Window Replacement: How to Choose Frames, Glazing and Installation Without Overpaying

Windows are the weakest point of an apartment's thermal envelope. Old wooden frames or poorly installed plastic windows lose a lot of heat in winter, cause drafts, and lead to condensation and mold on the reveals. Quality windows cut heating bills, keep out street noise and add to a home's value. But even the most expensive frame won't perform if it's installed incorrectly. Here's what to look for.

When Windows Should Be Replaced

• old wooden frames have dried out and drafts come through gaps;
• plastic windows fog up inside the glazing unit;
• condensation and mold regularly appear on the glass and reveals;
• the hardware doesn't work and the sashes have sagged;
• windows were damaged by a blast — in that case you may be eligible for compensation through eRecovery (see compensation for damaged and destroyed housing);
• street noise keeps you awake.

Sometimes adjusting the hardware and replacing seals is enough — and many times cheaper. Have a technician diagnose the windows before replacing everything.

Frame Material

PVC

The most common option: affordable, good thermal insulation and easy care. What to look for:

• number of chambers — 5–7 chambers insulate better than 3;
• frame depth — 70–80 mm or more for living spaces;
• reinforcement — a steel profile inside provides rigidity, especially for large sashes;
• wall class — thicker external walls are stronger and more durable.

Aluminum

Thermally broken aluminum suits large panoramic windows and modern architecture: it's strong and allows slim frames. Non-insulated aluminum is only for unheated balconies.

Wood

Wooden "Euro-windows" are eco-friendly and beautiful and let the house "breathe", but cost more and need regular care. Choose laminated timber with a quality finish.

The Glazing Unit Matters Most

The glazing unit makes up 70–80% of a window's area, so it has the biggest effect on heat loss.

• Single-chamber (two panes) — for unheated balconies and mild climates.
• Double-chamber (three panes) — the standard for homes in the Ukrainian climate.
• Low-emissivity (low-e) glass reflects heat radiation back into the room — a significant improvement without increasing thickness.
• Argon-filled chambers reduce heat transfer.
• A warm-edge spacer instead of aluminum reduces cold edges on the glazing unit.
• Multifunctional glass keeps heat in winter and reflects solar heat in summer — useful for south-facing windows.

The key indicator is the window's thermal resistance (or its inverse, the U-value). Minimum insulation requirements for the building envelope are set by building codes on thermal insulation and energy efficiency, and general policy by the Law on Energy Efficiency of Buildings. The ENERGY STAR program lists sealing drafts and insulating among the most effective energy-saving measures.

Hardware

• tilt-and-turn mechanism — the standard for living rooms;
• micro-ventilation — slot ventilation without drafts;
• burglar-resistant hardware for ground and top floors;
• a child lock on the handle;
• quality seals on two contours.

Ventilation: Don't Forget Supply Air

Old wooden windows "ventilated" the apartment through gaps. Airtight modern windows stop this, and without an alternative, humidity rises and condensation and mold appear. Solutions:

• trickle vents in the window frame or wall;
• regular airing and micro-ventilation mode;
• mechanical ventilation with heat recovery.

The causes of damp and how to control it are in mold and damp prevention.

Installation: 50% of the Result

Even a perfect window loses its properties through poor installation. A correct installation joint has three layers:

1. Inner vapor barrier — tape that keeps room moisture out of the foam.
2. Central insulating layer — expanding foam that fills the gap without voids.
3. Outer vapor-permeable waterproof layer — tape that protects the foam from rain and UV while letting moisture escape outward.

Without a vapor barrier the foam absorbs moisture, freezes and breaks down within a few years, and mold appears on the reveals.

Other requirements:

• the window is installed level and within the insulation zone or closer to the warm side of the wall;
• fixing with anchors or mounting plates at the correct spacing;
• an external sill sloping away from the building;
• an internal sill with a slight slope into the room and enough gap from the radiator for warm air to circulate.

Reveals and Window Sills

• Reveals — plaster, plasterboard or sandwich panels. They should be insulated underneath to avoid cold spots.
• Window sills — PVC, wood or stone. The overhang above the radiator mustn't block the flow of warm air.

