Ventilation in Period Homes
How Older Houses Manage Airflow and Moisture
Ventilation in a Victorian or Edwardian house was never designed in the way we think about it today. It simply happened.
Open fires burned for much of the day. Chimneys pulled warm air upwards and out. Sash windows rattled in their frames. Gaps around floorboards and joinery allowed air to move freely between rooms and voids. Air change rates were high, especially in winter.
These homes were not energy efficient, and they leaked air freely. Comfort was uneven and heat loss was significant. Moisture was often diluted and carried away by constant air movement, although cold surfaces and overcrowding still led to condensation in some properties.
Over the last fifty years, this has changed. Chimneys have been sealed. Gas boilers replaced open fires. Double glazing reduced draughts. Roofs, floors and sometimes walls have been insulated. Windows have been repaired or replaced.
Each step improves comfort and reduces heat loss. But each step also reduces accidental ventilation.
As homes are upgraded through insulation, extensions or broader refurbishment projects, airtightness often improves, even if only modestly. Once uncontrolled air leakage is reduced, ventilation can no longer be left to chance. It must be considered deliberately as part of a coordinated whole-house upgrade.
Why Ventilation Matters More as Homes Improve
Period properties were built with breathable materials. Solid brick walls, lime mortars and timber floors allow moisture to move gradually through the building fabric. They were never sealed systems. They relied on a steady exchange of air to remain in balance.
When we insulate and reduce draughts, we lower uncontrolled air movement. That improves comfort and reduces heating demand. But moisture does not disappear.
Some is generated daily through cooking, showering and breathing. In a leaky house, much of that would drift out through chimneys and gaps. In a more efficient home, it lingers unless deliberately removed.
At the same time, moisture already exists within the fabric itself. Solid brick absorbs rain. Timber stores and releases humidity. Masonry warms and cools seasonally. As insulation levels and airflow patterns change, so does the drying balance of the building.
Ventilation supports surface drying and moisture balance within the home, particularly on the internal face of walls and at junctions. When insulation, heating and airflow are not coordinated, problems can emerge. Condensation may appear on colder surfaces. Mould can develop in corners or behind furniture.
If you are already seeing signs of this, our guide to avoiding damp and mould in period properties explains how insulation, ventilation and heating interact.
Ventilation is therefore not just about fresh air. It is part of how an upgraded older home stays healthy.
The Spectrum of Ventilation Strategies
Not every home requires the same solution. The right approach depends on how far the building is being upgraded and what level of performance is being targeted.
Opening Windows
The simplest and oldest strategy.
Opening windows provides rapid air change and immediate cooling. However, it is manual and inconsistent. In winter, it results in significant heat loss. As insulation improves and draughts are reduced, relying solely on window opening becomes less reliable.
Trickle Vents and Background Ventilation
Modern replacement windows often include trickle vents that allow small amounts of background airflow.
They are simple and inexpensive, but airflow is limited and not precisely controlled. They are rarely a complete solution in more insulated homes. They are one component within a wider approach to insulating a period home.
Intermittent Extract Fans
Most bathrooms and kitchens use extract fans that activate with light switches or humidity sensors.
These systems remove moist air at source but operate only when triggered. They are reactive rather than continuous and do not provide balanced airflow across the home.
Continuous Mechanical Extract Ventilation (MEV)
Continuous mechanical extract ventilation removes stale air from wet rooms at a steady, low rate throughout the day. A central fan expels air outside while replacement air enters through background vents or natural leakage paths.
It provides more consistent moisture control than intermittent fans and can suit medium-depth upgrades where ceilings are not being fully reworked. However, it does not recover heat. In winter, warm air is expelled and replaced with cooler outdoor air, increasing heat loss compared to balanced systems.
MEV can be a pragmatic step where insulation is improving but airtightness is not being pushed to very high levels.
Demand-Controlled Mechanical Ventilation
Demand-controlled systems adjust airflow in response to internal conditions such as humidity. Instead of running constantly, they increase ventilation when moisture rises and reduce it when conditions stabilise.
Some systems, including those developed by Aereco, use humidity-sensitive inlets and extract units that respond automatically. This can reduce unnecessary airflow and limit avoidable heat loss compared to constant extract systems.
These systems are often suitable where improved moisture management is needed but a fully ducted balanced system would be too intrusive.
Mechanical Ventilation with Heat Recovery (MVHR)
Mechanical ventilation with heat recovery is the most controlled solution on the spectrum. It uses a balanced system of supply and extract ducts. Stale air is removed while fresh, filtered air is supplied to living spaces. A heat exchanger transfers warmth from outgoing air to incoming air, reducing heat loss.
In well-insulated and reasonably airtight homes, MVHR can significantly improve comfort and indoor air quality. However, it requires careful design, space for ductwork and early coordination within the project.
For a detailed explanation of installation constraints, costs and suitability in older properties, see our guide to mechanical ventilation with heat recovery in London homes.
Designing Ventilation as Part of an Upgrade
Ventilation decisions cannot be separated from insulation and heating.
Adding internal wall insulation changes surface temperatures. Improving airtightness reduces uncontrolled air leakage. Preparing a home for lower-flow heating systems requires predictable heat demand, which we discuss in our article on making your home heat pump ready.
Each of these influences how air should move through the building.
If ventilation is treated as an afterthought, problems can appear later. Moisture may collect at junctions. Air may stagnate in certain rooms. Heating systems may struggle to perform as intended.
The appropriate solution depends on the depth of upgrade, the constraints of the building and the level of performance being targeted.
When a Coordinated Approach Is Necessary
A whole-house ventilation strategy becomes particularly important when:
Undertaking a deep retrofit
Significantly improving airtightness
Adding substantial insulation
Reconfiguring layouts through extensions
Addressing persistent condensation or mould
At this point, ventilation becomes part of the design brief, not an add-on.
Next Steps
Ventilation is rarely an isolated issue. It sits alongside insulation, heating and layout decisions.
If you are planning a significant refurbishment or energy upgrade, our Retrofit Strategy Service sets out how insulation, airtightness, ventilation and heating should be sequenced to improve comfort while managing moisture risk.
An Architect’s Home Visit and Appraisal is an on-site feasibility review. We assess your building, budget range and constraints, and identify where ventilation and moisture risks may sit before further upgrades are planned.
If you are unsure where to begin, the best starting point is a free 45-minute Project Consultation.
