Some homebuilders have suggested that ASHRAE's ventilation proposal could add $1,500 to $6,000 to the cost of a new house, but ASHRAE's proposal could be easily and inexpensively done.
One continuously running 100 cfm bathroom exhaust fan that is exhausted to the outside would do the job for a 2,400 square foot house and this modification would cost only $75 to $100 more than the exhaust fan and venting that the builder would already be installing in the bathroom, said Max Sherman, also of the Lawrence Berkeley National Laboratory, who has studied indoor air for 20 years.
Putting a smaller continuously running fan in each bathroom is a more expensive solution, but it would distribute the fresh air more evenly.