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Lightweight energy retrofit solutions for existing transparent building envelopes

ESEC One-Way View-Through
ESEC Window Curtain

Blocks heat in summer · Keeps warmth in winter · One-way privacy · Shades sun, keeps the view
KEEP THE HEAT OUT · KEEP THE VIEW IN

Keeps solar heat outside and the view inside — daytime one-way privacy: clear from within, opaque from the street. No glass replacement, no facade tear-off — installed on your floor in a single day. A smarter option for glass curtain wall and window energy retrofit.

Book a Free Survey Calculate your savings in 30 seconds
ESEC HQ meeting area: curtain lowered — the corner glazing stays clear and the light soft
On-site photo · ZK Energy Control HQ meeting area, curtain lowered
3℃
Raise the AC setting in summer
2℃
Naturally higher room temperature in winter
88%
Total solar reflectance
15 yrs
Design service life
01
88%
Total solar reflectance
02
99%+
UV blocking rate
03
95%+
Infrared reflectance
04
92%+
View-through colour fidelity
Co-author of the Technical Standard for Energy Saving and Carbon Reduction Retrofit of Existing Hospital Buildings Energy-Saving and Carbon-Reduction Demonstration Product Four CNAS test reports, downloadable and verifiable
COVER STORY · About ESEC

Big glass brings bright, open views —
and an energy bill that never sleeps

Zhongke Energy Consumption Control (Beijing) Technology Co., Ltd. specialises in building-envelope energy efficiency. Its core product, the ESEC one-way view-through energy-saving window curtain, is a high-performance polymer multilayer composite film mounted on the interior side of curtain walls.

Unlike conventional curtains, window films or Low-E glass, it blocks infrared heat and cuts cooling energy use while keeping the outdoor view fully open.

Curtains buy coolness at the price of a wall of darkness; films buy insulation at the price of the view, permanently. The ESEC answer: let the window split the sunlight on its own.

In summer, solar radiation pours through the glass and air-conditioning loads stay high; in winter, indoor heat quietly drains away through the very same pane.

Suitable for office buildings, schools, hospitals, commercial complexes, residences and other buildings with glass curtain walls and exterior windows.

China Jin HQ 49F show floor: curtain half-lowered — city views clear and unobstructed
Curtain half-drawn · open views (HQ on-site photo)ESEC SOLUTION
Summer insulation · no more scorching west-facing sun Winter insulation · blocks heat loss Clear views · over 92% color fidelity Eliminates glare · softens harsh sunlight Privacy · no view in from outside Formaldehyde-free · healthy and odor-free 15-year service life No window removal · installed in a day On-site measurement and installation nationwide
Before / After

Before & After · Real photo comparison

Shot in the same room — harsh glare before installation, soft and comfortable light after.

Same window, same frame: the curtained upper half shades and insulates, while the bare lower half takes direct sunlight Upper curtain · soft, insulated Lower half bare · direct glare
One picture tells it all:Same pane of glass: the curtained upper half reflects heat with soft light, while the uncovered lower half shows harsh glare — lower it for coolness, raise it for the view.
Interior goes dark once the traditional blind is drawn; lights on in daytime Traditional blinds · dark and oppressive once drawn
Traditional roller blind:Shading by blocking only: once lowered the room turns dark and gloomy, lights on in daytime and the view gone.
ESEC curtain shades the sun while keeping the room bright; street view clearly visible ESEC Window Curtain · Shades without blocking the view
ESEC Window Curtain：Equal shading and heat insulation, yet the room stays bright and open, with street views and greenery clearly visible below.

Live-action video · Looking through the lowered curtain at the campus — shading without blocking the view (auto loop)

All on-site photos from Zhongke Energy Control (ESEC) projects · No rendering · What you see is what you get
Selected Projects

Flagship projects · Different buildings, same logic

From headquarters towers to high-rise facades, ESEC has completed energy retrofits on multiple flagship existing buildings.

  1. 01China Development BankHeadquarters office tower · Curtain wall energy retrofit→
  2. 02Raycom Info Tech ParkGrade-A office building · Glass curtain wall insulation upgrade→
  3. 03Jiaming CenterBusiness complex · West-facing facade retrofit→
  4. 04Minmetals PlazaHeadquarters office building · Dual-effect shading and insulation→
  5. 05Shanghai Sci-Tech Investment TowerHigh-rise curtain wall energy retrofit→
Thermal Principle

How It Works · Easy to understand at a glance

ESEC One-Way View-Through Energy-Saving Window Curtain: High Reflectance + High Clarity · Summer Heat Insulation, Winter Warmth.

