Bryan teaches how to stop sweaty ducts, vents, and systems. This class covers the myriad of moisture issues that come with the approaching wet and humid season. He talks about duct and air handler sweating, attics, and dew point.
Sweating air handlers and ductwork is generally outside the conditioned space. (Conversely, sweating vents are in the conditioned space.) We can help control attic conditions by adding vents or insulating to control the temperature in the attic, but controlling moisture is our main concern.
Getting to the dew point allows the attics to sweat, which gets moisture out of the air and onto surfaces. When the air runs over the cool duct surface, the moisture condenses and becomes liquid water. (It’s just like running air over a cold evaporator coil.) Insulating the attic is usually NOT the answer because it drops the temperature even more and makes the ducts sweat even more. (Sprayfoam is a type of insulation.)
If we didn’t have to worry about costs, we could keep an air handler or ducts from sweating by applying a space heater to the surface 24/7. Radiant barriers unfortunately have a similar effect as insulation; they keep the attic cooler, but they also cause the surface temperature to drop and be more prone to condensation.
The best option to control moisture in the attic is to seal it and dehumidify it. That option will cause your power bill to rise, but it will keep the attic drier. Sealing the attic, controlling the temperature, and controlling radiant gains inside the attic will have much more of an effect on duct sweating than changing the temperature of the air inside the ducts.
However, the best options will be expensive. We shouldn’t be afraid to offer expensive options, as it isn’t our job to decide the customer’s budget for them. The most important thing we can do is explain the consequences of each option and make sure the customer makes an educated decision.
Restaurants tend to have some of the worst rusting and dripping problems around their vents because it’s very difficult to control moisture inside the conditioned space. In the summer, low setpoints, moisture loads indoors (kitchens and baths), and increased moisture loads outdoors all increase the likelihood of vents sweating during the summer.
To combat summer moisture loads, try to get the customer to reduce the outdoor moisture’s likelihood of getting into the home (by closing windows and doors), ventilating in the kitchen and bathroom, and running the HVAC system longer with a colder evaporator coil.
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Great information! Sweating ducts and equipment have always stumped me. I would try those usual fixes, fan speed, insulation… Great class!!
I’m hoping another tech can help me out or even the guys at hvac school too.
Here’s my scenario:
I have an ahu on the second floor in a tight closet that is not conditioned.
The ductwork in that room sweats and drops down into 1st floor sheetrock.
Originally the closet was not sealed off of the attic air. So since I’m in a new build house the guys came back and sheetrocked the closet closed. But the supply duct goes up hits the ceiling then goes down into floor where the ducts are ran on 2nd floor. My humidity in the house is at like 60%. Anyone have any suggestions I’d love to hear. I’m a commercial tech and we’re generally pretty good with this type of thing but came back to hvac school to re-up on some humidity and duct sweating tips. Thanks guys
I have a 106 year old house in Houston with 5-ton HVAC in the attic. The ducts don’t sweat. Why? Because I have refused to install a radiant barrier or add more ventilation despite every idiot contractor saying I need more ventilation. I only have two small gable vents.
I don't like Bert
Paint the ducks black
I had this problem in my first place over 15 years ago. Instead of all those expensive and complicated solutions I just replaced all vents with plastic vests. Problem solved. Not sure last time I looked for them it was harder to find.
Such a good training video. We don’t deal with sweating ducts in an attic much in ohio but I totally get a Handel on dew point watching this video and many others. There are a lot of homes in valleys in my area where humidity can do some tricky stuff so this video gives me some ideas for solutions for them.
Great information.
i love your video guys, your random jokes makes iteven more enjoyable to watch
Why not just insulate the ductwork?? That'll stop the sweating
If I'm 50 years old and just getting my HVACR CERTIFICATE, am I still good enough for commercial work? Can you give me some advice?
I am that old guy engineer you spoke about in your video. I have a sweating coil. My house is a story and a half and my unit is in a walkin attic that is partially sealed. When the attic was almost sealed I had everything sweating and mold build up. I installed a 4” power vent that is humidity and temperature controlled to vent to the upper attic. That helped but did not solve the issue. I noticed the air was cold and stagnant around the sweating unit. I installed two very small fans. One blew air on the unit and the other blew air from the unit to the exaust fan . The two fans are controlled by a power ventilator temperature/humidity controller. The fans come on at 70% humidity. What the fans do is keep the attic air warmer so it does not condense easily on the unit and second, when it does condense it will helps dry the unit once it shuts off.
I have considered your idea with the dehumidifier and if the fans do not work, I may do it. Another option is to condition the space. All I need is to seal it off and tap into the duct work. I think my energy efficient fan method will work.
If you have a supply grill in a vaulted ceiling and its sealed and insulated perfectly but sweating put a curved blade register and it will cool the area near the sweating register done it many time after other company tried everything works every time. If you have sweating spiral duct in a restaurant and its dripping on the customers all you have to do is direct the air up instead of vertical or down then the area around the sweating duct work will be cooled down and no more sweating. If you have sweating equipment in an attic unvent the attic and seal the attic then put a small portable dehumidifier in the attic problem solved.
Alot of this doesnt apply to the area I live in. No one has a furnace or ducts in the attic. Its all in the conditioned space basement. (Northern states)
The big take away: It's absolutely asinine to put ducts in the non conditioned space of a house like an attic.
Increase the superheat on your air con. Dehumify and reduces cooling capacity. Stops the issue of cold and humid room. I used to use 2.4kw heater in humid summer untill i discovered 10 deg superheat on cool mode fixes this. Stops mouldy ceiling vents too
loved this!
