One way climate expresses itself is through heating degree days, which vary significantly depending upon geographic location. Heating degree day works as an index (or indices) designed to reflect the demand for energy needed to heat a home or business. The following is an explanation from online Wikipedia:
Heating degree days (HDD) quantify the energy demand needed to heat a home or business. Daily temperature observations provide these indices. The heating requirements for a given structure at a specific location directly correspond to the number of HDD at that location. A similar index, cooling degree day’ (CDD), reflects the amount of energy used to cool a home or business.
We define HDD relative to a base temperature – the outside temperature above which a building needs no heating. The temperature you heat the building to and the nature of the building determine the most appropriate base temperature. This includes heat-generating occupants and equipment within it.
For calculations relating to any particular building, select HDD with the most appropriate base temperature for that building. However, for historical reasons organizations often make HDD available with base temperatures of 18°C (65°F) or 15.5°C (60°F) – base temperatures that approximately suit a good proportion of buildings.
The government publishes average heating degree days of the last 30 days for hundreds of cities. You can obtain them from your local building department or on the Internet (search for heating degree days). You must take some of these figures in context, or the results could surprise you, as in the following examples:
Eureka is located on the Pacific coast in northwestern California. When the inland valleys in California heat up, the coast gets foggy. When the inland valleys cool down, the fog on the coast goes away. That part of the coast really does have very cool summers!
Flagstaff sits in the mountains of northern Arizona at an elevation of nearly 7,000 feet. While the index results would surprise those familiar with southern Arizona, they align with what you could expect in the northern part of the state.
The coldest month of the year, which is usually January, normally serves as the basis for calculating the heat requirement. If you have a supplementary heat source for peak periods of heat usage, you can reduce the January figure.
The total heating degree days for the year are indicative of the annual fuel consumption, but not necessarily of the heater size. Even though the total per year heat consumption for Burlington, VT and Flagstaff, AZ are similar, the January indices show that Flagstaff needs about three-quarters of the heat that Burlington needs. As a result, Burlington requires a larger heater than Flagstaff.
The heating degree day figure is not the only consideration in determining whether a larger heater is necessary in a colder climate. Building codes in areas with colder climates have stricter insulation requirements. If you are building a new home, ask your contractor or building department about the heating and insulation requirements that apply in your area for any given building type.
If you are considering installing a masonry heater in an existing home, be aware that in the long run more insulation and low-e glass are cheaper than more heat. Also, if you live in higher elevations make sure manufacturers produce your low-e glass in that higher elevation as the low-e factor does not tolerate shipping to a higher elevation. In addition, consider tightening up or replacing all doors and windows.