filtration

Part 10 of our 15-part Q&A series on all aspects of green building from the publishers of HealthyHouseInstitute.com. Click here for the introductory post and furthur details.

Question: Won’t a good air filter remove all the pollution in my house?

Answer: In most cases, filtration isn’t the single answer, but it can be part of the answer. To have good indoor air quality, you first need to apply the three Healthy-House Design Principles of eliminate, separate, and ventilate. Once that’s been done, the indoor air should be pretty good, and you can use a filter to remove any minor pollutants that are left. A good filter is not a substitute for ventilation because filters can’t remove moisture from the air and they can’t supply oxygen.

If you want to try and use filtration to clean up the air in a problem house, you’ll need a very powerful system that will filter the air several times an hour. This will be expensive, breezy, and noisy, and it won’t be as effective as applying the three healthy-house design principles first.

If you decide to use a filter, there are three ways to do so. First, you can use a portable room-sized filter unit. There are a number of companies that offer these free-standing units.

Portable filters work best in a single room, with the door closed, and the filter left running continuously. Second, for whole-house filtration, you can let the fan on your forced-air furnace or central air conditioner run continuously so its filter will remove pollutants passing through the system. Third, you can use a filter with a general ventilation system to filter the incoming air—air that isn’t always as clean as we’d like it to be. In some cases, it can make sense to combine a forced-air heating/cooling system with a ventilation system. That way, one filter (and one set of ducts) can serve both systems

Question: My furnace already has a filter. Isn’t that good enough?