Outdoors Solar Radiation ESECWindow Curtain Indoors Soft visible light passes through · infrared heat is reflected Infrared Heat ⇢ Reflected Visible Light ⇢ Soft light passes through
SUMMER

Summer · Reflects infrared heat

The high-reflectance functional layer bounces 88% of solar radiation heat back outside — the AC setpoint can go up 3°C or even switch off, keeping interiors cool and comfortable.

WINTER

Winter · Blocks heat loss

Blocking indoor heat loss through the glass raises room temperature by about 2°C naturally, cutting heating load — insulation savings you can feel.

Before / After

With the curtain installed · Where does the heat go

Same room, same pane of glass — the red arrows trace where solar heat goes. Tap to see the difference.

Outdoors Solar Radiation Indoors Solar heat reflected back outdoors at the curtain Heat reflected back outdoors Visible light · softly transmitted Visible light passes No curtain: solar heat pours straight in · room keeps warming Heat pours in · keeps warming
88%
Solar heat reflected back outdoors
99%+
UV blocked · furnishings age slower
+3℃
AC setpoint can be raised
52%
Near-infrared heat enters the room
0 blocked
No insulation layer · heat gain keeps building
High load
AC runs at high load for hours
Winter Edition

With the curtain installed · Winter heat stays in

Same room, same pane of glass — the red arrows trace where indoor heat goes. Lower the curtain to see the difference.

Outdoors Cold outdoors Indoors Indoor heat reflected back into the room at the curtain Heat reflected back indoors Visible light · softly transmitted Visible light passes No curtain: indoor heat drains through the glass · room keeps cooling Heat leaks out · room cools
+2℃
Naturally higher room temperature in winter
90+%
Indoor radiant heat reflected back inside
1.9–2.3 W/(㎡·K)
Whole-window K-value (thermal transmittance · lower is better)
0 barrier
Bare glass · heat leaks freely
Constant drain
Heat drains through the glass · room cools
High load
Heating runs at high load for hours
Thermal Comfort

Thermal Comfort · Three Channels × Four Modes

Radiation, conduction and convection — three physical channels managing summer heat gain and winter heat loss at once: passive thermal management that uses zero electricity.

RADIATION

Radiation · two-way reflection

In summer it reflects 88% of solar radiant heat back outside (near-infrared reflectance 96.5%); in winter it reflects 90+% of indoor radiant heat back inside — one film managing both directions.

Solar radiant heat reflectance88%
CONDUCTION

Conduction · air-cavity insulation

The curtain and the glass form a relatively sealed air layer — still air conducts at only about 0.026 W/(m·K), roughly 1/30 that of glass, like adding a blanket of still air in front of the window.

Whole-window K-value reduction (by glass type)26%–50%
CONVECTION

Convection · blocking the air wash

The curtain blocks warm indoor air from washing over the inner glass surface, raising the inner-pane temperature — the winter “cold draft” by the window disappears and the room temperature evens out.

+2℃
Natural winter temperature rise (all three channels combined)
↓26–50%
Whole-window thermal transmittance (K) · lower is better
K-value = thermal transmittance: how well the window insulates, lower means better · after installation 1.9–2.3 W/(㎡·K) (deployed 1.9 / retracted 2.3) · report BETC-T5CC-2025-00044
0.14
Shading coefficient SC
Cuts about 86% of solar heat gain · JGJ/T 151-2008 basis · report WT2025E09B00609
↓84%
Solar heat gain coefficient (SHGC)
Standard double glazing ~0.75 → ~0.12 after installation (converted from SC 0.14 via SHGC ≈ SC × 0.87)
Outdoors Indoors 88% reflected outside Visible light · softly transmitted
88%
Solar radiant heat is reflected back outside at the curtain — the heat-gain peak is cut at the source
+3℃
The AC setpoint can be raised, or the system paused altogether
28–35%
Measured overall energy-reduction range across projects
Outdoors Indoors Steady room temp Low heat gain
0 worse
The reduction scales with solar gain — during over-cooled periods (overcast, night, AC lag) the curtain never makes it colder
Swing ↓
Smooths inner-glass temperature swings and stops the see-sawing
ΔT ↓
Evens out the “cold blast / hot roast” unevenness by the window — fewer complaints from perimeter workstations
Outdoors Indoors Radiator (heat source) 90+% reflected back inside
90+%
Indoor radiant heat is reflected straight back inside — the glass stops being continuously heated
+2℃
Room temperature rises naturally and the heating load drops accordingly
1.9–2.3
Whole-window thermal transmittance K (W/(㎡·K), lower is better) after installation — cold-radiation discomfort by the window disappears
Outdoors Indoors Dual heat sources · peak-shaved together Heating source
88%
Daytime winter sun is reflected outside just the same — the “heating + west sun” overheat peak is shaved off
Swing ↓
The day-night temperature band narrows and the heating system runs steadier
Venting ↓
Opening windows when overheated is money straight out the window — peak-shaving sharply cuts the need to vent
Solutions Compare

