How to use chimneys for smart ventilation retrofits?
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Britain's housing stock faces a modern paradox. As we rush to retrofit our draughty Victorian terraces and post-war builds for energy efficiency, we're inadvertently creating new problems. The very improvements designed to slash our heating bills may be quietly undermining our health and home values.
The non-insulated Victorian and Edwardian homes were designed to “breathe” naturally through openings in the walls, fireplaces and chimney flues in almost every room. This historic ventilation worked well in an era before modern insulation.
Today, retrofits include sealing and insulating these homes to improve energy efficiency. While essential for reducing heat loss, these upgrades can unintentionally trap moisture and pollutants indoors – with consequences for both indoor air quality and property value.
The ventilation challenge
When a period home is sealed too tightly, moisture has nowhere to escape. Over time, this can lead to condensation, mould, and even structural damp. Poor indoor air quality can affect occupant health, while survey reports may flag risks that complicate insurance, lending, or resale.
The good news? These problems are not inevitable. By working with a property’s original design – rather than against it – we can preserve energy savings and heritage character, while ensuring healthy indoor air.
Smarter retrofits using existing chimneys
Because many heritage properties still have intact chimney flues, they offer ready-made ventilation channels. This means advanced systems can be installed with minimal disruption, avoiding costly and invasive building work.
Option 1: Central Mechanical Ventilation with Heat Recovery (MVHR)
A whole-house solution that supplies fresh air to bedrooms and living spaces while extracting stale, humid air from kitchens and bathrooms.
Quick install steps:
- Place MVHR unit in the loft
- Use existing chimney flues for air supply towards dry rooms
- Extract via hallways/stairwells, as well in bathroom and kitchen.
- Add recirculating cooker hood to protect ventilation system
Benefits:
- Minimal disruption to building and interiors
- No damp and condensation risk
- Guarantees optimal indoor air quality for occupants in insulated homes.
Discover DUCO’s Whole-House MVHR Ventilation Solutions
Option 2: Enhanced Natural Ventilation with Central Mechanical Extract Ventilation (CMEV)
Ideal where full MVHR isn’t feasible, this hybrid approach keeps natural airflow while controlling humidity and pollutants.
Quick install steps:
- Fit chimney draught excluders to limit heat loss
- Add window vents to supply fresh air in dry rooms, such as the living room.
- Install CMEV unit to extract from kitchens, bathrooms and toilets
- Sensors trigger extraction only when needed
Benefits:
- Run the ventilation pipes in the attic to minimize building impact. Up to 40% lower ventilation energy use via zonal control
- Lower capital cost and simpler installation
Discover DUCO's CMEV Natural Ventilation Solutions
Benefits for property professionals
Smart ventilation helps surveyors, architects, contractors, and developers achieve multiple goals:
- Meet building regulations without compromising heritage
- Reduce installation/setup time by up to 50 %
- Improve property marketability and lending prospects
The key is working with existing building physics rather than fighting against original design principles.
Sources:
- Retrofit Pattern Book – 5th Studio
- DUCO Residential Ventilation in-house experts