How to Specify European Windows: A Checklist for Architects and Builders

5 days ago

3 min read

Specifying European windows for a U.S. project is not harder than specifying domestic ones, but the paperwork looks different. Some numbers arrive in metric, some test names are unfamiliar, and a few values that matter a lot in the U.S. are easy to leave out. This is the checklist we wish every spec sheet started with.

1. Opening type for every sash

Before any performance numbers, define how each sash works: tilt and turn, turn-only, fixed, tilt and slide or lift and slide. In a multi-sash unit, write it per sash. It sounds basic, but it is the most common reason a quote has to be redone. If the team is new to the terminology, our article on how tilt and turn windows work is a quick primer.

2. Performance class and design pressure

Ask for the performance class and grade, not just a design pressure number. A line like "Class AW, PG60" tells you what the unit was tested for and at what size. As an example, our aluminum MB-79N windows are rated AW-PG60 at 60 x 99 in., with a design pressure of +/-60.15 psf. Our uPVC Ideal 4000 line is CW-PG50 at 47-1/4 x 71 in.

Also check:

Air infiltration, in cfm/ft2. Good European units come in well under 0.1.
Water penetration resistance, in psf.
Uniform load structural test pressure.
Forced entry resistance, for example ASTM F588 grade.

3. Thermal values: U-factor, SHGC and VT

These three belong on every spec, and they should be whole-window (NFRC) values, not glass-only values. Center-of-glass numbers always look better than the real window.

U-factor: how fast heat escapes. Lower is better. Watch the units: European documents often quote Uw in W/m2K. Divide by 5.678 to get the U.S. figure in Btu/hr-ft2-F.
SHGC: how much solar heat comes through. Low for hot southern climates, higher where you want winter sun.
VT: how much daylight you get. Easy to forget, and it drops quickly with heavy solar coatings.

For reference, our products range from about 0.24 for a standard double-glazed window down to 0.13 for the best triple-glazed combinations.

4. Acoustic performance

If the site is near a highway, rail line or airport, specify STC and, ideally, OITC. Standard double-pane windows usually land between STC 26 and 33. Acoustic glazing in a good frame gets into the mid 40s and higher. Ask for the actual test report, such as ASTM E90, rather than a marketing number. Ours are posted on the test reports page.

5. Glass build-up

Write the full glass make-up: number of panes, Low-E coating, gas fill, spacer type and any laminated or tempered lites. Our standard is Low-E double pane with argon and a black Swisspacer warm-edge spacer, with triple pane and many other build-ups on request. See all glass options.

Also note the maximum glass thickness the frame accepts. It limits what you can do later with acoustic or safety glass.

6. Sizes and limits

List the minimum and maximum size for a single unit and for an assembly. European frames often allow larger sashes than people expect, but the limits differ a lot between systems. For example, our MB-79N goes up to 106 x 106 in. for one unit, while the MB-86 and MB-104 Passive top out at 74 x 74 in. per unit but allow larger assemblies.

7. Installation method

Decide early how the windows will be installed, because it changes the rough opening and the waterproofing details:

Through frame, fastened with screws through the frame.
Mounting straps, installed from the interior.
Nailing flange, installed from the exterior like most U.S. windows.

Not every system offers every method, so check before you draw the details.

8. Certifications and documents

Ask for NFRC ratings, the relevant AAMA test reports and, in Florida, the state product approval or TAS testing. Request technical drawings early. We provide PDF drawings for fixed and operable units on each product page, which saves a lot of back and forth with the detailer.

9. Hardware, finishes and accessories

Specify handle type and finish, lockable handles where needed, frame color inside and out, window sills, screens and any blinds. On tilt and turn windows, micro-ventilation and hinge covers usually come standard, but it is worth confirming.

10. Lead time

Put the lead time in the schedule, not just in the spec. Depending on material and shipping method, our windows take roughly 3 to 16 weeks. Aluminum by ocean freight is typically 8 to 12 weeks.

Need help with a spec?

Send us your drawings or a window schedule and we will come back with a quote and the technical data for each unit within 48 hours. Builders and developers can also look at our B2B program, or just contact us with your project.