Aeroseal is a product that seals small leaks in the ductwork. No attic work is required by the crew to work the equipment. It is monitored by a computer program that tells when the pressure of the ductwork is low enough that most of the leakage has been sealed.

The plus side to Aeroseal is that:

1. It is able to reach inaccessible parts if the attic such as flat roofs.

2. No attic work has to be done.

3. Unlike radiant barrier, it reliably works regardless of how it was installed.

The down sides to Aeroseal are:

1. It does not seal larger leaks, which are the most important leaks you have. Since crews assume all the duct leakage was found and sealed, if they go into the attic, they will not look for large leaks in the ductwork.

2. Aeroseal is not cost effective. It is expensive, usually 3-4 times more expensive than sealing the ductwork by hand. Aeroseal costs starts from $2000 for each air conditioning unit. With the extra money saved by using hand duct sealing, you could have a super insulated attic, a variable speed pool pump or any other energy saving upgrades done. Hand sealing is not as glamorous as the Aeroseal technology but who cares if you are saving thousands of dollars on something that costs the same and no one will ever see?

3. It is easily misunderstandable. If you are not working with Aeroseal everyday, chances are the printout you receive from Aeroseal showing your leakage reduction will look great. But you need an experienced energy auditor to be able to tell you in the first place if you need it or not. Then if you have leaks which are larger than 5/8" which Aeroseal will not be able to close up. Chances are likely that if a company does Aeroseal, they will not train their sales staff and auditors to sell hand duct sealing and will not look for larger gaps in the ductwork.

4. Aeroseal only lasts 10 years according to the Aeroseal website, hand sealing with mastic has a life of 30 years.

In our opinion Aeroseal works effectively for smaller holes and is ideal for flat roof homes. On older homes, Aeroseal just doesn't come close to the effectiveness of hand sealing the ducts because a crew hand sealing will be able to secure the ductwork with metal screws, check the connections and spend a lot more time in your attic, which increases the chances for finding and fixing problems that the auditor did not find during his initial inspection. Aeroseal requires no time in the attic.

Ductwork leakage is caused by one or several of the following reasons: inferior workmanship, torn and missing external duct wrap, improperly installed duct sealants. By properly sealing your ductwork, you are avoiding lost of lost air and money thrown into your attic.

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Comment by Tucker Henne on June 13, 2014 at 12:25pm

David I will again go through your comments in chronological order and again you seem to be mislead.

1) I assume what you mean by platform return is what we call a joist bay return. Old school technique using sheet metal and floor joist to create a duct cavity. Aeroseal does in fact seal these as well, however as they are notoriously leaky, sometimes it does require manual sealing in conjunction with Aerosealing but I simply don't understand why you claim this as a downside to Aeroseal? As I mentioned before, Aeroseal sealant allows us to pinpoint these leaks the same way the fog machine technique works. During our initial visit if we notice joist plenums are present we make note and account for that. If it requires some caulking, expanding foam, tape etc. to create a tight seal then that's exactly what we do but one way or another we get it sealed just as you would. The cost to us for a little bit of foam or mastic to seal these large leaks is negligible and we have yet to charge a customer extra for these minor repairs. We also use manual sealing to seal the connections from the plenum to the equipment at no additional cost on both supply and return. This goes beyond Aeroseal obviously but after all we are there to seal the ducts.

When I say we must assume that the installer made proper mechanical connections and fastenings I'm not using that as an excuse. I'm not sure where you're going with this maybe you can explain. Is it not a reasonable expectation for a customer to assume that their HVAC installer who they paid thousands of dollars for a duct system that they would use screws and s-slips where needed as they were trained? And not skip them because they are hard to reach or out of sight? Again this is not an excuse but I don't have xray vision so how am I supposed to know if a mechanical connection is missing before we perform any diagnostics? If we encounter this scenario as we do often we simply fix it and keep sealing.

