Put a high-efficiency heat pump in a leaky building and you’ve got a leaky building with a heat pump in it.
That was roughly the argument Jason Kliwinski, CEO and founder of the Green Building Center, made on a panel at ASHRAE’s annual conference in Austin. His version was less polite: “One of the biggest problems of existing buildings is they’re crappy. They’re bad building envelopes, and I don’t care what sophisticated mechanical systems you have. If you put it in a bad building envelope, it won’t perform.”
The numbers on envelope-first sequencing
A 2023 ACEEE report gives the range. Modest weatherization, meaning air sealing plus better and thicker attic insulation, reliably cuts energy use 12% to 18%. Deeper work, adding insulation to walls, basements and rim joists along with higher-efficiency windows, gets you around 33%.
Kliwinski’s own figure for load reduction runs wider: 10% to 40%, except in buildings dominated by process loads, where the mechanical demand isn’t coming from the walls anyway.
The sequencing consequence is what matters commercially. Cut the load first and you size the heat pump for the building you’ll have, not the building you have. Skip it and you buy a bigger machine, pay for the bigger electrical service, and run it harder for the same comfort.
A case that pencils
Kliwinski pointed to a new building at Rider University in New Jersey, dropped onto an existing campus. LEED Silver, $200 per square foot, nine months of construction.
The mechanical choice was deliberately unglamorous: all-electric PTAC units, picked to match the existing dorms so maintenance staff wouldn’t have to learn a new system. The performance came from the shell. Energy Star-rated structural insulated panels delivered “a completely electric building on an existing campus that was 25% better than code, simply by changing the building envelope construction and making a much tighter, better insulated building.”
No exotic systems. No new maintenance regime. Better walls.
Why this is a hard sell anyway
Because envelope work is invisible. A heat pump is a line item an owner can point at, and there’s a rebate for it. Air sealing shows up in a blower-door number nobody sees.
Kliwinski’s closing line concedes the marketing problem and then ignores it: “Air sealing, weatherization, insulation and window replacements: they’re not glamorous, but that’s what makes existing buildings last another 150 years.” He also made the point that keeps getting cited and rarely followed: “the most sustainable building is the one that’s never built.”
For contractors, envelope-first is a business opportunity dressed as a constraint. Owners chasing electrification incentives will need someone to tell them the mechanical package they’ve budgeted won’t hit the numbers, and someone to do the boring work that makes it hit them. The ACEEE research is the ammunition for that conversation. Our listing for 2125 Telegraph Avenue shows an all-electric affordable building where the panelized envelope did the same work.