Understanding RdSAP 10: Navigating the Shift in Domestic EPC Assessments for UK Property Portfolios
As specialist decarbonisation consultants deeply embedded in the UK's built environment, Carbon Profile is dedicated to ensuring our clients – property managers, portfolio managers, and legal advisors – remain ahead of regulatory shifts impacting energy performance. A pivotal update, the introduction of the Reduced Data Standard Assessment Procedure (RdSAP) version 10, is set for June 15, 2025.
This represents the first significant overhaul of the UK's standard methodology for assessing existing homes and generating Energy Performance Certificates (EPCs) in several years. RdSAP 10 is more than a technical adjustment; it's a crucial step towards enhancing the accuracy and reliability of EPCs, aligning assessments with modern energy-saving technologies, and supporting the UK's ambitious net-zero targets.
For professionals managing UK property portfolios and navigating the complexities of EPC compliance, particularly Minimum Energy Efficiency Standards (MEES), understanding the nuances of RdSAP 10 is not just beneficial – it's essential for informed strategic decision-making.
Why the Update? The Drive Towards Greater Accuracy and Relevance
The government's implementation of RdSAP 10 stems from several key drivers:
Enhanced Assessment Accuracy: To provide a more precise and reliable evaluation of a dwelling's energy performance, moving away from older assumptions.
Reflecting Modern Technology: To properly account for the growing prevalence and impact of newer energy-saving measures, including advanced insulation techniques, solar PV diverters, battery storage, and modern ventilation systems.
Alignment with SAP 10.2: To bring the assessment methodology for existing buildings closer to the Standard Assessment Procedure (SAP 10.2) used for new constructions, fostering greater consistency.
Supporting National Goals: To ensure EPCs better support national objectives like carbon reduction, fuel poverty alleviation, and the transition to warmer, more comfortable homes.
Key Changes in RdSAP 10: What Assessors Will Now Capture
RdSAP 10 mandates a more detailed and evidence-based approach to data collection, influencing the final EPC rating and recommendations. Notable changes include:
Comprehensive Window Assessment: Previously, assumptions based on property age were common. Now, assessors must measure every window (width and height or area) and record detailed attributes: orientation, frame material, glazing type (single/double/triple/secondary), glazing gap, age, draught-proofing status, and the presence/type of shutters. This significantly improves the accuracy of heat loss calculations.
Granular Lighting Data: The focus shifts from counting light fittings to counting individual bulbs, categorised by type (LED, CFL, incandescent). This better reflects actual lighting energy consumption.
Enhanced Ventilation Recording: More emphasis is placed on ventilation's role. Assessors must note and potentially photograph systems like extractor fans. Crucially, various flue types (blocked chimneys, open flues, closed fire flues, boiler flues, etc.) must be recorded, moving beyond just open fireplaces. Mechanical Ventilation with Heat Recovery (MVHR) systems are also explicitly included.
New Property Age Band (M): A new band ('M') covers properties built from 2023/2024 onwards, acknowledging higher modern construction standards and incorporating updated U-values.
Incorporation of Modern Technologies: RdSAP 10 now formally recognises and accounts for:
Solar PV diverters and battery storage systems.
Small-scale hydro installations.
Air pressure test results (when available with documentary evidence), providing a direct measure of airtightness rather than relying solely on assumptions.
Refined Insulation and Wall Data: Assessors can input exact insulation thicknesses (where measurable) and use finer increments (e.g., 25mm). The ability to record two alternative wall constructions per building part improves accuracy, especially for flats or complex structures.
Updated Heat Pump Recommendations: Aligning with government low-carbon heating strategies, heat pumps will be recommended more frequently as an improvement measure, particularly where properties meet sufficient insulation levels.
Calculation and Scope Updates: The methodology uses updated fuel prices aligned with SAP 10.2 for more current cost estimations and expands its geographic scope to include the Isle of Man. Chimney/flue status recording is more detailed, and smart meter presence/export capability is noted.
Key Assessment Differences - RdSAP 10 vs. Previous Versions
Feature
Previous RdSAP Approach (RdSAP 2012 / 9.94)
RdSAP 10 Approach (Effective June 15, 2025)
Windows
Assumed typical glazing area based on property age; only atypical windows required full measurements.
Mandatory measurement (width & height/area) of ALL windows; detailed recording of orientation, frame, glazing type/gap/age, draught proofing, shutters.
Counted total number of fittings and the number identified as low energy.
Lighting
Records total number of individual bulbs and provides a breakdown by type (LED, CFL, Incandescent)
Primarily focused on open fireplaces; limited recording of other ventilation.