2) As far as the cost effectiveness of duct sealing, surely you as an energy professional must know from your training that ROI of any retrofit measure depends as much on the climate and geographic location of the project (ie. degree days) as anything else. I see that you work in Arizona, which is a notorious air conditioning climate. I on the other hand work in New England where home owners use both heat or ac virtually year round. As you must also know the heating season tends to cost homeowners more due to the greater variation of temperature from indoors to out. Due to our climate, our degree days and high concentration of older houses the DOE's estimates tend to be pretty accurate for us. However with that said, as any good energy conservation professional would say, I never guarantee energy savings with retrofit work. My biggest issue with your point here is that you say "those of us giving realistic energy savings without false promises." I honestly take offense to this because you are basically making the assumption that Aeroseal contractors are somehow less trustworthy and qualified then you...

3) You seem to be leading with the assumption that Aeroseal equipment is not suitable or capable of performing an accurate duct leakage test. As I mentioned previously Aeroseal utilizes the exact same DG-700 manometer that is sold with Minneapolis blower door/duct blaster equipment. It uses the same principle of cfms in vs duct pressure and cfms out that Minneapolis equipment uses. And as I also said, after using both techniques extensively, I would argue that the Aeroseal software eliminates much of the operator error possible with these tests. As far as our certificate being accepted for code compliance or within these programs- we have successfully used the post seal leakage certificate that Aeroseal produces on both residential and commercial projects where testing is required Including LEED, EnergyStar, IECC 2009 etc. Our certificate has been accepted by building inspectors, engineers and other compliance testing companies as sufficient for code compliance.

4) You're right mastic should be applied to a sufficient thickness, however your claim that Aeroseal sealant is equivalent to a very thin coating of mastic is just that....a claim. I'll let the 10 year manufacturers guarantee speak for itself. When dried the Aeroseal sealant remains flexible and does not crack...ever. Mastic however will breakdown and crack overtime or if, like you said, is improperly installed.

In conclusion, I agree that both Aeroseal or manual duct sealing can be effective. However it is my opinion for every reason that I listed and more, that Aeroseal does a more effective and comprehensive job at sealing ductwork than manual methods. I will agree that Aeroseal is not for everyone...there is a limit of cost effectiveness on very small duct systems. However it is simply the best solution for sealing inaccessible ductwork in both existing and new construction. With Aeroseal, we can seal and test an entire system in a matter of hours where it may take days with manual methods...and the quality is verified. A little anecdote to finish with...in the past, our crew has successfully sealed and tested 48 individual duct systems in a new LEED multifamily building in only TWO days with one Aeroseal machine. Now that's cost effective. I challenge anyone to do that with mastic and tape.

Comment by David Byrnes on June 12, 2014 at 6:30pm

Thank you Tucker for your feedback below is my rebuttal. As a disclaimer, I also use Aeroseal on homes that is suited for. Aeroseal may well become a standard of practice as it does seal leaks under 5/8" well, but it needs to be accompanied by a through manual sealing and BPI certified test out as well.

1. Many times leaks are larger than 5/8", especially on the return side. What about a platform return... leaks below 5/8"? Not in any of the hundreds of platform returns my staff or I have ever seen and the leakage on the return side is the most important leakage for a duct system!

I would say that assuming that a HVAC contractor made all the proper mechanical connections and fastenings is careless at best. My auditors would get fired for using that as an excuse and every company in the Home Performance With Energy Star Program would be kicked out if we used that excuse with the program administrators to justify our jobs not passing duct sealing.

You are correct and I pointed out that Aeroseal is ideal for hard to reach areas such as flat roof homes and I will amend that to also Victorian homes with the ductwork running up wall cavities, rectangular ductwork with one side unexposed when in a basement (as you point out) or along an attic floor.

