Tips for insulating small-family apartments with PVC windows

Why insulation matters in a small-family apartment

A small-family apartment (compact flat) often has limited space and old partitions. Even with PVC windows, heat can escape through gaps, installation joints and window slopes. Proper insulation reduces heating bills, increases comfort and lowers the risk of condensation and mold.

Basic principles

• Start by identifying heat leaks: window-frame joints, seals, and gaps between the frame and the wall.
• Combine external and internal measures: exterior sealing, correct slope installation and interior elements such as curtains and blinds.
• Ensure controlled ventilation: airtightness should not lead to stagnant humid air.

What PVC windows give and where they are vulnerable

PVC windows retain heat well when properly installed and fitted with quality seals. Problems usually arise not from the PVC itself but from:

• incorrect installation (thermal bridges in the mounting foam);
• worn seals;
• poorly finished slopes and joints;
• thin insulating glass units without low-emissivity coating.

Check the IGU and seals

• If the glass unit is single- or low-performance double-glazed without Low-E, consider replacing it or adding an energy-saving film.
• Worn seals should be replaced with new rubber or silicone gaskets.

Step-by-step insulation guide for a compact flat

1. Inspection

• Inspect windows in cold weather: move a lit candle or lighter (carefully) near joints — the flame will flicker where drafts exist.
• Check frame-to-wall joints for cracks, crumbling foam or visible gaps.

2. Sealing and adjustment

• Adjust sashes so the pressure is even and the seals meet uniformly.
• Replace seals and lubricate hardware with silicone grease.

3. Insulating the installation gap

• Remove damaged foam and fill with high-quality mounting foam, leaving space for a vapor barrier.
• From the outside, finish the gap with a waterproof and windproof profile.

4. Slopes and trim

• Insulate internal slopes with foam boards (e.g., extruded polystyrene) or mineral wool, covered with a vapor barrier and finished.
• For exterior slopes, seal with elastic caulk and, if possible, add façade-level insulation around the opening.

Fabric and blind solutions for extra insulation

• Thermal curtains with a lining significantly reduce heat loss at night.
• Roller or Roman blinds with a dense backing work well in small rooms.
• Vertical blinds are less effective for insulation; combine them with dense curtains for better results.

Tip: keep curtains slightly above the radiator (if present) to create a thermal barrier and improve circulation.

Ventilation: don’t suffocate the apartment

High airtightness increases condensation risk. Install supply air vents or use micro-ventilation modes on the windows. Monitor humidity — the ideal range is 40–60%.

DIY or hire a professional?

• Small tasks (seal replacement, curtains, joint sealing) can be handled by a competent DIYer.
• Window installation, IGU replacement, or exterior insulation should be performed by professionals to avoid errors in the installation seam.

Typical workflow and budget

• Inspection and adjustment — 0–1 day, minimal costs.
• Seal replacement and joint sealing — 1 day, moderate costs.
• IGU replacement / installation works — several days, cost depends on dimensions and materials.

FAQ — common questions

How to tell if the issue is not the glass unit?

If you feel drafts near the frame edges or see gaps around the frame, the issue is likely seals or installation rather than the glass itself.

Can insulation be solved only by curtains?

Curtains help, but they do not replace proper sealing and slope insulation.

How effective is replacing seals?

Well-chosen seals can restore 30–40% of performance in reducing drafts around a window.

What matters more — the IGU or the installation?

Installation matters most: even the best IGU won’t perform if mounted poorly.

Conclusion

Insulating a compact apartment with PVC windows requires a mix of targeted fixes and systemic measures: sealing installation gaps, replacing worn seals, insulating slopes and using thermal window treatments. Start with a diagnosis and simple fixes; leave complex jobs to professionals for reliable results.