These are hot topics in the building community. For years, there have been a plethora of codes that do not make sense from a building perspective. Since the committees that create these codes are generally well-meaning, they continue to do research and remedy poorly written codes on a regular basis.

However, like most things in our world, policies driven by other well-meaning agendas can actually create onerous unexpected and unintended consequences.

Let’s start with the 2021 and 2024 insulation codes in the US. I’m only mentioning the US because I haven’t studied the various codes in other countries. These codes have largely been driven by the desire to create homes that are more energy efficient, use less carbon fuels, and have a lower carbon footprint. Most people reading this would say, “Yes, that’s fantastic! We need to do that any way we can.”

However, holding carbon footprint reduction as the primary design objective can lead to some unintended consequences. So, let’s begin with answering a few questions, such as which building techniques could result in the highest degree of energy efficiency? 

The obvious answer, and it is how many codes have been developed, is to make the home as air tight as possible so the heated or cooled air cannot escape the house. The intent of this regime is to ensure the heating and cooling systems run as little as possible, regardless of whether they are electric-only or natural gas / propane.

Second, we would insulate the home with as high an R-Value as possible to further this effort.

At this point, it’s possible for me to say that, if your primary goal is to reduce your home’s carbon footprint and maximize energy efficiency, these would both be effective construction techniques.

However, there will be significant unintended consequence from pursuing this one carbon-driven goal.

Homes, which are built to the tightest standards possible, simply cannot breathe. Homes, like humans, need to breathe in order to remain healthy. This includes replacing old stale air with fresh air. You may have the most-efficient HVAC system on the market, but if that system is moving the same air around your home over and over, picking up cooking particles, dust, bacteria, mold spores, viral spores, etc., the air quality inside the home will begin to degrade.

The reason there are so much more cold, flu, bronchitis, pneumonia, and other cases in the winter, is because people are spending more time inside offices and homes, rather than outdoors, breathing constantly refreshed air. That’s just common sense.

The next hurdle to overcome is the insulation and possible toxicity of the products. Current and upcoming building codes require increased R-value in every attic, wall, floor, crawlspace, and basement to keep the warm or cooled air in the home. As an example, attic insulation 20 years ago had an efficiency value of R-30. But then technology and codes increased and, soon it became R-49, and now some jurisdictions require R-60.  The recent trend in what’s known as “passive homes” champions the concept of R-70.

It’s not that these ideals are incorrect; they aren’t. However, to achieve these levels of R-value in a home, there are design cost increases to consider.  And I mean costs go up by a lot – as in 100% to 150% more.

How are these R-values achieved? Let’s return to our attic and see how much vertical space in inches of installed product these R-values take up:

• R-30 – 10-12” of blown-in cellulose
• R-49 – 16.5”
• R-60 – 21.5”
• R-70 – 24.9”

Since each R-value increase requires more volume, one of two things would need to change. In the standard attic, you would just add more; but wait, if your eves are the same size as on older houses, that would mean you’ll have less insulation around the edges of your home, essentially reducing the potential efficiency increase.