Which window panes should you choose? An overview of parameters and new products in 2026
When selecting windows for their home, most people focus on the profile, frame colour, and price. Meanwhile, the glazing unit – occupying up to 90% of the window surface – determines thermal comfort for the next thirty years of use. Winter condensation on glass, summer overheating in the living room, or street noise waking residents at night – these are problems solved by proper glass selection, not the profile. A good window is a carefully balanced equilibrium between energy efficiency, natural light access, noise protection, and summer solar control. In this article, we explore all types of glazing available on the market – from standard energy-efficient packages to advanced specialist technologies.
Energy-efficient glazing – U-value and real savings
U-value and thermal insulation of glazing units
The Ug-value indicates how many watts of thermal energy penetrate through 1m² of glazing at a temperature difference of 1 Kelvin. A lower value means less heat loss and lower heating bills.
Old windows with single glazing achieved Ug levels of 5-6 W/(m²K). Windows from the 1990s with double glazing – around 2-3 W/(m²K). Contemporary double-glazed units with low-emissivity coating reach 1.0 W/(m²K), while triple-glazed units with two low-E coatings achieve 0.5-0.6 W/(m²K) – the standard for passive houses and low-energy construction.
Low-E coatings are invisible layers of noble metal oxides applied to glass through vacuum deposition. Their thickness is measured in nanometres – thousandths of a millimetre. Despite microscopic dimensions, this layer reflects infrared radiation (heat) back into the interior whilst simultaneously allowing visible light through. The spaces between panes are filled with argon – a gas with lower thermal conductivity than air, which further slows heat transfer.
What does this mean in practice? A 150-square-metre house with 25m² of windows loses several thousand euros annually on heating with old windows. Replacement with modern triple-glazed units reduces these costs by 25-30%. This also eliminates cold zones near windows and ensures comfortable internal temperatures even on frosty days.
Learn more about energy-efficient windows for passive houses in our offer.
Light transmittance Lt in triple-glazed units
Here we touch upon a problem rarely discussed during window purchases. Traditional triple-glazed units, whilst excellently retaining heat, transmit less light than double-glazed units. The difference is noticeable – particularly on overcast autumn and winter days.
Each additional glass pane and each low-E coating absorbs part of the light. A standard triple-glazed unit transmits approximately 70-71% of daylight. This means blocking 29-30% of solar rays before they reach the interior. In practice – noticeably darker rooms, earlier activation of lamps, less natural light in winter affecting residents’ wellbeing.
The solution lies in new-generation low-emissivity coatings, achieving Lt parameters of 75-77%. These additional 5-7 percentage points translate into a real difference in interior brightness. That’s an additional hour of daylight without artificial lighting during the autumn-winter season.
Modern new-generation coatings are optically almost invisible to visible light – they transmit the visible spectrum whilst reflecting heat-carrying infrared radiation. The health benefits of natural light are confirmed by scientific research – impact on melatonin production, vitamin D synthesis, mood, and productivity.
Solar control glazing – protection against summer overheating
g-value and solar gains across different seasons
In winter, sun entering through south-facing windows provides free heating that reduces bills. In summer, the same sun transforms a living room with large glazing into an overheated space requiring air conditioning.
The g-value (solar factor) indicates what percentage of solar energy penetrates through the glass into the interior. A high g-value (0.55-0.60) suits north and east-facing windows – maximising heat gains in winter. A medium g-value (0.35-0.40) offers a compromise for universal windows. A low g-value (0.28-0.33) provides protection against overheating on south and west-facing elevations.
The key parameter is selectivity – the ratio of transmitted light to transmitted heat. The best solar control glass transmits brightness whilst effectively blocking invisible heat-carrying infrared radiation.
Former tinted glass in brown and grey tones darkened rooms to 40-50% light transmittance and had a significant drawback – they heated themselves, then secondarily emitted heat into the interior. Contemporary selective glass transmits 60-70% of light whilst blocking 63-72% of solar heat. They have a neutral colour – the view through them retains the natural colours of the surroundings.
When solar control glazing is essential
Large terrace glazing is the hallmark of modern architecture. HST sliding doors spanning four to six metres open the house to the garden, creating a sense of space. In summer, each square metre of standard glazing transmits 400-600 watts of energy. Ten square metres equals 4,000-6,000 watts – power comparable to two air conditioning units.
A living room with large panoramic windows facing south without solar protection means: glare on the television screen making viewing impossible in the afternoon, fading furniture and flooring, temperatures exceeding thirty degrees requiring closing blinds and losing the view for which these windows were installed.
