Can A House Be Too Tight - ERV Fresh Air Experiment

The presenter explores the misconception that airtight houses trap odors and demonstrates how an energy recovery ventilator (ERV) rapidly removes moisture and odors from a tightly sealed house. The experiment highlights the benefits of a well-designed ERV in achieving fresh, filtered air while maintaining a tight building envelope, which is superior to traditional leaky houses relying on uncontrolled airflow.

Airtight House Experiment

• 00:00:00 The presenter built a very airtight house, with a blower door score at passive house levels. He aims to test the theory that such houses trap odors, particularly the idea that a fart would remain for a week. He utilizes a fog machine in his master bathroom to simulate odors and monitor air exchange.

ERV System Description

• 00:01:03 The presenter uses a Zehnder fresh air system with inputs and outputs in various locations, including the bathroom, kitchen, and master bedroom. The system runs at 130 CFM continuously, delivering and extracting a balanced amount of air 24/7, ensuring fresh air circulation and ventilation.

ERV Performance on Low

• 00:04:01 The initial fogging experiment with the ERV running on low speed shows a slow but steady reduction of the fog. It took roughly 20 minutes for the fog to significantly dissipate, implying effective air exchange, though complete clearance may take longer.

ERV Performance on High

• 00:06:36 The presenter reruns the test with the ERV on high (boost) mode. The fog clears considerably quicker than on low, demonstrating the system's ability to efficiently remove moisture and odor when necessary. After approximately 2 hours, the bathroom was completely clear of the fog.

Airtight House vs. Leaky House

• 00:10:17 The presenter argues that a super tight house with an ERV system is superior to a traditional leaky house. In standard houses, relying on wind for fresh air leads to unbalanced airflows, negative pressure, and infiltration of unfiltered air from undesirable locations, such as attics or exterior walls, potentially leading to moisture and condensation issues. Tight homes with a balanced ERV system, like the presenter's, ensure continuous, filtered fresh air and improved indoor air quality.