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Preventing Ductwork Condensation
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Please share your thoughts on this Best Practice.
 
Posts: 257 | Registered: 22 November 2004Reply With QuoteReport This Post
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As much as I appreciated your article - nothing was said about preventing condensation INSIDE the ductwork during the winter months. We live in New England and our a/c system is seperate from the oil hot water baseboard heat system. We run a humidifier during the winter but can only let the humidity levels get no higher than 30% or moisture goes up into the duct work. When we first moved in 6 years ago - our system collected over 12 gallons of water and finally relieved itself through a kitchen light fixture - we thought a pipe had ruptured not realizing it was the a/c ducts. $900 worth of repairs taught us a good lesson - how come you don't hear much about the prevention of this problem? We have to run the blower fan weekly to circulate the warm air throughout the ductwork during the winter.... it works - but the electric bill is higher. I'd like to hear more information on how to prevent this from happening.
 
Posts: 5 | Registered: 13 October 2006Reply With QuoteReport This Post
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Condensation is created when warm air contacts a surface that is made cooler by colder air blowing through it.. and vice-versa. The only real answer is to have the ductwork wrapped if it in a location that is exposed to non living area temp extremes. DO NOT let some simpleton try to sell you on fiberous glass duct lining. This is mainly for sound attenuation ad really does little for insulation. What it does do is trap moisture and dirt and then ... BINGO MOLD. To site a case I was called out on a job where the ductwork in the new addition was literally raining in the new garage area. The salesman told me it was because the a/c was running and the garage door was open. He actually thought it was fine that they couldn't open the garage door for fear of the condensation. Needless to the owner of the contracting company made the call to have the ducts wrapped. Problem solved.
 
Posts: 37 | Location: Columbus, Ohio | Registered: 16 August 2005Reply With QuoteReport This Post
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Thanks for the information - here's the situation.... some of the ductwork is the typical metal ( all nicely wrapped and insulated) then branching off of that are about 12 seperate ducts that have black plastic wrap with insulation on them that are flexible connecting to vents. In the winter we close the vents but you can still feel the cold air filtering through and down into the house. Attic is fully insulated but these ducts run above most of this insulation except where connected. Hence our problem of the peeing kitchen light. One metal duct that ran the kitchen soffet was filled with moisture - cold attic air = ice formation. Being clueless that first year of ownership we didn't know what the ticking noise was when the weather got warmer. It was the ice dripping down - once warm enough.... you get the idea a faucet - water hit the seam in the metal duct - relieved itself down and through the recessed ceiling fixture. We did try one guys approach of getting pink rigid insulation and cutting it to fit the vents and air exchange return. Didn't work though - had the vent in the master bedroom pee on the bed.Apparently it wasn't as 'tight a fit' as we thought. It's costly to replace lines and my son & myself are both allergic to mold. Now we leave the vents open - run the system at least twice a week ( fan only) and leave the humidifer set for 30%. If you've got any other suggestions I'd appreciate them. Would more insulation do the trick or is that just overkill?
 
Posts: 5 | Registered: 13 October 2006Reply With QuoteReport This Post
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I don't know how well ventilated your attic is, but even in the winter it needs to have proper ventilation to reduce moisture. I have nothing good to say about what you descride as "black plastic wrap with insulation on them". Flex duct is used by many contractors as an easy, cheap way to run ductwork. Air velocity is signicantly affected in flex duct as opposed to the same in regular galvanized sheet metal ductwork.(ACCA Manual D) Pressure drop and heat loss could affect the condensation in the duct. More insulation couldn't hurt although I don't know why you would use rigid insulation. Check the flex connections to the register boot. The inner helix of the flex should have a panduit sttight and screws through the strap into the boot. The insulation layer should have a panduit strap tight ove the tucked end of the inner helix duct. If this is not right, get it done right. Since air velocity is reduced in flex duct I would say that covering the duct and boot with blown in insulation would be a good idea. Anything to isolate the duct form the attic temperature would be helpful. Leave the vents open and insulate the ductwork.
 
Posts: 37 | Location: Columbus, Ohio | Registered: 16 August 2005Reply With QuoteReport This Post
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Properly sized,imstalled and sealed flexible duct will function just fine in your attic. I suspect your metal trunks (supply and return) are improperly sealed and insulated. I would take a hard look at the airhandler if it is also in the attic. Older units do not seal well and if you've had any service done the problem could have been inadvertantly made worse.Operating the fan from time to time during cold weather should actually make the problem worse and waste a tremendous amount of energy. Try finding a contractor in your area that specializes in duct renovations. The Florida Solar Energy web site has some really good information and a short video that you may find informative. Best to you and good luck!
 
