The Future of Heat Pumps (Hint: It's Air-to-Water) - A Conversation with Ross Trethewey

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When Ross Trethewey calls heat pumps "magic boxes," he's not being hyperbolic. As the founder of TE2 Engineering and building engineer for PBS's This Old House, Ross has spent 15 years designing some of the most sophisticated HVAC systems in North America — from 7,000-square-foot custom homes to 45,000-square-foot compounds.

The Foundation: Design Before Installation, Every Time

Ross's approach starts with proper Manual J, S, and D calculations — something he believes every HVAC contractor should master, not just mechanical engineers. "For any HVAC contractor, they should be well equipped to be able to provide that level of information and run those calculations."

The Future is Air-to-Water

Of all heat pump technologies, Ross is betting big on air-to-water systems. "If I had to pick a horse in the race, 15 years from now, 20 years from now, I think it will be air-to-water."

His reasoning is compelling:

Future-proofing against refrigerant changes. As the industry moves from R-410A to R-32, 454B, and eventually to A3l refrigerants, air-to-water systems keep the refrigerant contained in the outdoor unit.

What Separates the Top 5%

The best HVAC contractors are family-owned businesses with multi-generational thinking, not private equity-owned companies focused on short-term returns.

These top-tier contractors:

-Invest heavily in training. Ross regularly gets out-of-office messages saying entire crews are at air-to-water heat pump training.

-Provide proper tools and support for their technicians.

Episode Timestamps:

[03:56] - Ross’s origin story: 5th-gen plumber to mechanical engineer to TV educator

[13:22] - Benefits of heat pumps vs. conventional systems

[18:48] - Challenges of going 100% heat pump in older homes (no fossil fuel backup)

[32:06] - What’s coming with air-to-water heat pumps to get higher temperature output

[42:46] - Heat recovery and system optimization

[54:11] - What separates top 5% HVAC contractors from the rest

[59:49] - Ross’s top recommended resources and final advice to HVAC pros

Follow Ross Trethewey

LinkedIn: https://www.linkedin.com/in/rosstrethewey/

Facebook: https://www.facebook.com/rosstretheweytoh/

Instagram: https://www.instagram.com/rosstrethewey/?hl=en

Twitter: https://x.com/rosstret

Follow This Old House:

Company’s Website: https://www.thisoldhouse.com/

Company’s Facebook: https://www.facebook.com/ThisOldHouse

Company’s LinkedIn: https://www.linkedin.com/company/this-old-house-ventures/

Company’s Instagram: https://www.instagram.com/thisoldhouse/

Company’s Twitter: https://x.com/ThisOldHouse

Youtube: https://www.youtube.com/user/thisoldhouse

Follow TE2 Engineering:

Company’s Website: https://te2engineering.com/

Company’s Facebook: https://www.facebook.com/TE2engineering/?ref=br_rs

Company’s LinkedIn: https://www.linkedin.com/company/te2-engineering-llc./

Company’s Instagram: https://www.instagram.com/te2engineering/

Company’s Twitter: https://x.com/te2engineering

Company’s youtube: https://www.youtube.com/playlist

Follow the Hosts:

Ed Smith: https://www.linkedin.com/in/ed-smith-5aa8716

Eric Fitz: https://www.linkedin.com/in/ehfitz/

Amply Energy Website: https://www.amply.energy/

Amply Energy YouTube: https://www.youtube.com/@amplyenergy

Amply Energy Facebook: https://www.facebook.com/amplyenergy

Amply Energy Instagram: https://www.instagram.com/amply_energy/