What you need to know about windows before you buy?

Purchase windows This is not shopping on Allegro, where at most you order the wrong colour of sweatshirt and send it back. Here we are talking about a decision that will stay with you for the next 20-30 years. A window is not only glass in a hole. This warmth, silence, safety and aesthetics, and if something goes wrong - that's also stress, fungus on the wall and a draught in the living room. So before you click "order", read this guide to the end, and then you can confidently call us - at GM PLAST we know what it's all about 😎.

1. Not every window it's window. The type of profile matters

When choosing windows, most people are guided by whether 'pretty' and 'whether the colour matches the roof'. And the truth is what is most important sits inside. We are talking about the profile, i.e. the plastic 'skeleton' of the window. It is responsible for:

• thermal insulation (will it be warm),

• sound (can you hear your neighbour mowing at 7am),

• static (whether it will not bend after 5 years),

• appearance (whether it will be thick, slim, streamlined...).

The most popular systems today are:

• Kömmerling 76 AD/MD - tops when it comes to quality and durability.

• Decco - more economical, but still robust.

• Salamander, Aluplast, Veka - also very good, depending on the version.

AD stands for rebate seal (two gaskets), and MD - centre seal (three gaskets). MD gives better insulation, more airtightness and is recommended for energy-efficient homes.
If someone is pushing AD to you as 'passive', then something stinks here

2. Glazing packages - 2 or 3? Or maybe 6?

It's well known - it's not the number of panes that counts, it's how they were made 😅
But seriously - today the standard is 3-glazed packages, i.e. 2 chambers, 3 panes of glass, noble gas (usually argon), warm spacer and low-e coatings.

What is the difference between the panes?

Why choose windows is crucial in an energy-efficient home?

Modern construction increasingly relies on comfort, economy and ecologyand not just the appearance. The house has to be not only pretty, but also warm, airtight and cheap to maintain. You can invest in state-of-the-art heating, a heat pump or photovoltaic panels - but if you via windows energy escapesthen all the effort is in vain.

It is windows are one of key elements of an energy-efficient house. It is estimated that through leaking or ill-fitting windows may even escape 20-30% total thermal energy of the building. This is a huge loss - both to the household budget and to the environment.

Therefore, choosing the right windows is not just a question of aesthetics or matching the colour to the façade. It is a decision that directly affects living comfort, heating bills and the efficiency of the entire home energy system.

At GM PLAST, we have been advising customers for years on how to choose joinery that combines elegance with excellent thermal performance. Good windows is an investment that pays for itself with every heating season - in the form of lower costs and greater comfort.

1. heat transfer coefficient (Uw) - the lower the better

If we are talking about energy-efficient windows, the first term to know is heat transfer coefficient Uw. It is this parameter that tells us, how much heat "escapes" throughout the window - i.e. through the glass, the frame and the seals. Im lower Uw value, including improved thermal insulation and less energy loss.

In practice, this means that a window with a low Uw helps to maintain a constant, pleasant room temperatureregardless of the weather. In winter, the heat stays inside, while in summer the hot air from outside does not penetrate the interior. The result? Reduced heating and air conditioning bills and greater comfort in everyday life.

🔍 Which Uw values are really good?

Different values and promises can be found on the market, but it is useful to know which figures are actually worthy of consideration:

• Standard windows - usually have a Uw within 1.2-1.4 W/m²K. This is a level that was considered very good only a few years ago.

• Energy-efficient windows - should have Uw ≤ 0.9 W/m²K.

• Passive house windows - reach values of less than 0.8 W/m²K.

You also need to be careful about "marketing" tricks. Some companies quote a value of Ug (glazing alone)and not Uw (of the whole windows)which can be confusing. Ug 0.5 sounds great, but if the frame has an inferior performance, the whole window could realistically be 1.1 - and then the energy savings are half that.

Example from GM PLAST practice

Our windows Kömmerling 88 MD in combination with glazing Planitherm achieve a ratio of Uw as low as 0.72 W/m²K - that is the passive house standard.
This is the result of a combination:

• profile with depth 88 mm,

• triple glazing package,

• warm frame spacer,

• and seals in three planes.

This ensures that the window retains excellent thermal insulationwhile maintaining an elegant appearance and high durability.

By choosing low Uw joinery, you are not only investing in a warm housebut also in real savings over many years.
In the next section we will look at a second, equally important element - the the type of application glazingwhich can do wonders for thermal and sun comfort ☀️

2. type of application glazing - the key to energy efficiency

You can even have the best window profile, but if glass is poor, the whole thing will not work. Glass is as much as 70-80% of the surface area of the entire windowsso its parameters have huge impact on how much energy we waste - or save.

In modern, energy-efficient homes ordinary glazing is a thing of the past. The following come to the fore low-emission glazingwhich keeps the heat inside in winter and protects against overheating in summer.

