Introduction
If you've ever tried to specify windows for a building project and found yourself drowning in acronyms - U-value, SHGC, Uw, Ug, CRF, NFRC, WERS, NatHERS - you're not alone. Thermal performance specifications for windows are among the most technically dense areas in building specification, yet they directly determine your building's energy bills, comfort levels, and regulatory compliance.
This guide cuts through the jargon. We'll explain what every thermal performance metric actually means, how different international standards measure and report them, and - most practically - which specifications you need for your project based on your location and building type.
At SGL Doors & Windows, we supply thermally-optimized window and door systems to architects, developers, and builders in 30+ countries. Our products are tested and certified across the major rating systems covered in this guide, and our technical team supports specification decisions daily. Everything in this article reflects real-world specification experience.
The Fundamentals: What Makes a Window "Thermally Efficient"?
A window's thermal performance is determined by how much heat it allows to pass through - both conducted heat loss through the material and solar radiation gain through the glass. These are two separate phenomena requiring separate metrics:
| Item | English Term | Also Called | Meaning | What a Lower/Higher Value Means | Best For |
|---|---|---|---|---|---|
| Conductive Heat Transfer | U-value / U-factor | Thermal transmittance | Heat passing through the window due to the temperature difference between indoors and outdoors | Lower U-value = less heat loss = better insulation | General evaluation of window insulation performance |
| Solar Radiation | SHGC | Solar Heat Gain Coefficient / Solar Factor / g-value | Solar energy transmitted through the glass into the building as heat | Lower SHGC = less solar heat enters = cooler interior; Higher SHGC = more solar heat gain = warmer interior | Lower SHGC for hot climates; Higher SHGC for cold climates |
U-Value (Thermal Transmittance): The Complete Explanation
What Is U-Value?
U-value (also called thermal transmittance or U-factor in North America) measures the rate of heat transfer through a building element - in W/m²K (watts per square meter per Kelvin).
- Lower U-value = better insulating performance
- A U-value of 1.0 W/m²K means: 1 watt of heat flows through every square meter for every 1°C temperature difference between inside and outside
- For comparison: a well-insulated wall might have a U-value of 0.15–0.3 W/m²K; a single-pane glass window is approximately 5.5 W/m²K - about 20× worse
Whole-Window vs. Center-Pane U-Value
This is one of the most important distinctions in window thermal specification - and a common source of misleading claims:
| Term | What It Measures | Typical Value (good DG window) |
|---|---|---|
| Ug (Glazing unit U-value) | Heat transfer through the center of the glass only | 0.6–1.1 W/m²K |
| Uf (Frame U-value) | Heat transfer through the frame only | 1.0–3.0 W/m²K |
| Uw (Whole-window U-value) | Weighted area average of Ug + Uf + thermal bridge at edge | 1.0–2.5 W/m²K |
Critical Warning: Many marketing materials quote Ug (center-pane) U-values that are significantly better than the Uw (whole-window) value. A triple-glazed unit may have Ug = 0.7 W/m²K but Uw = 1.2 W/m²K once the frame and edge losses are included. Always specify and compare Uw (whole-window) values for compliance and energy modeling purposes.
U-Value Units: W/m²K vs. BTU/(h·ft²·°F)
North American standards (NFRC, IECC) use U-factor in BTU/(h·ft²·°F) while all other major markets use U-value in W/m²K. The conversion:
U-value (W/m²K) = U-factor (BTU/h·ft²·°F) × 5.678
Useful reference conversions:
| U-value (W/m²K) | U-factor (BTU/h·ft²·°F) |
|---|---|
| 0.5 | 0.088 |
| 0.8 | 0.141 |
| 1.0 | 0.176 |
| 1.2 | 0.211 |
| 1.4 | 0.247 |
| 1.6 | 0.282 |
| 2.0 | 0.352 |
| 2.5 | 0.440 |
| 3.0 | 0.528 |
SHGC, Solar Factor (g-value), and Total Solar Energy Transmittance
What Is SHGC?
Solar Heat Gain Coefficient (SHGC) - the North American term - measures the fraction of solar energy that passes through a window and enters the building as heat. It includes both directly transmitted solar radiation and the portion of absorbed solar energy that is re-radiated inward.
