K Glass – What It Is, How to Check It, and What It Costs

When we talk about K glass, the question of the insulating glass unit (IGU) inevitably arises – the most important component of a window in terms of energy efficiency. In this context, the term “K glass” is increasingly common in conversations with craftsmen, consultants, and manufacturers. But what exactly is this type of glass, why is it so popular, and how does it differ from the so-called “four seasons” glass?

K glass is a low-emissivity (Low-E) glass that has a special metal oxide coating applied to one of the internal surfaces of the insulating glass unit. This coating is almost invisible but plays a crucial role: it reflects heat back into the room while still allowing sunlight to pass through.

In other words, K glass prevents heat from “escaping” during winter. This makes it especially suitable for north-facing facades, homes with high heating costs, and any room where better insulation is needed.

Advantages of K glass compared to regular glass:

1. Lower heating bills – K glass retains heat indoors.
2. Improved thermal insulation – The U-value of a K glass unit is significantly lower.
3. Less condensation on the inside – because the interior surface remains warmer.
4. Comfort in winter – you feel less “cold” near the windows.

Verifying and identifying K glass

Many users assume that once they’ve ordered K glass, there’s nothing else to check – a common mistake. The coating must be placed on the internal side of the unit, facing the interior of the room. Incorrect installation can reduce the glass’s efficiency by up to 50%.

That’s why at Salamander-Koychevi Ltd., we offer professional K glass inspection – both upon delivery and for already installed windows. Make sure you’re getting what you paid for!

Identifying K glass can be done with a special device that measures the glass type. The device is placed on the surface, and it indicates whether the glass is energy-efficient. However, buying such a detector is often an unnecessary investment.

Before installation, K or “four seasons” glass can be tested using a multimeter in continuity mode. If the circuit is closed as described, and the multimeter signals continuity, the glass is K or four seasons due to its metallic coating.

Another method is the flame test. Hold a flame close to the glass. All glass will reflect two flames. Standard glass shows both flames in the same color, while K glass or four seasons glass will reflect the flames in different colors – due to the metallic layer.

The key characteristic of energy-efficient glass is that it reflects thermal radiation: indoor heat in winter and solar heat in summer. These windows protect your home from both cold winters and hot summers and help prevent fading of your walls and furniture.

K-Glass Price – Is it worth it?

K glass costs about 15–20% more than a standard white glass unit. However, the investment pays off quickly through lower heating costs and longer window life. Plus, better energy efficiency increases property value.

It’s important to note that the price of K glass varies based on the number of chambers in the IGU, glass thickness, frame type (PVC or aluminum), and whether argon is used between the panes.

K Glass or Four Seasons – Which to Choose?

Many clients ask: “K glass or four seasons – which is better?”
To answer this, we must first look at what “four seasons” glass is.

It’s also Low-E glass, but with solar control coating. It retains indoor heat in winter and blocks part of the solar heat in summer, making it more versatile.

The difference in summary:

• K-glass is better for cold climates or rooms with little sunlight.
• Four seasons glass is more suitable for south-, west-, or east-facing facades, where there’s significant sun exposure during the day.

If your apartment faces north, gets little sun, and has high heating bills – K glass is your best option.
If your home faces south and gets too hot in summer – four seasons glass would be the smarter choice.
You can learn more about Planitherm 4S glass.

K Glass and Double-Glazed Units – The Golden Combo

To get the most out of K glass, it should be paired with the right insulating glass configuration – most commonly: K glass + white float glass + argon gas. This combo provides excellent insulation, noise reduction, and improved indoor comfort.

There’s also the option for triple-glazed units with two K glass panes, ideal for passive buildings, mountain houses, and high-efficiency projects.

If your goal is to improve your home’s energy performance, cut heating costs, and stay comfortable in winter, K glass is a smart and proven choice. With the right IGU, proper installation, and exposure-optimized configuration, the results will be clear.

Contact our team for a personalized consultation, a free quote, and expert advice on whether K glass or four seasons glass is better for your home. We work with trusted partners and offer solutions that meet both your needs and modern energy efficiency standards!