Understanding weather data variables

There are certain elements of local climate data that impact the occupant comfort and subsequent loads of a building. Therefore, these climate data characteristics must be included in the energy modeling process and understood in order to improve the performance of an energy model:

• Weather patterns - refer to the general trends in weather conditions over a given period in a specific location. In energy modeling, these patterns help simulate the typical external environment a building will encounter throughout the year, allowing for accurate estimates of heating, cooling, and ventilation loads.
• Temperature data is essential in determining the heating and cooling loads for a building. It directly impacts energy consumption for maintaining indoor thermal comfort. Temperature values are used to model HVAC system requirements, considering both daily and seasonal temperature fluctuations.
• Humidity levels affect thermal comfort, indoor air quality, and energy use, especially for cooling and dehumidification processes. High humidity can increase the cooling load since additional energy is required to remove moisture from the air. Humidity data is used to accurately predict and size dehumidification systems and improve occupant comfort.
• Heating Degree Days (HDD) and Cooling Degree Days (CDD) provide a summary of how often and by how much temperatures are below or above a baseline (typically 65°F or 18°C). They are useful for estimating seasonal heating and cooling needs, providing a benchmark to compare energy performance between different locations and predict annual energy consumption.
• Wind Speed & Direction affects infiltration and ventilation rates in buildings. In energy modeling, wind data is used to estimate air leakage and its impact on heating and cooling loads. For buildings with natural ventilation, wind speed is particularly important for assessing airflow through open windows or other ventilation systems.
• Solar radiation data is critical for modeling solar heat gains through windows and other transparent surfaces. Solar radiation influences the cooling load, as more solar heat gain increases the cooling requirement. It’s also important for sizing solar shading devices, photovoltaic systems, and daylighting strategies

Other impacts include:

• Elevation above sea level (colder temperatures the higher you go)
• Proximity to large bodies of water (tempers extreme temperatures like a heat sink, increase winds and humidity, etc.) or mountains (impacts wind patters and humidity levels)
• Whether the project is in the northern or southern hemisphere (sun patterns)