A home office by an east-facing window without appropriate glazing means glare on the monitor from May to September.
Loft spaces with roof windows represent a separate category of thermal challenge. Warm air rises upward, and the sun shines through roof windows for most of the day. Temperature differences between ground floor and loft can reach 5-8 degrees, making summer use of the loft highly uncomfortable.
Modern selective glass vs. former tinted glass
The belief that solar control glass means dark windows derives from the 1990s, when the only solution was mass-tinted glass. Brown, grey, green panes genuinely darkened rooms and transformed the elevation into a mirror.
Contemporary selective glass with advanced coatings has a neutral, almost invisible tint. You look through them and see the world in natural colours. They transmit as much light as good standard windows whilst effectively protecting against excessive heating.
Acoustic glazing – Rw sound insulation for a peaceful home
Why acoustic insulation matters for health
The World Health Organisation classifies prolonged exposure to noise above 55 decibels as a serious health risk factor. Noise is a documented factor causing hypertension, sleep disorders, chronic stress, and concentration problems.
The Rw coefficient is a measure of acoustic insulation expressed in decibels. Every 10 dB reduction represents a subjective perception that noise has halved. The difference between Rw=32 dB and Rw=42 dB is the difference between hearing every car and silence allowing peaceful sleep.
A standard window has approximately Rw 32 decibels – sufficient for a quiet estate with local traffic. Rw 40-42 dB ensures comfort on typical urban streets. Rw 45-48 dB provides protection on busy arterial roads. Rw above 50 dB is reserved for extreme situations – proximity to motorways, airports, railway lines.
Construction of acoustic packages – asymmetry and laminate
A standard triple-glazed unit with three identical panes can have the same Rw as a double-glazed unit. Three identical panes resonate at the same frequencies, not dampening each other – sound waves pass through all panes equally.
The key to effective acoustic insulation is asymmetry. Panes of different thicknesses resonate at different frequencies. A 6mm pane responds to different frequencies than a 4mm pane. In an asymmetric package, each pane dampens frequencies where the other is weak.
Laminated glass introduces another element – PVB film acting as a vibration damper. A sound wave passing through laminate loses energy in the elastic layer between panes. Specialist films with a dampening core are designed to absorb vibrations across a broad frequency spectrum, with particular emphasis on the 100-300 Hz range – frequencies of lorry rumble, bass music, trams. These are sounds that ordinary windows transmit most easily.
For a typical urban street, a package with asymmetry and laminate achieving Rw 40-42 dB suffices. Rw above 50 dB makes sense when windows face directly onto a motorway, railway tracks, or are located in an airport flight path.
Safety glazing – burglar protection and injury prevention
Laminated glass – burglar protection classes P1A-P4A
Laminated glass consists of two or more panes bonded by PVB film layers. After breaking, the glass remains in the frame – the film holds everything together. A burglar may break the first pane, may break the second, but everywhere encounters a barrier whose penetration requires numerous blows generating noise and consuming time.
Class P1A and P2A provide basic protection sufficient for most detached houses. They safeguard against opportunistic burglary – when the burglar came unprepared and becomes discouraged after initial attempts. Class P3A and P4A offer enhanced protection for houses in remote locations or offices with valuable equipment. They withstand multiple deliberate axe strikes.
A significant additional benefit: the same film protecting against burglary dampens sound. A package with P2A laminate automatically has 3-5 dB better acoustic insulation compared to a package without laminate.
Tempered glass – safety during breakage
Tempering involves heating glass to over 600 degrees Celsius and rapid cooling with compressed air. This process “freezes” stresses in the glass structure, making it five times stronger. Upon breaking – and everything eventually breaks with a sufficiently strong impact – it disintegrates into thousands of small, blunt pieces the size of rice grains.
Tempering doesn’t protect against burglary – it protects against injury. Ordinary glass creates sharp fragments that can cause deep cuts. Tempered glass produces small pebbles that at most startle.
Tempering is mandatory in certain applications: large glass formats exceeding two and a half metres in height (exposed to internal stresses), solar control glass absorbing significant energy (heating to high temperatures), any glass partially in sun and partially in shade (temperature differences reaching 40-60 degrees between sections).
Specialist glazing – advanced technologies for demanding projects
Smart glass PRIVA-LITE – privacy on demand
Glass that changes from transparent to milky-matt with a single click. Liquid crystal technology enclosed between glass panes – without electricity, crystals are disordered, light scatters, glass is matt. Upon switching on electricity, crystals align, light passes freely, glass becomes transparent. The change occurs instantly.
