Here are a few recent building code trends:
- Airtightness requirements are becoming more stringent.
- An increasing number of jurisdictions are mandating blower door tests.
- An increasing number of jurisdictions are requiring homes to have ventilation systems.
Among builders, there is some resistance to these trends. During a visit to your local lumberyard, you may hear a builder grumbling: “No one wants to live in a plastic bag. The new airtightness requirements make no sense—these tight buildings are all going to rot. It’s always better to build your walls and ceilings to be a little bit leaky. You need some air movement to keep a wall dry. That’s why walls stayed dry in the old days. Back then, when walls were leaky, we didn’t have as many problems with mold and rot as we do now.”
While these opinions sound like common sense, they are ill-founded. Let’s delve a little deeper into these issues to understand why.
Why, exactly, do you like air leaks?
Builders who argue in favor of leaky walls aren’t always clear about their motivations. To address their concerns, we need to distinguish clearly between two entirely separate issues:
- Issue 1 is a concern about occupant health.
- Issue 2 is a concern about material durability—specifically, a concern about moisture accumulation leading to rot.
Both concerns are legitimate. In this article, I’ll explain why random air leaks aren’t a good way to address either concern.
Ensuring high indoor air quality
We can all agree that “no one wants to live in a plastic bag.” We want our indoor air to be high-quality air.
Most people agree that we don’t want indoor air to be stale or smelly. Others strive to attain a particular technical goal—for example, they may want to keep indoor…