Types of Glass for Wooden Windows | Double-Pane, Triple-Pane, Low-E

Types of Glass for Wooden Windows ? Double-Pane, Triple-Pane, Low-E

Decorative etched glass patterns

Patterns available on request via our partner CE Glass

Choosing the right types of glass for European wooden windows — also marketed as wooden windows in UK and Ireland — is, without exaggeration, one of the most important decisions when building or renovating a home. At SM Wood Prodcom, we have known this since 1997 - when we first began processing laminated wood in Floresti, Cluj. Over the years, we have installed hundreds of glazing combinations in new builds, renovations, and even for the restoration of two historic theatres in Paris. We have seen the long-term results of every choice.

Therefore, instead of a vague answer, we offer you this complete guide: what types of glass exist, what the real differences are, and what we in particular recommend based on your situation.

Types of glass available for laminated wooden windows

The glazing market has changed dramatically over the last 15-20 years. Today, you have much more efficient options and - surprisingly - they are not necessarily much more expensive when you consider long-term energy savings. Here is what we currently work with:

Triple glazing — Ug ≤ 0.7 W/m²K

Maximum insulation, recommended for passive houses, mountainous areas, or northern Romania

Low-E with argon fill

Reduces heat loss by up to 70%; invisible layer of metal oxide applied to the glass

Low-E with krypton gas

Better performance than argon at the same package thickness — for slim profiles

Vacuum glass — Ug ≤ 0.2 W/m²K

The most efficient glazing available today: thin, lightweight, extremely efficient

Acoustic glass (asymmetrical laminated)

35–42 dB Rw attenuation; advanced versions with acoustic PVB reach 46 dB

Decorative / sandblasted glass

Aesthetic design, protects privacy — ideal for bathrooms, walk-in closets, hallways

P4A / P6B burglar-resistant glass

Can be fitted with burglar-resistant glass for entry doors and ground-floor windows

Reflective / tinted glass

Controls overheating in summer — recommended for south- or southwest-facing facades

Glass Type / Glazing | Characteristics and recommendations | 2-pane double glazing - Ug <= 1.1 W/m²K | Good thermal insulation, affordable - solid for mid-range budgets and temperate climates | 3-pane triple glazing - Ug <= 0.7 W/m²K | Maximum insulation, recommended for passive houses, mountain areas or northern regions | Low-E with argon filling | Reduces heat loss by up to 70%; invisible metal oxide layer applied to the glass | Low-E with krypton filling | Better performance than argon at the same unit thickness - for thinner profiles | Vacuum glass - Ug <= 0.2 W/m²K | The most advanced glazing available today: thin, lightweight, extreme efficiency | Acoustic glass (asymmetric laminated) | 35-42 dB Rw attenuation; advanced versions with acoustic PVB reach 46 dB | Ornamental / sandblasted glass | Aesthetic design, protects privacy - ideal for bathrooms, dressing rooms, hallways | P4A / P6B security glass | Certified burglar resistance - mandatory for entrance doors and ground floor windows | Reflective / tinted glass | Controls overheating in summer - recommended for south or south-west facing facades

Insulating glass

Double or triple glazing for wooden windows - our recommendation

If you live in areas with harsh winters - such as Transylvania, northern Moldova, or mountain regions - our answer is direct: triple glazing with argon gas and a Low-E layer. We know it may seem more expensive initially. That is why we also tell you that the price difference compared to classic double glazing is usually recovered within 3 to 5 years through savings on heating bills alone.

The nZEB standard currently in force in Romania - Technical Regulation Mc001 - requires a thermal transfer coefficient for the entire window assembly (Uw) of maximum 1.0 W/m²K for new buildings. With our IV92 series featuring triple Low-E and argon (Ug 0.5 W/m²K), the overall Uw is 0.71 W/m²K for a standard 1230x1480 mm size.

For our IV78 and IV92 series, the wood profile allows for a glass unit thickness of up to 52 mm - sufficient for triple glazing with argon or krypton. This allows you to achieve maximum performance without any aesthetic compromise.

SM Wood Prodcom Tip: For the IV78 and IV92 series, we can install glazing units up to 52 mm thick. For maximum performance, combine triple glazing with argon and a Low-E layer on surface 3 of the unit - this is the configuration we recommend to architects for passive house projects.

How Low-E glass works - explained simply

Low-E stands for "low emissivity". An invisible layer of metal oxide - usually silver or tin oxide - is deposited on the inner surface of the glass, reflecting heat back into the room in winter and repelling it in summer. In short: you lose less heat in winter and avoid overheating in summer.

Condensation on the glass almost completely disappears because the temperature of the inner glass surface remains much higher. In laminated wooden windows, this technology works exceptionally well - wood has a thermal conductivity of 0.13-0.19 W/m·K depending on the species (compared to ~160 W/m·K for aluminium), so the profile does not create significant thermal bridges.

Acoustic glass - when it is worth it and how much noise it reduces

If you live near a busy street, a railway line, or in a city centre with heavy traffic, acoustic glass can transform the comfort of your home. Standard acoustic glazing reduces noise by 35-42 dB Rw. Versions with asymmetric laminated glass - different pane thicknesses plus acoustic PVB - reach 46 dB, which means that 75 dB of outside traffic becomes a background level of approximately 29-33 dB inside. Acoustic glass also combines easily with double or triple thermal glazing.

  • Ornamental or sandblasted glass - for bathrooms, dressing rooms, and hallways: protects privacy without sacrificing light. It can be combined with any thermal unit.

Other available glass types

Frequently Asked Questions about glass for wooden windows

What is the real difference between double and triple glazing?

Double glazing (2 panes) has a Ug coefficient <= 1.1 W/m²K and is suitable for temperate climates. Triple glazing (3 panes) has a Ug <= 0.7 W/m²K and reduces heat loss. The difference is most noticeable in winter, reflected in heating bills and thermal comfort.

What Ug value do you recommend for a new house in Cluj?

We recommend at least triple glazing with Low-E and argon – Ug ≤ 0.7 W/m²K. This exceeds the nZEB requirement (Uw ≤ 1.0 W/m²K) and ensures excellent long-term thermal comfort. The additional investment over double glazing is quickly recovered through energy savings.

Q3: Why does condensation appear on the exterior of the triple glazing in the morning?

This is a sign of extreme efficiency, not a defect. Triple glazing insulates so well that the exterior glass pane remains cold, not being heated by the warmth from inside the house. When external humidity is high, it condenses on the cold surface of the glass, just like on a car body, disappearing as soon as the air temperature rises.

Q4: What does "warm edge" spacer mean in a glass unit?

A warm edge spacer replaces the traditional aluminium spacer between the glazing with one made of thermoplastic composite material. This reduces the thermal bridge at the edge of the glass, increasing the temperature on the inner contour of the window by up to 4-6°C and eliminating the risk of condensation and mold appearing at the joint between the glass and the wood.

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Bespoke laminated wooden windows and doors since 1997 · Floresti, Cluj

Phone / WhatsApp | Email | www.smwoodprodcom.ro

P4A or P6B security glass - mandatory for high-quality entrance doors, also recommended for ground floor or basement windows.

Reflective or tinted glass - for south or south-west facing facades where summer overheating is a real issue.

Digital print glass or stained glass - for windows that become a decorative element, available in any graphic motif.

Decorative etched glass patterns