Home ventilation

Ventilation controls moisture, air quality, and comfort inside your home. If you're insulating or sealing draughts, getting ventilation right isn't optional - it's what stops those improvements from causing new problems.

Why ventilation matters

Every home produces moisture - from cooking, showering, breathing, and drying clothes. In an older, draughty home, that moisture escapes through gaps in the building fabric. But once you insulate or seal those gaps, the moisture has nowhere to go.

Without a ventilation strategy, trapped moisture leads to condensation, damp, and mould. Poor air quality builds up too - higher CO2 levels and stale air that affects how well you sleep and how healthy you feel.

Types of ventilation

The right ventilation approach depends on how airtight your home is and what other improvements you're making. Here's how the main options compare.

Type

Natural

Mechanical Extract

MVHR

How it works

Air moves through gaps, vents and windows

Fans extract moist air from wet rooms

Extracts stale air, recovers heat, supplies fresh air

Heat loss

High - uncontrolled draughts

Moderate - extracted air takes heat with it

Low - recovers up to 90% of heat

Where you find it

Older homes that haven't been insulated or upgraded

Most homes with bathroom or kitchen extractor fans

Well-insulated, airtight homes

Control

None - weather-dependent

Manual or humidistat-triggered

Continuous, automatic, whole-house

Most homes already have some form of extract ventilation - a bathroom fan or kitchen extractor. But these are often undersized or poorly fitted, which means they're not actually removing enough moisture to do the job properly.

What to be aware of

Ventilation and insulation need to be designed together. Insulating your walls changes how moisture moves through them, and sealing draughts removes the uncontrolled airflow your home was relying on. If you insulate without a ventilation plan, you risk trapping moisture inside the building fabric - which can cause damp and mould that's expensive to fix.

Material choice also plays a role. Breathable materials like wood fibre allow some moisture to pass through the wall, while plastic-based boards are more vapour-closed. Your ventilation strategy needs to account for whichever approach is used.

“Extraction fans are often undersized and underperforming, so they're not actually able to take moisture out of your home.”

Becky Lane, Founder and CEO at Furbnow

How Furbnow approaches ventilation

We assess your home's existing ventilation as part of every whole-house survey - measuring how well current fans perform, identifying moisture risks, and modelling how proposed insulation will change airflow. The result is a ventilation strategy designed around your home, not a generic recommendation.

Get ventilation right from the start

If you're planning insulation or draught proofing, ventilation should be part of the conversation from day one. A Furbnow home energy plan designs them together so nothing gets missed.