Mainstream retrofit options · Side-by-side comparison

Glass replacement, film, roller blind or curtain? One table shows every trade-off — we also compare interior vs exterior shading on cost.

SolutionGlass removal / structural changesView while shadedImpact on building facadeEnvironmental & healthLater replacement & maintenanceOverall cost
Replace with Low-E glass
Key comparison points for those seeking Low-E glass alternatives		✗ Full window demolition and replacement, long schedule✓ View visible✓ Upgrades the curtain wall✓ Glass is recyclable✗ Whole window scrapped, hard to retrofit againHigh
Window insulation film
Film is inconvenient to replace later		✓ No glass removal✗ Tinted, reflective film limits the look✗ 深色膜面改变幕墙统一色调，色差难复原✗ 劣质胶层High温释放甲醛、苯等 VOC✗ Film removal leaves adhesive residue, inconvenient to replaceMedium
Ordinary sun-fabric roller blind
Drawbacks of ordinary sun-fabric roller blinds		✓ No glass removal✗ 降下挡景发闷（拉满遮光时私密性好）✓ 室内安装，不改外立面✗ Fabric collects dust and dust mites✓ Easy to replaceLow-Medium
Sealed glass with built-in blinds
What if built-in blinds inside sealed glass break?		✗ Requires replacing the entire sealed unit✗ Blinds block the view✗ Requires replacing the whole glazing panel✓ No emissions inside the sealed cavity✗ Damage inside the sealed cavity is hard to repairHigh
Exterior shading systems (louvers / shutters)
Interior vs exterior shading: which pays off		✗ Touches exterior facade and structure, requires property management approval✗ Blocks the view✗ 改动外立面，破坏原建筑线条✗ Outdoor dirt build-up; high-altitude upkeep is hard✗ Weather-exposed outdoor parts need frequent upkeepHigh
ESEC One-Way View-Through Energy-Saving Window Curtain
Insulation in summer · warmth in winter — benefit both ways		✓ No glass removal · sealed, hole-free cavity design✓ One-way view-through without blocking the view · insulation without blocking light✓ 室内侧安装，Facade unchanged✓ 100% formaldehyde-free · no VOC emissions✓ The fabric can be replaced on its own without damaging the curtain wallMedium（15 yrsService life）

隔热窗帘、隔热膜、遮阳卷帘怎么选？膜的优点是几乎看不出来，帘的优点是可以调节。但贴膜颜色固定、撕除后会留胶，深色或High反光的膜面还会破坏幕墙立面的整体感，并可能对周边道路造成反射眩光；贴上之后也无法随季节和昼夜调整，隔热与采光只能二选一。综合隔热、视野、外立面观感和后期Maintenance来看，反射隔热、可透景的ESEC Window Curtain更值得考虑。

Common drawbacks of each option

The notes below reflect common industry practice and target no specific brand. Before purchase, ask suppliers for test reports and environmental certifications.

1. Glass insulation film (window film)

  • Breaks the facade's colour and stylistic unity：Dark, brown or highly reflective films change the original tone and reflectance of the curtain-wall glass. Film only some of the windows on a building and the colour difference stands out on an otherwise uniform facade; it clashes with the original design and is hard to reverse.
  • Questionable environmental performance of the adhesive：Some products use solvent-based pressure-sensitive adhesives to bond pigment to the film. Once the glass is in the sun and heats up, such adhesive layers may slowly release formaldehyde, benzene, toluene and other VOCs; as the glue ages it gives off a pungent smell, and residue from cheap film is very hard to clean and can corrode the glass surface and the sealed cavity.
  • Causes reflected light pollution outside：Reflective (sputtered) films have high surface reflectance: in bright daylight they act as mirrors, throwing sunlight onto nearby buildings and roads. Drivers and pedestrians can be momentarily dazzled, and at night multiple ghost images appear. That is exactly what local curtain-wall reflected-light limits are meant to control.
  • Fixed once applied — no adjustment：The film is applied once and nothing changes afterwards. Want strong shading? The room gets dark. Want daylight? Put up with the sun. It cannot switch with the seasons, open and close through the day, or be zoned to how each room is used.
  • Other knock-on issues：Insulation declines year by year as the film ages; light films insulate little and dark films cut daylight; long UV exposure brings fading, bubbling and peeling; and if the glass shatters, fragments stick to the film and are hard to clear, also disrupting the normal break pattern of safety glass.

