Dwellvance Climate Data
Heating Degree Days & Climate Data
Climate conditions are an important part of understanding home heating needs. Dwellvance uses verified climate datasets to provide geographic context and establish planning inputs for its heat pump analysis.
What Are Heating Degree Days?
Heating degree days, or HDD, are a way of describing how much heating demand is associated with outdoor temperatures over a period of time. Dwellvance uses heating degree days with a 65°F base temperature as climate context in its heat pump analysis.
The climate dataset used by Dwellvance is based on NOAA U.S. Climate Normals for the 1991–2020 period. The dataset contains climate-station information including station location, elevation, and annual heating degree days.
NOAA U.S. Climate Normals 1991–2020
Dwellvance uses NOAA National Centers for Environmental Information climate-normal data. The heating-degree-day field used in the dataset is the annual heating degree days normal with a 65°F base temperature.
- Dataset
- U.S. Annual/Seasonal Climate Normals 1991–2020
- Climate variable
- Annual heating degree days normal
- Base temperature
- 65°F
- Data source
- NOAA National Centers for Environmental Information
How Dwellvance Maps a ZIP Code to Climate Data
When a valid five-digit U.S. ZIP code is provided, Dwellvance first determines geographic coordinates for that ZIP code. If ZIP-level coordinates are unavailable, the system can fall back to the primary county and its coordinates.
Dwellvance then compares the ZIP location with the climate stations in its NOAA-derived dataset and selects the nearest station by geographic distance. The selected station provides the heating degree day value and associated climate record.
HDD65 vs. Design Heating Temperature
These are different climate inputs and serve different roles in the current Dwellvance methodology.
HDD65
NOAA-derived 1991–2020 heating degree days with a 65°F base temperature. In the current planning model, HDD65 is reported as climate context and is not directly used in the home-characteristics load-factor calculation.
Design Heating Temperature
Dwellvance uses a verified county-level design heating temperature from an ENERGY STAR reference dataset. The current planning load model uses this value to establish the planning design temperature.
How Climate Data Is Used in the Heat Pump Calculator
The current heating-load model is a planning model based on home characteristics. It begins with a planning baseline of 25 BTU per square foot and applies adjustments for insulation, window quality, and air tightness.
The model also uses the verified ZIP-level design heating temperature to establish the planning temperature difference. HDD65 remains available as climate context in the resulting analysis.
Planning Estimate, Not Manual J
Dwellvance describes this heating-load result as a planning estimate. It is not a Manual J calculation and should not be treated as a final equipment-sizing recommendation.
Final equipment sizing should be verified using an approved load calculation appropriate for the home and installation.
Data Sources & Verification
The climate dataset identifies NOAA National Centers for Environmental Information as its source and uses the 1991–2020 climate-normal period. The Dwellvance climate data was verified on September 4, 2026.
The design heating temperature used by the current planning model is sourced from the ENERGY STAR 2019 Design Temperature Limit Reference Guide, Rev11, and was verified on September 4, 2026.
Explore the Heat Pump Calculator
Use the Dwellvance heat pump calculator to explore planning-level heating costs, savings, installation costs, incentives, and other decision factors for your home.
Open Heat Pump Calculator