Return ducts infiltrated by air from unfinished garage

[leeannwc]

I am in a new construction home (about 9 mos now). We have a terrible dust problem that I had posted about back in the winter. We had a blower door test to evaluate potential air infiltrations. We found that the home falls within the normal range of infiltration for new construction, however we did identify that while the home was depressurized, air was entering rooms from the return vents that smelled like our garage. Our HVAC contractor panned the joists between the first floor and the finished basement ceiling. We have an unfinished garage adjacent to the finished portion of the basement. One of the return vents is located in a wall that runs down to the wall shared by that finished and unfinished space. The RECC gentleman conducting the blower door test suggested applying dow board to continue the drywall up above the dropped ceiling in the garage to isolate this unfinished space. I am wondering if this would alleviate the problem since this is the wall the return vent is in. We do consistently smell garage air from all return vents on the first floor when the fan is on. I wonder too if this is contributing to our horrible dust problem which we have still not remedied. Obviously we need to correct the problem in some manner and not have potentially hazardous fumes entering our living space. Any suggestions?

[skippedover]

It's reallly simple when you think about it. Picture this if you can. When one molecule of air leaves your home, another must enter to replace it. That's a fact of nature/physics. When the blower door test was done, you were actually accelerating the speed that air moves through the home so that it could be measured. You didn't specify what the leak rate was nor did you state what the actual duct leak rate was. In any event, in order for the returns to be sucking in air, an equal amount of air must be leaving the building. The best solution to the problem is not so simple but it is important. Panning a bay or bays should not be done unless the bay is made air tight. Generally a panned bay allows air to bleed over from other bays, walls, etc. You state that you can smell the garage and that's proof positive that the returns are leaking but it's also likely that the supplies are leaking equally. Our company fights the battle constantly where we are $2,000 more on a job quote but we thoroughly seal our systems while our competitors do not. There's no code in our state (Massachusetts) so they get away with it but our companies policy is to install the duct system so it's good for 100 years. I'd expect it will cost you all of $3,000 to get the system properly sealed but once done, your utility bill will likely be lower, the dust problem will be gone and when the AC system needs to be replaced someday it will probably be with a smaller unit, provided you have a proper load analysis done by a competent company.

[Shophound]

You should definitely get your returns sealed. What skippedover said about panned joists used as returns is dead on...if they are not sealed they will draw air from wherever they can, whether your supply side ducting is leaking or not. By sealing a return you are controlling exactly where the return ducting draws its air from...the return grill!

It would be better to have the panned joist return routes opened up and sealed vs. continuing drywall/dow board up past the drop ceiling in the garage in an attempt to isolate the joist bays over the finished section of the basement from the garage. Unless that extended wall is thoroughly air tight, you will continue to draw air from there if the panned joist return continues to be leaky. Even if you could make the extended wall air tight, unless the panned joist return is also air tight, it will continue drawing from a dusty region...adjacent bays between joists, which eventually lead to a rim joist, which is adjacent to outdoors.

Sealing the panned joist is the best, but most disruptive option, especially if finished ceiling is already in place. The present panning will have to be ripped open so the joist bay itself can be sealed. There is no other way to assure it will be air tight unless it is completely sealed at every seam, gap, etc.

[leeannwc]

Can someone tell me how air enters the home through the return vent? I would expect this air to be moving in the opposite direction and therefore the the air would be filtered before entering the living space (thus eliminating the dust). I am just ignorant of how it all works. Is tearing out the drywall ceiling the only solution?

[dash]

Unless you have great filters,pleated 4' minimum,dust could pass thru,dust probem may or may not be duct leakage.

Checkout www.aeroseal.com ,it works like "FixaFlat" seals leaks from the inside out.


If return air is pulling in air from outside the conditioned space,an equal amount of supply air is leaking outside the conditioned space,so look at seal ing all the ducts.

[leeannwc]

Would the Aeroseal work on the panned joists? I would expect this to be quite an open system. Thank you so much for your help. We've been trying for 8 months to find help in our area to no avail. I am so frustrated!!!

[dash]

Aeroseal can seal gaps/openings of 5/8" wide by how ever long they are.So I'd think and I've heard it's very effective of panned joists.

We use Aeroseal,but don't have panned returns in our area.Hope there's an Aeroseal guy in your area ,if not try conacting Carrier or bryant Factory or distribtor ,as they might be adding one soon.

[davidr]

Based on your descriptions sounds like your home is working against itself airflow wise.

You really need to have some type of testing performed on your home besides a blower door to determine the level of repair.

Just going around sealing up ducts might not provide you a real solution.

