Healthy Indoors Magazine
Issue link: https://hi.healthyindoors.com/i/929648
Healthy Indoors | 33 Do You Know Your Blower Door Number? I've already stressed how Home Performance revolves around comfort and that air sealing is the most important factor in delivering it. That means we need to measure leakage, since what gets measured gets managed. If you don't measure air leakage, how can you have any idea of whether or not an upgrade worked or is likely to work? The answer is that you can't. Comfort and balance are likely to elude you. A blower door is the tool Home Performance Specialists use to measure air leakage. The blower door number is by far the most important number I want to know about a house. Given the choice between square footage, year built, energy use, number of occupants, or blower door number, I want to know the blower door reading. Every. Single. Time. That means it's an awfully good number for you to know, too. Think of it like the blood pressure reading for your home. Every time you go to the doctor, they take your blood pressure. It helps give them a basic understanding of your health. For a better understanding, they need to ask questions and do more tests. The same thing goes for Home Performance projects and blower door readings. A blower door is a big fan that goes in the front door of your house. It can quite accurately measure how much air your home leaks. That number can be easily converted to the size of hole that is always open in your home, typically somewhere between a basketball sized hole and a win- dow. Just divide your blower door number by 10, and that's approximately how many square inches it is. Every 1500 points is about a square foot. It would be extremely difficult to do my job well without one. Imagine measuring blood pressure without a cuff. You can guess, but sooner or later those guesses are going to be wrong and hurt someone. Any competent Home Per- formance Specialist will test before, during, and after your project to gauge results and likelihood of success. The number on the left (50.0) is a pressure reading, which is measuring the difference between the pressure inside the house and the pressure outside of the house.