Field Test in a West-Facing Office: The Afternoon We Installed the Curtain, the AC Went Up 3 Degrees

Every summer, a certain set of desks endures punishment: from two in the afternoon the sun shines straight through the glass curtain wall, colleagues within three metres of the window feel their backs burning, and pulling the blackout blind makes the room oppressively dark. We tracked one typical office before and after retrofit; the measured timeline is set out below.

Before Retrofit (measured at 14:00)

• Desk-surface temperature by the window clearly higher than the middle of the room — ‘roasting on one side, steaming on the other’
• Blackout blind fully down: temperature slightly lower, but all the interior lights on and no view left
• AC set to 24 degrees C, yet the colleagues by the window still asked for it lower
• The bulk of the AC energy went into fighting the sun

Installation Day (09:00–17:00)

• The curtain was installed on a track on the interior side of the glass, with no existing finishes removed
• A typical office floor is completed in a day, the office keeps working, with no dust and no noisy work
• Usable as soon as it is installed, with no need to ventilate (the material passed formaldehyde testing, meeting Table 2 of JG/T 254-2015)

After Retrofit (measured at the same point, 14:00)

• 88% of solar radiant heat reflected back outdoors (third-party figure for the fabric) — the heat is blocked before it gets in
• With the indoor temperature unchanged, the AC set point can be raised about 3 degrees C for comparable comfort
• Blackout blinds no longer needed: the see-through design is clear looking out by day and blurred looking in
• No more screen glare; desks by the window went from ‘nobody wants to sit here’ to normal seating

The Bottom Line

A 3-degree C higher set point corresponds to a significant drop in compressor load — air conditioning is the biggest item in a west-facing office’s electricity bill. Add a natural winter room-temperature gain of about 2 degrees C and a matching drop in heating load, and the annual overall energy saving is 30%–50% (our site figure, depending on orientation and glass configuration).

Advice for Admin and Property Teams

1. Don’t rush to pull the blackout blind — that trades daylight for temperature and loses on both counts
2. To evaluate a retrofit, ask first for measured data, then for the test report number
3. The interior-side approach is the most tenant-friendly: no change to finishes, completed the same day, adjustable at any time