What to Specify for Windows in Cold-Climate Residential Projects (Glazing, U-Value, Thermal Break, Hardware)

A cold-climate window does not fail because of the brand on the frame. It fails at specification: a glazing build-up that was assumed rather than written down, a thermal break nobody inspected, a spacer nobody specified, hardware that was never matched to the opening mode. Owners do not experience these as specification errors — they experience them as cold rooms, condensation on the glass edge, or a sash that no longer closes cleanly after three winters.

This guide is the decision chain we walk through with builders, developers and distributors before a cold-climate order is confirmed. It covers four decisions in the order they should be locked: glazing, thermal break, warm-edge spacers and sealing, then hardware — followed by the one number that causes the most confusion, and what to request before you compare it.

The four decisions at a glance

1. Glazing: agree the build-up before the brand

Insulated glazing is written as a string, and the string is the specification. 5+12A+5 is double glazing: 5 mm glass, a 12 mm cavity, 5 mm glass. 5+12A+5+12A+5 is triple glazing: three panes and two cavities. In a cold climate the second cavity is not marketing — it is a second still-air chamber doing the same job as the first, which is why triple glazing is standard across most of our higher series and available as an option on our entry series, where the standard build-up is 5+12A+5.

What to ask: the exact build-up string for the actual window being quoted; whether each cavity is argon-filled and whether that is documented; the glass thickness on every pane; whether a low-emissivity coating is applied and, if so, to which pane; and the spacer type, which is covered in section 3. If a supplier answers "double glazing" without a string, the specification is not finished.

2. Thermal break: inspect the profile behind the number

A thermal break is a structural detail, not a feature label. The interior and exterior aluminum shells are separated by a low-conductivity barrier, so heat travels through the frame far less easily than through solid metal. Three things decide how well that works: the alloy and wall thickness of the profile, the barrier material, and whether the frame has one barrier or two.

Our profiles are 6063-T5 aluminum with a 1.5 mm wall on SERIES 70 and 1.8 mm on the higher series, and every series carries PA66-GF25 polyamide barriers in the thermal break. Windows built with our double-thermal-break construction — SERIES 100 — carry two independent barriers, which interrupts heat transfer twice rather than once. That construction is visible in the cross-section drawings on our products page, which show the chamber layout, the barrier and the glazing build-up for each series.

What to ask: the alloy grade; the measured wall thickness rather than a nominal figure; the barrier material by name; the number of chambers; whether the break is single or double; and the cross-section drawing for the exact series being quoted. If the drawing is not available, the thermal break cannot be verified.

3. Warm-edge spacers and sealing: the details that decide condensation

The spacer is the frame that separates the panes at the edge of an insulated glass unit, and it is the most under-specified component in cold-climate projects. A warm-edge spacer conducts less heat than a conventional metal bar, which raises the temperature of the glass edge — exactly where condensation and mould appear first in cold weather. Our standard kits use silver aluminum spacer bars; our higher series use black carbon-steel warm-edge spacers.

Sealing matters just as much. Our windows use EPDM weather seals around frame and sash, and glazing sealant is applied inside and out with no exposed screws on the glazing beads — a cleaner face, and a more reliable seal than a dry-glazed or single-face detail.

What to ask: which spacer is being used on which series; the seal material; and whether glazing is sealed on both faces. Specifications that name only the glass and not the spacer and seal are incomplete.

4. Hardware: match the hardware to the opening mode

Hardware carries the sash every day of the window's life, so it deserves the same scrutiny as the glass. Match it to the opening mode first: tilt & turn and casement use different mechanisms, and in tilt & turn the handle position defines the mode — ventilation, full opening, or locked.

Then specify the family and the locking points. Our higher series use concealed hardware from Roto or CMECH with Hoppe handle sets; our SERIES 90 aluminum-clad wood windows use surface-mounted Roto hardware as standard, with 180° opening available, and concealed hardware as an option; SERIES 102 uses concealed Roto hardware as standard. Multi-point espagnolette locking is the norm: what varies between suppliers is how many locking points are lost when a sash gets tall.

What to ask: hardware family and model; the number of locking points and how they scale with sash height; the handle position logic; how the sash is adjusted on site; and whether spare parts and adjustment instructions are supplied with the order.

Comparing U-values without being misled

U-value is the number buyers argue about most, and it is the one most often quoted without the information needed to interpret it. A window U-value (Uw) combines the frame (Uf) and the glass (Ug); a centre-of-glass figure is not a whole-window figure, and neither value is comparable across different window sizes, glazing build-ups and spacer types.

How to compare properly: ask for the test report, the standard it was tested to, the exact window size tested, and the glazing and spacer used in that test. A figure supplied without those four details cannot be compared with anybody else's — including ours. We do not publish a U-value without its corresponding test report, and we would rather send you the report than a number.

The specification checklist

Every window in these series moves through the same nine controlled production steps before it ships, including the thermal-break and sealing stages described above — the factory tour shows what happens at each one.

Frequently Asked Questions

What is the difference between 5+12A+5 and 5+12A+5+12A+5 glazing?

Both are insulated glass units, written as glass–cavity–glass. 5+12A+5 is double glazing: two 5 mm panes separated by a 12 mm argon cavity. 5+12A+5+12A+5 is triple glazing: three 5 mm panes and two 12 mm cavities, which adds a second still-air chamber to the assembly.

Is argon fill worth specifying in a cold climate?

Yes — argon is denser than air and slows the convection that carries heat across a cavity, so it is the cheapest performance gain available in a glazing spec. What matters commercially is that the fill is specified and documented, not assumed, because an air-filled unit looks identical from the outside.

What is a warm-edge spacer and why does it matter?

The spacer is the frame that separates the panes at the edge of an insulated glass unit. A warm-edge spacer conducts less heat than a conventional metal bar, which raises the temperature of the glass edge and reduces the condensation and mould risk that cold-climate projects are most likely to see in service.

How should I compare U-values between suppliers?

Never compare a number without its test conditions. Ask for the test report, the standard it was tested to, the exact window size tested, and the glazing and spacer used in that test — a centre-of-glass figure and a whole-window figure are not the same thing, and neither is comparable across different sizes and configurations.

Which hardware should I specify for a cold-climate project?

Match the hardware to the opening mode before the brand: tilt & turn and casement use different mechanisms and different handle logic. Then specify the family and the locking points — concealed hardware on our higher series, Roto or CMECH, with Hoppe handle sets — and confirm that spare parts and adjustment instructions will be supplied.

What wall thickness should I require in the aluminum profile?

Require a measured figure, not a nominal one, and ask for the alloy grade at the same time. Our profiles are 6063-T5 aluminum with a 1.5 mm wall on SERIES 70 and 1.8 mm on the higher series, and every series carries PA66-GF25 polyamide barriers in the thermal break.

Next step

If you are specifying windows for a cold-climate project, send us your window schedule, elevations and the climate conditions the project must meet. We will confirm which series fits, provide the cross-section drawings and specification sheets for the exact walls and glazing you are considering — and, where useful, build a sample unit before production. Start from our product range, read more about how we manufacture, or contact our export team directly.