One winter morning, the panoramic window in my apartment cracked. No warning, no impact, just a loud crack. The repair cost 27,000 CZK, but thanks to property insurance costing 5,000 CZK a year I did not pay a single crown extra. Here is the whole story and what I learned from it.
What happened
I live in a new building in Beroun, third floor, apartment facing south. I have large floor-to-ceiling panoramic windows. They look great, but as I found out, they come with risks.
One winter day I was sitting in the kitchen and heard a loud crack from the window. When I came closer, I saw a fracture running across the entire pane. Nobody had hit the window, nobody had thrown a snowball at it. It simply cracked on its own.
The diagnosis: thermal shock of glass
Since the apartment was still under warranty, I contacted the developer. The window manufacturer came, took the window apart, carried out a thorough assessment and delivered the verdict: thermal shock (a thermal stress crack).
What is thermal shock
Thermal shock happens when one part of the glass heats up much faster than another. The glass expands unevenly, internal stress builds up and leads to a crack. Typically:
- the sun heats part of the window while the edge stays cooler in the frame,
- the crack starts perpendicular to the edge of the glass,
- it happens most often in winter: frost outside, heating inside, plus direct sunlight.
How much can glass take? Approximate resistance to a local temperature difference according to glass manufacturers (NášDům.eu):
| Glass type | Withstands a temperature difference of |
|---|---|
| Standard float glass (most windows) | approx. 40 °C |
| Heat-strengthened glass | approx. 100 °C |
| Tempered (toughened) glass | up to 200 °C |
A sunlit pane can meanwhile heat up to 70 °C while the edge in the frame stays cold. Standard glass then does not need much. My apartment faces south and the sun shines on the windows from morning to evening. In winter, the difference between the sunlit area and the edge of the glass is huge. Perfect conditions for thermal shock.
Is thermal shock a warranty defect?
No. And that is the unpleasant news. The manufacturer explained to me that thermal shock is not a manufacturing or installation defect, it is a consequence of natural conditions. The warranty does not cover it.
I admit I did not believe it at first. I kept thinking: what if the window cracked because of poor installation? What if it is just an excuse?
The way out: a lawyer, or the insurance company?
I turned to a lawyer. He told me honestly:
A court case and an independent expert opinion can drag on for months. Try the insurance company first. If you have property insurance, thermal shock of glass should be covered.
And that was the turning point.
Apartment insurance: the best investment I ever made
Luckily I had apartment insurance in place. It cost me 5,000 CZK a year. I reported the claim and provided photos, the manufacturer's assessment and the repair invoice.
The result:
| Item | Amount |
|---|---|
| Window replacement | 27,000 CZK |
| Annual premium | 5,000 CZK |
| Claim payout | within 7 to 10 days |
| Deductible, disputes, courts | none |
The insurance cost me 5 times less than the repair itself. And that was just one claim in one year.
How much apartment insurance costs in 2026
Friends have been asking me one thing ever since: how much does it cost? Approximate prices based on data from the comparison sites Top-Pojištění.cz and Skrblík.cz (August 2026):
| What you insure | Example situation | Approximate price per year |
|---|---|---|
| Property insurance (the structure incl. windows) | 3+kk apartment in Prague, insured sum 5 million CZK | 3,500 to 6,000 CZK |
| Property insurance (the structure incl. windows) | apartment outside the big cities, insured sum 4 million CZK | approx. 3,500 CZK |
| Household insurance (contents) | contents worth 500,000 CZK | from approx. 520 CZK |
| "All risk" glass add-on | payout limit 100,000 to 500,000 CZK | tens to hundreds of CZK extra |
An important distinction: windows are part of the structure, so they are covered by property insurance, not household insurance. An all-risk glass add-on then covers sudden and unforeseen breakage from any cause, including thermal shock. The usual deductible is 1,000 or 5,000 CZK and assistance is often included: a glazier's visit and work up to 5,000 to 10,000 CZK (overview at RIXO.cz).
How insurers approach cracked glass
An approximate overview as of August 2026. Conditions change, so what always decides is the policy and the terms of the specific product tier:
| Insurer | How they typically handle glass |
|---|---|
| Generali Česká | glass surfaces (windows, doors, mirrors) covered within property insurance packages |
| ČSOB Pojišťovna | scope depends on the tier, the higher tier also includes a glass ceramic hob, assistance up to 7,000 CZK |
| Kooperativa | glass breakage is arranged as an add-on to household or property insurance |
| Allianz | coverage grows with the package tier, check glass coverage in the higher tiers |
When signing, ask explicitly for the wording "glass breakage from any cause". Only then can you be sure that spontaneous cracking with nobody at fault, which is exactly what thermal shock is, is covered too.
How much replacing a cracked window costs
To make clear what money is at stake, approximate glazier prices (ASOK price list, 2026):
| Item | Approximate price |
|---|---|
| Insulated triple glazing (material) | 1,500 to 1,800 CZK/m² |
| Glazier's work | 480 to 840 CZK/hr |
| Measurement | approx. 240 CZK |
| Glass replacement in a standard window | 2,000 to 6,000 CZK |
| Panoramic and large-format glass | 20,000 to 40,000 CZK and more |
My window came to 27,000 CZK. With larger formats or special glass (tempered, solar control) the bill can be even higher. The annual premium for the whole apartment is a fraction of that.
What you should know if you have panoramic windows
Who is most at risk of thermal shock
- apartments facing south and west,
- panoramic windows (a large glass area means larger temperature differences),
- higher floors (less shading from surrounding buildings and trees),
- windows with dark blinds or films (they increase heat absorption).
How to reduce the risk
- Do not stick dark or reflective films on windows without consulting the manufacturer.
- Do not block part of a window with furniture right against the glass, it creates a thermal shadow.
- Consider tempered or heat-treated glass, it is more resistant to temperature differences.
- And above all: have insurance.
What to ask when arranging apartment insurance
From my experience, three things are worth checking before you sign:
- Is glass insured separately, or within the property insurance? With some insurers, glass breakage is a separate add-on.
- Does the policy also cover "spontaneous" cracking, i.e. thermal shock? Some contracts only cover mechanical damage.
- What is the deductible and the payout limit for glazing? A panoramic window can cost more than the limit.
If you are buying an apartment with large windows, add insurance to your monthly costs from day one. In my case it paid for itself five times over in the first year.
