ASHRAE 90.1 energy simulations for LEED certification

The new municipal headquarters in Estepona brings all city services together under one roof while catalysing the urban renewal of the town centre. Officially inaugurated on 10 March 2023, the 13,068 m², eight‑storey building (plus basement) also includes a 131‑space public car park—part of a wider strategy to streamline access and public services.

Our client was Castaño & Asociados, who acted as LEED AP assessors on the project. Praxis was commissioned to undertake the ASHRAE 90.1 energy simulations required for LEED certification, using DesignBuilder–EnergyPlus. Our scope covered baseline vs. proposed modelling, daylighting controls, HVAC and envelope parametrisation, iterative responses to the LEED Preliminary Review, and documentation for the certification submittal.

Working from design documents and manufacturer data, we developed calibrated models for both the Baseline (per ASHRAE 90.1 Appendix G) and the Proposed building. The thermodynamic analysis tested envelope assemblies, glazing options and shading strategies—including a perforated metal double‑skin that tempers solar gains—together with balcony overhangs and a cool‑colour roof. On the active systems side, the proposed design featured high‑efficiency Swegon air‑handling units with rotary heat recovery (~84%); a VRF system with heat recovery and inverter compressors; and LED lighting with DALI daylight‑linked controls. We also modelled a 65.1 kWp rooftop PV array with an estimated annual yield of ~104 MWh, contributing a meaningful share of site electricity.

The modelling quantified how passive and active measures combine to reduce loads and operational energy: improved wall and glazing U‑values, the double‑skin façade and external overhangs mitigate summer gains, while winter solar access and airtightness limit heating demand; efficient heat‑recovery ventilation and VRF further cut space conditioning energy; and daylight‑responsive LED strategies lower lighting energy and internal gains. Our iterative submissions and narrative responses addressed reviewer comments on assemblies, lighting LPD distribution, daylight controls, outdoor air rates, secondary HVAC in assembly spaces, and baseline heat‑recovery provisions—ensuring that the final models reflected design intent and LEED methodology with full traceability.