Dew Point: Why Outside Walls Must Breathe

The Dew Point (DP) is the temperature to which air must cool down before water vapour saturates it. If the air cools further, the moisture ‘overflows’ as condensation. This is how dew forms in the garden when it’s cool overnight. When this happens inside a house the ‘dew’ condenses on any surface colder than the air.


The Relationship between Dew Point, Humidity and Freezing


There is a relationship between the Dew Point and humidity. A higher DP corresponds with more moisture in the air. Hence there is no absolute measure. The dew becomes frost when the air temperature drops below the freezing temperature of water.


condensation humidity calgary ventilation


How to Calculate the Current DP Where You Are


The classic formula for Dew Point (Tdp) uses the following data for the calculation

# Degrees Celsius (T)

# Relative Humidity (RH)


condensation humidity calgary ventilation


Thank heavens there are websites to do the calculation for us. Google “dew point calculator” if we raised your curiosity sufficiently to want to know more.


Why We Should Allow Exterior Walls to Breathe


Nature refreshes the air in most places outside our homes. This keeps it clean and healthy. We ought to do something similar inside our homes. It’s a simple matter of letting fresh air in, and expelling stale air as our lungs do. If we do not, then moisture, odours, gases, dusts and other pollutants may accumulate and that’s a bad thing.

City planners insist all buildings have doors and windows opening to outside unless there is a convincing reason. These are normally adequate for recirculating fresh air, provided we open them, that is.

Many Calgary homes rely on mechanical systems to bring in fresh air, and vent pollutants from kitchens and bathrooms. These systems often work best when there are filters to prevent second hand contamination.


Common Ways Our Homes Can Breathe Fresh Air


# Open windows and doors at opposite ends for at least ten minutes every day

# Avoid sealing joints, cracks and openings where parts of the building connect

# Use a mechanical whole house system to force air in and out the building.


How Poor Ventilation Can Trigger These Problems


# An overkill on energy efficiency can trap pollutants inside the house

# Carbon monoxide concentrations can increase until they reach danger point

# High outside humidity can transfer inside causing mold and wood rot.


Attic Ventilation Can Help Prevent this Happening


Speak to Valiant Exteriors (403) 829-1661) soon regarding our attic ventilation system. This draws old air out of a home, so new fresh air comes in. We are a small, family-owned business in Calgary, but we are big on imaginative ideas.


Related Posts

Introduction to Window Types Available in Canada

The Science of Attic Ventilation in Residential Homes

Condensation on Bottle: Liz West BY CC 2.0

Formula and Graph: Courtesy Wikipedia

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