Air sealing is an essential part of any home renovation project, but it's possible to seal a house too tightly. A certain amount of fresh air is necessary for good indoor air quality and there are standards that set the minimum amount of fresh air needed for a home. You want to seal hermetically and, if necessary, ventilate properly. The Complete Source for Building, Designing and Remodeling Green Homes provides a comprehensive collection of thousands of construction details organized by climate and part of the house.
It's important to note that you can never do too much air sealing work - there's no such thing as too tight. The point at which an old, leaky house becomes cramped enough to start worrying about indoor air quality varies from house to house. A small house is more likely to need mechanical ventilation than a large house. The greater the number of occupants, especially if the house is small, the more important mechanical ventilation will be.
Therefore, there is no magic number (in terms of ach50) where mechanical ventilation is needed. Every enclosed home needs mechanical ventilation, and every green home must be a closed home. If you smell odors in your rooms or if you see condensation inside your window panes in winter, you probably need mechanical ventilation. A mechanical ventilation system can be as simple as a high-quality bathroom exhaust fan connected to a 24-hour timer.
If improvements in attic ventilation cause leaks in a house, it means that there are serious air leaks in the roof that separates the conditioned space from the attic. If the air flow increased, the holes between the house and the attic widened - this is going in the wrong direction. There is no way that these results can be explained as if the building were responding as it should. You've probably wasted your money on sealing and air insulation. You should think about getting them to rip it off and do it right.
The increase in attic ventilation does not explain the increase in leaks in the house, unless the attic was previously unventilated and was also somehow better air-sealed than the house. The only explanation is more vanishing points in the conditioned envelope. When installing mechanical ventilation, it's important to consider how to add fresh air inlets. Shock absorbers can be used to open when the system is turned on, but not all mechanical ventilation systems have air inlets. Exhaust only systems rely on random cracks in the envelope.
These termination accessories include recoil dampers. At 5:46 I don't see the need for more ventilation unless you have more than 20 occupants. If I were you, I would be very upset with this contractor. They drilled bigger holes between the house and attic which caused an increase in leaks from the roof to the attic. In conclusion, it's important to remember that while it's possible to seal a house too tightly, it's unlikely in most older homes. A certain amount of fresh air is needed for good indoor air quality and there are specifications that set the minimum amount of fresh air needed for a home.
You want to seal hermetically and, if necessary, ventilate well.
