Questions tagged [ducts]

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1answer
742 views

Baseboard air return install

I've decided to move an old floor air return to the baseboard. I am going to use two adjacent wall cavities and a ~30" grille. Not sure what sort of duct I should use to run through the sill plate ...
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2answers
163 views

Should furnace fan run when return and supply are 'backwards'?

Our furnace supply vents are in the middle of the house and the returns are on the outside - which I understand is 'backwards'. When the furnace is running, plenty of hot air comes out, but seems to ...
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1answer
2k views

Can I reroute a return air duct if it adds length and several bends?

I'm doing some remodeling in my house and would like to finish the basement ceiling with sheetrock replacing the old drop ceiling. The only problem is the ducts both run on one side of the room as ...
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1answer
2k views

Safe to put old white paper-backed fiberglass insulation on metal ductwork?

We live in a very old house with an unfinished basement. The heat for the entire main floor is from a furnace in that basement that blows through the square style ductwork to vents placed in each room ...
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2answers
89 views

What is this rubber circle on duct

Can anyone identify? I'm hoping I can use it somehow to affect air flow. http://i.imgur.com/5q4T9nr.jpg
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0answers
52 views

Studio HVAC Solution

I have an interesting situation where I am in a studio that is approximately 300 sq. ft., and should require ~9,000 BTU/h (3/4 ton) heating/cooling capacity. There are three rooms--A bedroom (~11x8), ...
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0answers
2k views

Bathroom exhaust fan through clay tile roof

I've installed an exhaust fan in an upstairs bathroom and need to vent it through the clay tile roof. (pic attached) The standard 4" pipe jacks and flashings I'm finding at Home Depot don't seem to ...
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0answers
46 views

Central heat ducts(the ends that are attached to registers) in attic not securely attached to attic floor/room ceiling. How to secure?

When I removed the registers in the ceiling of our house I noticed that the ducting in the ceiling was totally loose. They are not secured in any way. The two screws of the register was what was ...
2
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1answer
124 views

running heat ducts outdoors

I'm building a small (160 square feet) granny flat about 20' away from our main house. Our main house has a great blend of pellet stove + solar collection to keep the home warm. Rather than run ...
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1answer
4k views

How to seal around ceiling duct?

We were painting our ceilings and removed the register for the central heating system. The hole is roughly cut. And I can see right through to the attic along the edges between the duct and the ...
2
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1answer
9k views

Best method for rear venting a microwave on an interior wall?

I am installing a new over-range microwave in my kitchen and would like to vent to the outside rather than recirculate. It will be mounted to an interior wall, so I either have to go up or down. ...
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0answers
61 views

No insulation behind duct work, basement wall

Insulating my basement with 1.5" thick XPS foam to achieve R-7.5. Great. All things happy. Except I ran into an issue. My rectangle ducting (the main trunk) line actually stops a 1/4" away from my ...
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2answers
231 views

Do truly air-sealed electrically-actuated duct damper exist?

I need to install an exterior makeup air duct to provide makeup air for my new stove hood. My house is fairly tight, and I've been making energy efficient improvements including tightening the ...
4
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2answers
7k views

Insulate rigid rectangular duct

The problem My vented attic in Virginia has a straight 28ft of 12" x 8" rigid rectangular trunk duct with seven 6" branches. The insulation is quite low around R-4, and also has many tears and rips, ...
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2answers
3k views

Pull insulated flex duct over rigid duct

The problem My vented attic in Virginia has rigid 6" ducts with insulation that is quite low around R-4, and also has many tears and rips. I would like to replace the insulation with R-8. After ...
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0answers
276 views

Noisy ducts, problem with insulation?

I have what I'm coming to believe is a unique noise issue with the HVAC ducting in my house. I've spoken to four different professionals and they are all somewhat dumbfounded. The problem is that my ...
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0answers
47 views

Basement duct installation with fire sprinkler pipe

Can I install a metal HVAC duct with register into the same ceiling joist bay as an orange fire sprinkler pipe, parallel to it? The sprinkler pipe has 2 heads on it.
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1answer
125 views

does it make sense to replace plastic flex ducts with metal ducts?

