ST90 Window System
Exceptional thermal performance for the modern home.
The ST90 Window System represents the pinnacle of APA’s design innovation — combining elegant proportions with advanced insulation technology to create a window that delivers warmth, comfort, and architectural refinement to any luxury residence.
Engineered to achieve whole-window U-values as low as 0.71 W/m²K, the ST90 provides superior energy efficiency and acoustic comfort. Its precision-engineered frame forms a highly insulated barrier against heat loss, ensuring a quiet, comfortable living environment year-round.
With identical sightlines across the ST window suite, the ST90 allows for consistent design language throughout your home — blending seamlessly across elevations, extensions, or floor levels for a refined, balanced appearance.
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Crafted for Longevity
Built from durable, low-maintenance materials, the ST90 offers a service life of up to 30 years. Every component is carefully selected for strength, sustainability, and recyclability, reflecting APA’s long-standing commitment to both performance and environmental responsibility.
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Sustainable by Design
The ST90 system incorporates up to 50% recycled aluminium and polyamides, ensuring minimal environmental impact without compromising strength or finish. For homeowners who value design innovation and sustainability, the ST90 delivers both.
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Versatile Operation
Designed for flexibility and lifestyle comfort, the ST90 is available in multiple opening styles, including:
• Tilt and Turn (standard or Lifetime Homes configuration)
• Side-Hung and Top-Hung Open-Out
• Bottom-Hung Hopper or Open-In
Every configuration includes multi-point, wrap-around locking for enhanced security and smooth operation, even with large-format panes.
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Acoustic & Glazing Options
The ST90 accommodates triple or quadruple glazing from 38 mm to 62 mm, achieving exceptional thermal and sound insulation. This ensures a peaceful interior environment and significantly reduces heat loss — perfect for both city homes and rural retreats.
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Finishes
Available in single or dual colours, finished to Qualicoat Powder Coat standards, the ST90 offers timeless style with lasting durability. Whether fabricated in APA’s manufacturing facility or supplied in stock lengths, it combines precision craftsmanship with enduring performance.
You can download our the ST90 Brochure here or access the manual by registering for our Technical Library above.
- Designed for the ultimate in thermal efficiency.
- Whole window Uw value as low as 0.78 W/m²K.
- Tested to Pas 24 standards.
- Elements of the window were chosen for their end of life recycling.
- Tested to EN12101 smoke ventilation.
- Single or dual colour available.
- Triple or quadruple glazing up to 62mm in thickness.
- New low conductive polyamides used in the window assembly.
| Frame Depth | 90mm | |
| BS 6375-1 | Air Tightness: | Class 4 - 600 Pa |
| BS 6375-1 | Water Tightness: | Class EN1050 - 1050 Pa |
| BS 6375-1 | Wind load resistance: | Class 5 up to 3000 Pa |
| BS 6375-2: | Operating forces: | Class 1 |
| BS 6375-2: | Mechanical strength: | Class 3 |
| BS 6375-2: | Repeated opening & closing (30,000): | Class3 (Heavy Duty) |
| PAS 24: | Security classification: | Certisecure |
*Whole window U values are a combination of the frame and glazing thermal performance and as such will vary with the specification of glass utilised. Please consult with the APA technical team for more specific performance information.
