·S1 E43

#43 Manual J vs. Utility Bills: A Sizing Debate with Nate Adams, Alex Meaney, and Eric Fitz

Dec 11, 2025

58 mins

Episode Description

Want to win on trust, not price?

Start with our Trust Checklist to see if your business is doing the things that truly set you apart.

👉 https://bit.ly/the-heatpump-business-model-matrix

Then, head to our latest article to learn how the top contractors protect their margins and stay competitive.

👉 http://info.amply.energy/blog/win-on-trust-the-heat-pump-business-model-matrix

------------------------------------------------

Live from the U.S. Heat Pump Summit, the panel explores one of the most debated topics in the heat pump industry — real-world energy data versus modeled load calculations. With growing demand for heat pump adoption and improving installation practices, understanding how best to size systems is more critical than ever.

Moderated by Ross Trethewey, the session brings together three leading voices in building science and HVAC system design: Alex Meaney, Nate Adams, and Eric Fitz. Together, they debate the merits and limitations of load calculation methods—from the precision of Manual J to the practicality of energy bills and the gut-check of contractor “rules of thumb.” It's an honest, unscripted, and high-energy conversation aimed at bridging the gap between building science nerds and real-world contractors.

Key Takeaways:

Every load calc is a model. Treat outputs as working estimates, not facts.
Triangulate. Combine Manual J, past energy, and field observations. Watch where they agree.
Respect air leakage. Inspect attics, listen for wind noise, ask about comfort. When red flags pile up, get a blower door.
Question black-box tools. The less data they ask for, the more you should worry.
Build feedback loops. Log runtimes, check design-day performance, and refine your assumptions over time.

Timestamps:

[00:00] - Episode Teaser

[02:17] - Intro by Ross Trethewey & guest intros

[03:22] - Nate on sizing via utility bills: "I can do it in 2 minutes"

[05:10] - Bridging the Adoption Gap

[09:16] - Alex defends Manual J: “It’s not that hard if you know your stuff”

[12:14] - How to assess infiltration without a blower door

[25:21] - Eric breaks down regression modeling using heating degree days

[34:36] - The Role of Human Behavior & Assumptions

[40:05] - The danger of outliers & the limits of AI-driven sizing tools

[52:51] - Triangulation: why using multiple methods is key

[59:06] - Final thoughts: pick a method, stick with it, and build your feedback loop