Understanding Window-to-Wall Ratio (WWR) Calculation: A Step-by-Step Guide with Example
Window-to-Wall Ratio (WWR) is a crucial parameter in building design that determines the proportion of window area to the total wall area. It is an essential factor in energy performance analysis, daylighting design, and visual comfort. In this article, we will provide a step-by-step guide on how to conduct WWR calculations, along with an example for better understanding.
Step 1: Measure Window Area The first step in conducting WWR calculations is to measure the total window area. Measure the height and width of each window in the building in square meters (m^2). Add up the areas of all the windows to get the total window area (WA).
Step 2: Measure Wall Area Next, measure the total wall area (WA) of the building. Measure the height and length of each wall that does not have windows or doors in square meters (m^2). Add up the areas of all the walls to get the total wall area (WA).
Step 3: Calculate Window-to-Wall Ratio (WWR) Once you have the total window area (WA) and total wall area (WA), you can calculate the Window-to-Wall Ratio (WWR) using the following formula: WWR = WA / WA
Step 4: Interpret WWR Results The calculated WWR value will be a decimal or a percentage, representing the proportion of window area to wall area. For example, a WWR value of 0.25 means that 25% of the total wall area is occupied by windows.
Step 5: Example Calculation Let’s consider an example to illustrate the WWR calculation. Suppose a building has a total window area (WA) of 40 square meters and a total wall area (WA) of 200 square meters. Using the WWR formula, we can calculate the Window-to-Wall Ratio (WWR) as follows: WWR = 40 / 200 WWR = 0.2 or 20%
In this example, the WWR of the building is 0.2 or 20%, indicating that 20% of the total wall area is occupied by windows.
Step 6: Analyze and Optimize WWR Once you have calculated the WWR, it’s essential to analyze and optimize it based on specific design goals and requirements. A higher WWR means more window area, which can result in increased daylighting, views to the outside, and natural ventilation. However, it can also increase heat gain or loss, depending on the orientation and shading of the windows. Therefore, it’s crucial to strike a balance between daylighting, energy efficiency, and visual comfort.
Here’s a sample table for Window-to-Wall Ratio (WWR) calculation for a commercial building on all sides of the facade:
| Facade Orientation | Total Window Area (m^2) | Total Wall Area (m^2) | WWR (decimal) | WWR (%) |
|---|---|---|---|---|
| North | 60 | 300 | 0.20 | 20% |
| South | 40 | 250 | 0.16 | 16% |
| East | 50 | 200 | 0.25 | 25% |
| West | 30 | 180 | 0.17 | 17% |
| Total | 180 | 930 | 0.19 | 19% |
Note: This is just a sample table for illustration purposes. The actual window and wall areas may vary based on the specific building design and project requirements. The WWR values in the table are calculated by dividing the total window area by the total wall area using the WWR formula: WWR = WA / WA, where WA is the window area and WA is the wall area. The WWR is expressed both as a decimal and as a percentage to provide a clear understanding of the proportion of window area to wall area for each facade orientation.
In conclusion, the Window-to-Wall Ratio (WWR) is a critical parameter in building design that can impact energy performance, daylighting, and visual comfort. By following the step-by-step method outlined above and optimizing the WWR based on specific design goals, architects and designers can create more sustainable and comfortable buildings.
References:
- U.S. Department of Energy (DOE). (2016). Energy Design Guidelines for High-Performance Schools: Window-to-Wall Ratio. Retrieved from https://www.energy.gov/sites/default/files/2016/09/f33/w2w_ratio.pdf
- Whole Building Design Guide (WBDG). (2022). Window-to-Wall Ratio (WWR). Retrieved from https://www.wbdg.org/design-objectives/sustainable/water-efficient-strategies/window-wall-ratio-wwr