2. The cost effectiveness of Aerosealing was not judged on the DOE's generic ROI for duct sealing, but based on running thousands of energy models on homes with the cost savings of duct sealing ranging from $50 - $200 maximum, and that is with the ductwork located in unconditioned space. It gets even lower if the ducts are in conditioned space where air sealing and capping wall chases becomes the most cost effective measure. If you take the DOE's inflated duct sealing savings, yes Aerosealing and manual sealing both become much more cost effective. Also after performing hundreds of retrofits and following up with customers, the savings from our energy models has been validated. Believe me, I would be the first to claim $400-$850 savings from duct sealing if that is what we were seeing in the field, but that claim is misleading and gives a bad reputation to those of us giving realistic savings and not burning bridges with our customers from false promises.

3. Aeroseal does perform a pre and post leakage test, but I would like it to be validated and adopted by RESNET and BPI as acceptable standards of practice. In the BPI training I have given, I have not seen this as an acceptable standard of measuring duct leakage. If it does become ANSI, BPI or RESNET certified, I agree it should be an acceptable standard of practice.

4. According the the DOE's Home Performance Handbook, mastic needs to be applied "to the thickness of a nickel". Aerosealing applications I have seen remind me of a newbie installer painting mastic very thin where our crew lead has to go back and make them apply it much thicker. It makes sense that the thicker the layer of sealant, the more weathering protection it provides whereas a thin layer of sealant would more easily crack with natural weathering.

Comment by Tucker Henne on June 12, 2014 at 3:38pm

I would like to begin with a disclaimer that I am an Aeroseal contractor. One of the reasons I joined this forum is to address some of the misconceptions about the Aeroseal process laid out in this article. I will go through them in chronological order.

1) First misconception- Aeroseal only seals very small leaks. Aeroseal easily seals leaks up to 5/8". It is possible to seal slightly larger leaks but it is not cost effective due to the cost of sealant. When we enter a home we must assume that the original installer made all proper mechanical connections and fastenings with slip joints, screws etc. The fact is that if they installed the ductwork according to their training and manufacturers specs. there will not be leaks larger than 5/8". Obviously in the real world this is not always the case and we do often encounter larger leaks or disconnected ducts. Where the misconception lies in this article is that only small leaks can be sealed. In actuality, in field the Aeroseal process allows us to easily pinpoint these leaks. For example, the sealant looks similar to smoke in the air. When Aeroseal technicians notice on the computer that the leakage has not continued to seal, they are trained to look for a concentration of sealant (smoke) escaping from one part of the duct system. Often in one end of the attic or basement we would see a cloud of sealant and then easily find the leak even if it is covered by duct insulation. In fact using this method we have found leaks that would be virtually impossible to find using manual sealing methods without some kind of visual aid to locate it.

2) The second misconception is that Aeroseal is not cost effective. Our typical charge to residential customers is $1200-1600. I cannot speak for other Aeroseal dealers. According to the Dept of Energy the ROI for duct sealing should be between 2-4 years with an average annual savings of $400-850. With our pricing we try to hit that range of expected ROI. Furthermore, since Aeroseal seals leaks that are inaccessible for manual duct sealers we are in fact doing a more comprehensive job. Where manual duct sealers can seal down to ~150 cfm we often seal to less than 10 or 20 cfm. An ideal duct system is a closed loop where air is only circulated from and to the living space. The conditioned air lost in that last 150 cfm costs you just as much in energy as the first 150 you removed from the duct system if it is leaking to unconditioned space so why not seal it all if possible?

3) The third misconception is that Aeroseal is misunderstandable. Aeroseal performs a pre a post sealing leakage test. This is the same test an energy auditor would perform on your duct system and actually uses the same DG-700 manometer which is industry standard. I would go further to argue that Aeroseal removes much of the user error that is possible in these tests because it is computer generated, therefore if we did miss covering one or two registers the computer software can often pick it up because the duct pressure fluctuates too much or the % of leakage is higher than expected for inputted HVAC system information. Also, as one should reasonably expect, anyone running duct tests for sales purposes or otherwise has been trained and certified to use that equipment. Everyone in this capacity at our company is BPI trained.