Today I get my ducts cleaned. It's extremely dirty. And I noticed my house which was built at 2003 was using plastic flex ducts. I just feel metal duct are stronger and easier to clean and never ...
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1answer
38 views

Will Galvanized Steel React with this Ductwork?

I plan to use a galvanized steel patch on this ductwork. Will it react with this ductwork? I'm not sure what it is made out of. Is this ductwork galvanized steel? It's ductwork from a house built in ...
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1answer
727 views

How to Fix Ductwork that I Crushed?

I stumbled off of a step ladder and crushed this ductwork. It's in a bathroom and runs along the floor on a concrete slab between joists. The house is 50 yrs old. The ductwork looks like it's ...
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1answer
564 views

Range Vent Hood Ducting - Can two 5“ ducts work in place of one 10” for a range vent hood?

Purchased a Kitchenaid Range Hood Vent that has a 1200 CFM blower. Instructions say to install a 10" duct vent. My existing venting duct was a rigid but small 6 inch duct. Unfortunately at demo ...
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1answer
497 views

Should I change the routing of the return air flex duct?

I've been in the attic quite a bit before the summer, and every time I look at the duct work, I keep wondering if some crazy/lazy person did it. For example, I have a flex duct running from the main ...
2
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1answer
323 views

How to open this air return duct between joists

I got dead rodent in return duct, at least I hope I will find it there. My returns on bottom and supply on top. Strong smell from return in one bedroom. Attached is pictures how this duct look from a ...
7
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4answers
3k views

How can I be sure all the asbestos particles are gone?

So we got rid of the popcorn ceiling that had asbestos. Now my wife is worried about the particles that might still be lingering in the air. How long until it settles down? Wet-mopping, HEPA vacuuming ...
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0answers
3k views

Using PVC pipe for bathroom exhaust fan duct

I have to run a length of about 3 meters of duct (from the fan to the outside), where there will be 2 90° bends. I was going to use plastic flexduct, but I can make the bends bends and some of length ...
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1answer
1k views

Supply/return plenum box: OK to use top of box?

For sheet metal supply/return plenum boxes, I noticed the builder didn't make holes in the top for any of the ductwork. I figure it's because it wouldn't make sense considering every duct works its ...
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1answer
79 views

Making HVAC duct flush with floor

I removed a interior wall with a heat/A/C duct in it. I need to lower into floor. I currently stands about 8 inches from floor. What do I need to do in order to make flush with flooring?
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1answer
980 views

Shorter runs should get smaller duct sizes?

We have some long runs in our house. Assuming there isn't too much blockage in the flex duct, would it make sense to reduce some of the very short runs from 6" to 4", for example a bonus room window ...
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1answer
563 views

Can I vent a window air conditioner through a joist space for 30 feet?

The situation: We live in a one bedroom + den (rental). We're using the den as a second bedroom, as we're a family of four and that's what we can afford right now. The den has no windows, however, and ...
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0answers
2k views

HVAC Return Duct - Joist Panning alternative

Joist Panning(Lining) seems to still be popular. However, a have read in a few places that joist panning is difficult to seal and can pull air from unconditioned spaces. I am looking for an ...
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1answer
331 views

Low Voltage cable run thru Flexible Aluminum Pipe

Are there any code issues with running CAT6 and Coax thru flexible duct that is not part of a ventilation system? Basically I want to use something like this as conduit into an unfinished attic ...
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2answers
509 views

Brown Spots Above Ceiling/Ductwork

Any idea what these spots might be? They're isolated to just one spots on my ceiling. My ductwork is right above this area. Thanks!
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1answer
664 views

How can I seal HVAC duct damper?

My bypass humidifier is designed to run in a loop between the supply and return, and has a damper to close airflow for the summer. The problem is that the damper is by no means airtight when closed ...
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2answers
1k views

Should I vent 2nd floor bathroom exhaust down?

