Just got sent this article (thanks Paula Olsiewski) “The Passive House in New York” which is an interesting article about the increasingly popular concept of passive houses. As the name suggests, passive houses maintain an appropriate ambient temperature without heating or cooling, mostly through airtights seals, a lot of insulation, and some sort of air exchange system.
Energy savings and comfort aside, what I’m really curious about is the effect of this sort of design on the microbiology of these environments. With work showing for example that in a hospital with sealed windows the indoor environment looks mostly like a sick person, it’s not clear that “sealed in” is the best state for a healthy building microbiome (if such a thing exists). I’m obviously on board with energy savings, but wonder if there are long term negative microbiological effects. More detail on the filters in the air exchangers would be helpful… if they really do bring in a lot of outdoor air and don’t filter out the microbes maybe there isn’t a problem.
At the least, seems ripe for a detailed longitudinal study!
One thought on ““Passive Houses” seem ripe for study of microbes”
I completely concur that passive houses are ripe for investigation of their indoor microbiome. I am less concerned about the details of the filtration (although that is an issue) and much more concerned about moisture. The Passive House approach originated in Northern Europe: a climate that is characterized by a need for heating in the winter and much less of a need for air conditioning. One of the classic problems in sustainable buildings is when we take a design that is specific for one climate and adapt it to another. If you overlay that with some important differences in building materials and construction processes, there is the potential for some big problems. Some specific examples:
a)Passive House (and similar) designs are characterized by very air-tight construction. This obviously saves energy and gives some control to air movement in the house (both good things). However, it also means when things get wet, they don’t dry as fast. As every researcher working in the built environment should know: water can mean moisture problems and moisture problems negatively impact health.
b)In a predominantly cold climate, it is best to depressurize a building. Outdoor air is dry and therefore you will help dry the building envelope as the air moves into the building. In a predominantly hot climate it is best to pressurize because the moisture/humidity is coming from outdoors. Joe Lstiburek said it best “Yankees suck, Rebels blow.” In the mixed climates of the midwestern and eastern US and Canada, it gets a little trickier and sometimes the materials that are used in Passive House construction don’t deal well with the moisture in the other season.
c)Related to b), consider something as simple as a clothes dryer. A dryer works by venting a large amount of humid air from the dryer to the outside. If you combine that with an air tight envelope, you can get a phenomenal amount of depressurization. In some climates and seasons, this can mean a dramatically increased potential for a moisture problem. There are such things as condensing dryers that don’t vent, but this kind of issue highlights the importance of the “house as a system” and the complexity of buildings that many of us on the building science side talk a lot about.
I want to be clear that I am encouraged by the idea of Passive House and there have clearly been many success stories from construction like this. But, there is also a strong need to think much more about the microbiology (and more generally the indoor air quality) that arises with energy-efficient construction.