Facts
On 21 February 2012 the municipality of Vaz/Obervaz granted a building permit for a photovoltaic installation (18 solar panels, total roof area 35 m²) on the roof of the multi-family house on parcel 40. The installation as built deviates by approx. 75 cm towards the mountain-side roof edge from the approved plans.
Neighbours (owners of parcels 36, 37 and 38) complained about light reflections on their balconies. Following a reflection report by Basler & Hofmann AG (2012), a decision of the municipality of 27 March 2014 and a remittal decision of the Administrative Court of 12 March 2015, the respondents [B.C.] and [D.C.] demanded, by building police notice of 17 March 2014 (supplemented on 30 June 2016), the restoration of the lawful condition or emission-limiting measures.
The municipality commissioned an expert report from the office vogtpartner (measurements of 26 July 2018 on the respondents' balcony, expert report of 19 December 2018, supplement of 23 September 2019). A reflection duration of roughly one hour (15.56 to 16.58 h) was measured, with luminances between 31'000 and 230'000 cd/m². The expert assumed reflections of more than 50 minutes per day on several weeks of the year, i.e. well over 30 hours annually, and considered the nuisance no longer permissible.
On 20 February 2020 the municipal executive board found that the installation violated Art. 11 para. 2 EPA and ordered that within 30 days a building application for elevating the installation be submitted or the installation be removed; otherwise removal would take place at the appellant's expense. The court costs of CHF 15'223.40 (including the expert report of CHF 12'863.40) were imposed on the appellant. The Administrative Court of the Canton of Graubünden conducted an on-site inspection on 29 July 2021 and dismissed the appeal on 13 October 2021.
The appellant (with the consent of the owners' association) filed a public law appeal with the Federal Supreme Court. He requested the annulment of the prior-instance decisions, that the expert costs be borne by the municipality or the opposing party, and in the alternative the admission of further proportionate measures, in particular reducing the installation to 15 m². The FOEN held the ordered measures to be compliant with Art. 11 para. 2 EPA. The respondents and the municipality requested dismissal.
The subject matter of the dispute was in particular: admissibility of the appeal (final or interlocutory decision), complaints regarding the establishment of facts on the duration and intensity of the glare, applicability of the EPA to light reflections, proportionality and costs of elevating the installation, consideration of the deviation from the building permit, the alternative request to reduce the installation, and the allocation of costs for the expert report.
Considerations
Admissibility: The Federal Supreme Court leaves open whether the decision is a final or interlocutory decision (Art. 90, 93 FSCA), since in the case of an interlocutory decision the appellant faces irreparable harm. He would have to prepare a building application against his will before it is decided whether the measure is lawful. The appeal is therefore admitted.
Facts: The Federal Supreme Court examines complaints concerning the establishment of facts only for arbitrariness (Art. 97 para. 1 and 105 FSCA) and subject to strict requirements of substantiation. The Administrative Court's assumption that the reflections occur over several weeks and well over 30 hours annually is not arbitrary, as it is consistent with the reflection studies, the respondents' photographs and the FOEN. The measurement of roughly one hour of reflection duration is confirmed by the calculations. The intensity (maximum 231'000 cd/m²) is supported by measurement data. That the appellant was able to look into the glare for 15 seconds does not alter the absence of arbitrariness, particularly as the court was entitled to rely on its own perception during the on-site inspection.
Legal framework: Sunlight reflected by an installation is considered radiation and thus an impact within the meaning of Art. 7 EPA. For visible light there is no federal ordinance, which is why the authorities apply Art. 11-14 and 16-18 EPA directly. The installation is not subject to a remediation obligation under Art. 16 EPA, as the norms have not changed since the permit was granted. The subsequent imposition of emission limits is, however, permissible, in particular where the immissions were not foreseeable at the time of the permit; it requires a balancing of interests taking into account protection of legitimate expectations and legal certainty.
Precautionary measures: The question whether the immissions are already excessive within the meaning of Art. 14 lit. b EPA (threshold of excessiveness) may remain open if precautionary measures of the first stage (Art. 11 para. 2 EPA) are sufficient. This presupposes suitable measures that are technically and operationally feasible, economically reasonable and proportionate, and to which no overriding interests, in particular of protection of legitimate expectations, are opposed. The elevation is considered suitable and is not disputed by the appellant; it even increases efficiency. The deviation from the building permit did not give rise to an obligation of the municipality to object, but it must be taken into account in the balancing of interests, as the builder's protection of legitimate expectations carries less weight where he himself has deviated from the permit.
Proportionality: The costs of elevation (offer of roughly CHF 10'000 to 11'000) are not negligible, but are not…