Scale: 0 to 1 (0 = no solar heat passes through; 1 = all solar heat passes through)
Clear glass: SHGC approximately 0.82–0.87
Standard Low-E double glazing: SHGC approximately 0.25–0.50 depending on coating
Solar control glazing: SHGC approximately 0.20–0.25
SHGC vs. g-value vs. Solar Factor
These three terms describe the same physical phenomenon but are used in different regional standards:
| Term | Region Used | Standard |
|---|---|---|
| SHGC | North America | NFRC / IECC |
| g-value (solar factor) | Europe / UK | EN 410 / EN 14351-1 |
| Solar factor | Australia | AS/NZS 4667 / WERS |
Numerically equivalent - an SHGC of 0.40 = g-value of 0.40 = solar factor of 0.40. The metric is identical; only the terminology differs by region.
Why SHGC Matters More Than Many Specifiers Realize
In hot climates, a window with SHGC 0.25 versus 0.50 can reduce cooling energy demand by 15–30% for a west-facing office facade. This is often more impactful than the U-value difference between double and triple glazing.
Conversely, in cold climates with significant solar access, high-SHGC south-facing windows (northern hemisphere) can provide passive solar heating that reduces heating demand - meaning that always specifying low-SHGC is actually an energy penalty in cold climates.
The optimal SHGC strategy:
- Hot climates (UAE, QLD, FL, TX): Low SHGC (0.20–0.30) across all orientations
- Cold climates (Canada, Scandinavia, UK North): Moderate-to-high SHGC (0.40–0.60) for south-facing; low (0.25–0.35) for east/west
- Mixed climates: Model it - orientation-specific specification is most effective
What Is a Thermal Break in Windows?
The Problem with Standard Aluminum
Aluminum is an excellent structural material - but it conducts heat approximately 1000× better than UPVC and 8,000× better than still air. In a standard (non-thermal-break) aluminum window frame, this high conductivity creates a continuous "thermal bridge" between the cold exterior and warm interior:
- Interior condensation: Cold aluminum surface drops below dew point, causing moisture condensation on frames
- Discomfort: Cold radiant surface reduces occupant comfort near windows
- High U-value: Standard aluminum frame Uf ≈ 3.5–7.0 W/m²K - dramatically worsening whole-window thermal performance
- Energy code non-compliance: Standard aluminum frames typically fail energy code requirements in all but the warmest climate zones
How Thermal Break Construction Works
A thermal break (also called thermal barrier) interrupts the aluminum's conductive path by inserting a strip of low-conductivity material between the interior and exterior aluminum sections:
Thermal break materials:
- Polyamide (nylon/PA66): Most common, excellent structural properties, 20mm–40mm typical width
- Polyurethane foam (PU): "Poured and debridged" construction; slightly better thermal performance but less structural efficiency
- Composite profiles (fiberglass, plastic): Used in highest-performance systems
Thermal Break Width vs. Performance
Wider thermal breaks generally improve frame U-values, but with diminishing returns:
| Thermal Break Width | Approximate Frame Uf | Application |
|---|---|---|
| 0mm (no break) | 3.5–7.0 W/m²K | Non-compliant in most regulated markets |
| 20mm polyamide | 2.0–2.8 W/m²K | Entry-level compliance; warm climates |
| 28–32mm polyamide | 1.4–2.0 W/m²K | Standard specification; most regulated markets |
| 40mm+ polyamide | 0.9–1.4 W/m²K | Enhanced performance; cold climates |
| Poured PU + widened break | 0.6–1.0 W/m²K | Near-passive house specification |
SGL's Thermal Break Range: Our thermal-break aluminum windows feature 28–40mm polyamide breaks depending on product series, achieving whole-window Uw values from 0.9 to 1.6 W/m²K depending on glazing unit specification.
International Thermal Performance Standards Reference
🇬🇧 United Kingdom: Part L 2022 + Future Homes Standard
The UK uses W/m²K notation throughout, with Uw (whole-window) as the compliance metric.
Current Part L 2022 requirements for dwellings:
- Maximum replacement window U-value: 1.4 W/m²K (whole window)
- New dwelling notional specification: typically 1.2 W/m²K for SAP energy modeling
- Part L 2022 fabric efficiency: Window specification feeds into SAP calculation
Future Homes Standard (FHS, 2025/2026):
- Targeting 75–80% CO₂ reduction vs 2013 baseline
- Implied window performance for compliant designs: Uw ≤ 1.2 W/m²K
- Many FHS-compliant designs are already specifying triple glazing (Uw ≤ 0.9 W/m²K)
Additional UK metric - Window Energy Rating (WER):
- BFRC (British Fenestration Rating Council) rates windows on a scale A++ to G
- WER combines U-value, solar gain, and air infiltration into a single net energy balance number
- Part L accepts WER Band C or better as an alternative compliance pathway for replacement windows
- Recommended minimum: Band B or better for new-build quality
🇦🇺 Australia: NatHERS / WERS / NCC 2025
Australian window thermal performance sits within the NatHERS (Nationwide House Energy Rating Scheme) framework for residential buildings, using the WERS (Window Energy Rating Scheme) for product rating.