I am looking to install an exhaust fan in a bathroom where one does not already exist. I've read that it is preferable to run exhaust ducts down instead of up, but does that apply here? We would be ...
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2answers
243 views

How to clean dryer ducts . Home is built on a slab

My home sits on a slab, I can only assume that the dry duct runs from the wall and under the house ( no crawl space.). there is a large pipe that exits the house on the outside where the cap is ...
3
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4answers
3k views

Can one use large-diameter rigid plastic pipe for HVAC ducting slash why is this never done?

Lots of buildings have rigid metal ducts. And lots of buildings have (much-maligned) plastic flex ducts. But why do rigid plastic ducts not seem to be a thing in North American construction? Such ...
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3answers
113 views

Mount horizontal 6" metal exhaust pipe to wall economically?

I'm trying to add more ventilation to the back room of my garage. The only available outside air exit location is 25' horizontally along the front room of the garage's wall. I have 6" 30ga sheet ...
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1answer
2k views

What is 3" (750Pa) wg class?

According to Sheet Metal & Air Conditioning Contractors’ National Association (SMACNA) - leakage test manual, It is not recommended that duct system constructed to 3" (750Pa) wg class or lower be ...
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4answers
1k views

Duct Cleaning: Is Duct Sealer Necessary, Non-Toxic?

A professional contractor is cleaning AC Ducts, and after he scrubs the ducts, he wants to apply an acrylic duct sealer and de-odorizer. The container of the duct sealer has minimal lableing and does ...
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1answer
318 views

Metal around wall register boot for trim

Below are two images of what im talking about. Around the duct boot for the wall register is a metal box to make up for the difference between the wall and where the trim ends. What is it called and ...
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1answer
701 views

On wall near floor or ceiling for supply ducts in basement

I'm starting to finish my basement and I'm curious if I should put my supply ducts in the ceiling or the exterior wall near the floor. I have the configuration to easily do either. Any thoughts on ...
3
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2answers
17k views

How to address loud cold air return

The cold air return on my forced air furnace is too loud. While it is is tolerable, there is a noticeable sound of rushing air when the furnace is running (not a whistling sound, just a blowing sound)....
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1answer
2k views

how to measure CFM in digital animometer [closed]

dear friends how to measure CFM in digital anemometer and tell how its calculated in both practical and theoretical
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3answers
2k views

Sealing gas duct vents with silicone

Is it okay to use silicone to seal gas furnace heater supply ducts? If so, do you know how long the silicone will need to cure before the system is useable? Some background: I've been trawling around ...
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2answers
9k views

What's the minimum safe distance from the back of a dryer to a wall?

Let's say I have a side-venting dryer. If I don't need to run ductwork behind the dryer, how close can I safely place the dryer to the wall?
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1answer
305 views

Should I plug unused chimney ports in basement?

My house used to use the basement for gas heat and the water heater that were using these, 3.5" and 5" ports in the chimney stack. The whole chimney is no longer used but I want to keep the option ...
3
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0answers
5k views

Can I use flex duct for a range hood exhaust? [duplicate]

I am replacing an old range hood with a hood/microwave/convection oven. The vent from the old hood does not line up with the vent position on the new unit. I know how to remove the old vent and patch ...
2
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2answers
363 views

How can I get better HVAC airflow?

I recently purchased my house which was a new construction. Several of the vents are getting poor airflow but the installation company simply said it was normal but I suspect otherwise. I recently ...
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3answers
168 views

Duct sizing impact on flow

We have a ranch with a wood fireplace in the living room. It's fantastic at heating the main living area, but the bedrooms down the hall get left in the cold. I'm going to install insulated flexible ...
2
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1answer
3k views

90 degree angle in air conditioning ducts, should I avoid them?

I have forced air at my home and air ducts run pretty much straight. However I want to add bathroom in the basement and because of low ceiling hight, the main air conditioning duct has to be re-routed ...

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