Applications: partition walls in apartments, master bathrooms connecting to bedrooms, home offices requiring discretion during video conferences, conference rooms in offices. In matt mode, the glass transmits light whilst ensuring privacy without darkening the room.
Heated glass EGLAS – heating integrated into the window
An invisible current-conducting coating integrated into the glazing unit transforms the glass into a flat heater. This solves the problem of cold draughts with large HST sliding doors – where there’s no space for traditional radiators and underfloor channels spoil aesthetics.
Power adjustable according to needs: low level (50-100 W/m²) eliminates condensation – end of steamed-up bathroom windows. Medium level removes cold draughts at glazing. High level replaces traditional radiators. Highest power (350-600 W/m²) melts snow on roof windows – without climbing onto the roof in winter.
Self-cleaning glass BIOCLEAN – reduced risk of cleaning at height
Two coatings working in tandem: photocatalytic activated by UV rays breaks down organic dirt at molecular level; hydrophilic changes water behaviour on glass – instead of droplets leaving streaks, water flows as a uniform sheet carrying away decomposed dirt.
Real benefits: standard windows require cleaning 4-6 times yearly; self-cleaning – once or twice for removing mineral deposits. For upper-floor windows, this eliminates dangerous cleaning at height. Limitation: glass must have direct rain contact – doesn’t work under canopies or balconies.
Inter-pane blinds – maintenance-free solar protection
Aluminium slats hermetically sealed inside the glazing unit. Completely isolated from dust and dirt, magnetic or electric control.
Closed slats block 92% of solar energy (g=0.08) – effectiveness unattainable for the best static solar control glass. Open, they give g at level 0.27. For allergy sufferers, elimination of a dust accumulation source; for minimalists – aesthetics without compromise.
Requires wider packages (48-54mm thickness), meaning deeper window profiles. Contemporary premium systems accommodate such packages without difficulty.
Anti-reflective glass VISION-LITE – view without mirror effect
In the evening with lights on in the living room, the window acts as a mirror – instead of a garden view, you see interior reflection. Anti-reflective coating reduces reflections from 8% to below 1%. Effect: in the evening, you see garden, city, stars – not your own interior. For houses with panoramic views, a way to maximise what you paid for when purchasing the plot.
Selecting glass packages according to window orientation
North-facing windows – maximum light and heat gains
North-facing windows never receive direct sunlight – they receive only diffused skylight. Maximising this limited light is crucial: triple-glazed unit with Lt transmittance 75-77% and high g-value 0.55-0.60. Capture every ray, every calorie of heat. These are windows that will never have an overheating problem.
East-facing windows – morning sun and parameter balance
Morning sun – low, intense – provides natural waking in summer, bright kitchen at breakfast. It’s also blinding glare on the monitor when working from early morning and waking at five in June in a bedroom without appropriate protection.
East-facing windows need balance: high light transmittance (most of the day lacks direct sun), moderate g-value (protection against July morning sun). Universal package with Lt 75% and g 0.50-0.55 is the golden mean.
South-facing windows – maximum selectivity
South is the most demanding orientation. In winter, low-hanging sun entering through south-facing windows provides free heating for several hours daily. In summer, high sun shines for shorter periods but with great intensity.
The key is selectivity: glass admitting light (dark living room is a year-round problem) whilst effectively blocking excess summer heat. g-value 0.30-0.37 at light transmittance 65-70%.
West-facing windows – most intensive sun exposure
Afternoon sun from the west – low, shining at an acute angle – represents the most challenging conditions for thermal comfort. It penetrates deep into the interior and heats rooms for several hours.
West requires packages with low g – 0.28-0.33. Some brightness can be sacrificed for protection, as western rooms have light for half the day. A western living room without good solar protection becomes a space where comfortable afternoon presence is impossible in summer.
Special requirements – noise and security
A busy street enforces acoustics as priority. Package with asymmetry, laminate, and acoustic film delivering Rw 42-48 dB transforms street noise into distant background.
Ground floor facing street or car park represents burglary risk. Laminate class P2A or P3A provides discreet protection whilst simultaneously improving acoustics.
Bathroom with window condensation resolves with heated glass at 50-100 W/m². Warm glass prevents steam condensation.
What to consider when choosing glazing
Glazing selection is a fundamental decision for living comfort over three decades. It’s the difference between a house where you live comfortably and a house with problems – darkness in winter, overheating in summer, noise every night.
There’s no universal “best” package. There’s a package matched to the specific house – considering each window’s orientation, local noise sources, priorities between brightness and insulation. A north-facing house needs maximum light and high solar gains. A south-west living room needs solar protection. A bedroom facing a busy road needs silence.