Key metrics:
- U-value (W/m²K): Used as in European/UK markets
- SHGC (or Solar Factor): Critical for compliance - often more important than U-value in warm-climate zones
NCC 2025 Requirements (Class 1 buildings - residential):
- Minimum NatHERS 7-star rating
- Window selection typically modeled in AccuRate, BerS, or NatHERS online tools
- WERS-rated products provide input data for these calculations
Climate zone implications for glazing in Australia:
| Climate Zone | Priority | Typical U-value Target | Typical SHGC Target |
|---|---|---|---|
| Zone 1 (Hot-humid: Darwin, Cairns) | SHGC critical | ≤ 4.0 | ≤ 0.25 |
| Zone 2 (Warm: Brisbane, Perth north) | SHGC important | ≤ 3.5 | ≤ 0.30 |
| Zone 3 (Hot-dry: Alice Springs, inland WA) | Both | ≤ 2.5 | ≤ 0.25 |
| Zone 4 (Mild: Sydney, Adelaide) | Balanced | ≤ 2.0 | 0.30–0.50 |
| Zone 5 (Cool: Canberra ACT, Blue Mtns) | U-value important | ≤ 1.8 | 0.40–0.55 |
| Zone 6 (Temperate: Melbourne) | U-value critical | ≤ 2.0 | 0.40–0.55 |
| Zone 7 (Cold: Tasmania coast, alpine) | U-value critical | ≤ 1.4 | 0.50–0.65 |
| Zone 8 (Alpine: Snowy Mtns, Mt Hotham) | Max insulation | ≤ 1.2 | 0.55–0.65 |
🇺🇸 United States: IECC 2021/2024 + NFRC
The US uses U-factor (BTU/h·ft²·°F) and SHGC in the NFRC (National Fenestration Rating Council) system, with compliance governed by the IECC (International Energy Conservation Code).
NFRC Label - what it tells you:
- U-factor: Whole-window value (equivalent to Uw in European terminology)
- SHGC: Whole-window solar heat gain coefficient
- VT (Visible Transmittance): Fraction of visible light transmitted
- AL (Air Leakage): CFM per square foot at 75 Pa pressure
IECC 2021 Fenestration Requirements (select climate zones - U-factor in BTU/h·ft²·°F):
| Zone | Fenestration Max U-factor | Max SHGC |
|---|---|---|
| Zone 1A (Miami) | 0.40 | 0.25 |
| Zone 2A (Houston) | 0.40 | 0.25 |
| Zone 3B (Los Angeles) | 0.32 | 0.25 |
| Zone 4A (Washington DC) | 0.32 | 0.40 |
| Zone 5A (Chicago) | 0.30 | NR |
| Zone 6A (Minneapolis) | 0.30 | NR |
| Zone 7 (Fairbanks) | 0.28 | NR |
Convert to SI: Multiply U-factor by 5.678 for W/m²K equivalent
🇪🇺 European Union: EPBD + EN 14351-1
The EU's Energy Performance of Buildings Directive (EPBD) mandates energy performance requirements, with national codes implementing specific U-value limits:
Representative EU national requirements (residential windows):
| Country | Typical Max Uw (W/m²K) | Notes |
|---|---|---|
| Germany (GEG) | 0.9–1.3 | Varies by climate zone and building type |
| France (RE2020) | 1.3 | Also includes embodied carbon (Bbio) metric |
| Netherlands (BENG) | 1.5–1.7 | BENG energy performance criteria |
| Sweden | 0.9–1.1 | Strict cold climate requirements |
| Italy | 1.4–2.0 | Varies significantly by climate zone |
| Spain | 1.4–2.7 | Wide variation by climate zone |
The CE marking under EN 14351-1 requires declared thermal transmittance values - but does not itself set a minimum performance threshold. Compliance with national energy codes is separate from CE marking.
