How Does a Blower Door Test Work?
A blower door test uses a machine (called the blower door) to verify the airtightness of new and existing homes. The equipment is comprised of an adjustable metal frame with a canvas shroud that’s meant to be fitted within the opening of an exterior door. A round fan is inserted into the canvas shroud and connected to a manometer, which is an instrument used to measure the rate of airflow. The measured airflow is called Air Changes Per Hour or ACH.
A Blower Door test for a new home takes place at the very end of the construction process. Most cities and towns in Rhode Island, Massachusetts, and Connecticut require a document generated by a HERS rater or other certified technician verifying a passing grade.
What is a Passing Grade for a Blower Door?
As mentioned above, all new homes built in Rhode Island, Massachusetts, and Connecticut are required to have a blower door test at the end of the construction process. Passing results for a blower door test are measured in ACH. Presently in Rhode Island, no more than five ACH are permitted. In Massachusetts and Connecticut, it’s three.
Let’s take the Massachusetts requirement of three ACH as an example. Basically what this means is that under normal winter conditions (windows and exterior doors closed) it is acceptable that all the conditioned air within a home will be exchanged with unconditioned outside air three times per hour.
It’s worth noting, that in most states the maximum acceptable ACH requirement is lowered at regular intervals. As the price of energy and environmental concerns continue, at some point in the not so distant future it may be common for most states to have ACH requirements of less than one.
How Hard is it to Pass a Blower Door Test?
Most insulation contractors working in new homes today offer an air sealing option as part of the insulation package. This air sealing plan, if properly installed, should bring the home near to where it needs to be to pass the test. Additionally, good communication between the builder and the sub-contractors working on site is important. Framers, plumbers, electricians, and HVAC contractors are all likely to make numerous penetrations in the building envelope. Make sure the sub-contractors are aware of your air sealing plan and agree to seal all their penetrations or eliminate them when possible.
What Happens if You Fail a Blower Door Test?
Most builders today are aware of the blower door test requirement and create an air sealing plan at the very start of the job. This helps to assure a passing test result at the end of the project. Here are some options a builder can employ should the home fail to make the grade during a blower door test.
- Make sure the attic hatch is tightly weather-stripped and closed.
- All windows should be closed and locked.
- All doors leading to the exterior should be weather-stripped closed and locked.
- Caulk sill plates in the basement if not already done
- Block the dryer vent penetration if the appliance is not yet installed.
- If the basement is not heated make sure the door leading to it is weather-stripped and closed.
- Retest.
How to Make Sure You Pass a Blower Door Test
Before starting your next building project contact the Staff at Energy Geeks. From the design stage at the very beginning to the Certificate of Occupancy needed at the very end, we will advise and guide you, thus helping to assure that your next building project will be a success.
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