#friction rate

Tech Tips:

A few weeks ago, I was hired to consult on a multi-family new construction project. The building was already framed, and the ducts were roughed in. The owner of the building was concerned with the quality of the ductwork. He noticed that the HVAC company was not following the mechanical engineer's plans. This was my […]

Manual D Speedsheet Walkthrough

Bryan recently released a podcast on rules of thumb and how they can really get us in a pickle with sizing ductwork. With that in mind, I thought this might be a good time to do a walkthrough of Manual D from start to finish on a project I just finished up. My good friend […]

The Friction Rate Chart (and What it Means)

A lot of proper duct design comes down to an understanding of available static pressure and friction rate. We've covered this topic several times on this site and the podcast, but I wanted to focus on this ACCA chart specifically (shown above). If you want a deep dive, I highly recommend listening to my podcast […]

How to Determine the Friction Rate for Residential Duct Design

This article is written by one of the smartest guys I know online, Neil Comparetto. Thanks, Neil! Recently, I posted a question in the HVAC School Group on Facebook that went like this: “When designing a residential duct system, what friction rate do you use?” As of writing this, only one answer was correct according […]

Starting Pressure is Key

Friction Rate. Why the Fuss? (WTF)

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Edilson
#air flow #CFM #duct #duct design #friction rate #static

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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 this episode of the HVAC School podcast, Bryan welcomes back Brynn Cooksey from Air Doctors and HVAC U to discuss critical topics facing the HVAC industry today. Brynn brings his unique perspective as both a successful contractor in southeast Michigan and an industry educator who has made the transition to focusing primarily on workforce development and training.

The conversation begins with a deep dive into indoor air quality (IAQ), where Brynn challenges the common industry approach of throwing products at problems without proper testing. He emphasizes that effective IAQ solutions start with comprehensive testing to identify specific issues like high particles, volatile organic compounds (VOCs), or excessive carbon dioxide levels. Rather than relying on “magic bullet” products, Brynn advocates for a holistic approach that prioritizes ventilation strategies, source control, and proper filtration. He particularly stresses the importance of the “V” in HVAC, ventilation, which he believes is often overlooked in favor of flashier solutions. His company’s protocol of testing on every customer visit, from first encounters to maintenance calls, has created a culture where technicians become comfortable discussing IAQ solutions based on actual data rather than assumptions.

The discussion transitions into ethical sales practices, a topic that resonates strongly in an industry where pressure to sell can sometimes conflict with customer needs. Brynn defines unethical sales as pressuring customers into products that won’t benefit them or failing to provide complete information about benefits and consequences. His approach centers on thorough customer surveys to understand actual problems and budget constraints, followed by tying specific solutions to identified issues. This methodology puts the customer in control of decisions while positioning the contractor as a trusted advisor rather than a high-pressure salesperson. Brynn argues that price alone doesn’t determine ethics – rather, it’s the intent behind recommendations and the transparency of communication that matters most.

The final segment focuses on workforce development, an area where Brynn has found significant success. His company’s registered apprenticeship program, developed through the Department of Labor, has become a competitive advantage in attracting talent while providing structured, in-house training. The program requires minimal cost beyond commitment to ethical treatment of apprentices and systematic tracking of their progress. Brynn’s transition from contractor to educator demonstrates the growing need for comprehensive training programs that go beyond basic technical skills to include building science, customer service, and ethical business practices. His ongoing weekly training sessions focus on field trends and callback prevention, contributing to an impressive callback rate of less than 0.5%.

Topics Covered

Indoor Air Quality Testing and Assessment
- Using monitors like Air Advice for comprehensive IAQ evaluation
- Implementing testing protocols on every customer interaction
- Moving beyond product-focused solutions to holistic approaches
Ventilation Strategies and Building Science
- The importance of mechanical ventilation and ERV systems
- Understanding the relationship between building envelope leakage and humidity issues
- Source control as the foundation of effective IAQ management
Ethical Sales Practices
- Defining unethical sales and pressure tactics
- Customer survey techniques and solution-tying methodologies
- The concept of fiduciary duty in HVAC contracting
Equipment Sizing and System Design
- The impact of oversized equipment on IAQ and comfort
- Proper load calculations and duct system design
- Static pressure testing and airflow optimization
Workforce Development and Training
- Implementing registered apprenticeship programs
- Weekly training sessions focused on field trends and callback prevention
- Transitioning from contractor to educator and industry trainer
Building Envelope and Duct System Integrity
- Air sealing strategies for improved humidity control
- The relationship between leaky envelopes and indoor air quality
- Duct modifications and system upgrades
Customer Education and Professional Positioning
- Using testing data to support recommendations
- Overcoming price objections through professional credibility
- Building long-term customer relationships through transparency