2. Ordinary shading roller blind (sun fabric)

  • Good privacy — its strong point：The fabric is dense and can be drawn fully across, blocking outside views; thicker heat-insulating fabrics work even better, suiting spaces with high privacy needs.
  • Drawn, it blocks the view entirely and the room feels noticeably darker and stuffier over time. Shading and daylight rarely come together — draw it fully and natural light is effectively gone.
  • The fabric collects dust and cooking grease easily, and in damp conditions can harbour dust mites and mould.
  • It blocks direct light only; solar radiant heat that has already passed through the glass is barely stopped, so insulation is weak.
  • A single layer insulates poorly and does nothing for winter heat retention.

3. Sealed glass with built-in blinds

  • It must be custom-built with the sealed glass unit, effectively replacing the whole pane — expensive to retrofit.
  • The slats always sit inside the glass cavity, blocking the view and offering poor see-through.
  • Once the drive mechanism in the sealed cavity fails, it cannot be repaired alone — the whole unit must be replaced.
  • Only a limited angle range is available after fitting, and since insulation relies on slat reflection, performance has a ceiling.

4. Exterior shading systems (louvers / shutters)

  • It alters the facade and structure and usually needs property and planning approval; especially hard on high-rises.
  • The projecting components break the building's original lines and facade cohesion, with an obvious visual impact.
  • Exposed year-round to wind, rain, sun and dust, the weather seals and drive parts need frequent service.
  • Maintenance demands work at height — costly and risky — with added hazards in strong wind.

5. Fabric curtains / honeycomb shades

  • Fabric and honeycomb cells collect dust easily and the cells are hard to clean — special tools are needed for regular deep dusting; near a kitchen, grease soaks in and becomes almost impossible to remove.
  • Bulky, with tracks that take up space; on large floor-to-ceiling windows it looks heavy and installation depth must be reserved.
  • Most fabrics need periodic removal for washing, and repeated handling shortens their life.
  • Insulation relies on fabric and air layers alone, so performance is limited — and drawn, it blocks both view and daylight.

6. ESEC one-way view-through energy-saving window curtain

  • No glass removal, no facade change：Fitted on the interior side: the exterior stays as it was, with no property approval needed.
  • No smell, eco-friendly：100% formaldehyde-free with no VOCs in the film — usable the moment it is fitted.
  • No reflected light pollution：Insulation works by blocking solar radiant heat and releasing it indoors — no mirror-like reflective layer required.
  • Raise and lower as needed：Stop anywhere or half-lower; adjust by season, orientation and time of day — the user decides between insulation and daylight.
  • Reversible and replaceable：The fabric can be replaced on its own without harming the curtain wall or glass, keeping long-term maintenance cheap.
ESEC one-way view-through energy-saving window curtain — product structure
ESEC Product

ESEC One-Way View-Through Energy-SavingWindow Curtain

A high-performance polymer multilayer composite film mounted inside the glass curtain wall. Without altering the facade structure, spectral-selective reflection delivers four benefits in one: heat insulation, warmth retention, clear views and glare control.

  • Total solar reflectance 88% — only about 12% of solar energy enters the room
  • Blocks 99%+ of UV, protecting people and furnishings
  • Near-infrared reflectance 96.5%, intercepting the main cause of indoor heat gain at the source
  • Lightweight and formaldehyde-free, no harm to the curtain wall structure, 15-year service life
  • Optional motorised smart control, integrates with building automation systems
View Product Details
Solutions

Widely suited toAll types of glass-envelope buildings

Over 1.2 billion m² of existing curtain walls; about 50% built before 2005 need energy retrofits.

01

Office Buildings / Corporate Headquarters

West-facing glass walls scorch and AC costs soar — the ESEC curtain significantly cuts cooling load and peak electricity use.

02

Hospital Buildings

Co-author of the Technical Standard for Energy Saving and Carbon Reduction Retrofit of Existing Hospital Buildings, delivering compliant retrofit solutions for hospitals.

