The Virginia Residential Building Code allows two options for verifying air tightness in new construction. The first option is a Blower Door Test and the second is just a visual inspection, which as you can imagine, is the most commonly used method as it is generally cheaper (up front) and does not require any equipment.

Additionally, the building code requires new residential construction to have less than 5 air changes per hour when negatively pressured to 50 pascals (ACH50). This reduces energy usage and the amount of outside air coming into the home from unhealthy places such as crawlspaces and attics.

The code also requires greater than 3 air changes per hour under natural conditions (ACHn). If the new construction is less than 3 ACHn, the code requires the installation of additional mechanical ventilation to remove stale air containing pollutants and moisture generated within the home before reaching harmful levels.

So how do you know how tight or leaky the building is with just a visual inspection? You don’t!

if the building is too tight and air pollutants and moisture cannot exit the home, the indoor air can become a toxic soup and all that moisture typically leads to high levels of mold growth. Conversely, if the building is leaky, you can look forward to higher energy bills, uncomfortable buildings, and unhealthy air and living conditions.

Diagnosing and mediating these problems can come at a high price, particularly if hired “experts” incorrectly diagnose the problem and recommend expensive solutions that do not work. We’ve seen it happen many times.

Since changes in Building Codes only occur every few years, and this particular code may or may not change, our hope is that contractors will elect for the Blower Door scenario. If you are to be the homeowner, please, request that your contractor have a Blower Door Test.


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