The Role of Roof Windows in Sustainable Construction
Daylighting has become a central strategy in sustainable building design. Architects and homeowners alike now seek ways to bring natural light into interior spaces without compromising thermal performance. Roof windows and skylights offer an elegant solution, turning dark attics and upper-floor rooms into bright, habitable areas while maintaining the energy integrity of the building envelope. Among the manufacturers leading this movement, FAKRO stands out as a global innovator with a strong commitment to energy efficiency and modern skylight technology that meets rigorous Passive House standards.
FAKRO, founded in 1991 by Ryszard Florek in Poland, has grown from a small family enterprise into the second largest roof window manufacturer in the world. The company now operates 11 production facilities and 17 distribution companies, employs over 4,000 people, and exports products to more than 50 countries. What makes FAKRO particularly relevant in the context of sustainable building is its focus on airtightness, thermal efficiency, and certification under both the Passive House Institute (PHI) and Phius standards. These credentials make FAKRO products a preferred choice for architects and builders pursuing high-performance building certification.
FAKRO holds more than 180 individual patents and maintains a research and development team of over 100 engineers. This investment in innovation has produced a product lineup that includes roof windows, skylights, attic ladders, flat roof solutions, blinds, light tunnels, and even vertical joinery under the INNOVIEW brand. Each category is engineered with the same philosophy: bring natural light into buildings while keeping energy loss to an absolute minimum.
Flat Roof Windows Expanding Design Possibilities
While traditional pitched roof windows remain FAKRO’s core product category, the company has invested significantly in flat roof solutions. The DXW flat roof skylight is a specialty product designed specifically for roofs with low or no slope. This product addresses a growing demand in contemporary architecture, where flat roofs feature prominently in modern home designs, extensions, and commercial buildings. The DXW model provides the same level of thermal performance and airtightness as FAKRO’s pitched roof products, making it suitable for high-performance flat roof window applications in energy-conscious construction projects.
FAKRO also manufactures the FNP fixed roof window, which can be installed on both sloped and flat roofs. This model was developed in response to designer feedback that many pivot windows were installed in unreachable locations and effectively used as fixed windows anyway. The FNP comes in two triple-glazed variants: the P5 with laminated glazing for enhanced safety and the U5 with standard glazing. Both are filled with krypton gas for superior insulation and deliver a U-value of 0.97 W/m²K.
The company’s approach to flat roof products is complemented by its range of flashing kits, membranes, and installation accessories specifically engineered for low-slope applications. These components ensure that the entire roof penetration assembly maintains the airtightness that Passive House projects demand. As noted during FAKRO’s Component Spotlight presentation on the Passive House Accelerator, the company has deliberately pursued PHI certification for several of its products to demonstrate their suitability for Passive House construction and meet the exacting standards of the high-performance building community.
Passive House Certification and Product Range
FAKRO’s product range includes several models that are certified Passive House components. The FTT U8 is the flagship model, a quadruple-pane center pivot window with tempered glass on the exterior. This window achieves an extraordinary U-value of 0.58 W/m²K (0.1 Btu/ft²h°F), making it one of the most thermally efficient roof windows available. Its solar heat gain coefficient (SHGC) of 0.48 balances natural daylight with heat management, allowing passive solar gains during winter while preventing overheating in summer. The FTT U8 is particularly well-suited for cold climate Passive House projects.
For projects where the budget or performance requirements are slightly different, the FTT U6 offers a triple-pane alternative. It provides a U-value of 0.77 W/m²K and an SHGC of 0.50. The FTT U6 comes in over 20 different dimensions, offering considerable flexibility for architects working with various window sizes and configurations. Standard sizes such as 21 by 38 inches are kept in stock for rapid delivery through distribution partners, while custom sizes may require a lead time of 8 to 10 weeks.
The FPP model provides a top-hung and pivot switching mechanism, allowing users to open the window in two distinct ways. The pivot position makes cleaning easier and safer, especially for windows installed in high locations. Both the FTT and FPP series support the Passive House building concept by maintaining the continuous insulation line and airtight barrier that these projects require. FAKRO’s commitment to certification is reflected in its PHI and Phius accreditations, giving specifiers confidence that the products will perform as expected in energy modeling calculations.