🇦🇪 UAE: Al Sa'fat + Pearl Rating System
Both UAE systems require energy performance documentation for glazing, with particular emphasis on:
- SHGC / Solar Heat Gain: Critical in UAE's extreme solar climate
- Typical specification target: SHGC ≤ 0.25 for Dubai / Abu Dhabi
- U-value: Less critical given mild outdoor temperatures; Uw ≤ 2.0 W/m²K typically sufficient
- Shading coefficient (SC): Sometimes used in older documentation; SC ≈ SHGC ÷ 0.87
Glazing's Role in Thermal Performance
The glazing unit (insulating glass unit, IGU) typically contributes 60–75% of a well-designed window's thermal performance. Understanding glazing options is therefore central to thermal specification:
Double vs. Triple Glazing: When Does Triple Make Sense?
| Factor | Double Glazing (Low-E) | Triple Glazing |
|---|---|---|
| Ug (glass U-value) | 1.0–1.3 W/m²K | 0.5–0.7 W/m²K |
| Typical Uw achieved | 1.0–1.6 W/m²K | 0.6–1.0 W/m²K |
| Cost premium | Baseline | +20–40% vs double |
| Weight | Baseline | +30–50% heavier |
| SHGC reduction | Low-E available 0.25–0.60 | Additional pane further reduces SHGC |
| Visible light | 70–80% VT | 55–70% VT (slightly darker) |
| Best application | Most regulated markets | Cold climates, passive house, Zones 5-8 IECC |
Rule of thumb: Triple glazing becomes cost-effective when Uw < 1.0 W/m²K is required - typically for passive house projects, cold climate zone 6-8 US, German GEG energy house standards, or UK Future Homes Standard high-performance designs.
Low-E Coating Types and Their Effect on SHGC
Low-E (low emissivity) glass coatings are thin metallic oxide coatings that reflect long-wave infrared radiation (heat), dramatically reducing U-values, while their effect on SHGC depends on coating type:
| Low-E Type | SHGC Range | U-value Effect | Application |
|---|---|---|---|
| Soft coat (sputtered) - high solar gain | 0.45–0.60 | Reduces Ug by ~40% | Cold climate passive solar - max heat in |
| Soft coat - moderate solar gain | 0.35–0.45 | Reduces Ug by ~40% | Temperate climate balanced |
| Hard coat (pyrolytic) - standard | 0.50–0.70 | Reduces Ug by ~20% | Lower cost, more durable; limited SHGC control |
| Solar control Low-E | 0.20–0.35 | Reduces Ug by ~40% | Hot climate / east-west orientations |
| High solar control | 0.15–0.25 | Reduces Ug by ~30% | Extreme solar gain climates (UAE, Florida, QLD) |
Specification tip: Always specify Low-E coating position (typically surface 3 of a double-glazed unit = inside face of outer pane) - the position affects both thermal performance and reflected color appearance.
Warm-Edge Spacers: The Overlooked Detail
The spacer bar that separates the two panes of a double-glazed unit contributes to the overall thermal performance of the window edge zone. Traditional aluminum spacers are thermal bridges at the glass edge.
Warm-edge spacer alternatives:
| Spacer Type | Thermal Performance | Vs Aluminum |
|---|---|---|
| Aluminum spacer | Baseline (poor) | - |
| Stainless steel spacer | +10% improvement | Marginal |
| Foam spacer (TPS) | +20–30% improvement | Notable |
| Thermoplastic spacer (Superspacer) | +20–30% improvement | Notable |
| Composite spacer (Swisspacer) | +30–40% improvement | Significant |
For compliance calculations, particularly in cold climates and passive house applications, specifying warm-edge spacers can make the difference between a marginal pass and comfortable compliance margin.
Condensation Resistance Factor (CRF)
CRF (Condensation Resistance Factor) is a North American metric (NFRC 500) measuring a window's resistance to interior condensation formation. Scale: 0–100 (higher = more condensation resistant).
In practice:
- CRF 50–60: Adequate for most North American climates
- CRF 60–70: Recommended for cold and humid interiors (hospitals, natatoriums, commercial kitchens)
- CRF 70+: Required for extreme cold climates (Zone 7-8 IECC) or very humid interior conditions
CRF is not commonly used outside North America - European and Australian markets use condensation assessment per EN ISO 10077 calculations.