Ventilation/Flues
Requires noting/photographing extractors; mandates recording of various specific flue types (blocked, open, closed fire, boiler, etc.); includes MVHR assessment
Insulation Data
Generally used broader thickness categories (e.g., 50mm increments).
Allows input of exact measured insulation thickness where possible; offers finer increments (e.g., 25mm) for selection.
Wall Construction
Limited options for recording alternative wall types within a single dwelling part.
Allows recording of two alternative wall constructions per building part (improves accuracy for flats/complex layouts)
Hot Water Cylinder
Basic data recorded, often relying on defaults.
Allows input of exact cylinder capacity and specific heat loss value (kWh/day) if available on data plate
Not explicitly considered or input into calculations
Air Pressure Testing
Option to input actual air pressure test results (requires documentary evidence), providing a direct measure of airtightness
PV & Battery Systems
Limited consideration, especially for diverters and storage.
Explicitly accounts for PV diverters and battery storage systems, reflecting modern technology integration
Heat Pump Recommendations
Often recommended mainly as an alternative to electric storage heaters.
Recommendations logic updated; heat pumps recommended more frequently for properties meeting adequate insulation criteria
Implications for UK Property Professionals: Preparing for the Shift
The transition to RdSAP 10 carries significant implications for those managing and advising on property assets:
More Accurate, Potentially Different, EPCs: The primary goal is increased accuracy. This granular approach may result in EPC ratings shifting for some properties – potentially benefiting well-maintained or retrofitted buildings whose features were previously underestimated, while potentially highlighting inefficiencies in others. Understanding this potential shift is vital for portfolio analysis.
Impact on MEES Compliance: With Minimum Energy Efficiency Standards (MEES) requiring domestic private rented properties to meet at least EPC Band E (and future proposals potentially targeting Band C), the accuracy of EPCs is paramount. RdSAP 10's detailed assessment will provide a more robust basis for compliance verification and identifying properties needing upgrades. Managers and landlords must anticipate how new assessments might affect compliance status.
Informed Retrofit and Decarbonisation Strategy: More detailed EPC reports, including refined recommendations (like heat pumps ), offer better data for planning strategic retrofits and developing portfolio-wide decarbonisation pathways. This aligns perfectly with Carbon Profile's mission to deliver future-ready efficiency beyond mere compliance.
Potential Impact on Assessment Time and Cost: The increased detail required means assessors will likely spend more time on-site. This may lead to an increase in the cost of obtaining an EPC survey, a factor to consider in operational budgets.
Due Diligence in Transactions: For property lawyers and portfolio managers involved in acquisitions or disposals, understanding that an EPC generated under RdSAP 10 reflects a more thorough assessment will be crucial for due diligence.
Carbon Profile: Your Partner in Navigating Regulatory Change
At Carbon Profile, we specialise in translating complex energy regulations into actionable strategies for the UK property sector. We recognise that the transition to RdSAP 10, while positive for accuracy, requires proactive management.
Our services, encompassing EPC assessments, portfolio EPC compliance management, strategic energy reporting, and net-zero pathway development, are designed to support you through this change. We combine deep real estate expertise with innovative thinking, ensuring your assets not only meet compliance requirements but are optimised for future efficiency and value. RdSAP 10’s focus on detail aligns with our commitment to helping buildings evolve and leave a positive legacy.
Looking Ahead: RdSAP 10 and the Future of Energy Assessment
While RdSAP 10 marks a significant improvement, the industry acknowledges potential implementation challenges, including the need for consistent assessor training and adaptation. It's also widely viewed as an interim step before the potential future rollout of the comprehensive Home Energy Model (HEM), intended eventually to replace both SAP and RdSAP.
For now, preparing for RdSAP 10 is key. Understanding its implications allows property and portfolio managers to maintain compliance, manage risk, and make strategically sound decisions that align with long-term decarbonisation goals.
Take Control of Your Portfolio's Energy Performance
The introduction of RdSAP 10 underscores the increasing importance of accurate energy performance data in property management and investment. Don't wait for compliance deadlines to dictate your strategy.
Contact Carbon Profile today for:
RdSAP 10 Compliant EPC Assessments: Ensure your properties are assessed accurately under the new methodology.
Portfolio EPC Review & MEES Compliance Strategy: Understand how RdSAP 10 impacts your portfolio's compliance and develop a proactive plan.
Strategic Decarbonisation Advice: Leverage the insights from more detailed EPCs to inform your long-term energy efficiency and net-zero roadmap.