I wish he start teaching Straight talk and stop talking a whole lot of shit
Some interesting info. One point of correction is moisture moves by vapor pressure not air pressure (airflow). air curtains don't keep moisture out. Doors only help if they are sealed. Kitchen pressurization only reduced infiltratration or fresh air. You still need vapor barriers to keep moisture from migrating in and out of buildings
My air handler unit is in the garage and it was sweating like crazy all the time (FL-Southeastern) until I bought a dehumidifier and placed it in my living room. It runs about 1 hour everyday keeping my humidity below 40%. I haven't seen a drop of water again around the air handler since then. Its perfectly dry all the time. This channel is awesome. Thank you
Had a teacher put ice cubes in a Ziploc, inside a Ziploc, inside a Ziploc. Then asked, which one(Ziploc) sweats first.
How about you get a smaller unit or inverter unit that runs constantly and keep the insulation. And how about you only put the ductwork in conditioned space. You are so smart you miss the obvious.
You can seal and insulate the whole attic and partially condition it as a solution as well .
Good stuff
This video came to me at the perfect time. I’m going to a customers house to finish an air handler and condenser install, but also the vents in two of her rooms are sweaty and my boss wants me to put foam tape on the backside of the air tech registers to seal it from the attic air.
I'm a HVAC tech like most of us here. I personally had sweating vents in my 2nd floor system ( hvac in attic) . I found the original hvac contractor had not sealed the boots off the ducts right around the sheetrock and the boots were poorly insulated. Some had no insulation on the boot. The moist hot attic air was coming around the boot , gaps ( 1" or more ) mixing right at the diffuser face. So very cold and very moist hot air cause vents to condense on the face. Everyone of them were like this. I end up pulling every boot and redoing some of the runs completely. Everything was sealed tight from the condition space and boots were properly insulated . No more sweating vents….
5:52 – A glass of cold water as a dehumidifier – what a concept!
Great explanation. Can you please do a video on how to set an hrv in conjunction with the hvac system throughout the seasons of a year.
I love Burt 😊
Have been a fan of your teaching methods, there are many channels which put light on the subject, but the way you describe things, it's just so simple and easy to grasp. Keep up the good work.
Great info but alot of this is regional to yalls area but it is still great knowlegde
I dont think the solutions in this video could be the best. Obviously if you dehumidify the space around the ductwork you are not going to have trouble with ducts sweeting, but I think is not practical. I think the best solutions is a good insulation in the ductwork, if you insulated the ductwork, the external temperature of the duct is going to be above the dew point and the ducts are not going to sweet. Same thing with the air handler unit. The best way to avoid this problem is selecting the right equipment in the beginning of the project. This could be a solution if it is too late and anything else solves the problem.
Variable speed fan motor with Hyperion cabinet with BK enabled. Trane folk here.😅
Where I live we don’t have much moisture. One thing that intrigues me is how come coolers don’t sweat ?they are well insulated and you put ice and keep your beers cool, but no seating
I enjoyed your style…,sounds like a bunch of Florida attic problems. Attics in terrible climates should have to have to be wrapped with some type of Armaflex on them.
Bob
As always , great teaching Bryan!
My air handler inside home. I insulated drain pan with armaflex, 1/4" steel drip pan under that, cork under drip pan. Walls pour foamed that air handler is in. Coil room insulated on inside with armaflex. All duct solid steel, air sealed 100%. All ducts insulated with bioceramic r7 (hy tech) paint then insulated with reflectix, no gaps anywhere. Positive pressure condensation drain with skupper valve. 4" fresh air intake triple filtered, shut down in extreme temps. Ecm main fan and ecm fresh air fan. 6 uv lights surrounding coil set to timer. Crawlspace partially conditioned with temp and humidistat. If you have more than 10% diff you will reach dewpoint from what i understand. House is confortable. All walls, subfloors painted with insulating ceramic paint (hy tech) with concrobium and zinser paint. You are right you need to lower humidity in home to prevent condensation or keep the variation of temps below dewpoint. Btw bath walls do not sweat ever, only windows. Bath fans set with auto humidistats. All wall and ceiling and floor protrusions sealed 100%
Great info, Thank you.
Put the air handler in the home's envelope.
Equipment, Supply Duct and Return Duct should never be outside the envelope. If energy conservation were paramount, Energy Star, DOE ect would make building code require equipment to be located inside the home. No one wants to give up 12-14 sq foot of foot print.
OSHA should require this also, I've been in 130-150 degree attics, not a safe condition.
Had me at butt connections. 😂🤣
Great educational class. Thanks Bryan.
A plugged up drain line or off-slope drain pan will also kill your dehumidification process
Increase the R value on the ducts and glue duct board on the air handlers!🤣🤣🤣
Thanks again for the videos!
🍺🍺🍺🥃🥃⛳🎳
Stay safe.
Retired (werk'n)keyboard super tech. Wear your safety glasses!
Rick Sims gave a amazing speech at the symposium I was blown away and it lifted my interest of humidity and Dehumidifiers to a new level.
It got me thinking to even learn more and experiment
Great information as usual 👍 thanks for sharing.
Hey Brian, This subject came up at my company last week. I live in Charlotte, NC. Tropical climate. My boss said in order to prevent sweating on ductwork with a two stage system is to design the ductwork for 1st stage only due to velocity issues and ducts being to cold on inside. Do you agree with this?
I have a question, wouldn't insulating/sealing the ducts better and insulating the outside of the air handler also solve the problem because by doing so you are increasing the temperature of the surfaces of the ducts/airhandler. In theory you could just increase the amount of insulating material until the surface temperature is close to that of the attic?
🤯🤯🤯🤯🤯🤯🤯🤯
You blinded me with science.