Thermo-Active Foundations for Net-Zero Buildings: A Transferable Energy-Geostructure Design Framework from the United Kingdom to the Peruvian Andes

Technical Summary: Thermo-Active Foundations for Net-Zero Buildings

Problem Statement
Energy geostructures (EGS)—foundation elements like piles and walls integrated with ground heat exchangers—are a mature, low-carbon strategy for building heating and cooling in the United Kingdom and the United States. However, a significant knowledge gap exists regarding their application in seismically active, geologically distinct regions of Latin America, specifically Peru. Despite Peru's high seismic risk necessitating deep bored cast-in-place piles for most mid- and high-rise buildings (per National Building Code NTE E.030), and a growing demand for mechanical cooling in Lima, there are no documented EGS installations in the indexed scientific literature for the country. Furthermore, no local design guidance exists for coupling foundations with ground heat exchange, and there is a lack of mapped shallow soil thermal conductivity data for the Peruvian Andes, which is critical for design.

Methodology
This study is a structured, literature-based comparative engineering analysis. It does not involve new field instrumentation, laboratory testing, or human data collection. The methodology consists of three primary components:

1. Synthesis of UK Frameworks: A consolidation of United Kingdom geotechnical, thermal, and thermo-mechanical design parameters and governing equations (e.g., Fourier conductive heat flux, transient radial response, restrained thermo-mechanical axial stress) used for energy piles.
2. Quantitative Comparative Matrix: A matrix constructed exclusively from data reported in peer-reviewed, DOI-verified sources for the UK, the US, and analogous Andean soil conditions (specifically a 2025 geospatial mapping of Ecuador). For parameters where Peruvian data is absent, values are explicitly labeled as "projected" based on the closest available Andean analogues.
3. Adaptation Pathway Proposal: A proposed, staged construction and instrumentation route for Peru that integrates EGS construction with mandatory seismic and geotechnical codes (NTE E.050, E.060, E.030).

Key Contributions
The paper provides the first systematic, quantitative translation of UK and US energy pile experience to the Peruvian context. Its specific contributions include:

• Design Basis Synthesis: Organizing complex thermo-mechanical design frameworks into a form usable by practicing engineers in Peru.
• Comparative Analysis: Establishing a source-cited matrix contrasting UK, US, and projected Peruvian parameters (including soil thermal conductivity, dominant technology, and life-cycle performance).
• Code-Compliant Pathway: Proposing a specific construction procedure where the energy-exchange function is treated as a retrofit addition to the seismic piles already mandated by Peruvian law. This pathway details the integration of HDPE U-loop circuits with reinforcement cages, ensuring compatibility with seismic detailing requirements.
• Pilot Specification: Defining the requirements for Peru's first instrumented pilot energy pile in Lima, including the use of thermal response testing, strain gauges, and thermocouples to validate projected values.

Results
The study highlights that while EGS technology is mature in the UK and US, its application in Peru remains theoretical.

• Performance Projections: Based on international life-cycle assessments, ground-source systems are projected to reduce operational energy consumption by approximately 40% and carbon emissions by roughly 35% relative to fossil-fuel-based HVAC baselines. However, the paper notes these figures are contingent on local grid emission factors; Peru's hydro-dominated grid may alter the carbon-avoidance logic compared to coal-dependent grids.
• Thermal Conductivity: Using data from Ecuador as an analogue, the study projects that over 70% of Andean sites (including Peru) likely have soil thermal conductivity exceeding 1.25 W·m⁻¹·K⁻¹, with a projected range of 1.0–2.3 W·m⁻¹·K⁻¹.
• Economic Logic: The marginal cost logic for energy piles in Peru is deemed favorable in principle, as the deep piles are already required for seismic safety, meaning the incremental cost is limited to the heat exchanger loops and heat pump, similar to the logic in London and North American cities.
• Data Gap: Crucially, the results confirm that no instrumented Peruvian energy pile currently exists. Therefore, all Peru-specific quantitative values in the study are projections, not empirical measurements.

Significance and Claims
The paper modestly claims to close a specific knowledge gap by assembling a defensible, code-compliant, and cost-logical adaptation pathway for Peru. It does not claim to have generated new field data or to have validated the technology locally. Instead, its significance lies in:

1. Bridging the Gap: Providing a structured framework to translate established international practices to a seismically active, under-researched region.
2. Defining the Next Step: Explicitly identifying the construction of a single, fully instrumented pilot energy pile in Lima as the necessary next step. The authors state that without this pilot, the projected values presented cannot be upgraded to validated design parameters.
3. Distinguishing Fact from Projection: Rigorously maintaining a distinction between documented field results (from the UK/US) and hypothesis-generating estimates for Peru, ensuring that the proposed framework is transparent about its theoretical nature pending local verification.