I'm interested in installing a bath fan and am currently planning ou the project. The fan specs (https://www.homedepot.com/p/Delta-Breez-GreenBuilder-Series-100-CFM-Wall-or-Ceiling-Bathroom-Exhaust-...
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1answer
65 views

Flexible duct behind dryer looks a little sketchy

So we just noticed that the air flow in our house is always bad when we run the dryer. Looking behind the unit, we found a foily looking mess of a flexible duct behind the dryer. It looks almost like ...
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0answers
33 views

Bought a home, return air vents on ceiling have R19 insulation shoved in them?

Checking filters and seeing what needs to be replaced, I opened the return air grate on the ceiling and what I find inside is a hunk of R19 insulation. Seems it should be some proper return air filter ...
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1answer
39 views

implications of small bottleneck in ductwork

I need to vent a sauna room (~200F) with an inlet duct that will open below the heater and an outlet that will open near the ceiling at the opposite side of the room. The ducts will be small (2"). ...
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30 views

use of conduit for ducts

I need 2" ducts in this room I'm building. Flexible ducts and conduit are about the same price. I have high heat requirements. Can I use conduit for ductwork? What are the pros / cons? Thanks
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28 views

CAR duct in same bay as electrical wire

I'm going to install a cold air return (CAR) duct through an interior wall that has some electrical running through it. The CAR duct will run vertically, but near the bottom third of the bay there is ...
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3answers
56 views

Can I connect my two HVAC systems?

My house has two HVAC systems. One is in the attic and has supply and returns in the ceiling of the second floor. The other is in the basement with supply and returns at the floor of the first floor. ...
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17 views

Fan duct through cabinet

I have an auxillary ceiling fan in my kitchen and its duct needs to go 90° down the wall but the problem is I can't go around the corner. Can this go out the ceiling, go into the cabinet, and from ...
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1answer
55 views

Tape vs screw joining 4" duct

When joining 4" round duct, like for fart fans or dryers, is it sufficient to just use sealant and aluminum tape but no screw or should I be using screws also? It seems that the tape alone would be ...
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1answer
88 views

Can I remove the top plate at top of an interior NLB wall?

Is it safe to remove the top plate in one section of an interior non-load bearing wall between two studs space 16" apart? The reason I ask is because I need to run some ductwork to my cold air return ...
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1answer
32 views

How to minimize ceiling “backwash” of air circulation in an attic HVAC system

I'm remodeling and placing a new HVAC unit in the attic. The dining room is central on the house, adjoined by the living room, kitchen, service bathroom, and (directly or via a hall) all three ...
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2answers
254 views

How can I fix this furnace filter slot to prevent filters bending?

I noticed a problem with my furnace filter. In the vertical slot where it gets installed, there is a channel along the bottom but not along the top. As a result, the top corner of the filter ...
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1answer
44 views

Whole house dehumidifier- freestanding vs vented

I’m considering the purchase of a Dehumidifier for our basement, to avoid mustiness in the unfinished/unconditioned portion. I want a nicer quality HVAC-grade unit, both for energy-usage reasons and ...
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3answers
61 views

What type of crawlspace setup do I have?

New home owner here - I’m working on sealing the furnace ducts that run through our crawlspace. Previous owner used silver duct tape and not the proper mastic or UL approves aluminum tape. Long story ...
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2answers
41 views

Is a gravity or spring damper sufficient for a make up air vent?

I am planning on installing a make up air vent in my cold air return. I don't want to install an electric system that I have to wire to 3-4 different appliances. Is a gravity or spring loaded damper ...
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1answer
44 views

Will a make up air vent cause an issue in the winter?

I recently installed a gas range and I will soon be installing a 300cfm range hood. Since I primarily burn wood in the winter for heat and I don't want any back-drafting issues, I am planning on ...
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2answers
68 views

Is there any reason that plumbing can't be adjacent to a heating/cooling duct?

I'm installing a utility sink and the only place to put the plumbing (if it's going to be right under the sink) is either directly behind or infront of this vent... Is there any reason not to put it ...
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41 views

Round metal duct leaking water at crimped joint

Noticed a water leak stain in my ceiling in the drywall. Cut a hole and noticed water drops dripping from the joint of a metal round air duct. This duct leads to an external air vent on the side of my ...
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55 views

How do I calculate fan size for a single room exhaust system to reach a desired cfm when restricted to specific duct size/route?

