Over the last 10-20 years a significant battle has occurred between the green building movement and the indoor air quality movement. The conflicts are rarely conscious, but the underlying goals of each side often create divergent results. What is good for one is bad for the other.
Ventilation is an excellent example of this tension. The energy efficiency crowd would prefer to maintain low ventilation rates, because ventilation decreases efficiency. Or, at a minimum, makes it much more expensive to maintain the same level of efficiency. Alternatively, the IAQ crowd would prefer dramatic increases in ventilation rates as a means to exhausting indoor pollutants. Ironically, this creates a scenario where the techniques that most benefit the planet (energy efficiency) offer the least benefit to the health of the people (ventilation).
Of course, this creates a bit of a false dichotomy. Builders have found clever methods for increasing ventilation without dramatically reducing energy efficiency. Heat recovery ventilators (HRVs) are a great example of this. However, the systems are not cheap, especially in retrofit projects. Thus, unless an unlimited budget is available, a sacrifice is often inevitable.
Lately, several fascinating studies have bolstered the side arguing for increased ventilation. The first study measured the performance of office employees in a call center. Performance measurements were collected on items such as information processing, telephone interaction time, etc. These measurements were collected before and after IAQ adjustments were made. In this study, two changes were used to improve the IAQ: 1st, remove 20 year old carpet and 2nd, increase the ventilation rates. Below are the changes in performance based on these changes.
Another similar study (Seppänen et al.) attempted to quantify the effect of specific levels of ventilation on performance. Both work and school performance factors were utilized. Perhaps most interesting was the significant improvement in performance achieved when ventilation was increased above building codes. It isn’t just underventilated buildings that negatively influence performance, but even normally ventilated buildings may be insufficient.
Far less research has been conducted on the effects of ventilation in a residential environment. Much of this is due to the difficulty of obtaining objective measurement points in a non-work setting. The most conclusive studies to date have instead focused on the secondary effects of ventilation, i.e. reduced humidity and dampness. Many studies have found a correlation between indoor dampness and negative health effects such as asthma and allergies. Improved ventilation, of course, can dramatically reduce the dampness of a building, and in turn, improve the health of the occupants.
According to the Lawrence Berkeley Laboratory, “the few studies that have directly investigated whether lower ventilation rates in homes are associated with a worsening of health have had mixed findings. These studies have considered only respiratory health outcomes such as asthma symptoms and wheeze. However, for indoor pollutants that have been clearly linked with adverse health effects, the reductions in indoor pollutant concentrations in homes with higher ventilation rates would be expected to improve health.”