Humidification—Pros and Cons
Photo credit: http://energetechs.com
We are often asked to provide humidification in residential projects in the mountains. The request is understandable, especially if the owners spend most of their time in a moist climate. (Let’s face it, almost anywhere is more humid than the high and dry Rocky Mountains.)
However, there are some good reasons to be cautious about humidifying a home in a cold climate. You can re-create bayou conditions if you really want to, but you may create a host of other problems. Here are the main ones:
- Condensation. When you add moisture to the air in a house, you are increasing the dewpoint of that air—the temperature at which it will form condensate. Any surface colder than the dewpoint—typically, window frames—will sweat and accumulate water and even ice. This gets messy, and if it continues, can create mold and rot. Condensation can also happen in less-visible locations such as roof and wall framing, especially if vapor barrier installation was not done correctly (or at all).
- Maintenance. All humidification systems require maintenance. The very act of turning water from liquid to vapor leaves behind dissolved salts, which accumulate and must be removed by media replacement or cleaning. When we investigate problems in existing homes, we find that humidification systems usually aren’t running properly, and are often disabled from lack of maintenance.
- Cycling. High-value objects made of wood (i.e. fine furniture, custom guitars, etc.) can suffer from dryness. However, going back and forth between humidity and dryness usually creates the most damaging situations. Stability and consistency are more important than absolute humidity levels.
We are not saying that humidification systems should never be installed—just that owners and architects need to consider the whole picture when deciding to humidify. If it’s still important enough to go forward, here are some measures to minimize potential problems:
- Carefully design and detail the building envelope, using good insulation techniques, high-quality windows with low U-values, and proper vapor barrier installation.
- Aim for the lower end of the humidity range—25–30% instead of 35–45%.
- Design humidification equipment for easy access and proper maintenance.
- Control for consistent humidity levels rather than turning it up for a few weeks each winter.
- Consider using table-top humidifiers instead of building them into the HVAC system. The fact that they are visible has benefits: you know when they are working, you can directly control them for your own comfort, and maintenance issues will be more obvious.
Download one-page pdf with this information: Humidification Pros Cons