Shatter Protection and Safety

In explosions, most injuries are caused by flying glass. Protection options:

• laminated glass — holds together on its film when broken;
• tempered glass — breaks into small blunt fragments;
• protective film on existing glass — a budget solution;
• the two-walls rule — during an air raid alert stay away from windows.

Soundproofing

The World Health Organization's environmental noise guidelines link long-term exposure to traffic noise with sleep disturbance and other health risks. For windows facing a noisy street:

• glazing units with panes of different thickness (for example, 4–16–6 mm) dampen resonance;
• laminated glass with an acoustic interlayer;
• tight-fitting sashes and quality installation.

Balconies and Loggias

Cold glazing protects from rain and dust but doesn't insulate. Warm glazing turns a balcony into part of the living space. Remember that glazing changes the building's facade, and moving radiators onto a balcony is prohibited. More in apartment redevelopment.

When to Replace Windows

The best season is April to October: foam cures better and the apartment doesn't get chilled. Winter installation is possible with winter-grade foam, but choose milder days. During a major renovation, windows are replaced before plastering — see the sequence in our apartment renovation guide.

How to Choose an Installer

• the company has its own production or is an official dealer of the profile system;
• measurements are taken by a technician, not a sales manager;
• the contract states the profile, glazing unit, hardware, type of installation joint, timeline and warranty for products and installation;
• payment is staged;
• you can see completed projects.

Your rights as a consumer are protected by the Law on Consumer Rights Protection. More on choosing contractors in how to choose a renovation contractor.

How to Care for Your Windows

Modern windows need little attention, but a few simple steps extend their life:

• lubricate the hardware once a year with a special lubricant or acid-free machine oil;
• clean the seals twice a year and treat them with a silicone product so the rubber doesn't crack;
• check the drainage holes at the bottom of the frame — if blocked, water collects in the profile;
• switch the hardware between winter and summer modes — tighter pressure in winter, looser in summer, reducing seal wear;
• adjust the sashes if they start catching on the frame — it takes a few minutes with a hex key;
• clean the frames with mild non-abrasive, solvent-free products.

Will New Windows Pay Off?

Payback depends on the condition of the old windows, tariffs and glazed area. If you replace drafty wooden frames with energy-efficient glazing properly installed, the heating savings and extra comfort are noticeable from the first winter. If you're replacing relatively new plastic windows with slightly better ones, payback will be long — sometimes it's better to adjust the hardware and replace seals. To measure the effect, compare heat or gas meter readings for similar months before and after, adjusting for weather.

Don't forget the non-financial benefits: no drafts or condensation, quiet, dust protection and a higher apartment value when selling.

Common Mistakes

• saving on the glazing unit while buying an expensive frame;
• "foam-only" installation without vapor barrier tapes;
• no supply ventilation after replacement;
• a wide sill that blocks the radiator;
• oversized fixed windows that can't be cleaned from outside;
• replacing windows after plastering and painting.

Frequently Asked Questions

How long do plastic windows last? A quality profile lasts several decades. Hardware and seals need servicing: lubricate and adjust once a year.

Can I replace just the glazing unit? Yes, if the frame is in good condition. It's cheaper and improves insulation.

Why do windows "sweat" in winter? Condensation on the inner pane means high indoor humidity and insufficient ventilation, while condensation at the edges points to a cold spacer or poor installation. Air the room, use micro-ventilation and don't cover the radiator with a wide sill.

Do I need a permit to replace windows? Replacing windows within an apartment without changing the openings doesn't require permits. But changing the facade's appearance, especially in historic buildings, may require approvals.

Is there state support? OSBBs can use Energy Efficiency Fund programs that reimburse part of the cost of thermal modernization, including windows in common areas.

Conclusion

A good window combines an energy-efficient glazing unit, a quality frame, reliable hardware and correct three-layer installation with planned ventilation. Don't skimp on glazing and installation, and insist on a detailed contract and warranty. And remember: new windows work best together with wall insulation.

Sources

• Law of Ukraine on Energy Efficiency of Buildings.
• ENERGY STAR: seal and insulate.
• WHO: Environmental noise guidelines.
• EU Energy Performance of Buildings Directive.
• Energy Efficiency Fund of Ukraine.
• Law of Ukraine on Consumer Rights Protection.

Read Also

• Apartment insulation inside and out
• Mold and damp prevention
• Compensation for damaged and destroyed housing
• Apartment renovation guide