Posts: 72 | Location: Northeast Georgia | Registered: 18 October 2006Reply With QuoteReport This Post
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Without trying to sound like I'm flogging something here I wish to share my experiences with you simply because I offer an effective solution for condensation control that works and frankly I am surprised this has never been mentioned before.

We use a multi-ceramic insulation coating called Super Therm for our condensation issues. It's the most effective insulation product that actually stops heat from coming into contact with the coated surface which means, no opportunity for dew point to occur.

I am a skeptic and looked at this product inside and out when I was first introduced to it. This product is well supported through third party testing but that still wasn't enough for me. I needed to see first hand that it works.

The distributor in the area I live coated his bathroom walls and ceiling after solving a big condensation issue at the Richmond Ice Arena. In seven years I have yet to see one single drop of water and believe me I looked. I also work at a group home for teens in care where I had the same product applied in the bathroom while doing a major renovation. You can well imagine how often the only bathroom in the house with a shower and five teens gets used. After five years now we experience the same results. I have yet to see any moisture on the walls. The one major difference in the reno other than the use of the coating was that we replaced the existing fan with a Passivent which essentially opperates automatically by humidity levels without the use of an electric fan.
 
Posts: 11 | Location: Vancouver | Registered: 28 March 2007Reply With QuoteReport This Post
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Kapple, I too have condensation inside my ducts, live in New England, have hot water baseboards, insulated flex duct A/C, and cheap louvered ceiling vents that don't fully close. After replacing my ductwork two years ago I have been using small squares of heavy clear plastic, fully taped to my louvers and a garbage bag around my return filter without problem. I had tried to use white sheet magnet cut to fit until I realized the louvers were aluminum. I have priced out louvers that have rubber seal bulit into the boots above the louvers for a tight seal but almost $500 for 8 of them. Plastic works for now. Two alternatives, put the attic floor insulation up into the rafters with rafter vent to make it a semi-heated space or install a hot water coil in your attic blower for forced hot air during the winter months. I can relate.
 
Posts: 1 | Registered: 07 December 2007Reply With QuoteReport This Post
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I don't see putting insulation in the rafters as a great solution as you will be creating yet another problem for the warmer months. You need to be able to vent the heat out or you are going to have a lot of heat building up which will migrate into the living space as heat travels towards the cold. if you use air conditioning this will drive your utility bill up significantly.

That leads to another issue. If the solution relys on the use of electrical fans then you are going to use more energy. In this day and age we need greener solutions. The solution I discussed in a previous posting uses zero utilities and in fact reduces utility cost.
 
Posts: 11 | Location: Vancouver | Registered: 28 March 2007Reply With QuoteReport This Post
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I wanted to thank everyone for their input. To give you some further information - No can do on the additional insulation. Our attic is vented through the soffet and we do have have a ridge vent. Need to keep these clear. Looks like we might be replacing the unit in the next year or two. The unit is coming up on 8 years now and it was one of the cheaper units and the fellow who installed it ( original owner) - was a Jack of all trades and master of non. For the time being - we close the vents - use Glad Cling wrap on the return in the hallway and that seems to help. The humidifier broke last year and we decided to leave a container of water on the pellet stove. The evaporation rate seems good enough to keep the family from itching and zapping itself for the time being.
 
Posts: 5 | Registered: 13 October 2006Reply With QuoteReport This Post
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That's the beauty of using the ceramic insulation coating. I have found that you control the thickness unlike other types of insulation. The minimum requirement is about 10 dry mils which is only as thick as a business card. Actually it's thinner as my business card is 12 mils thick. This means you don't take up any space. It also stays where you apply it. No shifting, settling or falling appart.
 
Posts: 11 | Location: Vancouver | Registered: 28 March 2007Reply With QuoteReport This Post
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quote:
Originally posted by Tsimshianman:
That's the beauty of using the ceramic insulation coating. I have found that you control the thickness unlike other types of insulation. The minimum requirement is about 10 dry mils which is only as thick as a business card. Actually it's thinner as my business card is 12 mils thick. This means you don't take up any space. It also stays where you apply it. No shifting, settling or falling appart.
Do you have UL, CSA or other documentation for your product?
 
