Healthy Buildings - Issues

Before the "energy crisis" of 1974, houses were typically so leaky that the air in them changed as much as ten times an hour, diluting any contaminants in the air enough so that they weren't a problem.  Homes are not only much tighter now, the also typically contain numerous man-made compounds that are either known toxins, or suspect1.  These are not just ones that are part of the buildings construction, but brought in with furniture, cleaning supplies, pesticides, herbicides and various other chemicals.  Improperly constructed tight houses are also very prone to mold problems, particularly when moisture control techniques have not been used.  For the chemically sensitive, even natural materials can be toxins, its just that at the levels they normally occur, most people aren't affected by them.

Why not just stop building so tight?  The obvious reason is that air leakage results in a lot of wasted energy, and someday that energy is likely going to be very precious.   Plus drafty buildings aren't very comfortable.  Even is energy were cheap, the alternative question is: why not just use healthy materials?  Its true that they're often more expensive, but its also true that they often last longer and look better.

Isn't the indoor air cleaner than outdoors?  Emotionally, we often think of our indoor air being cleaner than outside, but in reality there is nothing in a house that would naturally filter the incoming air, and pollutants that are introduced inside tend to stay there for a long time.  Contaminants are everywhere and so avoiding them completely is impossible, although it is possible to seal a house very tight and use mechanical ventilation and sophisticated filtration to make the indoor air cleaner than the outdoor.  Some pollutants are naturally occurring, some are floating around in the air almost everywhere (pesticides, combustion by-products, and various industrial chemicals), while others are introduced into the house.  Unless a home is located in a very dirty location (eg most cities near a road or dirty manufacturing, although some cites are clearly worse than others), the outdoor air is usually considered "clean enough". 

What's a contaminant? When the chemical in question is naturally occurring, such as formaldehyde, it is often possible to find out what the range typically occurring amounts is, and use that as a benchmark.  In spite of all the News coverage of VOCs, particulates and molds are often are more significant health problem.

The contaminants in a house can be grouped into four broad categories: particulates, molds, VOCs (volatile organic compounds) and radiation.   For more information on these, see the section on Contaminants.

Being healthy involved more than avoiding the deleterious affects of the environment, but also promoting the positive ones.  People need daylight, a comfortable temperature and both private and public space that support their daily indoor activities.  This positive effect of the environment is much harder to quantify and is covered in the design section because of the great affect they have on architecture.

What are the strategies?  Healthy house construction is really a series of techniques that could be grouped into levels by how big of an impact the technique will have on the health of a typical occupant.  Although some effort has been made to classify what these levels should be, there is no consensus, as human physiology is notoriously variable, and for many people there is an emotional issue concerning what makes them feel safe.  The government often publishes standards for toxics, which come as two numbers: the amount below which there is no apparent health consequence and the amount above which most people are negatively affected.  But of course, these are just averages, and any given person may be more of less affected.

With this big picture in mind, making a house healthy can be boiled down to just a few strategies:

  1. Keep water out; which breaks down into three major components: keep rain out, keep groundwater out, and keep water vapor from condensing. Any time any material that contains cellulose (e.g. wood, straw, paper) gets wet, mold will begin to grow on it, and some molds are highly toxic.

  2. Keep toxics out.  While much attention has been given to VOCs in building materials, it is equally important to not bring toxics into the house, such as solvents, some cleaners, pesticides etc.

  3. Ventilate and filter.  Since some buildup of toxic compounds is likely, and we also need a constant supply of fresh air, it is important to provide fresh air.  Filtering the air removes dust and allergens, although unless the air in or out is especially dirty, filtration is often not necessary.  Contrary to common belief, the air inside your house is never cleaner than outside because it comes from outside (unless you filter it first), and typically it is much more contaminated than outside air, as the contaminants tend to stay confined to the house.

  4. Insulate for comfort. Insulation not only saves energy, but it  makes the house more comfortable.  This is discussed in the energy section, under envelope.

  5. Provide adequate daylight.  This can help prevent Seasonal Affective Disorder (SAD).  For a discussion on daylighting, see the lighting section  and windows in the design section.

Each of these issues are non-trivial and require significant attention to detail on the part of the contractor.  Even if  construction is done completely negligent, problems often don't show up for a year or so, and often more than that.  For example, by the time mold spots begin showing on sheetrock, there is typically a huge infestation of it hidden in the wall.  In other cases, small construction errors results in a slow buildup of mold, and problems may not show up for ten years or so. Finally, the human body is quite good at protecting itself against contaminants up to a point, but unfortunately by the time a persons symptoms become obvious, they can easily be so sick that there is no easy cure.  Obviously it is important to remove yourself from the contaminants before your immune system stops functioning correctly.

There is also an issue in how much effort is worth it, and to some degree that depends on whether a person has a compromised immune system or not.  There tends to be a fairly large gap between what code requires you to do and what the various healthy house advocates recommend.  The American Lung Association is creating a national "health house" standard, which as of this writing (spring 2003)2 is quite strict, and as a result probably won't get a large following.


1: the treatment here is that suspect toxins are treated as toxins. which would seem to be the conservative (ie safe) choice.

2: Jan 2010: I heard progress was made, but have not checked back in on this.