Deep Energy Retrofits vs. Building New

Deep Energy Retrofits vs. Building New

opti_ffLiving Green: Should I Build New, or Retrofit an Existing home?

by Rick Reynolds

At some point in every owner/builder’s decision making, there comes a critical calculation: Do I build a new home on my own land, or buy an existing one. And if that existing home is poorly constructed or simply outdated, how will that impact the homeowner over time?

Aside from the obvious fact that existing buildings are where they are, as opposed to where you’d like them to be, they also come with hidden costs that may not be immediately apparent to the average home buyer. As one example, getting older existing houses up to current energy code, let alone the stringent standards of today’s high performance buildings, can involve impossibly long payback periods.

Martin Holladay, in writing for Green Building Advisor, indirectly addressed this issue in his March, 2014 article, “The high cost of deep-energy retrofits.” In the article, he asks the question, “How much does it cost to perform a deep-energy retrofit on a 100-year-old single-family home?”

His findings? Around $100,000.

Mr. Holladay based his finding on a study that was sponsored by the New York State Energy Research and Development Authority (NYSERDA). The program, centered in the Utica, New York area, had paid for deep-energy retrofits of four wood-framed buildings.

So, how were the “deep energy retrofits” defined? In a nutshell, the goal was to reduce energy use by 75% by retrofitting slab floors to R-10, below grade walls to R-20, above-grade walls to at least R-40, upgrade windows by adding either low-e storm windows or new windows to achieve a U-factor of 0.25, achieve an airtightness goal of 0.15 cfm @ 50 pascals per square foot of surface area, and update to the latest HVAC systems.

Without going into the myriad steps required to achieve the above, the retrofits resulted in impressive levels of energy reduction. Though the goal of a 75% reduction was not met, overall energy usage was reduced by 60-65%.  But while the retrofits resulted in draft-free comfort, and new siding, windows, and HVAC systems, the energy savings alone, in Mr. Holladay’s words, “…can’t possible justify the very high costs of this type of retrofit.”

Indeed, when factoring in the retrofitting costs to the energy savings, at least on houses built in the early 20th century, the study found that the simple payback period was 139 years; longer than the houses were old!

So, getting back to the original question, how does the green home buyer evaluate building new vs. retrofitting an existing building? It’s a complex subject, with many variables, but what becomes immediately apparent is that it’s easier, more efficient, and often less expensive to build your high performance home from scratch than to retrofit an existing older home.

That’s not to say that existing homes shouldn’t be updated to improve their performance. To achieve the aggressive climate goals the US has set for the coming decades, all homes will need to do their part in forestalling climate change. But with the sustainably-built, Net-Zero ready homes with Passive House levels of airtightness available today, it’s hard not to see “building new” as an attractive, responsible option.

2017-01-12T13:48:52+00:00 November 5th, 2014|0 Comments