Jack Woolfe wants to build a small, airtight house with an attached garage. The house will have an exhaust-only ventilation system, meaning the system will expel stale air from the house without providing a specific source for replacement air.
That’s one of several options for whole-house ventilation, but Woolfe is weighing the possible risks.
“I’m concerned that the negative pressure in the house may draw unwanted fumes in from the garage,” he writes in a post at GreenBuildingAdvisor’s Q&A forum. “Are there any recommendations for supplying makeup air to the house so that there isn’t negative pressure in the house, or perhaps a well-sealed door between the house and the garage? Any other ideas, besides a HRV system or a detached garage?”
Woolfe’s question is the subject of this week’s Q&A Spotlight.
Consider occupant-sensing ventilation
Peter Smith suggests Woolfe consider something called occupant-sensing ventilation, available through Conservation Technology. The company describes it as a “continuous, multiport, exhaust-only” system. An efficient exhaust fan is connected to bathrooms, laundry and kitchen with a trunk duct and motion-sensing exhaust grilles. When the rooms are unoccupied, airflow rates are modest. When a room gets too humid or is occupied, airflow rates jump sixfold.
John Klingel has two additional ideas: install a high-capacity fan that starts up whenever the garage door is opened and runs for 20 minutes. The system would have an inlet for fresh air specifically for the garage. And second, Klingel suggests, install the door between the house and the garage so it opens into the garage. That way, any negative pressure in the house will draw the door more tightly closed.
Or, make the garage a detached structure
“If it’s not too late,” says GBA senior editor Martin Holladay, “consider a detached…