🧧 Ready your envelope – Part 3

Ready your envelope – Part 1 is an overview of the role of a tight building envelope.

We covered the first of the three basic laws of physics that relate to building tightness in Part 2.

Why it matters: The leakiness of your house is directly related to your ability to control the conditions inside.

  • Tightening your house is often the first step to controlling your comfort and indoor air quality.

🏃‍♂️ Quick review

👉 Hot moves to cold

👉 Wet moves to dry

👉 High pressure moves to low pressure

🔬 Zoom in: Water and water vapor are moving — down and sideways and even up — toward dry materials.

  • Water will find the path of least resistance and exploit weaknesses in your roof, siding, windows, etc.
  • Water vapor can go THROUGH most building materials like brick, stone, stucco, concrete and wood
  • Example: Humid air in a crawl space is moving toward dryer air in the house — even if you have insulation between the floor joists

✅ For your Smart Homeowner list

  • Keep this in mind when you think about your comfort — most people will find 75 degrees and 50% relative humidity to be very comfortable.
  • 70 degrees with 70% humidity is not.
  • In a humid climate you tighten the house to keep humidity out and then add dehumidification to handle the rest.



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