Specifying Thermal Performance: A Practical Workflow
Step 1: Establish Regulatory Requirements
- Identify the applicable energy code and climate zone for your project location
- Look up the maximum U-value and SHGC requirement for your building type
- Check if a green certification (LEED, BREEAM, Green Star) adds beyond-code requirements
Step 2: Establish Whole-Window (Uw) Target
- Use the regulatory maximum as your floor (minimum performance), not your target
- For comfortable energy modeling compliance margin, aim for Uw 10–15% better than code minimum
- Consult your energy modeler for projects where window spec significantly affects overall building energy balance
Step 3: Frame Selection
| Performance Target | Recommended Frame |
|---|---|
| Uw ≤ 3.0 (minimal) | Standard aluminum (warm climates only) |
| Uw 1.6–2.5 | Thermal break aluminum (20mm break) or standard UPVC |
| Uw 1.0–1.6 | Thermal break aluminum (28–40mm) or quality UPVC |
| Uw 0.7–1.0 | Advanced thermal break aluminum (poured PU) or triple-glazed UPVC |
| Uw ≤ 0.7 (passive house) | Certified passive house frame (special aluminum or composite) |
Step 4: Glazing Specification
- Select appropriate Low-E type for your climate zone and orientation
- Determine double vs. triple glazing based on target Uw
- Specify warm-edge spacer for projects targeting Uw ≤ 1.2 W/m²K
- Check SHGC of selected glazing unit - don't optimize for U-value alone
Step 5: Verify Whole-Window Performance
- Request NFRC-certified data sheet (for US projects) or EN 14351-1 CPD / CE declaration (for EU/UK/AU)
- Confirm Uw = whole-window value, not center-pane glass value
- Request test report reference numbers for independent verification
SGL Thermal Performance Product Range
Aluminum Thermal Break Windows
SGL's thermal break aluminum window range achieves:
| Product Series | Thermal Break | Typical Uw Range | Target Markets |
|---|---|---|---|
| Standard TB | 28mm polyamide | 1.2–1.6 W/m²K | UK Part L, AU NCC, EU moderate zones |
| Enhanced TB | 36mm polyamide | 0.9–1.2 W/m²K | UK FHS, BREEAM Excellent, EU strict zones |
| Passive-Ready | Poured PU + 44mm | 0.7–0.9 W/m²K | Passive house adjacent, Zone 6-7 IECC |
Available glazing configurations:
- Double Low-E argon: Ug typically 1.0–1.1 W/m²K
- Triple Low-E argon: Ug typically 0.6–0.7 W/m²K
- Solar control Low-E: SHGC range 0.20–0.35 (hot climate specification)
Certifications available: CE (EN 14351-1) with declared Uw; NFRC data; WERS rated (Australia)
UPVC / PVCu Window Systems
SGL's UPVC window systems provide excellent thermal performance without requiring a thermal break:
- Multi-chamber profiles (5-chamber, 7-chamber) reduce frame heat transfer
- Typical Uf: 1.0–1.8 W/m²K depending on profile and reinforcement
- Typical Uw with Low-E DG: 1.2–1.6 W/m²K
- Triple glazing options available (Uw ≤ 1.0 W/m²K achievable)
- Ideal for UK (FHS-compliant capable), Northern Europe, Canada, cold-climate Australia
Steel Windows (Thermal Break Options)
For projects requiring the aesthetic of slim steel profiles with thermal compliance:
- Standard hot-rolled steel: High conductivity; fine for heritage but thermally challenging
- Thermally-broken steel: Polyamide or PU core break; Uw 1.2–1.8 W/m²K achievable
- Fire-rated thermally-broken steel options for compartmentation + energy code compliance
Conclusion: Thermal Performance Is Now a Core Specification Competency
Understanding U-value, SHGC, and thermal break technology is no longer optional for building professionals - it's a core competency required for regulatory compliance in virtually every regulated construction market.
The key principles to carry forward:
- Always use Uw (whole-window), never Ug (center-pane) for compliance and comparison
- SHGC is climate-dependent: low in hot climates, higher (south-facing) in cold climates
- Thermal breaks are mandatory for aluminum windows in any energy-regulated market outside tropical zones
- Triple glazing makes sense above certain performance thresholds (Uw < 1.0) but adds cost, weight, and reduced visible light
- Warm-edge spacers make a measurable difference in cold climate compliance
- Request certified data, not marketing claims - NFRC, WERS, CE, and BFRC labels provide independently verified performance data
- At SGL Doors & Windows, we provide full certified thermal performance data for all our product ranges across the major international rating systems. Our technical team can advise on optimal glazing and frame combinations for any climate zone, building type, and certification requirement.
FAQ
Q: Q1: What is the difference between U-value and U-factor?
