What is a potential disadvantage of balanced ventilation as described?

• A. It may require makeup air when exhaust-only systems are also installed for combustion appliances
• B. It eliminates humidity completely
• C. It requires no maintenance
• D. It works perfectly in all climates

Answer: (A)

Balanced ventilation moves equal amounts of outdoor air in and indoor air out to control air quality and pressure. A key drawback is that when there are combustion appliances that vent exhaust separately, those appliances pull air from the living space. If the house is already balanced, that exhaust can create negative pressure unless additional makeup air is provided. In such cases, a makeup air source may be needed to supply the needed air for combustion and to keep the indoor pressure from pulling in air through leaks or causing backdrafting. This is why the potential need for makeup air when exhaust-only systems exist is the best answer. Humidity isn’t eliminated by balancing ventilation, maintenance is still required, and no system guarantees perfect performance in every climate.