Technical Performance Specifications at a Glance
To help architects and builders compare FAKRO’s key roof window models, the table below summarizes the most important thermal performance parameters. These values are critical inputs for Passive House Planning Package (PHPP) energy modeling and can make the difference between certification success and failure.
| Model | Glazing | U-value (W/m²K) | SHGC | Application | PHI Certified |
|---|---|---|---|---|---|
| FTT U8 | Quadruple-pane | 0.58 | 0.48 | Pitched roofs, center pivot | Yes |
| FTT U6 | Triple-pane | 0.77 | 0.50 | Pitched roofs, center pivot | No |
| FNP P5 | Triple-pane laminated | 0.97 | 0.20 | Fixed, sloped or flat roofs | No |
| FNP U5 | Triple-pane krypton | 0.97 | 0.20 | Fixed, sloped or flat roofs | No |
| FPP P5 | Triple-pane laminated | 1.00 | 0.48 | Top hung and pivot | No |
| FPP U5 | Triple-pane standard | 1.00 | 0.53 | Top hung and pivot | No |
The FNP P5 deserves special mention: its laminated glazing and low SHGC of 0.20 make it ideal for spaces where solar heat gain must be minimized, such as rooms with extensive south-facing glazing or cooling-dominated climates. This model has become one of FAKRO’s most popular in the US market, and its popularity means it can ship in as little as 8 days. The P5 designation indicates laminated safety glass, which also provides superior acoustic insulation and UV protection for interior furnishings.
Beyond the roof windows themselves, FAKRO also manufactures integrated accessories and flashings that preserve the thermal envelope. Proper flashing is essential for roof windows, as water intrusion and air leakage at the roof penetration are among the most common failure points in high-performance construction. FAKRO designs its flashing systems as complete assemblies rather than generic components, ensuring compatibility between the window frame and the roofing material.
Design Considerations for Specifying FAKRO Products
When specifying roof windows for a high-performance building project, several factors influence the choice of product and installation approach. Here are the critical design considerations:
- Slope requirements: Most FAKRO roof windows require a minimum roof slope of 15 degrees. For roofs below this threshold, the DXW flat roof skylight or FNP fixed window are the appropriate choices. Verifying the roof pitch early in the design phase prevents costly specification changes later.
- Positioning for daylight access: Roof windows should be positioned to maximize daylight while controlling glare. North-facing roof windows provide consistent, diffuse light, while south-facing units can contribute passive solar heating when specified with appropriate SHGC values.
- Airtightness detailing: The junction between the roof window frame and the roof structure must be meticulously detailed to maintain the continuous airtight layer. FAKRO offers专门的 EPDM gaskets and vapour control layers that integrate with the building’s airtightness membrane.
- Solar control: In cooling-dominated climates or rooms with large glazing areas, FAKRO’s awning blinds and external shading accessories can be integrated to manage solar heat gain. These products are designed to work seamlessly with the window frames.
FAKRO also offers a range of internal and external accessories that enhance the performance and usability of roof windows. These include:
- Electric opening mechanisms with rain sensors for automated operation and ventilation control
- External roller shutters that provide additional insulation and solar protection during summer months
- Internal blackout blinds and pleated curtains for light control in bedrooms and media rooms
- Insect screens that maintain natural ventilation without compromising indoor comfort
Integrating roof windows into a comprehensive energy-saving building strategy requires a holistic approach. The windows must work in concert with the insulation layer, vapour control, and mechanical ventilation system. In Passive House projects, this integration is verified through blower door testing and PHPP modeling, ensuring that the installed roof windows do not compromise the building’s overall energy performance. FAKRO’s complete product ecosystem from the window itself to the flashing kit and accessories makes it easier for designers to specify a coordinated system rather than assembling components from multiple manufacturers.
Conclusion: Daylight Without Compromise
FAKRO has established itself as a serious contender in the high-performance roof window market, offering products that meet the demanding thermal and airtightness requirements of Passive House construction. With certified components like the FTT U8, a growing range of flat roof solutions, and over 30 years of manufacturing expertise, the company provides architects and builders with viable options for bringing natural light into energy-efficient buildings. As building codes continue to tighten and the demand for net-zero construction grows, products that can deliver daylight without compromising thermal performance will only become more essential. FAKRO’s product roadmap and commitment to PHI certification position it well to meet these evolving market needs.