BOB KENYON
Special to Hutch Post
HUTCHINSON, Kan. — A Net Zero home produces as much electricity as it consumes.
To reach that goal, you'll need a solar system or some renewable source of energy like wind or hydro. More on solar in future articles. I would often tell my children: There are two ways to have more money, make more or spend less. Likewise there are two ways to get to Net Zero: produce more electricity or use/waste less. Let’s focus on wasting less - a useful goal for any home.
The envelope of your home refers to the exterior: the ceiling/roof, walls, basement, windows and doors. The better insulated and sealed your home is, the less heat or cool you will lose. The low hanging fruit in optimizing your envelope is insulation. While you should be concerned with all 6 sides of your home, the most significant is the attic.
Recall from your science class that heat rises and cool falls. That’s why your basement is always cool in the summer even if you don’t actively cool it - your cooled air
automatically drops through the floor or staircase to the basement. Note also that the earth is about 55 degrees year round which is why geothermal heating/cooling is so effective.
All the heat you produce will attempt to escape through your ceiling. Insulation is rated by the R value. The higher the R value, the better the barrier against loss, and therefore the more heat your house retains. You intuitively get this since you might wear a hoodie when the temperature is in the 60’s, a light jacket in the 50’s and your thickest coat with hat and mittens on the coldest winter day.
Your attic is an easy place to add insulation and will be the most bang for your buck. My Maryland house was built in 1900 and barely had 2” in the attic. When built, there was little concern for energy efficiency. Since home builders won’t be paying the heating or cooling bill, there is little motivation for them to provide an optimized envelope. The present building code is R-38 in the attic. That’s roughly 11” of insulation. If you want R- 50, that requires 17” of insulation. If you’re a do-it-yourselfer, Lowes and Home Depot sell loose insulation that can be blown in. Home Depot offers a free 24 hour blower machine rental with the purchase of 10 bags. Your return on investment depends on your bills. If you blow $1,000 worth of insulation into your attic and save $1,000 in a year on heating/cooling bills, you’ve broken even in a year and will have reduced bills for as long as you own the home. I plan to go R-50 - more is better. Maybe 60.
The pink rolls of insulation at your local home improvement store are R-19 for 6 inch thick walls. The rolls for 2X4 walls are R-13. If you’re building a house, exterior walls should be at least 6” thick. It’s pretty hard to upgrade existing walls although there are companies who will drill holes in your walls and blow in more insulation.
The other component of maximizing your envelope is checking how leaky your house is.
You can have all the insulation in the world but if air blows through cracks, you’re just chasing your tail. How tight your house is can be determined by a blower door test.
A blower door test will establish how well sealed your home is. A temporary door or window is installed with a fan blowing inside air to the outside. The fan is calibrated to blow at a constant rate. Monitors are placed inside the home to measure air change per hour.
The air change per hour at 50 Pascals is the standard unit of measure and is denoted ACH50 (Air Change per Hour at 50 Pa). ACH is the number of times the volume of air in your house will blow out the fan in an hour. Less is better. Early building codes required an ACH of less than 8. Newer codes require less than 3. For a home to be certified as a passive house, it must be less than 0.6.
Having an exceptionally well sealed home has multiple advantages. Indoor air quality can be controlled to improve overall health. If you have a family member with asthma or other breathing difficulties, you will want air absent of pollen, dust or other pollutants.
You want the ability to control the humidity in your home to avoid mold or overly dry air - hard to do with a leaky house. No leaks means no insidious insects entering your home.
Lastly and perhaps most importantly, you want to maintain a constant temperature, which is far more costly with drafts.
If the test discloses a number you consider too high, you have some detective work to do. If the outside temperature is significantly different than the inside temperature, you may be able to feel the temperature difference with your hand. Windows, doors, can lights and electrical outlets will be your prime suspects. An infrared camera may also disclose a disparity in temperature. Should the leaks still elude your detection, theatrical fog can be used so you can see air movement.
While essential for constructing an efficient new building, the test can be used for an existing building to identify leaks. Google “Door blower test near me”. Get yourself some caulk and plug up those drafty cracks! Paraphrasing Nancy Reagan: “Just say no to crack”.
Mike Pfeifer at Green Factor Insulation (https://www.gfipro.com/) will perform an analysis of my home including a blower door test. I’ll report back how that goes. GFI adds insulation as well. Note that they are based in Kansas City and Hutch is not in their normal service area. If they receive enough requests for service, perhaps they’ll add us to their normal service area.
Comments? Questions? Drop me a line. [email protected]
Bob recently retired as a professor of Computer Science at Loyola University Maryland.
Carla retired from Sandy Springs Friends School in Maryland where she was a teacher of upper level Mathematics including AP Calculus. She previously taught AP Statistics at Wichita Collegiate School in Wichita. They have family in Kansas City, Dallas, Western Arkansas and Wichita. They now live in Hutch.