On occasion I need to look up the heating degree days (HDD) for an area over a period of time to complete an energy audit. Weather data can be useful for estimating heating costs. So, what is a heating degree day?
A heating degree day is a unit of measurement comparing an average outdoor temperature to a 65°F indoor temperature over a 24 hour period. The 65°F temperature is used because this is considered a heat balancing point, or a temperature where heating will not be required inside a home or building. Of course HDD is used if you live in a heating climate like me. If you live in a cooling climate, cooling degree days (CDD) is more important. CDD uses a balance point temperature of 78°F.
HDD are figured by averaging the daily temperature (24 hour period) and subtracting that value from 65°F. Lets say you have daily high temperature of 20°F and a low temperature of -20°F, the average daily temperature is 0°F. Subtract that from the 65°F and you have 65 heating degree days.
A very cold climate, such as one of the colder cities in the US, International Falls, Minnesota has a HDD of 10,000 over the course of a year. In comparison, Washington DC has around 4,200 HDD in a year. Some areas of Alaska see more than 12,000 HDD.
I find HDD data from the Weather Underground web site, https://www.wunderground.com/history/. A very handy tool I use when needing weather related information. A good example is the weather for my area at the end of January of 2019. We were under a polar vortex with average daily temperatures of less than -20°F. These single days were producing 80-90 HDD. Check out zip code 55744 over the date of January 31, 2019, a very cold day in Northern Minnesota.
So, how can this be helpful with an energy audit? Lets say your monthly heating bill is higher than normal. The reason may be outdoor temperature related. Higher than average heating degree days over the course of a month will require more indoor heat to maintain comfort, increasing heating costs. I often compare data from previous years to the current period to confirm heating costs to temperatures comparisons. Weather data can also be used to compare summertime cooling needs and the associated air conditioning costs.
HDD and CDD, another tool used in energy auditing.
During an energy audit, I occasionally come across a homeowner living in a newer home they had built or had purchased that did not received any training on the home’s systems or how to maintain the home. In my opinion, understanding the basics of how your home works is an important detail in owning a home. Continue reading “Energy Audit-Homeowner Education”
Thermal imaging is a tool I use for energy auditing, but it’s usefulness goes way beyond. I often use my camera during building projects and at my own home to help detect problems. Continue reading “Energy Audit-Thermal Imaging”
During an energy assessment or audit, I often test household equipment and appliances for energy usage. Over the years, many people have been surprised that some devices use the amount of energy they do. This weeks blog will be all about how much it costs to operate the electrical stuff in a home. Continue reading “Energy Audit-Common and Not So Common Appliance Energy usage”
Many of you know by now I have a part time gig conducting energy assessments and energy audits for a few local power companies. Basically I help their customers who have a high bill complaint or are looking for solutions to heating and cooling problems in their homes. Continue reading “The Energy Audit-Report”
One of the questions I always ask while conducting an energy audit or assessment is if there is a build-up of frost or water vapor on any of the windows during the heating season. Usually, the answer is no. But I do occasionally get a yes, what is this piece of information telling me? Continue reading “The Energy Audit-My Moisture on Window Question”
A plug-in load is any electrical device that uses electricity that is not heating (including water heating), cooling or refrigeration. These plug-in loads account for approximately 20 percent of a home’s electricity use Continue reading “The Energy Audit-Plug In Loads”
All buildings that use a fossil fuel source for space or water heating, such as natural gas, liquid propane (lp), fuel oil or wood, have the risk of back drafting burned exhaust gasses into the structure.
Continue reading “The Energy Audit-Combution Appliance Zone (CAZ)”
As an energy auditor, I am often in homes because of high electrical bill complaints. Conducting electrical testing and calculating energy costs are part of my job. There is a formula for figuring these electrical costs. Continue reading “The Energy Audit-Ohms Law”
Summer has arrived, bringing warm temperatures and higher humidity. As a kid, I remember hot nights sleeping in the upper story of an old farm house, often also suffering from sunburn. Now, I can’t imagine not having at least one cool room in the house for relief. What a wimp I’ve become. Many homes in Minnesota have some sort of air conditioning today. This blog posting is going to discuss the different types, efficiencies, and operating costs of common air conditioners along with the basics of how they operate.
Continue reading “The Energy Audit-Air Conditioners”