Q&A – Condensating Vents – Short #208

In this short Q&A podcast episode, Bryan answers Kenton's question about how to stop vents from condensating, especially when sealing and insulation don't do the trick.

When approaching a condensation problem, we have to consider the source of moisture and where the condensation is happening. Moisture that builds up on top of the vent comes from attics with a high dew point. (It's not because hot meets cold! Relative humidity and dew point are a lot more important, though hot air is able to hold more moisture.) Warm, moist air with a high dew point hits a colder surface when there is improper sealing and insulation where the duct attaches to the boot.

People often attempt to solve condensation issues by adding insulation, which actually has the opposite effect because it reduces the surface temperature; condensation worsens. Some people also increase attic ventilation, but that may cause pressure imbalances that drive moist air into the conditioned space.

The best way to control attic conditions is to seal and then dehumidify the attic, though it is an expensive and time-consuming measure. Exhaust vents that end in the attic also add moisture to the attic. Sealing vents and other areas where attic air can seep into the space is another best practice, as is deploying a humidity control strategy. Reducing humidity can happen with a dehumidifier and proper sizing so that the HVAC equipment has long runtimes with a cold evaporator coil (achieved with lower system airflow).

Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool.

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#condensation #dehumidification #dew point #humidity #humidity control #hvac #insulation #sweating #vents

Author:

Bryan Orr

Company: HVAC School

Position: Founder

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HVAC School – For Techs, By Techs

Real training for HVAC ( Heating, Ventilation, Air Conditioning and Refrigeration) Technicians. Including recorded tech training, interviews, diagnostics and general conversations about the trade.

In today’s podcast, Bryan talks with legendary Hydronics author and trainer Dan Holohan about the history of steam heating and some practical applications of old ideas. Recently, Dan has been working on more novels, having published two of them over the past few months.

Steam heating is a “lost art” nowadays; it has become increasingly uncommon and has been disappearing since the Vietnam War. Many people who understood steam heating either retired or died after the Vietnam War. Many elements of steam heating are difficult to understand or surprising. (For example, steam pressure has a surprising relationship with velocity: low-pressure steam moves through piping much more quickly than high-pressure steam.) So, Dan Holohan is on a mission to revive that knowledge and teach the newer generations about the lost art.

There are many older steam heating systems still operating today, especially in the older large buildings in New York. Dan learned a lot about steam heating when working on these old systems and optimizing them. Most of the time, he optimized those systems by removing unnecessary accessories, not by adding components like steam traps.

Many old boilers used coal as a heat source. Nowadays, many old boilers have been fitted with conversion oil burners with thermostats, but they are still piped for coal. Some systems now have multiple risers or massive vents on the main riser to prevent the thermostats from getting too hot too early and satisfying the thermostat too early. We call that master venting, which reduces pressure and allows steam to move very quickly and efficiently.

Dan also discusses:

The 2-PSI standard
Transportation metaphors for BTUs in steam
Harmful renovations for old boilers
Replacement vs. restoration mindsets
Gaps in steam boiler education
Monopolizing the market if you HAVE the education
Boiler piping and venting
Two-pipe vs one-pipe steam

Find out more about Dan and hydronic heating at HeatingHelp.com.

Have a question that you want us to answer on the podcast? Submit your questions at https://www.speakpipe.com/hvacschool.

Purchase your tickets or learn more about the 6th Annual HVACR Training Symposium at https://hvacrschool.com/symposium. Subscribe to our podcast on your iPhone or Android. Subscribe to our YouTube channel. Check out our handy calculators here or on the HVAC School Mobile App for Apple and Android.