🔬 What is glass low-carbon?

Glass A low-emission coating is one that is covered with a special metal oxide coating (e.g. silver), invisible to the naked eye, but acting as a thermal barrier. It ensures that heat radiation is reflected back into the interior instead of "escaping" to the outside.

💎 Examples of such glazing include:

• Planitherm - classic low-E glazing, improving insulation in winter.

• Planistar SUN+ - modern glass selective, which protects against heat loss in winterand in the summer reduces heat build-up, i.e. it works in two directions.

💨 The role of noble gas and warm frame

Between the panes in the package shaft (usually 2 or 3 panes of glass) there is no 'ordinary air'. There is noble gas - usually argonwhich conducts heat more slowly than air and thus reduces heat loss by up to 20-30%.

The second element is warm distance frame - Instead of traditional aluminium, which conducts the cold, plastic or stainless steel frames are used. The result? Better insulation and no glass dew at the edges.

🌟 Example from our range: glass Planistar SUN+

• Ug = 0.5-0.6 W/m²K - i.e. excellent thermal insulation.

• Light transmittance LT = 64% - bright interiors without compromise.

• Solar factor g = 0.35 - only 35% of solar energy gets through, which means much lower risk of overheating in summer.

• Plus: elegant, slightly tinted glasswhich gives a modern look to the façade (instead of the typical 'blue' panel).

This is ideal for houses with large glazing, conservatories, living rooms with southern and western exposure - that is, wherever it gets hot in the summer hot as in a greenhouse 🔥

Thanks to glazing such as Planistar SUN+ and the use of argon and warm frame, your windows can achieve real Uw of 0.72as our models Kömmerling 88 MD - i.e. meeting standards passive house 🏠🌿

3. installation depth and number of profile chambers

Window is not only glass. Frame and leaf, the entire profile, are responsible for structural rigidity, thermal insulation, acoustics and overall durability. And one of the most important technical parameters is precisely installation depth and number of chambers in profile.

📏 Why is the 70 mm profile a relic?

Until a few years ago, 70 mm deep systems were standard. But today... it's simply not enough. 🔚

• At 70 mm, it is difficult to achieve a very low Uweven with the best glass.

• Less thickness = less space for insulation, thinner walls, poorer stability.

• Compatibility issues with modern triple glazing packages (which are thicker).

👉 In brief: this is no longer compatible with modern, energy-efficient construction. Such a profile can still be used, for example, in gazebos, cellars or garages - but not in the living room of your dream home 😉 .

 New standard: 82-88 mm

Today, depth systems are king 82 to 88 mm - they allow:

• use of wider triple-glazed packages,

• improved profile insulation,

• higher thermal insulation parameters (even Uw < 0.8!),

• greater structural stability (important for large glazings),

• and the possibility of using aluclipuor aluminium overlay for a more exclusive look.

Number of chambers - is this just a marketing ploy?

Not really! The number of chambers influences, how warm the profile itself is, although of course it is not the only factor.

• 5 chambers is the minimum these days.

• 6-7 chambers is already a premium level, where the profile itself holds heat and sound well.

• More chambers = better thermal insulationbut also greater rigidity and weight - which improves durability.

Attention: it's not just about the number ofbut also about distribution and size of these chambers - because some systems have 7 chambers only "on paper" and do not actually improve performance. This is why it matters trusted manufacturer and real tests.

✅ Our recommendations:

🔹 Kömmerling 88 MD - the absolute top in terms of energy efficiency.

• 88 mm deep, 7 chambers, triple-glazed packages up to 56 mm, aluclip possible.

• A great choice for passive houses and discerning customers.

🔹 Salamander bluEvolution 82 - An excellent compromise between quality and price.

• 82 mm, 6 chambers, excellent insulation, modern design, aluclip version available.

• Great for single-family homes and premium developments.

To sum up:
Profile depth and number of chambers really do make a difference. If you want a warm, durable and modern window - look no further than the 70s. Go for 82-88 mm, preferably with a good sealing system and a well thought-out profile.

🔧 4. Type installation - standard or warm with tapes?

You can have the most expensive, warmest and best looking windows, but if you install them poorly... 💸 then all your bill savings just fly through the cracks. Assembly is not just "putting windows into a hole" is a key element of the whole building insulation system.

🔨 Differences in practice - what does each look like?

👉 Assembly standard:

• Most common - attachment windows on polyurethane anchors/foams.

• Sealing only with installation foam - which can soak up moisture, lose volume and air vapour over time.

• OK for flats, blocks of flats, less demanding developments - but not sufficient for modern low-energy houses.

👉 Warm assembly (layering):

• Three-layer sealing:

  1. vapour-proof tape on the inside,

  2. PUR foam inside,

  3. vapour-permeable tape on the outside.

