Air Tightness Testing For Existing Homes

Air Tightness Testing for Existing Homes 

Is your home cold and draughty ?

Have you considered having an air test of your home – did you know up to 15% of your homes heat, escapes through what we call air infiltration or cold draughts.

Air infiltration refers to the unintended or uncontrolled flow of air into a building from the outside through leaks, cracks, and openings in the building envelope. This can occur through gaps around doors and windows, electrical outlets, plumbing fixtures, and other openings. Infiltration can lead to higher energy consumption as heating and cooling systems work harder to maintain a comfortable indoor temperature, and it can also impact indoor air quality.

Examples in a Residential Home:

  1. Gaps around windows and doors: Older or poorly installed windows and doors often have small gaps around their frames where air can leak in.
  2. Cracks in walls and ceilings: Over time, houses can develop cracks in the walls or ceilings, particularly around seams and joints, through which air can infiltrate.
  3. Openings for utilities: Areas where pipes, electrical wires, or ducts enter the house can be sources of infiltration if not properly sealed.
  4. Attic hatches and basements: Unsealed or poorly sealed attic hatches and basement doors can allow air to move freely in and out of the home.

Cold Draughts

Cold draughts are noticeable streams of cold air entering a living space, typically felt near windows, doors, or other openings. They are usually the result of air infiltration and can cause discomfort, particularly in colder climates, as they create localized areas of lower temperature within a room.

Examples in a Residential Home:

  1. Draughty windows: Single-pane windows or poorly sealed double-pane windows can allow cold air to enter, causing a noticeable cold spot near the window.
  2. Under-door gaps: Exterior doors without proper weatherstripping can have gaps at the bottom, allowing cold air to flow in, especially during windy conditions.
  3. Fireplaces: Chimneys and fireplaces, if not properly sealed when not in use, can be significant sources of cold draughts as air flows down the chimney and into the living space.
  4. Ventilation fans: Exhaust fans in kitchens and bathrooms that do not have backdraft dampers can allow cold air to enter when the fans are off.

Mitigation Strategies:

To reduce air infiltration and cold draughts, homeowners can:

  • Seal gaps and cracks: Use caulking and weatherstripping around windows, doors, and other openings.
  • Upgrade windows and doors: Install energy-efficient windows and doors designed to reduce air leakage.
  • Insulate properly: Ensure that the home has adequate insulation in the walls, attic, and basement.
  • Use draft stoppers: Place draft stoppers at the base of doors to block cold air from entering.
  • Maintain HVAC systems: Regularly service heating and cooling systems to ensure they are operating efficiently and can better maintain indoor temperatures.

Air tightness testing of existing homes is crucial for several reasons:

  1. Energy Efficiency: Identifying and sealing air leaks in existing homes can significantly improve energy efficiency. Leaky homes allow warm or cool conditioned air to escape and outdoor air to infiltrate, leading to higher heating and cooling bills.
  2. Comfort: A more airtight home can provide greater comfort to occupants. It helps maintain a stable indoor temperature, reduces drafts, and minimizes temperature variations, enhancing overall comfort.
  3. Indoor Air Quality (IAQ): Proper air sealing ensures that the indoor environment remains free from outdoor pollutants, allergens, and contaminants. It contributes to better IAQ, which is essential for occupant health.
  4. Moisture Control: Air leaks can allow moisture to enter a home, potentially leading to mold growth, rot, and structural damage. Air tightness testing helps prevent moisture infiltration, promoting the durability of the building.
  5. Noise Reduction: Airtight homes are generally quieter because they block out exterior noise, creating a more peaceful living environment.
  6. Carbon Footprint Reduction: Improved energy efficiency through air sealing reduces a home’s carbon footprint, contributing to environmental sustainability and combating climate change.
  7. Cost Savings: By reducing energy consumption, air tightness testing can lead to long-term cost savings on heating and cooling bills, making it a cost-effective investment.
  8. Health Benefits: Enhanced IAQ resulting from air tightness improvements can lead to health benefits, including reduced respiratory issues and allergies among occupants.
  9. Compliance: In some regions, air tightness testing may be required to meet energy efficiency or building code standards. Ensuring compliance is essential to avoid legal or regulatory issues.
  10. Resale Value: An energy-efficient, air-tight home often has a higher resale value and can be an attractive feature for potential buyers.

In summary, air tightness testing for existing homes is essential for improving energy efficiency, occupant comfort, indoor air quality, and overall building performance. It plays a crucial role in reducing energy costs, promoting sustainability, and maintaining a healthy living environment.

How we can help reduce air leakage in your home?

The most common way to test for air tightness and to carry out diagnostic analysis is with a blower door.

A blower door test is a diagnostic tool used to measure the air tightness or air leakage of a building, typically a home or commercial structure. It is a crucial part of building performance evaluation and energy efficiency assessments. Here’s how a blower door test works:

  1. Equipment: The primary component of a blower door test is the blower door itself. It consists of a powerful fan that is temporarily installed in an exterior door or window of the building. The fan is connected to a computer or a pressure gauge to measure airflow.
  2. Procedure:
    • All exterior doors and windows are closed.
    • The blower door fan is installed in one of the exterior openings, typically the front door.
    • The fan is turned on to create a pressure difference between the indoor and outdoor environments. It either blows air out of the building (depressurization test) or sucks air into the building (pressurization test).
    • As the fan runs, the pressure inside the building is adjusted to a standard pressure, often 50 Pascals (Pa) of pressure difference between indoors and outdoors.
    • A technician or auditor monitors and records the airflow required to maintain this pressure difference.
  3. Data Collection: During the test, data is collected on the airflow rate (usually in cubic feet per minute, CFM) required to maintain the desired pressure difference. This data is used to calculate the air changes per hour (ACH) at 50 Pascals, which is a measure of the building’s air tightness.
  4. Interpretation: The results of the blower door test provide valuable information about the building’s air tightness. A lower ACH50 value indicates better air tightness and less air leakage. Higher ACH50 values suggest that the building has more air leakage, which can result in energy loss, discomfort, and reduced energy efficiency.
  5. Recommendations: Based on the test results, recommendations can be made to improve the building’s air tightness. This may include sealing gaps, cracks, and other air leakage points in the building’s envelope (walls, windows, doors, roof, etc.) to reduce air infiltration and exfiltration.


For more information please call us on 0121 493594 or email

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