Order of Operations Matters with Heat Pumps: PART 1

Way back in the late 2000s, when I first took my BPI Building Analyst training and got into home performance, one of the first lessons I can remember learning was the importance of working through the proper order of operations. Things like “always seal the high and low bypasses first” and “air seal then insulate because the pressure boundary and thermal boundary must align.”

During the American Recovery and Reinvestment Act (ARRA) funds era, the HVAC Industry was at odds with the home performance industry. The HVAC guys thought the funds should be able to be used towards high-efficiency equipment swap outs whether thermal ECMs (Energy Conservation Measures) had been installed or not.

The home performance guys said, “oh no, it’s a mortal sin to replace HVAC equipment for the sake of efficiency without using the funds to first address the envelope.” Phrases like “putting lipstick on a pig” were thrown around very loosely when describing the “equipment first” approach. The program guys administering the funds agreed mostly with the home performance crowd, but often let an energy model determine the order of operations in a retrofit solely based on which measures provided the biggest energy savings.

Equipment replacement without implementing any kind of thermal measures rarely won that game. Around the same time, California Solar Initiative (CSI) required energy audits prior to providing solar incentives because what was the point of slapping solar panels on a home that was a thermal suck hole? More lipstick on a pig.

Decarbonization has always been the goal

Now that the cost of solar has come down, some incentives are no longer available. The catchphrase has turned from making a “home energy efficient” to “decarbonization” and “electrification. “Hasn’t the goal always been decarbonization? Why are we now hearing it suggested that somehow installing a heat pump is the single best upgrade you can make in a home?

Some even go as far as to say things like, “It is not necessary to put down one decarbonization strategy to promote another,” in reference to making sealing and insulating a home a priority before suggesting installing a heat pump. So, what has changed? Does having a solid thermal building — having, at a minimum, a “pretty good house,” — no longer matter? If it does still matter, does it matter more or the same for heat pumps as other (combustion-derived) heating plans? Let’s look at why the order of operations still matters.

Health, comfort, and decarbonization

Okay, first, what I consider the obvious stuff. The primary goal of home improvement should never just be decarbonization. If you approach a home performance project using best practices, then energy savings will be a byproduct of health and comfort-driven measures. All three things (health, comfort, and decarbonization) are synergistic with one another. Even if decarbonization is your biggest drive for spending money on your home, the design imperative should be to make your home a better place for you and your family to live while achieving your goal. That is not going to happen by just “slapping lipstick on a pig.”

In my friend Allison Bailes’ awesome new building science fundamentals book “A House Needs to Breathe …Or Does It,” he states in the chapter entitled “Integrating Sustainability with Indoor Environmental Quality” under the subtopic “saving energy,” “reducing energy consumption and cutting your energy bills is easy…and it does not mean being less comfortable. You do it by making the house airtight and well insulated, putting in good windows, using high-efficiency heating and cooling systems (including distribution), and just not doing stupid stuff.”

Whether intentionally or subconsciously, I don’t believe the order of this list of “energy-saving improvements” is an accident. This is the order of improvement operations that has been pounded into the heads of every building science practitioner for as long as I’ve been involved in the industry. It also is made clear anytime you model energy savings, aka “upfront carbon savings via building improvement,” on a given building.

All things being equal, in a building not built to very recent building code or in a green building program with a diligent Energy Rater doing inspections, air-sealing followed by insulation improvements will always yield the biggest energy savings.

Bailes further reinforces the idea that the quality of the home’s living conditions should be considered before any immediate or future carbon savings later in the same section stating, “indoor environmental quality should always come before energy savings.” You would be hard-pressed to improve the indoor environmental quality of a home by going straight to a heat pump installation.

But there’s more…

In part two of this blog, I do a deeper dive into why insulation and air sealing before installing a heat pump is the right approach.

This article originally appeared on the Insulation Institute blog and is republished with permission.