Facts
The [B.] spouses rented an apartment in Geneva, of which Compagnie d'assurances X. is the owner. The initial rent was increased three times, due in particular to the rise in the mortgage rate. The tenants accepted the first two increases, but contested the third. The Rental Tribunal of the canton of Geneva approved this third rent increase, a decision confirmed by the Appeal Chamber in rental matters. The defendants appealed to the Federal Tribunal, arguing that the previous decreases in the mortgage rate had not been passed on to their rent.
The parties involved are the [B.] spouses (tenants) and Compagnie d'assurances X. (landlord). The key dates are June 9, 1989, December 8, 1989, and December 7, 1990, the dates on which the rent increases were notified. The main issue is whether previous changes in the mortgage rate should be taken into account when examining a rent increase based on an increase in this rate.
Considerations
The Federal Tribunal examined the provisions of art. 13 al. 4 RRBPO and art. 9 al. 2bis OSL, which provide that previous changes in the mortgage rate must be taken into account when examining a rent increase based on a change in this rate. The question is how far back in the past it is appropriate to examine these changes.
The Federal Tribunal considered that the most appropriate solution is to only go back to the last modification of the rent following a change in the mortgage rate. This solution is based on the principle of contractual fidelity, which prohibits challenging a rent agreed upon by the parties. The Federal Tribunal also considered that judgments related to the admissibility of a rent adjustment based on a change in the mortgage rate acquire the authority of res judicata and can no longer be challenged later.
The Federal Tribunal also examined cases where the rent was fixed or declared non-abusive under the absolute…