# Using Pipes instead of joist spaces for cold air return



## RPWin (Feb 8, 2011)

I have a new house and have a question. All the duct work for heat uses 5 and 6 inch pipes which is fine and makes no noise. All my cold air returns use the space between the joists with sheet metal screwed against the joists. These sheets of metal make constant noise when we walk on the floor above the return duct. I have been told this is called tin canning. I have made scratches in the metal, banged it, put weights in it and nothing stops the noise for long. Is there a problem with me replacing the metal between the joists with pipes the way the warm air uses? I would only do this for the noisiest sections. Any other suggestions would be appreciated. The joists are 2x8s


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## Jackofall1 (Dec 5, 2010)

Hello and welcome RPwin, to the best dary DIY'r site on the web.

Have you tried bracing the adjacent floor joist. Sounds to me like your floor joist are flexing inward when under strain, by adding cross bracing you should be able to reduce or eliminate this.

Mark


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## RPWin (Feb 8, 2011)

I have tried cross bracing which greatly reduced the banging, but was told that replacing the sheet metal with an actual pipe would eliminate the problem. I think I should have asked for 2x10 instead of the 2x8s as the floor does feel a bit bouncy. I was just really wondering why pipes are not used? Is there a reason that pipes are not used?


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## Jackofall1 (Dec 5, 2010)

$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$, isn't that always the reason.

Mark


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## hvac benny (Dec 29, 2009)

One option is to replace the sheet metal with thermopan. It's cardboard faced with aluminum.


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## RPWin (Feb 8, 2011)

*This Thermopan may be the way to go. If it works the way it says, it should get rid of sheet metal noise. I see Home Depot carries it.

Still curious if using pipes and an angled boot would work for some of the spots. 
*


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## unicursalhex (Jan 18, 2011)

I have never heard of return panning making noise when you walk on the floor... You should look at your framing closer, floor joists should flex like that. Sometimes the panning can make noise because the screws were not angled away from the metal on both sides essentially not stretching the metal tight enough.


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## RPWin (Feb 8, 2011)

This is my 4th new house and you are correct about the noise. My last three homes didn't make as much noise but did make some. Perhaps I should redo the screws. The builder says there is nothing wrong and banging is normal with metal duct work. The sheets are not stretched and the screws actually look like they are either straight or angled in towards the metal. The entire assembly of heating ducts both warm and cold make noise. I was able to get rid of the warm air duct noise by using metal duct tap on all the joints and re doing the hangers by putting rubber washers between the hangers and the joists. All the ductwork and pipes are very tight against the joists and make a banging sound when heating and cooling.


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## HVACDave (Oct 16, 2007)

I only use thermo-pan in new housing any more. The cost difference between running individual returns "ducted" compared to thermo-pan will be significant. You also don't have to worry about working around wiring and other piping systems etc. I staple it up with a air stapler and it is soo quick to do. overlap the joints an inch or so and put a strip of foil tape along the seem and you are good to go. No more noise.


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## RPWin (Feb 8, 2011)

Thermo-pan definitely seems the way to go. I will check it out at home depot. So cost is the only reason for NOT using pipes. I was told it had something to do with cleaning the duct work. If large items fall down a return duct, it is difficult to retrieve as it would get sucked down the pipe where as it would just sit at the bottom when using sheet metal and floor joists.


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## pyper (Jul 1, 2009)

RPWin said:


> If large items fall down a return duct,


My BS meter is going off on this :laughing: 

When's the last time you ever dropped something into a return?

Regarding the problem you're having, I wonder if bluetac would keep them from banging. It might add just enough mass to keep them in one position. Our new house has returns going across the joists, so they're fabricated metal boxes. The old house had insulated flex.


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## RPWin (Feb 8, 2011)

I have never heard of bluetac. I am in Winnipeg Canada and don't know if it's available here. My main return line goes across the joists as well however it looks like they fastened the sheet metal to the joists before putting up any of the ducts as the screws are between the joists and the duct with about a 1/2 inch gap so removing the sheet metal is going to be a job. That was one reason I was considering using a pipe. I could cut the sheet metal away from the screws, but then it would be impossible to get anything else there until i removed the screws somehow.


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## HVACDave (Oct 16, 2007)

Just remove as much of the joist liner as you can and replace it with the thermo-pan. Cut it as close to the ducts as you can and bend about a 1/2 inch up to make an angle that will strengthen the remaining few inches of joist liner so it won't bother you with noise any longer and add on the thermo-pan from there. The return duct will be cut open on the top so the air from the joist space can get into it. I am in Winnipeg also. You may be able to pick thermo-pan up at Wholesale Heating on Century street and it may be less expensive than the big box stores. I think they sell to the public if you have cash or credit card. I would predict you have 16" spacing on your joists, just make sure before you pick it up, it comes in 2 widths by 4' of length per sheet.


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## RPWin (Feb 8, 2011)

Looks like I have my weekend project. I have 4 places where I will put the thermo-pan. It will be nice to get rid of the noise. 

Thanks.


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## RPWin (Feb 8, 2011)

*SUCCESS*! I replaced the sheet metal with the thermo-pan and the results are amazing, not only is the banging noise from walking gone, but so is the whistling noise. The returns were always noisy when the furnace came on and now are much quieter. The hardest part was removing the sheet metal as it was obviously put up before the main duct lines. While removing the sheet metal, I was greeted to piles of debris that was left over from construction. Every thing from drywall pieces to pencils, pens and even a hammer and screwdriver where in there.


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## veesubotee (Nov 22, 2008)

RPWin said:


> I have tried cross bracing which greatly reduced the banging, but was told that replacing the sheet metal with an actual pipe would eliminate the problem. I think I should have asked for 2x10 instead of the 2x8s as the floor does feel a bit bouncy. I was just really wondering why pipes are not used? Is there a reason that pipes are not used?


Are your joists 'real' wood or 'Frankenwood"?


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## RPWin (Feb 8, 2011)

The joists are real wood.. I've attached some pictures of the hardest part.


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## heatycooly (Mar 11, 2011)

You could check the headers, where the panning is sealed off in the floor joist, I have seen that pop more than panning, usually need to reposition it or cross break it


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