A: A: U-value (W/m²K) and U-factor (BTU/h·ft²·°F) measure the same thing - thermal transmittance, or heat flow through a window. U-value is used in the UK, Europe, and Australia; U-factor is used in North America. To convert: U-value = U-factor × 5.678. Both describe the whole-window thermal performance - a U-value of 1.2 W/m²K equals a U-factor of approximately 0.21 BTU/(h·ft²·°F).
Q: Q2: What U-value do windows need in the UK to comply with current regulations?
A: A: Under Part L 2022, replacement windows must achieve a maximum Uw of 1.4 W/m²K for dwellings. New-build windows in energy-modeled designs typically target 1.2–1.4 W/m²K for SAP compliance. The emerging Future Homes Standard (2025/2026) implies whole-window targets of approximately ≤ 1.2 W/m²K for most compliant designs, with high-performance designs achieving 0.9–1.0 W/m²K using triple glazing.
Q: Q3: What is a thermal break in aluminum windows and why does it matter?
A: A: A thermal break is a strip of low-conductivity material (usually polyamide/nylon) inserted between the interior and exterior sections of an aluminum window frame to interrupt the conductive heat path. Without it, aluminum conducts heat approximately 1000× faster than UPVC - making standard aluminum frames non-compliant with energy codes in most regulated markets. With a thermal break, aluminum windows achieve frame Uf values of 1.0–2.5 W/m²K compared to 3.5–7.0 W/m²K without. SGL's thermal break aluminum windows use 28–44mm polyamide breaks depending on product series.
Q: Q4: When should I specify triple glazing instead of double glazing?
A: A: Triple glazing makes economic and performance sense when your project requires a whole-window Uw below approximately 1.0 W/m²K, typically for: passive house or near-passive house projects, IECC climate zones 6-8 (very cold US climates), German GEG "energy house" standard buildings, UK Future Homes Standard highest-performance designs, or BREEAM Outstanding / LEED Platinum chasing maximum energy credits. For most standard compliance in temperate and mixed climates, double Low-E argon achieves compliance with better SHGC flexibility and lower cost.
Q: Q5: How does SHGC affect building energy performance differently in Australia vs the UK?
A: A: In Australia, most climate zones prioritize low SHGC (0.25–0.35) to limit cooling loads - especially in tropical, subtropical, and hot-dry zones (Darwin, Brisbane, Perth, Adelaide). In Melbourne and southern Australia, a more balanced specification (0.40–0.55) allows some solar gain for winter heating. In the UK, south-facing windows with higher SHGC (0.45–0.55) contribute meaningfully to passive solar heating and can improve overall energy balance in cold months. The key insight: SHGC optimization is always climate-zone and orientation specific, not a universal "lower is better" decision.
Q: Q6: What is a WERS rating and is it mandatory for Australian projects?
A: A: WERS (Window Energy Rating Scheme) is Australia's energy rating system for windows, administered by AFRC (Australian Fenestration Rating Council). A WERS rating provides star ratings for heating and cooling performance in each of Australia's 8 climate zones, plus an energy index value used in NatHERS compliance modeling tools. WERS is not mandatory as a product label in itself, but NatHERS compliance (now 7 stars under NCC 2025) typically requires WERS product data for modeling input. In practice, specifying WERS-rated products is effectively necessary for residential compliance documentation in Australia.
About SGL Doors & Windows
SGL Doors & Windows is a premier manufacturer of thermal-break aluminum windows and doors, UPVC/PVCu systems, steel windows, composite doors, and glass door solutions. With products certified to CE (EN 14351-1), AS2047, WERS-rated for Australia, and NFRC data available for North American projects, SGL delivers thermally compliant fenestration solutions across 30+ countries.
Thermal Performance Certifications: CE (EN 14351-1) | AS2047 | WERS Rated | NFRC Data Available
Products: Thermal-break aluminum (Uw from 0.9 W/m²K) | UPVC systems (Uw from 1.2 W/m²K) | Triple glazing options
Markets Served: UK, Australia, USA, Canada, UAE, Europe, Philippines, Singapore, and more
Website: https://www.sgl-doors-windows.com
Contact for Thermal Specification Support: Request Thermal Performance Data
Tags: thermal break windows, u-value windows, window u-value, SHGC windows, thermal performance windows, low-e glass, double glazing u-value, triple glazing, NatHERS windows, WERS rating, NFRC windows, Part L windows, Future Homes Standard windows, energy efficient windows, aluminum thermal break, SGL thermal windows