03

Schools / Public Venues

Cuts glare to protect eyesight while balancing daylight and shading, improving comfort for teaching and events.

04

Industrial Plants / Parks

Insulates large skylights and facades, improving workshop conditions and reducing annual energy spend.

Eco & Health

Eco & Health · The Safe Choice

An interior-mounted material whose eco and safety performance is backed by third-party reports from CABR (China Academy of Building Research).

FORMALDEHYDE

Formaldehyde · Compliant

Formaldehyde content complies with Table 2 of JG/T 254-2015 (roller shades for buildings) — safe for long-term interior use.

Report No. BETC-T6AC-2025-00515
FIRE SAFETY

Fire Performance · Class B1

Rated B1(B-s1, d0) under GB 8624-2012 — low smoke, no flaming droplets for assured fire safety.

Report No. BETC-T4BC-2025-00042
GREEN FIT

Green Fit · Non-invasive

Interior-side mounting: no window removal, no facade damage, one-day completion in typical spaces.

Facade untouched · Ready on day one

Download and verify all reports on the Third-party Test Reports page

Certified

Authoritative Certification · Industry Endorsements

Dual recognition of product and technology, with verifiable certificate numbers.

Energy-Saving & Carbon-Reduction Demonstration Product Recommendation Certificate
Energy-Saving & Carbon-Reduction Demonstration Product Recommendation CertificateFiled with the Energy Conservation Department of MIIT
Co-author of the standard for energy-saving retrofit of existing hospital buildings
Co-author of the standard for energy-saving retrofit of existing hospital buildingsDrafting member of the energy-saving standard for transparent building envelopes
FAQ

FAQ · Glass insulation, question by question

West-sun offices, curtain-wall insulation, floor-to-ceiling window shading — the questions clients ask most, answered。

01How to fix west-sun heat in office buildings?
Keep the glass and curtain wall untouched — add the ESEC One-Way View-Through Energy-Saving Window Curtain inside: lower it in the daytime to reflect solar heat. West-facing workstations feel noticeably cooler, and the AC setpoint can go up by about 3°C.
02What curtain wall heat-insulation and sun-shading options exist?
Three mainstream routes: Low-E glass replacement, heat-insulation film, interior shading curtain. The ESEC curtain keeps the glass untouched and business running — 88% solar heat reflection, 95%+ near-infrared reflectance, the best value for existing curtain walls (see the comparison table above).
03How to insulate a curtain wall without removing glass?
Interior hole-free view-through shading curtain: tracks fixed inside the window frame, no drilling into glass, no facade alteration, motorised lift — ideal for accepted curtain walls and buildings that should not be structurally touched.
04How to protect floor-to-ceiling windows from sun yet keep the view?
The view-through fabric lets sight pass naturally while reflecting 88% of solar heat and blocking 99%+ of UV — sun protection, glare control and clear views all in one.
05How do curtain walls lower AC energy use?
Cuts solar heat gain at the source: SHGC drops sharply, lowering cooling load. Measured projects show 28–35% overall energy reduction.
06How much AC cost can building shading save?
It depends on city, orientation and window-to-wall ratio: enter three inputs in the calculator on this page and get an annual savings, cost and carbon report in 30 seconds — verifiable results.

How much could your building save? Run the numbers

Enter city, orientation and window area — get an energy report in 30 seconds: annual kWh saved, money saved, carbon cut, payback period

Try the Energy Savings Calculator — Free →
About Us

Zhongke Energy Consumption Control (ESEC)(Beijing) Technology Co., Ltd.

Experts in energy efficiency for transparent building envelopes and a core drafter of the Technical Standard for Energy-Saving Retrofit of Existing Hospital Buildings. With its self-developed ESEC One-Way View-Through Energy-Saving Window Curtain, the company delivers retrofit solutions for existing glass curtain walls — no structural changes, no business interruption.

  • Headquartered at China Jin, Wangjing, Chaoyang District, Beijing, with a nationwide service network
  • “Assess first, retrofit second”: annual savings, cost reduction, carbon cut and payback reports delivered before construction
  • Complies with Jianbiao [2015] No.38 and other existing curtain wall safety and energy supervision requirements, providing a compliant retrofit path
Learn More
Wangjing SOHO glass facade landmark: ESEC one-way view-through energy-saving window curtain in service

Free on-site survey · with a detailed energy savings plan

National Service Hotline 18610685811(Mr. Guo) · Email esec001@zkesec.com

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