Temperature and design numbers

Every number here comes from the station's typical-year record. They're planning aids: check design values with your engineer, and check code values with the jurisdiction.

Temperature, month by month #

The first card says which month runs warmest and coldest, and how many months see freezing. The chart has a bar for each month, in °F:

• The light bar spans the typical year's coldest hour to its hottest hour that month.
• The darker band spans the average daily low to the average daily high, when the station has hourly data.
• The solid tick is the daily average.
• Blue dashes mark freezing.

The coldest and hottest hours are from the typical year, not all-time records.

Design numbers #

The Design numbers card starts by saying whether the climate is heating-dominated or cooling-dominated, and gives the station's ASHRAE climate zone. Then:

• Heating design 99.6% and Heating design 99%: the 99.6% temperature is what to size heating for.
• Cooling design 0.4% and Cooling design 1%.
• Heating degree days (base 65°F) and Cooling degree days (base 65°F), for the year. Degree days compare this site's heating and cooling load to anywhere else's.
• Elevation of the station, in feet.
• Köppen climate class.

A line under the list names where the design temperatures came from: the ASHRAE Handbook the station's file names, or the station's own record.

Station zone vs. county zone #

The climate zone here is computed from the station's weather (ASHRAE 169). For code compliance, use your county's zone (IECC Table C301.1 / R301.1). Near zone boundaries the two can differ.

Set the project's climate zone #

When the scheme is in a project, the Design numbers card offers to set the project's climate zone from the station. Walls checks wall assemblies against the project's zone.

1. Click Set "Maple Street clinic" to climate zone 5 (the button names your project and the zone).
2. Read the confirm. It repeats the station-versus-county caveat above.
3. Click OK.

Only project owners and admins can do this. Everyone else sees the project's current zone and "A project admin can set it." If the project already has that zone, the card says so.

You can also set the zone, or ask for a suggestion, from the project page.

Heating and cooling demand #

Heating demand by month and Cooling demand by month show the degree days for each month, base 65 °F. Taller bars mean more heating (or cooling) that month.

Humidity by month #

Humidity by month charts the average dew point each month, in °F, and says which month peaks. Above 62 °F, most people call the air muggy. A line under the chart gives the average relative humidity for each month.

Comfort hours by month #

Comfort hours by month splits each month's hours into four groups:

• below 68 °F;
• in the band;
• in range but muggy (dew point over 62 °F);
• above 80 °F.

The percentage on top of each bar is the share of hours in the band, and the sentence above gives the share for the whole year and the best month.

The band is simple: outdoor air 68–80 °F with a dew point at or below 62 °F. It's a rough read of when outdoor air is pleasant as it is (open windows, outdoor rooms), not an ASHRAE 55 or adaptive-model comfort calculation.

The charts follow the Colors setting above the study. See Chart colors.

Related #

• Thermal overview
• Export and print
• Weather stations