Are Building Codes Enough?

June 29, 2017

Are Building Codes Enough?


The tragically horrific fire at the Grenfell Tower in London is a sober reminder of the importance of health and safety in buildings. Fortunately, building codes in the U.S. forbid the application the highly flammable materials used on the Grenfell Tower. Can Americans be confident that building codes provide sufficient protection for their families so they never experience such a tragedy?




With over 1,200 pages of codes and layers of building inspections regulating the construction of new homes in NC, you would think we’ve got it covered. Unfortunately that is not the case.


There are several reasons why building codes are never enough:


(1) The voluminous nature of codes makes it impossible for code enforcement officials to verify every element. NC Code limits the number of trips an inspections department can actually perform. In the end, the process moves more toward spot checks as opposed to a comprehensive examination. 

(2) Codes do not address every conceivable way things can be done improperly.

(3) Some things in building codes are just wrong. And making changes can take a long time. 

(4) With thousands of inter-related dynamics involved in building a home, there are very few code officials with the knowledge and skill to properly apply every facet. 

(5) In every volume, the practitioner is reminded, building codes represent "minimal standards". Building codes should never be held as synonymous with best practice.


A recent evaluation provides an example of how the code failed to protect a family in their beautiful new home.


Of course it’s said, “there is nothing like cooking with gas.” Naturally (no pun intended), the professionally designed kitchen included a dazzling six-burner gas cooktop. But cooking with gas creates an enormous amount of indoor pollution. And with the emphasis on energy efficiency, those pollutants linger almost forever in a new substantially airtight home. Fortunately, a well-designed exhaust fan over the cooking surface can capture the noxious fumes and direct them outside.


The “Capture Efficiency” of the hood reflects a percentage of the cooktop fumes the hood collects. The keys are, the size of the hood, its geometry and the distance from the cooktop to the capture hood. The closer the hood, the more stinky stuff it collects. Best practice mandates 24-30 inches.


Unfortunately, the code inspector misread the instructions and insisted the hood be lofted more than 48” above the cooktop. From that distance, it will be difficult for the for this hood to capture more than 50% of the “plume” off the cooktop. Moreover, the owner has to stand on her tiptoes and use a knife to cut the exhaust fan on.


Secondly, NC Code requires a “make up air” system for all homes with exhaust hoods removing greater than 600 cubic feet per minute (CFM). That means every cup full of air removed by the exhaust hood must be replaced or “made up” with an exact cup full of air from the exterior.


In this case, make up air is provided through a grille located in the ceiling of the kitchen. This grille is connected to a duct that delivers the make up air from otuside. Ideally, when the exhaust fan is energized, a damper opens and allows outside air to flow through the duct, out the ceiling grille and into the kitchen, where it replaces the air being exhausted.


Unfortunately, the damper didn’t open. Further investigation determined it was never wired.


So what’s the danger? When an exhaust fan pulls air from a home, physics dictate that an equal amount of air be pulled in from outside the home. (It’s called the Conservation of Mass) With the make up air damper closed, outside air must come from somewhere else. “Somewhere else” is always through the largest available hole with the least amount of resistance. In this home, that would be the fireplace flue. It is located approximately 20 ft. from the exhaust hood. So, when the hood is energized, the make up air comes backwards down the fireplace flue.


Here’s the scenario:  The Thanksgiving meal is being prepared, while the rest of the family is watching football by the fire in the family room. The exhaust fan is going full blast and the flue gases from the gas logs are being pulled backward, spilling into the living space. The hazardous exhaust fumes mix with the air in the space and are eventually inhaled by the family. After lunch, everyone gets sleepy. But hopefully everyone wakes up.


So how do you protect your family from this threat? Don’t assume building codes are enough. Become involved in the process. Take time to focus on the aspects of your home that will support better health and wellness. Select a builder who understands that houses work as a system and will work with you using good building physics to protect the health, safety and comfort of your family. A good place to start is search for professionals who partner with the EPA using their Indoor Air Plus Program.


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