Open-plan living is a defining feature of modern homes—creating light-filled, spacious interiors. However, when it comes to Energy Performance Certificate (EPC) assessments, open-plan layouts introduce specific challenges that can lower your property’s efficiency rating if not properly accounted for.
At EPCrate, we frequently assess lofts, kitchen-diners, and entire open-plan floors where EPC algorithms don’t fully recognise the design’s thermal dynamics—leading to heating zone and airflow efficiency penalties.
How EPC Assessments Handle Heating Zones
EPC methodologies, particularly RdSAP for existing dwellings, are structured around “heating zones”:
Primary Heating Zone: The main living area.
Secondary Heating Zones: Bedrooms, bathrooms, secondary lounges.
Unheated Areas: Garages, utility rooms, conservatories.
In open-plan homes where walls and doors are removed:
The primary zone enlarges significantly.
Secondary zones may effectively merge with primary zones.
Without physical barriers, the EPC assumes higher heat losses, particularly for spaces that were once thermally separated.
Challenges Open-Plan Living Poses to EPC Ratings
1. Larger Heated Volume = Increased Energy Demand
The larger the heated zone, the more energy is assumed to maintain desired temperatures—especially in high-ceiling, open staircases, or mezzanine layouts.
2. Loss of Zoning Control Credits
Traditional zoned heating systems (separate thermostats or TRVs in each room) gain EPC efficiency points.
Open-plan spaces lose this zoning advantage, leading to efficiency penalties in the software’s calculation.
3. Airflow & Heat Stratification Issues
Open spaces often suffer from warm air stratifying near ceilings while occupants feel cooler at ground level. EPC software may interpret this as increased demand on the heating system to compensate.
4. Assumptions of Higher Infiltration Rates
Larger uninterrupted internal volumes can be penalized with default assumptions about draughts and uncontrolled air leakage, particularly in period properties with open-plan retrofits.
How to Mitigate EPC Penalties in Open-Plan Properties
Install & Document Smart Zoning Controls
Multi-zone thermostats, smart TRVs, and zoning via underfloor heating systems can counteract default software assumptions.
Providing documentation of these systems ensures EPC assessors can apply control credits.Conduct an Air Tightness Test
Proving airtightness through a blower door test can offset penalisation from large-volume heat loss assumptions.Optimise Heating Distribution Systems
Ensure heating systems are appropriately sized and positioned to account for open-plan airflow dynamics (e.g., destratification fans, low-level heating emitters).Provide Architectural Plans Showing Thermal Strategy
Detailed drawings showing insulation continuity, glazing specs, and passive solar strategies help when assessors need to input custom data, especially in full SAP assessments.Consider Full SAP for Complex Open-Plan Conversions
For unique or high-end designs, RdSAP defaults may misrepresent efficiency. Full SAP allows for more accurate modelling of building-specific heating and airflow dynamics.
The Aesthetic vs Efficiency Trade-off in EPCs
While open-plan designs offer lifestyle and aesthetic benefits, EPC methodology still leans towards zoned, compartmentalised spaces as the efficiency ideal. Without proactive documentation, open-plan homes may underperform on paper, even if their real-world energy use is well managed.
Book an EPC Assessment for Open-Plan Properties with EPCrate
Does your open-plan layout accurately reflect its energy performance on your EPC?
EPCrate’s assessors specialise in open-plan home assessments, ensuring software limitations don’t drag down your rating.
Book an assessment or explore our pricing plans for complex architectural layouts.
