Prague Apartment Window Adjustment: Winter Mode, Draught Fixes & Cam Settings | TUTEL

A window that lets in cold air around the frame isn't a failing seal — in most cases it's simply a cam (čep) that hasn't been rotated to the winter position. This is a free fix that most tenants and owners don't know exists.

Modern tilt-and-turn windows (plastová okna) have hardware that can increase or decrease closing pressure. Here's how to do it correctly — and the one mistake that destroys the gearbox.

01 -- Start with the Diagnosis

Step 1: The Paper Test

Before touching any hardware, confirm where the leak is.

What you need: A single sheet of paper. Nothing else.

How to do it: Close the window. Try to pull the paper out from between the frame and the seal at four positions: the hinge side, the lock side, the top, and the bottom.

Interpreting the result: If the paper slides out easily anywhere, the closing pressure is insufficient at that point. That is exactly where cold air is entering. Note the position — it tells you which cam to adjust.

02 -- Find and Turn the Cams

Step 2: Locating the Cams (Čepy)

This is where the actual adjustment happens.

Where they are: The cams (čepy) are the small oval or teardrop-shaped metal pieces embedded along the outer edge of the window sash — the moving part. A standard window has 4–6 of them.

Summer vs. Winter position: Each cam has a small slot (like a flathead screw). When the slot is horizontal, the cam is in 'summer mode' — lower pressure. When the slot is vertical (pointing inward toward the room), the cam is in 'winter mode' — maximum pressure.

How to rotate: Use a flathead screwdriver or a euro-key (imbusový klíč). Turn the cam 90° so the thickest part faces the interior seal. The Guardian Secret: the offset principle. The cam is not perfectly round — its thickest side, when rotated toward the interior rubber seal, pushes the sash harder against the frame, compressing the gasket and eliminating the draft.

03 -- The Limit You Must Not Cross

Step 3: The Over-Tightening Risk

Knowing when to stop is as important as knowing how to start.

What over-tightening does: If you rotate all cams past the vertical position toward the 'extra-tight' mark (some hardware has a third position), you can increase frame stress beyond the design tolerance.

The gearbox (převodovka): ⚠ Risk. If you force the window closed when the cams are over-tightened, the internal gearbox — the multi-point locking mechanism — can snap. Replacement costs 2,000–5,000 CZK per window and requires a specialist.

The right limit: The vertical position (winter mode) is sufficient for 95% of Prague apartments. If the window still drafts after full winter adjustment, the problem is the rubber seal gasket itself — which requires replacement, not further cam tightening.

⚠ RISK: When Adjustment Isn't the Answer

If your windows are single-glazed, have visibly cracked or brittle rubber seals, or were manufactured before 2000, no amount of cam adjustment will stop heat loss. The seals need replacement. Forcing adjustment on a degraded window can damage the frame and accelerate seal failure.

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Still Getting Drafts After Adjustment?

A draft after correct winter-mode adjustment usually points to failed rubber seals or frame distortion. TUTEL can assess whether your windows need seal replacement or realignment.

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