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Fraser Valley Weather

River Fog and Humidity: Hidden Enemies of Your Roof

Josh Vickers
December 2024
6 min read

The Fraser Valley's high humidity and persistent river fog create unique roofing challenges most homeowners overlook.

The Fraser River creates a microclimate of persistent fog and humidity that quietly damages roofs over time. While dramatic storms get attention, it is this constant moisture that causes the most insidious damage.

How Humidity Attacks Roofs

  • Promotes moss and algae growth that holds moisture
  • Causes wood rot in sheathing and rafters
  • Degrades shingle adhesive strips over time
  • Creates condensation in poorly ventilated attics
  • Accelerates rust on metal components

The Fraser Valley averages 80%+ relative humidity for most of the year. This is significantly higher than BC's interior regions.

Ventilation Is Critical

Proper attic ventilation prevents moisture buildup. Your attic needs both intake vents (at soffits) and exhaust vents (at ridge or gable ends) to create airflow that carries moisture out.

Moss Prevention

  • Install zinc or copper strips at roof peak
  • Trim overhanging tree branches
  • Clean gutters to prevent debris dams
  • Schedule annual roof cleaning before fall rains
  • Consider algae-resistant shingles

Zinc strips release ions when it rains that kill moss and algae. A single installation can protect your roof for years.

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