Wet Subfloor from lack of insulation

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  #1  
Old 06-28-11, 06:59 AM
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Wet Subfloor from lack of insulation

Last Fall we had our hardwood floors redone (water damage due to rotted door frame and leaky toilet) This is not the problem now. I went under the house and found out that the AC duct going under the sink had no insulation around it. I was also told that there needed to be insulation around where the duct went into the subfloor as there was none. I found out 2 more areas that were lacking and we are getting warping again. Can I dry the subfloor from underneath with a fan? What goes around the duct to stop so much sweating? I attached some pics that I managed to get. We just had this done by professionals and I am upset. Maybe they tore the insulation down when they redid the floor and now it is showing up. I do not have proof of that. It was an insurance job

 
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  #2  
Old 06-28-11, 11:12 AM
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From what I can see in the picture it looks like someone has madeup some kind of floor box that allows the cold air to blow out between that and the subfloor. Is this true or that I am not seeing it all correctly? Normally floor boxes are sized for the register hole and extend into the subfoor sitting flush with the top floor surface. They are then tacked into the edge of the subfloor opening. Is your box some kind of adapted box that has been somehow modified to roughly fit an opening and then cut and nailed 'over' the floor opening? If so you need the correct box and then ensure that the insulated duct is securely sealed onto it. Once corrected, I would wash the plywood with soap and water to remove any minor surface mold, and it should dry out in a day or two as long as no cold air is leaking from the duct.
 
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Old 06-28-11, 12:07 PM
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I think you are seeing that correctly. We do get air out of the register, which was closed until a few days ago. Did not know it was there. So you are saying those tabs that are nailed into the subfloor with that white foam is al, there is. The white foam is wet and has fallen off. Maybe they (flooring people?) did that as well as not put back insulation between the studs. Is this a tough project that a homeowner can do?
 
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Old 06-28-11, 12:39 PM
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See if you can buy a right sized floor box perhaps from HD or another, install it up into the subfloor, and properly secure it, and then connect your ductwork to it and ensure that the connection is well sealed. Take what is there out. It will never work properly as you found out. This is a pretty easy job and won't take you long. Is that ductwork the flex type, or metal pipe wrapped in insulation? If it is metal, screw it to the floor box connection, and foil tape the joint.
 
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Old 06-28-11, 12:50 PM
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I believe it is flex as It does sag throughout the crawlspace and I had to push it up slightly to get under some. Does that mean it is the flex type? Thanks
 
  #6  
Old 06-29-11, 10:00 AM
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It sounds like it is. All it means is that when you connect it to the new floor box you will slide the inner plastic sleeve over the box connection using a mastic product to help seal things up, then use a pull tie to tighten it, and then pull the outer insulation over it all. If you are not comfortable doing all this yourself, then consider calling in someone competent to have it done before more problems occurr with your floor including mold issues. It does look like the guys that installed your floor made a real mess of things around your HVAC pipe. It is unfortunate that you were at least not told of the situation, and given the chance to call in someone to take care of it the correct way.
 
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Old 06-29-11, 10:26 AM
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So what I need is a new floor box that fit the hole (I measured a 6" hole in the floor), some mastic or foil tape, not sure what you mean by a pull tie, isn't that a zip cord? Also, in the box where the air goes into first need to be measured? Maybe I can tak eit down altogether and block all the air, rather not. I have a window today that I can do this.
 
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Old 06-29-11, 11:47 AM
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Assuming that this duct was always there and is part of your HVAC air flow system you should keep it active. You may need to buy a 6 inch wide rectangular box and new register grill to match, so may end up needing to cut the floor once you buy the new box. I think there are a variety of lengths up to 14" inside dimension. I have never seen a 6 inch round opening. The ones I am familiar with are rectangular and the grills defuse the air flow into the room. Yes, you need to use a zip tie, but if you decide to also tape, rather than use a mastic product don't use duct tape. Despite the name, it is not suitable for this. A foil tape around the plastic liner/box connection would be more permanent. You want to completely seal the connection as well, and then pull up the insulation over it.
 
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Old 06-29-11, 12:20 PM
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The duct has always been tnere. At some point in time someone screwed it (looks like a 6 inch pipe) to the subfloor. There was foam insulation to prevent moisture loss. That is falling down now the ac it coming into the house as well as the subfloor. Also, how do I dry the subfloor, a fan, hairdryer...?
 

Last edited by Nightfly; 06-29-11 at 12:22 PM. Reason: left out ?
  #10  
Old 06-30-11, 05:58 AM
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Question

I detached the duct from the subflorr and unscrewed the homemade floor box. It looks like it was a pipe cut several times at the top so it could be attached to a flat surface. It then had this white foam applied to seal it. Well, the moisure let the sealant fall and wet the subfloor. What I am thinking of doing is attaching that same pipe to the top of the subfloor rather than the bottom. The pipe is 6" and the hole is slightly bigger. I did buy some expansion foam, even bondo. I don't have access to the stuff the pros use.[IMG][/IMG]
 
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Old 06-30-11, 04:21 PM
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Most advice you receive on this forum will help you in doing things the correct and proper way, and reinstalling the current air duct configuration is not that. Doing it right may cost a little more but in the end it will last , and not be a problem if you sell the house later and the buyers obtains a home inspection for example.
 
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Old 06-30-11, 05:07 PM
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What would be the correct way? Could you list piece by piece as I want to not have to go back?
 
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