Insulating glass and thermal glass refer to the same product - a hermetically sealed glass element where 2 or 3 glass panes are joined together with a spacer bar. Other common names include IGU (insulated glass unit), sealed unit, double glazing, triple glazing, and energy-saving glass. All these terms refer to the same product. Note: sometimes the term 'sealed unit' or 'vacuum glass' may refer to actual vacuum glass, which is an entirely different product. Vacuum glass is next-generation technology where a vacuum exists between two glass panes instead of air or gas - this enables an extremely thin structure and excellent U-value. Vacuum glass is only just beginning to enter the market.

No - insulating glass is the glass element itself, the heart of the window structure, not a complete window. Insulating glass does not include the frame, sash or other window components. From us you order the ready-made glass elements to your measurements, and fit them yourself into your existing window structure, old frame or new frame.

The U-value (W/m²K) indicates how much heat passes through the glass per square metre for each degree of temperature difference. For example, when it is -30 °C outside and +20 °C inside (50 degree difference): an old single pane (U ≈ 5.0) loses 250 W/m², double glazing with selective+argon (U ≈ 1.0) only 50 W/m², and triple glazing with selective+argon (U ≈ 0.6) only 30 W/m². A good U-value pays for itself in two ways: besides the direct energy saving, the inner glass surface stays warmer, reducing the draught sensation so you do not need to keep the indoor temperature as high to compensate.

The normal air between the glass panes in insulating glass is replaced with argon. Argon is a colourless, odourless and non-toxic noble gas that insulates heat approximately 30% better than ordinary air, which is why it significantly improves the U-value of insulating glass. Argon is very common - in almost all modern insulating glass the air between the panes has been replaced with argon.

Selective (low-E) glass has an extremely thin, nearly invisible metallic alloy coating on its surface. This coating reflects room heat radiation back inside while allowing sunlight to pass through well. The selective coating is always positioned on the inside of the insulating glass unit for protection. Modern selective coatings are virtually colourless and do not change the appearance of the glass.

Solar control selective glass, such as Pilkington SunCool 70/40, is a double selective glass that reflects both escaping interior heat back inside and solar heat radiation back outside. It allows light through well (approximately 70%) while solar energy transmission in triple glazing is only approximately 40%. The appearance is neutral without strong tints or reflections.

Yes! Replacing insulating glass in an old window frame is a common renovation measure that significantly improves energy efficiency. The most important thing is to accurately measure the outer dimensions and total thickness of the old insulating glass. Double glazing often fits in old thin frames where thicker triple glazing does not fit. We recommend removing the trims and measuring carefully before ordering.

Yes! By tempering all panes in the insulating glass, the glass becomes approximately 3-5 times more durable than untempered glass. Tempered glass also withstands temperature differences better. When broken, tempered glass crumbles into small granules, which is safer than the sharp shards of untempered glass.

Tempering is strongly recommended whenever the glass is exposed to thermal stress: tinted and body-coloured glass heats up significantly in sunlight, solar selective glass absorbs part of the solar energy, and shadow patterns on the glass (fire escape ladders, pillars, eaves etc.) cause thermal imbalance that can crack untempered glass. Always check current building regulations and consult a structural designer.

Laminated glass is mandatory in fall-risk locations - tempered glass is not sufficient as it when broken crumbles into small granules and does not prevent falling. Laminated glass reasonably holds together when broken, slowing down fall-through. Lamination is also recommended for better sound insulation (the laminating film effectively dampens sound), partial UV protection, or to slightly slow down break-in attempts (official burglar-resistant glass is also available).

Building regulations require safety glass (tempered or laminated) in public spaces when the lower edge of the glass is less than 1500 mm from floor level or less than 300 mm from a door opening, in homes when the lower edge is less than 700 mm from floor level, and in doors always when less than 1500 mm from floor level. In fall-risk locations tempered glass alone is not sufficient - laminated glass is required. Always check current building regulations and consult a structural designer.

The maximum operating temperature of insulating glass as a unit is +65°C, as the hermetic sealant may begin to deteriorate at higher temperatures. Insulating glass is not suitable for saunas or other very hot environments.

This is a question we are asked frequently. Although window manufacturers produce insulating glass windows for saunas, insulating glass has no warranty when used in a sauna. The maximum operating temperature of insulating glass is +65 °C, and at high temperatures the sealant can begin to deteriorate at the edges and the butyl seal can flow onto the inner glass surface. If you want to use an insulating glass element in a sauna, it should preferably be tempered insulating glass due to thermal shock - however, there is still no warranty for sauna use, and tempering does not prevent sealant degradation. That said, there are cases where ordinary small insulating glass has lasted decades in a sauna without major issues and even without tempering. However, the likelihood is that at some point it will start to leak or the glass may crack from thermal shock. If you absolutely want to make a sauna window from insulating glass elements, we recommend using an oversized rebate depth so that the sealant area is well hidden inside the wood and does not heat up first. As a rule, insulating glass has no warranty for sauna use.

Interior surface condensation is caused by excessive indoor humidity relative to the glass surface temperature. A better U-value keeps the inner surface warmer and reduces the problem. Exterior surface condensation is a normal phenomenon indicating the glass insulates well. Permanent condensation between the panes indicates failure - the seal of the insulating glass has broken and the glass must be replaced. However, sometimes moisture remaining from the manufacturing process can temporarily evaporate from the molecular sieve under certain conditions, appearing as light fogging. This is not a leak and disappears when conditions change.

The fixing strip must be tall enough to cover the black sealant area (polysulphide, typically about 12 mm wide) and the installation clearance. With 2-4 mm clearance on each side, the minimum strip height is approximately 14 mm. The strip must also be structurally strong enough. A metal fixing strip must always have a seal/gasket between the strip and the glass, while with plastic or wooden strips a seal is not strictly necessary. Instead of a seal, you can also use glazing silicone, which seals and lightly "bonds" the glass in place. Please note that larger metre-class windows require a greater installation clearance on each side. Crucially important: silicone or sealant must always go between the glass and the structure - never on the edge of the insulating glass (the polysulphide sealant), as chemicals react with the polysulphide and will damage the seal of the insulating glass.

Yes, the black polysulphide sealant should be covered. If only a couple of millimetres of sealant remains visible, the issue is mainly aesthetic - the sealant does not look attractive. If more sealant is left exposed, UV radiation from the sun will degrade it over time, compromising the seal of the insulating glass unit. If a couple of millimetres remain visible, you can apply a thin, neat bead of UV-protective surface silicone over it - this protects the sealant and gives a clean finish.

Absolutely not! The warranty on insulating glass is voided immediately if any type of film, tint or sticker is applied to the glass surface. Film changes the thermal behaviour of the glass - it absorbs solar radiation and heats the glass surface significantly more than normal. Glass naturally expands and contracts with temperature changes, but the film prevents this even movement. This creates uneven stresses and distortions between different parts of the glass - the film-covered area heats up and expands differently from the free edge area. This leads to the glass cracking from thermal stress. If you need solar protection, choose solar control glass, solar selective glass or body-tinted glass directly as the pane in the insulating glass - these are designed to withstand thermal loads as part of the insulating glass structure.