AIR LEAKAGE AND CODE
A typical existing home can be very leaky by today’s standards. The metric used to measure the leakiness of a home is air changes per hour (ACH), often measured at 50 Pascal’s (ACH50). In many existing homes this number can approach or even exceed 10 ACH50. For context, the International Energy Conservation Code (IECC), which sets minimum standards with regards to energy efficient construction, requires all new construction to meet certain air leakage requirements. In the 2009 edition the limit was 7 ACH50 (air changes per hour @ 50 pascals), which was then tightened to 5 ACH in the 2012 edition, and again to 3 ACH50 for the most recent 2015 edition. It is widely accepted throughout the industry that anything less than 5 ACH50 is considered to be a tight home.
CONDUCTING A BLOWER DOOR TEST
To measure a home’s air leakage, we use a tool known as a blower door. To conduct a blower door test, a fan is mounted into a frame of an exterior door, which pulls air out of the house thus lowering the air pressure inside. Because the outdoor air pressure is now higher than the air pressure inside the home, the outdoor air is pulled in through all penetrations, crack and openings in the buildings envelope.
To measure the airflow, a manometer is connected to the fan and includes reference hoses inside and outside of the home that monitor airflow and pressure. The manometer measures airflow at cubic feet per minute reading (CFM) measured at 50 Pascal’s. Using this number and the volume of the home, we can calculate the infiltration or leakage rate.
Formula for calculating the ACH on a house using a blower door:
ACH50 = CFM50 x 60 ÷ House volume
THE BENEFITS OF A TIGHTER HOME
The benefits of having an energy efficiency home with little air leakage are great. Here are some advantages:
HOMEOWNER REQUESTS BLOWER DOOR TEST - AUGUST 2016
Many people look forward to selecting paint colors, countertops and appliances when designing their new homes. One other item that they may want to add to the list is how tightly the home is built.
Recently a builder in the Capital District contacted Newport Venture’s asking us to visit one of their newly framed homes. The reason was to make sure this home would pass a blower door test with results at or below 4 ACH@50 Pascal’s. The new energy code requirement of 3 ACH@50 Pascal’s does not go into effect until October of this year. The reason for this request was so that the builder would meet the requirement as part of the contract agreement with the new homeowners. Read More...
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