Part O & HEM
Part O overheating compliance calculations and Home Energy Model assessments that prepare your stock for the next regulatory standard. From solar gains analysis to four-metric HEM scoring — readiness for 2027 and beyond.
Future-proofing properties against the next regulatory standard.
Building Regulations Part O (2021) requires new dwellings to be designed to minimise overheating risk. Our simplified method compliance check calculates solar gains against limiting values and verifies minimum free areas using the discharge coefficient and equivalent area method.
From 2027, the Home Energy Model (HEM) replaces EPC as the statutory energy assessment methodology. HEM scores properties across four headline metrics — fabric, heating, smart readiness and energy cost — giving you a complete picture of energy performance long before the regulatory deadline.
Every assessment includes
Our Part O & HEM assessment process
Data Collection
Property geometry, orientation, opening types and construction details captured for both Part O and HEM assessment.
Part O Calculation
Solar gains checked against limiting values, minimum free areas verified using discharge coefficients and equivalent area method.
HEM Assessment
Four headline metrics scored — fabric, heating, smart readiness and energy cost — benchmarked against 2027 targets.
Recommendations
Gap analysis with prioritised improvement measures, score impact breakdown and compliance certification.
The four Home Energy Model metrics.
From 2027, the Home Energy Model replaces EPC as the statutory energy assessment. Every property is scored across four headline metrics — each decomposed into its contributing factors for actionable improvement.
Fabric Performance
U-values and thermal bridging — how well the building envelope retains heat.
Heating System
Efficiency of the primary heat source and its contribution to overall energy performance.
Smart Readiness
Capability to integrate smart energy management, monitoring and demand-side response.
Energy Cost
Modelled annual energy cost — the resident-facing metric that drives affordability.
What you get back.
Part O Compliance
Solar gains and free area calculations that demonstrate Building Regulations Part O (2021) compliance for new dwellings.
HEM Readiness
Properties assessed against the Home Energy Model — the four-metric standard replacing EPC from 2027.
Score Breakdown
Every HEM metric decomposed into its contributing factors, showing exactly which measures move the needle.
Ventilation Strategy
Cross-ventilation analysis and opening schedules that satisfy both Part O free area requirements and resident comfort.
Ready to get started?
Access the Gaia Energy Ltd portal, download the full brochure, or watch the presentation to see how we deliver complete property intelligence.