Where is the Dew Point in your home?

Yesterday we talked about condensation

  • Moisture in the air – gas
  • Condensation – gas changes to water
  • Deposition – gas changing to water
  • Evaporation – water changing back to its gas state

The Density of the air is another critical aspect of condensation.  As the air pressure and density increase the air and its moisture are squeezed and squeezed so that the air becomes saturated and it is at that saturation point when the moisture condenses back into droplets of water.

If the droplets of water are allowed to remain in parts of your home that will lead to mold, mildew, and eventually rot.  All of which are significantly bad.

Recently we were asked if the structure of a home was allowed to be drenched with water would it damage the building.  The answer is simple, no it is not completely harmful.  For example, when a home is built onsite (a stick-built home) it is frequently exposed to the harsh elements such as rain, snow, and ice.  That exposure isn’t really all that awful but, only if the lumber and building products are allowed to thoroughly dry out.  It is when moisture is trapped in a building’s envelope that it becomes a significant problem.

If droplets of water are allowed to collect in a confined area where they can not evaporate then it’s bad.

The DEW POINT is the temperature where moisture collects as droplets of water.  The DEW POINT is that combination of temperature and humidity where the air born moisture has saturated the air and it condenses into droplets.

We see references to the Dew Point all the time in the weather reports, it tells us whether it is apt to rain or snow.

One of the biggest questions in building science today is how do we have the Dew Point not occur inside the insulated wall.  Several years ago we delivered a home that had 3” of Polyiso Continuous Insulation on the outside of the home’s framing.  The theory was that the Dew Point would always fall outside of the insulated wall cavity.

What is your opinion?  We would love to hear from you!

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