• Each layer has a function - the vapour-proof blocks moisture from inside the house and the vapour-permeable allows moisture to escape to the outside. Foam does its job on the inside - it insulates.

• Provides tightness, no draughts and no mould, as well as longer-lasting materials.

• As a result, you gain real savings on heating and cooling your home.

💡 Why warm installation increases the efficiency of the entire window?

Because. so what if you have glazing with Ug=0.5when there is a gap next to it through which frost enters in winter and hot air in summer? 😩

Warm installation:

• eliminates thermal bridges,

• protects foam from degradation,

• extends service life windows,

• prevents walls and frames from becoming damp,

• maintains high air-tightness and insulation performance over many years.

✅ Tip from us - GM PLAST:

With us warm installation is not a "luxury accessory", only standard for energy-efficient and passive houses 🏡💪

• Our installation teams are trained in sandwich assembly,

• We use professional Illbruck or Soudal tapes,

• Each window is suitably prepared for such an installation (including the rebate, shims, extensions, etc.).

Is it worth paying a few hundred extra for warm installation?
If you are thinking long term - YES, definitely worth it.
In practice, this is an expense that will pay for itself after just a few heating seasons and will keep you comfortable for years to come.

🔇 5. Sound insulation - not just warmth, but also silence

The modern energy-efficient home is not just about not letting heat escape. It is also about inside was calm, comfortable and quiet, even if for window life is in full swing.

🔍 How to choose glass and profile to cut through the noise?

Not every triple-glazed pane is a guarantee of silence. This is where appropriate glazing configurationThe different thicknesses of the glass panes and the adequate space between the panes.

Here are a few things to look out for:

• Uneven glazing thickness, e.g. 6/14/4/14/4 - disperses sound waves better than the classic 4/18/4/18/4.

• Acoustic packages - special sound attenuation films in glass (e.g. VSG with PVB film).

• Noble gas (argon or krypton) between the glass panes also does a job - it reduces the permeability of sound waves.

• Window frames with MD (centre) seal have better damping properties than ordinary AD.

• And professional installation - Here we are back to warm installation, because what good is a pane of glass if the wind whistles between the frame and the wall like in a Polish western?

❓Does a triple-glazed package always mean better?

Not quite. Standard triple glazing package (4/16/4/16/4) may be acoustically weaker than, for example, a double-glazed package with 6 mm glass and sound-absorbing film. It all depends on glass composition, frame and thickness of glazing.

It's a bit like eating - more ingredients doesn't always mean better 😅

✅ Recommendation from GM PLAST:

? Package 4/18/4/18/4 z SWISSPACER Ultimat framee - is our golden mean 
Provides very good thermal insulation and at the same time very decent acoustic performance.

➡️ And if you care about really high noise insulation, we can offer:

• Packages with laminated glass (VSG)

• Or asymmetrical glazing sets - great for flats in the centre, next to tracks, next to schools, motorways, etc.

💨 6. Ventilators - ventilation without losing heat

An energy-efficient home is not just about keeping warm, but about there was also something to breathe - literally.

Lack of adequate ventilation is:

• dampness on the windows,

• mould in the corners,

• stuffy air,

• and... health problems 👃😮‍💨

Therefore ventilators is not an "unnecessary extra" - it is a must haveif you don't have mechanical ventilation with recuperation.

❓Why should they not be forgotten?

Because tight windows are... all too tight 😅

In modern, well-sealed windows natural airflow is virtually non-existent. Even if sometimes something 'blows over', it is neither healthy nor controlled. Ventilators allow:

• control of fresh air supply,

• prevent condensation,

• provide ventilation in accordance with building standards.

📈 When is it worth investing in ventilators hygroregulated?

If you want to:

• ventilation operated automatically - without your participation,

• air supply adapts to humidity levels in a room (e.g. more in the bathroom, less in the bedroom),

• avoid heat lossbecause the vents only work when needed.

It is ventilators hygroregulated (e.g. Aereco or another proven manufacturer) are then the best choice

Our solutions at GM PLAST:

📌 We assemble ventilators with up to 42 dB attenuation, which:

• They work well in houses next to busy streets,

• provide fresh air without having to open the windows in winter (i.e.: zero heat loss),

• may be either pressureas well as hygroregulateddepending on the client's needs.

🎨 7. Aesthetics and functionality - energy efficiency need not be boring

We often hear: "if something is energy efficient, it probably looks like it's from the communist era...".
That's right: NO! Times have changed. Now you can have designer windowswhich at the same time retain heat, let the light in, a do not heat up like an oven 🌞❌🔥

✨ Windows with aluclips - modern design and durability

What is this "aluclip"? It's aluminium cap for PVC profile, which:

• gives the window minimalist, industrial designas from the architecture catalogues 🏙️

• increases immunity weather conditions, e.g. sun, rain, snow

• allows for painting in any RAL colouror even an anodised or woodgrain finish

 Veneer colours and the effect on space heating

When choosing a window colour, it is important to think not only about appearance, but also about... temperature ☀️🌡️

• Dark colours (anthracite, black) heat up more, so with the wrong glass this can result in overheating in the summer.