4) The biggest misconception of all is that Aeroseal only lasts 10 years. In actuality, Aeroseal offers a 10 year manufacturers GUARANTEE on all installations. It has been lab tested under simulated conditions to 40 years without a failure. Good luck finding any HVAC installer to guarantee their manual duct sealing with tape or mastic. The only exception, and this is made clear in Aeroseal specifications, that homes with Ozone generators should not be Aerosealed because of a chemical reaction with the sealant that causes it to potentially breakdown. I have seen very few homes with ozone generators.

With all these misconceptions cleared up, I respectfully disagree with Mr. Byrnes. Aeroseal is superior to manual duct sealing on virtually every front. I would be happy to discuss the process or provide information to back up my claims to anyone interested or considering the Aeroseal process. It is my feeling and goal as an energy conservation professional to make Aeroseal duct sealing the new standard for installations in the future due to its superior performance over manual duct sealing. This is in fact why Aeroseal was developed in the first place, to provide a solution to the leaky duct problem in our industry which has come about from inferior traditional duct sealing methods.

Comment by Ric Secor on March 22, 2014 at 9:47am

We have done Aeroseal for a year and have seen awesome results that we never achieved with the mastic approach. Our crews do go into the crawlspace and attic prior to sealing (the salesperson has done this too) and this catches 90% of the exposed leaks.

You still  will have cases where a building cavity was used as a return and sometime sheetrock MUST be removed  or a new ducted return installed to get a complete result.

Not uncommon to have jobs down to 1-2% leakage at cfm50 including the furnace or air handler :)

The warranty is 10 years and the technology has been out for almost 20 years.

Comment by Eric Kjelshus on December 11, 2013 at 2:20pm

best way is to fog the ducts and when the mist tops you are done.   Thats old school.

Comment by David Byrnes on December 11, 2013 at 2:00pm
Yes 5/8's is a large gap but the problem is many Aeroseal crews never check the entire run and connections in the attic or take off registers to see them in the first place. I have audited homes with Aeroseal done and generally the duct leakage was low on the supplies but still high on the returns with visible gaps that were never sealed. Aeroseal still requires all the registers be taped off to pressurize the system but you're right, it requires less attic work which makes for a happy crew. I am a little old school in preferring manually sealing but I think the more time spent in the attic, the better, because it gives us the chance to find and fix more problems that may be over looked by a walk through.
Comment by Joe Provey on December 11, 2013 at 1:48pm
Several comments:
*5/8-in. is not a small gap. Bigger ones, unless buried, should be easy to detect.
*In existing construction, sealing ducts with mastic is labor intensive, disruptive, and time consuming.
*I agree with author that $2000 seems steep, but I don't know all the upfront costs dealers incur. Perhaps, as more dealers are introduced, fees will come down. Regardless, improving ducts from 20% leakage to 10% will pay for itself well before the warranty period ends (assumes costs of $3000 for annual heating and cooling).
With regard to warranty, I can find no information stating that Aeroseal becomes ineffective after 10 years. Please supply a source? the fact that the warranty is for 10 years doesn't mean the product will only last that long. Just because a refrigerator has a 5 year warranty, it doesn't mean that it's going to stop working any time soon.
Comment by Daryl Senica on December 5, 2013 at 7:34am

It's hard to determine how long Areo Seal lasts. But when we do a job our techs first check all existing duct work to see if there are any large holes, breaks or if the duct work is damaged then they repair, replace (at additional cost to home owner) and mastic any leaks they find the Aero Seal ten takes care of the rest it works and we have the prof. We have hundreds of very happy homeowners and we never even advertise the service its all word of mouth.

Comment by Eric Kjelshus on December 1, 2013 at 9:31pm

Aeroseal works well on small holes  but the big one I find in wood studs or wood/sheet rock path get to be 2",  Just blows by.   Most returns are to small so is what I do is on air systems is to add a extra filter and drop and run to top floor.   drop the presser on return and will spend less on power, and compresser just last longer

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