Musty or Stale Smells in the Home

Musty Smells Indoors: Why Homes Smell Stale and How Proper Ventilation Removes Odours

What the Problem Is

Musty or stale smells are often described as “damp”, “heavy”, or “stuffy” and can linger even after cleaning. These odours are commonly noticed when entering the home after being away, in bedrooms in the morning, or in wardrobes and enclosed spaces.

Unlike temporary smells from cooking or pets, musty odours tend to persist and return, indicating an underlying air quality issue rather than a cleanliness problem.

Why Musty and Stale Smells Exist

Stale odours are caused by air that isn’t being replaced often enough.

In modern homes, smells become trapped due to:

  • Low air change rates
  • Excess indoor moisture
  • Limited natural air leakage
  • Closed internal doors restricting airflow

Moist air holds odour-causing compounds from furnishings, building materials, cleaning products, and biological growth. Without ventilation, these compounds build up rather than being flushed out.

Musty smells are often linked to:

  • Hidden moisture or minor mould growth
  • Damp wardrobes or storage areas
  • Poorly ventilated bedrooms overnight
  • Subfloor or roof space air entering the home

How Ventilation Fixes Musty and Stale Smells

Ventilation removes odours by diluting and exhausting contaminated air and replacing it with fresh outdoor air.

Effective ventilation:

  • Prevents odours from accumulating
  • Reduces humidity that feeds musty smells
  • Flushes out stale air consistently
  • Improves overall indoor air freshness

Unlike opening windows occasionally, ventilation provides controlled and reliable air exchange throughout the home.

Recommended Ventilation Systems

1. Home Ventilation Systems

Home ventilation systems provide continuous or regular airflow through the entire home, preventing stale air from lingering.

They are effective for odour control because they:

  • Maintain regular air changes
  • Ventilate multiple rooms simultaneously
  • Operate automatically without relying on occupant behaviour

These systems are well suited where musty smells are present throughout the house.

2. Heat Recovery Ventilation (HRV/ERV) Systems – Airtight Homes

HRV and ERV systems are ideal for modern, airtight homes where odours build up quickly due to limited natural leakage.

By supplying fresh air and extracting stale air at the same time, they:

  • Remove odour-laden air at the source
  • Maintain balanced pressure
  • Provide consistent ventilation even with doors closed

This makes them particularly effective for bedrooms and living areas.

3. Subfloor Ventilation Systems – Persistent Musty Odours

Musty smells can sometimes originate below the home.

Damp subfloors allow moisture-laden air and odours to migrate upward through gaps in floors and wall cavities. Subfloor ventilation helps reduce this source of odour by improving airflow beneath the home.

Subfloor ventilation is particularly helpful where musty smells are strongest near floors, wardrobes, or external walls.

4. Targeted Exhaust Ventilation With Make-Up Air

Bathrooms, laundries, and kitchens are common sources of odour and moisture.

Targeted exhaust systems:

  • Remove odours at the source
  • Prevent smells spreading through the home
  • Work best when paired with make-up air so extraction is effective

Quiet, efficient exhaust fans are key to long enough run times.

Other Helpful Fixes (Non-Ventilation)

Ventilation addresses the root cause, but these steps can support better results:

  • Identify and remove hidden moisture sources
  • Avoid storing damp items in wardrobes
  • Improve airflow around furniture and storage
  • Clean existing mould or mildew properly
  • Use lids when cooking and vent bathrooms effectively

Key Takeaway

Musty or stale smells are a sign that air inside the home is not being refreshed often enough. Without ventilation, moisture and odour-causing compounds build up, leading to persistent smells that cleaning alone cannot fix.

Home ventilation systems and HRV/ERV systems provide consistent air exchange, while targeted exhaust and subfloor ventilation address specific odour sources. Proper ventilation restores fresh-smelling, healthier indoor air and prevents odours from returning.