[dcmcm5]

Keep in mind that if the garage is ever used as a garage, you have the potential to suck in carbon monoxide into the return and throughout the house. I'd be very careful and get the return sealed.

[be12c]

Everyone seems to be pretty dead on... Leaky ducts increase air infiltration by as much as 300%, pressure imbalances can add to it. You need someone to do a duct blaster test and then get your system sealed so that you have less than 5% leakage. Especially that return. You may also need to look at how the air in other parts of your house gets back to a return. If you have rooms closed off or your return is too small your problem could be further compounded.

[energy_rater_La]

did the person who did your blower door test offer duct blaster testing?
get them back to do this testing & ask who they work with to achieve the savings & health benefits you need.

[mr horsepower]

at the risk of recommending something too simplistic, esp. given the lengths you've gone to in researching your problem - a.) have you ruled out your vacuum cleaner from having anything to do with the dust problem? and b.) i'm not sure where your laundry room is in relation to the living area so this may or may not apply - i've seen the felt gasket that seals the drum area to the dis-charge shoot/piping not seal around the joint and allow lint to enter the household (that didn't necessarily look like the lint you get out of the lint screen). sometimes its the simple things. good luck one way or the other.

[ar_hvac_man]

Do you have a fresh air intake?
I have seen fresh air intakes in attics. If your garage is unfinished and your fresh air is drawn from the attic then you could be pulling fumes from your garage.

[pstu]

Do you have a fresh air intake?
I have seen fresh air intakes in attics. If your garage is unfinished and your fresh air is drawn from the attic then you could be pulling fumes from your garage.
Is that not a terrible practice? As a homeowner, just wondering. All the formal plans I have ever seen, include a duct to outside the roof.

Thanks -- Pstu

[leeannwc]

Thanks to everyone for your replies. I have ruled out common causes such as vacuum or drier. The dust was problematic prior to the purchase of my new HEPA filter super-duper vacuum, I have checked the drier venting thoroughly and dust accumulates rapidly even when the drier is not used for several days. Can anyone recommend someone in our area that does duct-blaster testing (Campbellsville, KY). I have not found anyone who offers it, but as I have ruled out more and more, I am convinced that the HVAC system is somehow to blame for the TERRIBLE dust. Unfortunately, our HVAC contractor doesn't seem to see it that way despite 8 months of complaints. We did, by the way have the ductwork vacuumed in October. We also have obvious spots throughout the house where the temperatures vary considerably. In an attempt to isolate the cause as being in the ductwork, I covered all of the registers on the first floor with cheesecloth last night (suggested by HVAC contractor). I dusted well and went to bed. By 8 AM we were a dust bowl again....could write your name on the tables, etc. It looks to me like the cheesecloth is too open a weave to catch much and was quite particulate itself. I probably just blew cheesecloth dust all over the house. We are certain the garage smell is coming from the return grille openings...seems worse when the fan is running too. We don't appear to have a CO problem as I have a CO detector on each floor and one is actually quite close to a return. Interestingly, the filter for the unit that supplies the main floor has not needed changing since we've been here. We check it monthly and can still see daylight through it (again, how our HVAC contractor told us to check it--he has actually been present a few times and said himself it does not yet need replacing). It is a thick pleated filter, MERV 8, I believe.
I did find a company about an hr. from here that does the Aeroseal. Would they offer duct-blaster testing? My fear is that since they are trying to sell their product they would certainly detect leaky ducts in order to get a job. After the experience we have had building this home, I really don't have much trust. And we keep pouring money into trying to solve the problem to no avail after already purchasing a VERY EXPENSIVE Carrier Infinity system with UV and humidifier. I'm at my wits end! I have 3 children under 5 and miss out on time with them cleaning up dust constantly and trying to resolve the problem.

[pstu]

>>My fear is that since they are trying to sell their product they would certainly detect leaky ducts in order to get a job.

Not to worry this time. There is so *much* bad ductwork available to sell Aeroseal for, little profit in making false diagnosis. I would hope you could get less than 3-5% leakage after using Aeroseal, in any event it should be a lot better. I'm a homeowner and trust Dash when he says what Aeroseal is good for.

Hasn't somebody had a dust problem and largely eliminated it via simple media filter (e.g. Aprilaire 2200) and fresh air intake? I seem to remember cases such as this from earlier posts on the board.

Best of luck -- Pstu

[dash]

Aeroseal test is based on pascals pressure difference(think very small difference.

The test is run using a laptop ,which would make it difficult to show leakag when there isn't much.

Then before the actuall sealing process,if needed,It is a duct blaster test,again it works through a laptop.Final test,after sealing works the same way.

