Ffenestri DERWEN Windows offer a 10 year guarantee on all products.

1. Ffenestri DERWEN Windows guarantee to repair or replace free of charge (both labour and materials), any unit which develops a fault due to defective materials or construction.
2. The guarantee includes the fault of condensation between the glass in sealed units. Any cracked glass not reported within 7 days will be charged.
3. The guarantee does not apply to minor imperfections in glass.
4. The guarantee does not extend to damage or faults due to accident, misuse or neglect.
5. The guarantee is given in addition to and not in substitution for all the customer rights under construction law and by statute.