Attic Ventilation Must Be Comprehensive

Most buildings in Calgary have insulation in their ceilings, to prevent outside temperature entering the occupied space below. This keeps their interiors warmer in winter, and cooler in summer when the sun blazes down. Attic ventilation must be comprehensive so the airflow continues uninterrupted, and prevents condensation in the roof space.

A Touch of History – Where Does Condensation Come From?

Few buildings had insulation in pioneering years long past. The outside temperature leaked in through cracks and openings, and so occupants had their heating turned up high in winter. Any moisture in the air leaked out through cracks in the ceiling and escaped from roof space. They had little mold in those days!

And then along came the oil crisis in the early 1970’s, and the need to conserve fuel consumption. Two insulation strategies became popular:

  • Seal the building envelope to reduce air leakage either way,
  • Increase the insulation in walls and roofs to lower HVAC costs.

This well-meaning strategy caused higher humidity in the living space, relatively cooler roof space, and potential for more condensation in the unprotected attic.

Why Attic Ventilation Must Be Comprehensive

Uncontrolled condensation can have serious consequences if not attended to promptly. These unfortunate results may include:

  • Premature deterioration of roofing materials, including timbers and sheathing / decking.
  • Damage to thermal insulation reducing effectiveness, damage to interior finishes.
  • Growth of fungi and molds that may adversely affect the health of occupants.

Managing Attic Condensation With Ventilation Flows

There is only one practical, affordable way to remove condensation in an attic. This moisture can originate in the living space below from bathing, cooking, showering, washing clothes, and even houseplants.

The best way is to allow natural breezes to draw the moist air out via roof vents. However, this can create a semi-vacuum inside, if the attic is otherwise well sealed.  The solution is to provide fresh air intakes lower down in the roof structure.

This is where soffit vents come into play under eaves. Sometimes these use fans to increase their effectiveness, although most times this is unnecessary. So why then is the well-ventilated roof overhang so damp in our picture?

How This Comprehensive Attic Ventilation Failed

We detected this problem during a free inspection, when we noticed water dripping through the soffit vents. When we went into the roof space to inspect, we found the ceiling insulation extended into the soffits, and covered over the vents, which we immediately exposed.

A simple failure to accept that attic ventilation must be comprehensive, had ruined the soffit overhangs with continuous damp! We replaced them all, feeling sad all this work was necessary because a previous contractor had let our client down.

You don’t need to choose Valiant Exteriors just because of what we shared here. But you do need to choose a Calgary roofing, siding or eaves trough contractor carefully, when you need the job done right.

More Information

Avoid Capillary Action with Fiber Siding

Best Exterior Insulation Practice in Calgary