All of theses test reports are download to Carrier/Aeroseal once a month.not saying it's impossible to show leakage when there's none ,preseal or post seal,but it would be difficult.

For testing they would need access to make a leak,and for sealing they would need access to close the leak very slowly,as there is a graph showing the sealing rate,a leakage is sealed up.

[dash]

Check for supply leakage;

If the supply grille are in the ceiling or wall,check for leakage there.
Remove the grille and check to see that the drywall fits tightly to the "box" on the other side of the drywall.

Here in Florida,with ducts in the attic ,the boxes are mounted on rough-in,then the drywallers often cut the opening much larger then the one for the supply grille.When the grille is installed it creates resistance to air flow,and if there's an opening between the "Boxlip" and the drywall,you have duct leakage outside the conditioned space.

Tests by our utility company have shown leakage due to this only ,as high as 15% of the airflow.We have seen similar when doing Aeroseal.

[leeannwc]

Thanks for the reply. The Aeroseal process sounds very reassuring. My husband is meeting again Tuesday with our HVAC contractor and if we don't get satisfaction, I think I will call the Aeroseal people to have them take a look. Our supply vents are in the floor on our main floor where we have most of the problem. I have indeed found on our second floor, where the vents are in the ceiling, that there were pretty big gaps between the boot and the drywall. I caulked these in myself from the ceiling side. We are currently looking at having someone come seal all the penetrations from the attic to conditioned space--something that was not done during construction. We have a very open floorplan and so it has been difficult to determine whether the source is upstairs or downstairs. We have blown-in insulation in the attic, so I first thought it was somehow being pulled in. The blower door test was repeated with the upstairs vents covered and per this method of testing, I was told that there was little leakage in the upstairs ductwork unless perhaps the total amount was all on one side (supply or return). Since I have no expertise in HVAC or building science, I keep hopping from theory to theory trying to piece it together. It is perplexing as 30-yr-old homes don't have the dust problem that we do. I appreciate all the help you guys are giving me to get me going in the right direction. I am so anxious to put this problem behind us!

[jrbenny]

There isn't an Aeroseal contractor in your market. I know a non-Carrier contractor trying to get it, but they won't let him. They are only allowing Carrier or Bryant dealers to buy into the franchise.

I've sent an email to a contractor that is very good with airflow issues. It's a haul for him, but I've asked him if he's interested in saving the day. I'll let you know what he says.

[dash]

Floor grilles could leak the same way ,to a crawl space,did you check them?

[leeannwc]

Thanks for the help! Per the Aeroseal website, a place called King Comfort in Nancy, Kentucky does the Aeroseal. Is that not correct? No crawl space--finished basement and the boots appear to be pretty tight to our hardwood and tile. Thanks again! I appreciate everyone's help!

[jrbenny]

If they do, they're distributor is in Tennessee. Nancy is in my former territory, and I've never heard of that company.

Click here (http://hvac-talk.com/vbb/member.php?u=17837), and send davidr an email. This type of thing is his specialty.

[dash]

If they do, they're distributor is in Tennessee. Nancy is in my former territory, and I've never heard of that company.

Click here (http://hvac-talk.com/vbb/member.php?u=17837), and send davidr an email. This type of thing is his specialty.



Nancy must have been in a better ,bluer life!!!lol!!

[davidr]

If they do, they're distributor is in Tennessee. Nancy is in my former territory, and I've never heard of that company.

Click here (http://hvac-talk.com/vbb/member.php?u=17837), and send davidr an email. This type of thing is his specialty.



I will help out however I can just send me an e-mail.

[jrbenny]

Unfortunately, I left Koch the day after Leeann's problems were brought to my attention. It would have been an interesting challenge to conquer. I'm sure David will get it resolved.

[davidr]

Maybe we can have a "York problem" that day. :D ;)

[jrbenny]

If my schedule is open, I'd more than happy to be your tool boy for the day. :)

[leeannwc]

So, David, are you the Carrier rep for our region now? I asked my HVAC contractor several times for that contact information months ago, but he never gave it to me. I am so excited to have knowledgable contacts in my neck of the woods!
I'm sorry to belabor the issue, but after mopping yesterday, I awakened again today to dust-covered floors...I'm noticing that the dust contains large particles, much larger that I would expect to pass through any filter. It really looks like our air is not being filtered at all....every bit of dust is accumulating. Is it possible that the return side is not functioning at all? Or could the filter be getting bypassed somehow? As I mentioned before, it never gets dirty despite a filthy house! When the sun shines in, you can see the air is full of dust.

