The question building owners and property managers care about most is not technology but money: how much goes in, how much is saved, and how soon it pays back. Today we run the numbers on a 1000 m2 west-facing curtain wall retrofit using an open, reproducible method.
Assumptions (all transparent — plug in your own numbers)
- Subject: a standard office floor with 1000 m2 of west-facing glass curtain wall
- Present state: single-pane clear glass or standard double glazing, with high summer cooling loads
- Solution: ESEC One-Way View-Through Energy-Saving Window Curtain installed on the interior side of the glass
- Basis: the material reflects 88% of solar radiant heat, whole-window U-value improves 26%–50%, and the shading coefficient SC is 0.14 (all third-party tested); actual savings depend on orientation, glass configuration and operating hours
Where the Summer Savings Come From
The bulk of the cooling load on a west-facing elevation is solar heat gain. An SC of 0.14 means nearly nine-tenths of the sun’s heat is blocked before it enters — the air conditioner no longer has to spoon out heat that has already come in. Referencing a measured case (Raffles Ascott Beijing apartments, SHGC 0.9 to 0.3, overall energy use down 35%), summer cooling costs fall markedly.
Winter Savings Too
With the U-value improved by 26%–50%, the path through which indoor heat escapes via the glass narrows, winter room temperature rises naturally by about 2 degrees C, and the heating load drops accordingly. In northern China the heating season runs four months, and this saving is easily overlooked.
The Full-Year Figure
Our site figure for annual overall energy saving is 30%–50% (depending on orientation, glass configuration and operating hours). Taking the common industry ratio of office air-conditioning at 40%–60% of a building’s total energy use, for a 1000 m2 west-facing standard floor the annual electricity saving is typically in the tens of thousands of yuan — for your own figures, enter your parameters into the free savings calculator on our website.
How to Read the Payback Period
Payback period = retrofit cost / annual saving. All three variables are controllable:
- Interior-side installation touches no curtain wall, so the investment is far below the glass-replacement route
- West-facing elevations yield more than others — start with the west face
- Buildings running 24 hours (hotels, apartments, hospitals) amplify the returns and pay back faster
What to Do Next
- Run your own area, orientation and glass type through the free calculator first (see ‘Savings Calculator’ on our website)
- Book an on-site survey to get measured data rather than estimates
- Ask that any proposal state the test report numbers and the basis for its figures
The numbers are worked out, not talked up. Only when the figures add up should you talk about signing.