Energy efficiency of older buildings

Today we conducted an EPC assessment of a heritage community building in Hampshire, as part of a broader initiative to establish its baseline carbon footprint.

This can be used as the foundation for a long-term retrofit strategy aimed at substantially improving the building’s energy performance and reducing operational emissions.

We thought it would be useful to highlight some of the key technical considerations often encountered when assessing energy efficiency in older buildings.

1. Lack of documentation - original construction drawings, renovation records, or system specifications are often unavailable. Materials can be uncertain, it’s hard to identify insulation levels and wall compositions without invasive inspections.

2. Construction complexity - older buildings may feature non-standard methods of construction or solid walls and may have been built with materials no longer typically used. Buildings have often also been extended and adapted over the years, leading to a mixture of construction types and resulting thermal performance.

3. Poor or degraded insulation - insulation may have settled, deteriorated, or become less effective over time.

4. Outdated HVAC systems - older inefficient systems consume more energy and may be oversized or improperly maintained. They may also lack controls such as thermostats or zoning, skewing usage patterns.

5. Air Leakage Issues - gaps in windows, doors, chimneys, or floorboards are common but hard to quantify without testing (e.g. blower door test). Moisture balance is important, and existing gaps shouldn't be sealed without considering how the building will be ventilated.

6. Historical preservation constraints - upgrades may be limited by regulations protecting the building’s architectural integrity.

7. Mixed-use or irregular Layouts - many older buildings have been repurposed over time, extended or divided. Room sizes can be irregular in shape and size affecting heating, lighting, and ventilation dynamics.

8. Unknown occupant behaviour - energy use often depends heavily on human habits, which are hard to standardise or model.

Despite the inherent challenges, older buildings offer significant opportunities for impactful upgrades. With the right approach, it’s possible to retain their character while achieving meaningful energy and carbon savings.