[jrbenny]

Send him an email. He's not the Carrier rep. He's an independent contractor that is an expert in air measurement and testing. He just happens to be a friend of mine and a contributor here.

If you remember our email exchange, I was your Carrier rep. There is a rep there now that took my place, but I assure you that he can't come close to David's abilities.

[davidr]

Send him an email. He's not the Carrier rep. He's an independent contractor that is an expert in air measurement and testing. He just happens to be a friend of mine and a contributor here.

If you remember our email exchange, I was your Carrier rep. There is a rep there now that took my place, but I assure you that he can't come close to David's abilities.


Gosh, now I'm blushing. :D

[zupchuck]

Does the dusting occur during heating, cooling, or any time the fan is running?
If heating - somebody mentioned air intake. Could something be incinerating within the furnace and the ash dust being blown around (hence, the "garage" odor)?
Is there a plenum that is concealed and perhaps sucking construction debris dust in a gap?
Could there be a return and supply that are mixing somewhere?

[leeannwc]

The dust occurs year-round regardless of heating or cooling. It is constant...accumulates within a few hours of dusting a surface. I literally have to clean my kitchen table BEFORE AND after serving meals. The garage smell really is our garage...I'm sure. It smells exactly like walking into the garage and when my husband starts his lawnmower, that smell bleeds into the house.

[ar_hvac_man]

leeann are you taking your medication like your supposed to?

[leeannwc]

If this continues much longer I will definitely need medication! I am not exaggerating a bit! Come visit me and I will give you a dust cloth or mop. :)

[davidr]

leeann are you taking your medication like your supposed to?


The problems that she is experiencing are wide spread with a lot of HVAC installations.

No medication needed just proper diagnosis & remediation.

[skippedover]

It is possible to test the duct leakage rate during a blower door test without a duct blaster. All the supplies and returns need to be blocked air tight with plastic (it's available in rolls with a sticky side so you just cut it and stick it on) except for one or part of one large one. Then the The the test is begun with the blower door blower. A flow hood put to the one open grille will reveal the total duct leakage. Keep in mind that this also tests the air handler/furnace for leakage. Dry smoke can be used to locate the specific leak areas. Several universities have been commissioned by the federal government over the years to test and determine the cost/value of leaky ducts and they've found that duct leakage (either supply or return) can account for up to 30% of the annual costs of heating/cooling an average home. It costs more to have a duct system sealed when it's put in but generally a company that does that as a matter of routine is also the company that does all the rest of the job properly.

[davidr]

No need to simulate fictitious operating conditions to test duct leakage, it can be tested in live field conditions like it operates on a daily basis.

[leeannwc]

I need some help again, please. We have identified our problems to be primarily significant leakage in our HVAC ductwork (most of which is panned joists between hardwood flooring and a drywall ceiling :)). Now we are having difficulty finding anyone to make the repairs. We are wanting to take down the ceiling to access the ductwork to make repairs. Does anyone know of anyone qualified to do this type of work near Campbellsville, Kentucky? We want to be sure to find a very competent thorough contractor. Someone who will look at the whole building science picture. We have been through enough trouble already and want to get this behind us quickly and forever! I have a son with severe allergies now diagnosed as probable asthma who has been breathing this dust for a year now. It really is critical that we get this job done! Thank you for your help!

[dash]

For the leaking ducts,try www.aeroseal.com seals from the inside out,like fixaflat for a car tire.

[leeannwc]

You had recommended this to me in the past. We have only one contractor in our area...I contacted him and he was not confident that Aeroseal would take care of this extent of leakage. For the price of this product/service, we didn't want to gamble as he said the only way we would know would be to try it and see if we got results. So....we're looking at the traditional approach of opening up the ceiling and re-doing the duct-work.

[Advanced Response]

Did you contact david?

He thinks of the system as a complete system and will provide proven results..

If he can't fix it to your approval then I don't think anyone can..

Goodluck
J

[jrbenny]

David did the diagnosis. However, he's 2-3 hours from her. Kind of hard to do a multi-day job from that distance. If you know someone in her area, give them a shout.

[davidr]

I would love to do more to help in Lee Ann's situation but unfortunately it is close to a 2 hour drive from our office one way.

I found one company in your area Lee Ann who has been through the same training that we have that might be worth talking to.

I will e-mail you their name.

I really hope you get this resolved soon.

[cyro]

Mike Holmes from Holmes on Homes says, code states no return in a Garage, fumes!

I love that show.

[davidr]

It's not an intentional return path in her garage just the path of least resistance.

Due to framing methods of the floor joist & the dropped ceiling acting as a return plenum this was the result.