heating degree day

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Heating Degree Days Drop Again in 2017

It’s not happening everywhere, but Atlanta, Aspen, and other places saw the downward trend of HDD continue

Posted on May 24 2017 by Allison A. Bailes III, PhD

We've had some beautiful cool weather here in Atlanta this spring. It's about 50°F outdoors as I write this, one week into the month of May. The high yesterday was only about 70°F.

We're getting a few more heating degree days (HDDThe difference between the 24-hour average (daily) temperature and the base temperature for one year for each day that the average is below the base temperature. For heating degree days, the base is usually 65 degrees Fahrenheit. For example, if the average temperature for December 1, 2001 was 30 degrees Fahrenheit, then the number of heating degrees for that day was 35.) in the middle of May. (Heating degree days are really just another way at looking at temperature, which I explained in more detail in a look at the fundamentals of degree days.) We occasionally pick up some HDD even in July and August. But it's the winter HDD that matter for heating — and that give us a clue about the climate.

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Image Credits:

  1. Image #1: Energy Vanguard. Two bar graphs were created by Energy Vanguard using data from Weather Underground

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Nest Thermostat Data Revealed for First Time

At the recent ACI conference, Michael Blasnik showed big data on home performance collected from hundreds of thousands of homes

Posted on May 13 2015 by Allison A. Bailes III, PhD

The Nest thermostat has been around since October 2011, quietly collecting data on how your home — and the homes of hundreds of thousands of your neighbors — operates. It gathers information about indoor temperature, relative humidity, air conditioner runtime, auxiliary heat operation for heat pumps, and much more. Unlike the Ecobee thermostat, however, Nest doesn't let its owners see all those data (which is a problem only for energy geeks really). Enter Michael Blasnik.

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Image Credits:

  1. Energy Vanguard

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Choosing a Base Temperature for Degree Days

This reference point is important when using degree days for energy consumption analysis

Posted on Dec 17 2014 by Allison A. Bailes III, PhD

Degree days are a combination of time and temperature. We looked at their uses and where they come from in Part 1 of this series, and now it's time to go a little deeper.

The temperature enters as a temperature difference, ΔT (delta T), but it's not the ΔT between inside and outside of the building. It's the difference between the outdoor temperature and the base temperature. But what is this thing called base temperature?

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Image Credits:

  1. Hans Splinter, from flickr.com

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