I am wanting to exhaust a sealed room (except for air intake and exhaust). The room is 512 ft3, and due to positioning, orientation, and existing construction, I am restricted to using 6" flexible ...
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2answers
4k views

What is this device I found in my HVAC duct?

I was looking through my HVAC ducts with a camera and found this device attached to the side of a floor joist. It is about 2-3 feet from the air return vent. What is it?
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1answer
243 views

How can I reduce noise from tenants coming through my heating duct?

I live in an old house with a wood frame and forced air heating. My family lives upstairs and we rent out the bottom floor. My problem is that the sound from my tenant's bedroom travels directly into ...
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2answers
101 views

Is there some type of coating I can use to prevent condensate on my HVAC ducts?

I'm getting a lot of condensate on my HVAC ducts that run though my first floor (and HVAC blower) especially in July / August when humidity levels are outrageous (in NJ). The 1st floor space space is ...
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1answer
38 views

6" Ducting straight to in-wall rectangular ducting

I have a vent for the microwave-range that goes from an interior kitchen wall to the outside of the house. I need to re-locate this, but I can't move the exterior vent fixture. It currently comes in ...
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1answer
117 views

Can a motorized damper be installed inside existing ductwork?

My HVAC system consists of a fan, furnace, compressor-driven AC, and evaporative cooler. The problem is that there is a large air volume used only by the evaporative cooler that is generating a lot of ...
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1answer
143 views

Is my plan for moving return duct a few inches ok?

Below is my ac unit and the return duct that connects to the blower. I currently slide my 1-inch filter under that pvc pipe that's inside the furnace. PVC is in the way and there is no L-shape latch ...
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3answers
661 views

How to Sync Booster Fan with Furnace Fan

I own an old house. Some of the rooms in the house that are too far away from the furnace are not getting enough air, the airflow is too weak. I tried to close as many of the other ones as possible, ...
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0answers
28 views

Hood vent duct in floor - sealing it

I have an 8" duct that comes up through the kitchen floor (runs in subfloor between basement and 1st floor and vents outside) and through a kitchen cabinet bottom that will house a pop up vent. I can'...
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1answer
689 views

Should vent directly above furnace be open or closed

There is a vent in the duct directly above my furnace. This is in the air out side, not the return duct. Is there a reason I should have this duct open? It was open when I bought the house a few ...
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2answers
664 views

Sloped ceiling - remove hot air with exhaust fan

I have what I think is an unusual setup of a sloped ceiling that may offer an easy fix to my problem, but wanted to get some opinions from you guys. Our master bedroom, on the 2nd floor (top floor), ...
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1answer
45 views

Is there a way to change the location of HVAC air filter location?

We bought the house recently. Heating system was recently installed by the previous home owner. I cannot believe they did not think of this but the place for filter is inside the furnace. The problem ...
2
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1answer
100 views

Is it safe to use a flexible duct near the end of an 18ft dryer exhaust run?

I'm replacing a gas dryer in a condo that previously had 2 plastic flex pipes and a 5ft aluminum rigid duct. I planned to replace it with rigid steel. I got most of it dry-fitted correctly, except ...
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1answer
120 views

What purpose does the lining inside sheet metal duct serve?

Sheet metal ductwork is often lined inside with a black fiberglass insulation material. What purpose does the lining serve? Insulation is one answer, but ducts can be insulated on the external ...
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1answer
107 views

Do I need a wall thimble for thermal separation with a category III venting appliance?

I bought a tankless water heater that allows me to vent using category III. I've seen that wall thimbles are included in many category III termination kits, but am wondering if they are really ...
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1answer
271 views

How do I patch a subfloor over a return duct cavity

I need to patch these holes in the subfloor where the vents are. These holes are from a return vent that is being moved, the joist cavity below these holes is a return duct. I'm assuming using ...
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0answers
21 views

How to fix noise in my bedroom since change of furance/ac but not air ducts?

I had furnace company back out and he told me it is probably a problem with a damper but it would be hard to find out where. It is only loud in my room on second floor but not in other bedroom next ...