• Bright colours (white, grey, cream) reflect more light - so they work better in sunny living rooms, for example.

• Our solution? Planistar SUN+ + suitable veneer = style + thermal comfort 😎

Note: we also have special veneers with technology acrylic colourswhich they heat up lessdespite its dark colour!

Selection handles and accessories - external blinds, mosquito nets

Your window can be beautiful and practical:

• Handlesclassic, with push button, with key (ideal for children's rooms or ground floor)

• Mosquito netwithout it in summer! We install frame versions, roller shutters, sliding versions - whatever you want

• External blindsThey protect against sun, cold, noise and... thieves 😉 - we can integrate them into the window already at the production stage

8 Certifications and standards - how to know a good one window?

Good window is not only "nice" and "warm", but also tested, certified and compliant. In the world of energy efficiency, it is papers do the job. Why? Because they let the customer know that they are not buying a cat in a bag, but a product that has been tested by independent research institutes.

✅ What do the CE, ETA, IFT Rosenheim designations mean?

• CE - a sign that the product meets the minimum requirements of the European Union. But be warned: it's a bit like "approved for circulation" - doesn't yet mean it's great 😉 .

• ETA (European Technical Approval) - is already a tangible document certifying that a product is suitable for use in construction in the EU. Often required for large investments.

• IFT Rosenheim - it's like Harvard in the world of windows 😄 A German institute that tests products for tightness, wind resistance, water resistance, thermal and acoustic insulation. IFT-certified window = top quality.

🏠 Is "passive" window is it a marketing ploy?

Unfortunately, this is increasingly the case. Some companies are calling 'passive' windows that have Uw = 1.1... And this is nowhere near true passive construction 😒

A genuine passive window should meet stringent standards, including:

• Uw ≤ 0.8 W/m²K (preferably 0.72-0.75)

• Psi coefficient of less than 0.04

• tests carried out by the IFT or Passivhaus Institut

GM PLAST - certified quality, not marketing

With us, there is no rubbish. Our top systems, such as:

• Kömmerling 88 MD

• Salamander bluEvolution 82

• Reynaers Masterline 8 (aluminium)

...meet Passive house standards, which are accepted in countries such as:

• Germany - the most demanding window market in Europe

• France - specific standards RT2012 and RE2020

• Belgium and the Netherlands - stringent thermal insulation regulations

We work with manufacturers who supply complete technical reports, tests and certificates - not just "advertising brochures" 😉

Summary:

👉 Certificates are not just paper. It's guaranteethat your window:

• really protects against heat loss

• stands the test of time and extreme weather

• will be accepted on every construction projectincluding abroad

By choosing GM PLAST, you are choosing windows with papers - and not just with promises

🤝 9. With whom is it best to order such windows? - it's not just the price that counts

The choice of manufacturer and installation company is last but crucial step on the way to a warm and comfortable home. And although many builders look mainly at price, it is the experience and quality of workmanship have the greatest impact on the end result.

🚫 How do you avoid a sham and not overpay?

Unfortunately, there is no shortage of 'magicians' in this industry:

• who assemble cheaply from low-cost components,

• will not provide any coefficients,

• and a team will come to install it with a drill from the market and glue "by eye" 😬.

The result? Steaming windows, blowouts, sashes that do not close and complaints that nobody wants to accept. And all this at a "super bargain" price.

👀 What to look out for?

Before you place an order, check the company for:

• Experiences - How many years has it been operating in the market? How many implementations has it had?

• Warranty and service - Does it offer a written guarantee? Can you count on service?

• References and opinions - what do other customers say? What does the installation look like in practice?

• Quality of assembly - Do they do warm installation? Do they know the standards and techniques?

• Quality of components - do they use branded profiles, glass and fittings?

🏢 GM Plast - 25 years of experience, hundreds of implementations, zero incidents

We are a company with more than 25 years of history. Our windows go not only to customers in Poland, but also to France, Belgium, the Netherlands, Germany and Scandinavia. This obliges - because there is no room for half-measures there.

✔️ We produce on the best systems: Kömmerling, Salamander, Reynaers, Aliplast
✔️ We provide professional installation - from the dismantling of old windows to the finishing touches
✔️ We advise, design, deliver and service - or from A to Z
✔️ We have our own production facility - we are not an intermediary
✔️ We give a full guarantee on products and installation

With us, the customer is not an order number - only a partner in building a better home.

💡 Summary:

When choosing a company to manufacture and install windows:

• Don't just look at the price - look at experience and quality

• Check feedback, guarantees, references and customer approach

• Bet on those who have been doing it for years and with passion