Window shading recommendations: the fixed shading device for each facade

Five fixed devices on eight facades

C4B takes one typical room with one window and turns it to each of eight facade orientations. On every facade it compares five fixed shading devices with the same window left unshaded. The optimiser sizes each device for that facade, and the device with the largest annual energy saving becomes the recommendation. A facade where no device saves at least 1% stays unshaded.

• Overhang: a horizontal plate above the window that blocks the high summer sun.
• Vertical fins: a plate at each side of the window that blocks low sun from the side.
• Eggcrate: overhang and fins combined into a frame that blocks sun from above and from the side.
• Horizontal slats: a screen of tilted blades that blocks sun from above while keeping a view out.
• Vertical slats: a screen of vertical blades that blocks low sun from the side while keeping a view out.

What the analysis shows

• A recommendation overview: a compass of the eight facades with each one's recommended device and its annual saving, and the share of direct sun that device blocks in the cooling season and lets in during the heating season.
• Drawings of each device as an oblique view, a plan and a section, naming the dimensions the results report.
• An annual savings matrix of five devices by eight facades, with the size the optimiser chose for each one and the recommended device highlighted.
• The saving of every device by season and by month, as a share of the unshaded window's annual energy.

How the saving is calculated

Every facade and every candidate device runs through a full year, hour by hour, in an ISO 13790 simple hourly (5R1C) model of the room, on the project's weather file: the nearest weather station's or the site-specific one. A Perez sky model splits the diffuse light into its circumsolar, sky-dome, horizon and ground parts, and the shade each device casts is calculated for the direct sun and for each of those parts.

The saving counts heating, cooling and lighting together, in source energy, and the lights dim with the daylight that reaches the room. A device that keeps out useful winter sun, or darkens the room, therefore counts against itself. Wall and window U-values are the ASHRAE 90.1-2022 prescriptive values for the site's ASHRAE 169 climate zone, and each facade's heating and cooling seasons follow its own balance point, not the calendar.

Your room and your building

The room starts from the project's building type, one of 31 types, each with its own occupancy, equipment and lighting loads, schedules and set points. You can change every input, and the project saves them:

• Room width, depth and height, and the window's size and position on the wall.
• Building type and thermal mass, from very light to very heavy.
• The glazing's solar factor (g-value or SHGC), from 0.10 to 0.87.
• Slat depth and tilt, where the overhang and fins are mounted, and, if you already know them, a fixed overhang depth, fin depth or slat spacing.
• The deepest overhang and fins the optimiser may choose, from 0.10 to 3.00 m (1.50 m unless you change it).

In projects and in the PDF report

Window shading recommendations are part of design direction, in projects on a paid plan. The first time you open it, it runs on the project's defaults; after you change the inputs, Run analysis updates the results. The project's PDF report adds two pages from the weather-station data: the recommendation overview with the inputs used, and the annual savings matrix.