Posts: 72 | Location: Northeast Georgia | Registered: 18 October 2006Reply With QuoteReport This Post
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There is no shortage of testing done with these products however CSA or UL are not included and have not been required. Those testings that have been done were intended to satisfy the requirements of architects and engineers for applications in various fields including the building industry in North America.

Here are a couple of links regarding this product (SUPER THERM)

One is a listing of Architectural Specifications which essentially provides most of the answers architects and engineers are likely to ask.

ARCHITEC SPECIFICATIONS

The other link shows a listing of certifications and testings such as ASTM which support product performance

CERTIFICATIONS
 
Posts: 11 | Location: Vancouver | Registered: 28 March 2007Reply With QuoteReport This Post
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quote:
Originally posted by Tsimshianman:
There is no shortage of testing done with these products however CSA or UL are not included and have not been required. Those testings that have been done were intended to satisfy the requirements of architects and engineers for applications in various fields including the building industry in North America.

Here are a couple of links regarding this product (SUPER THERM)

One is a listing of Architectural Specifications which essentially provides most of the answers architects and engineers are likely to ask.

ARCHITEC SPECIFICATIONS

The other link shows a listing of certifications and testings such as ASTM which support product performance

CERTIFICATIONS
That is a very impressive list. Today has been a good day, because I've learned something new.
Thanks so much! Sorry if I was a bit skeptical; I just get a little suspicious of "miracle" products.
 
Posts: 72 | Location: Northeast Georgia | Registered: 18 October 2006Reply With QuoteReport This Post
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I would hope that we should all be cautious if not skeptical especially if it sounds too good to be true. This is why extensive testing is so important by certified third party testing labs. There are always going to be knockoff products but this is the only one that can provide proof both in the labs and out in the field. I have to speak with architects and engineers on a regular basis so unless you can assure them you have the proper certifications in place they will not waste their time listening to a mere sales pitch. As a consumer the rule of thumb should always be to request the testing and certifications.
 
Posts: 11 | Location: Vancouver | Registered: 28 March 2007Reply With QuoteReport This Post
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hi, isn't there special foil duct wrap that can be wrapped around ducts to prevent the moisture? hasn't anyone ever come up with the idea to make ducts out of this material to prevent moisture from accumulating on the inside as well? -Fishfool @ The Reef Tank
 
Posts: 20 | Registered: 16 June 2008Reply With QuoteReport This Post
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Foil wrap allows for condensation and ultimately corrosion of your ductwork. Often water collects so much you can see a bulge devellop and eventually drip. This is common with wrap and clad insulation systems on piping.
 
Posts: 11 | Location: Vancouver | Registered: 28 March 2007Reply With QuoteReport This Post
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The trick to preventing condensation on the outside of ducts is to prevent the air from reaching the metal duct. Duct wrap has a metal foil face on it. Once its wrapped around the duct metal tape is used on the seams. This prevents the moisture from reaching the cold duct and causing it to condense. Its exactly like the method used in a house with a vaopor barrier behind the finished walls. The area in which you live determines how much insulation you require around the outside of the duct to prevent the cool temps from reaching the foil face and cause the moisture to collect on the outside of the foil face.
 
Posts: 1933 | Location: New Jersey | Registered: 31 January 2006Reply With QuoteReport This Post
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quote:
The most commonly used duct wrap is a flexible fiberglass insulative blanket that is applied to the exterior of sheet metal ducts. It is easily cut and fitted to achieve an insulation blanket over rectangular, round, oval or irregularly shaped duct surfaces. The duct wrap is made of a liner of insulative material laminated to a moisture impermeable vapor barrier on the external surface.

Condensation forms on the metal air ducts wherever the duct surface reaches the dewpoint. The moisture may remain in place due to the vapor barrier encouraging microbial growth and moisture damage. The duct wrap is likely to become a moisture trap because of poor installation, taped joint failure, inefficient insulation, or damage to the vapor barrier where the warm moist ambient air is allowed to come in contact with cool air in contact with the metal air ducts.


Such methods as this are very labour intensive. Also, when installed the material cannot or must not be compressed otherwise those areas will have significantly reduced R Value because the material then becomes a conductor. The challenge then is to install a tight fit without compressing the material.
 
Posts: 11 | Location: Vancouver | Registered: 28 March 2007Reply With QuoteReport This Post
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