The Importance of Good Ventilation
for Humidity and Temperature Control

CASA ventilation diagram


This diagram of a recent CASA project in Leschi shows a simple but highly effective passive ventilation system based on careful positioning and sizing of windows. In addition, external solor shades on the large, south-facing windows allow regulation of solar gain and convection currents.


PDFDownload large version of ventilation diagram


It's important to maintain an even temperature and humidity range in a home to stay healthy and stabilize the structure.


In our climate, relative humidity is around 40 percent in winter and around 60 percent and more in summer. With humidity lower than 40 percent you may get breathing issues; higher than 60 percent, you may see mold issues. If you maintain a constant temperature of, say, 68 degrees F in your home, then a good target for humidity is around 50-55 percent.


Aside from health issues, fluctuations in temperature and humidity cause expansion and contraction of construction and finish materials, especially wood. Wood expands as humidity increases and shrinks as it decreases, changes that are magnified if temperature moves in the same direction as humidity. These changes affect all wood in the house: a hardwood floor may warp and crack, and framing members will expand and contract, possibly causing nail pops in drywall and cracks in paint where there are joints, typically in corners. To maintain finishes in a home it is important to monitor and maintain consistent humidity and temperature levels.


Whether building a new house or a remodel, a whole-house ventilation system is the best way to manage air flow and humidity in every part of the house. A constant air flow maintains even humidity and temperature levels and removes harmful off gassing and airborne particles, resulting in a house that smells clean and fresh all the time and whose finish surfaces stay tight.


Using devices such as a heat recovery ventilator in conjunction with whole-house ventilation will result in a constant mixing in of fresh filtered air. It also allows precise and energy-efficient control of humidity in the ventilation system as seasonal conditions change.


In winter, before stale air is returned to the exterior, 80 percent of the heat is recovered, resulting in a more efficient use of energy and lower carbon footprint. In summer it works in reverse to help keep the house cooler. These devices will work with a variety of mechanical systems such as a forced-air furnace or hydronic system, or can be implemented as a stand-alone system in the case of passive-house technology.


Here are several informative web sites and online articles explaining how to maintain a healthy indoor environment, improve energy efficiency, and lower your carbon footprint:


Elementary Energy: Sustainable Solutions Engineered to Save


Passive House (Passivhaus) Standard for Energy-Efficient Design


Air-to-Air Heat Exchangers for Healthier Energy-Efficient Homes