Drying Stuff vs. Drying Air - Humidification, Dehumidification and Ventilation

HVAC School - For Techs, By Techs

Bryan Orr

Training, Careers, Airconditioning, Self-improvement, Hvac, Business, Education, Refrigeration, Heating, Ac, Apprenticeship

4.8 • 985 Ratings

🗓️ 3 July 2017

⏱️ 45 minutes

🔗️ Recording | iTunes | RSS

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Summary

This episode is a rebroadcast of a very useful episode from the Corbett Lunsford's Building Performance Podcast at https://buildingperformancepodcast.com/. Corbett talks to building moisture control expert Lew Herriman about moisture, ventilation, and what happens when you're drying "stuff."

When we think about humidity control, we have to ask if we're drying air or drying "stuff." Dehumidification is about drying the air, but many people think about it when they actually want to dry "stuff" like fabrics and other absorptive surfaces often found in residential applications. However, drying out "stuff" does affect how we would dry out the air.

Commercial buildings often don't have a lot of absorptive materials, as many have tile floors. Residences tend to have carpet and upholstery, making them challenging cases in building performance. The HVAC system controls moisture, whether they have a humidifier, dehumidifier, or neither. HVAC systems create pressure differences, which contribute to dry air infiltration. Homes heated solely by radiant heat would not be as good at drying the air, but good ventilation could supplement radiant heat.

When we have humidity control problems that affect comfort or moisture on absorptive surfaces, we might start thinking about controlling absolute humidity. Absolute humidity refers to the actual moisture content in the air, not the moisture relative to the temperature. However, most homes don't have the ventilation systems that would help dilute the humidity, including HRVs.

Then, when drying "stuff," you have to put heat in to get the moisture out.

Corbett and Lew also discuss:

Absolute vs. relative humidity
Dry-bulb temperature changes and dew point
Duct leakage
HVAC and building performance strategies for mixed climates
Energy-recovery ventilators (ERVs) vs. heat-recovery ventilators (HRVs)
Exhaust at the source
Dehumidifiers
Dehumidifying incoming fresh air
Hypothetical makeup air systems for residential applications
Comfort metrics

Learn more about Corbett's work at buildingperformanceworkshop.com.

Transcript

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0:00.0	This episode of the HVAC School Podcast is made possible by the Carrier Corporation.
0:10.0	And I want to give Carrier some props because recently they had a recall.
0:14.0	Normally you'd think that would be a bad thing, but the way that Carrier handled the
0:17.8	recall was really exemplary. They had an issue with some of the carrier
0:21.0	Green Speed systems with some boards that had the
0:23.8	potential of overheating. Now it caused zero property damage, zero fires, but
0:29.0	they knew they had an issue because some of the heat shields were coming
0:31.6	back where they showed that there was
0:33.7	some excessive heat.
0:35.1	And so they did a quick recall.
0:36.6	They gave us a list notifying us of the customers that fell under the recall, the systems
0:40.9	that we had installed.
0:42.1	We were able to go out really quickly and take care of it.
0:44.4	And that's exactly what you want to see from a manufacturer.
0:46.4	There's no manufacturer that's going to be perfect all the time.
0:49.1	But the most important thing to me is that they support their products, they take care of their customers, and they communicate
0:54.4	with their contractors.
0:55.4	And Carriers always done a good job of all of those with me.
0:58.6	We're also proud to have Testo Tools as a sponsor.
1:02.0	You know I talk a lot about Testo. A lot of guys kind of razz me about it, but I am a big fan of
1:05.6	Testo and you can get all of the great Testo products by going to TrueTech Tools.
1:10.3	Use the Africa Get Schooled for a great discount.
	...

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