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BUILDING A HEALTHY HOUSE

Universal Principles for Building Healthy Homes

There are several principles that need to be understood and practiced when designing and building a healthy house. In fact, I would encourage these principles to be considered and applied to any project.

There are four universally accepted principles in building any healthy home that were crucial in building this MCS house:

1. Eliminate toxic materials as much as possible.

2. Separate sensitive or toxic materials that can't be eliminated by sealing them off from the living spaces.

3. Ventilate with fresh air.

4. Filter the air to remove any pollutants, particulates, and gases.

It was imperative that extreme care be taken in every aspect of this project since accidental contamination would, in effect, defeat our purposes. Consequently, extra time and attention was necessary to ensure that the separation, encapsulation, ventilation and filtration were done correctly. In determining exact specifications, all materials and systems were researched and tested for toxicity.

Healthy House Principle No. 1: Elimination

Our client is sensitive to most synthetic and petro-chemically-based materials including fungicides and pesticides, most adhesives, smoke particulates, all perfumes and scents, toluenes, solvent based materials (including cleaning solvents), mildew and molds, cedar, pine, and formaldehyde (especially the urea form). This eliminated the use of most of the construction and finish materials used in standard building practices today.

Every material that was used in this house was researched, and then reviewed and tested by the client. Her involvement in this process was essential. For every product used, two to four others researched and rejected. We kept an ongoing log of materials that had been tested and approved in a Quick Reference List. Throughout the job the contractor and subcontractors referred to this list to verify acceptable products.

The availability of non-toxic and less toxic materials is increasing. We obtained and reviewed the Material Safety Data Sheets (MSDS) describing all materials that were in any products we were considering to determine if they contained unacceptable materials. Whenever possible we chose products that were not only non-toxic, but also considered sustainable. Too often, however we would find resins, adhesives, or preservatives which prevented our using certain products. This was particularly a problem in composite, and engineered products.

We also followed construction methods commonly used prior to WWII such as use of solid, natural materials like stone, solid wood, etc.; thick-set mortar rather than mastic; and overall, avoided synthetic, tar-based, quick-drying, composition, and solvent-based materials.

Healthy House Principle No. 2: Encapsulation

Once we knew what materials could be used and which ones would be a compromise, the next step was to detail ways to encapsulate or separate the more toxic materials from the interior living spaces.

Standard exterior products that create good moisture-barriers were very toxic to our client. However, we were very concerned with the long--term durability of the house exterior. After serious consideration we chose an oil-based stain for the exterior shingles because it out gasses quickly, will hold up longer to wind and rain, and allow more years between repainting. For durability and warranty reasons, we used a toxic but standard, tar impregnated building paper in the roof sheathing, under a metal roof.

We were willing to compromise the non-toxic aspect of the exterior wall and roof assemblies only because we could keep these products several layers away from the interior spaces. We achieved this separation by wrapping the exterior plywood sheathing with Tyvek, and the framing of all interior spaces with a moisture and vapor barrier foil-backed kraft-paper. All joints in the framing including the mud sills of all exterior walls were caulked to the plywood sub-floor. The gypboard and plywood sheathing were caulked at the seams, and a vapor barrier primer paint was used to seal the gypboard. Finally, throughout construction, all holes and cracks from gaps in the framing, electrical, ducting, or plumbing penetrations were filled with either a silicone caulk, silicone foam seal, backer rod, or insulation.

Healthy House Principles Nos. 3 & 4: Ventilation & Filtration

Constructing a building this air tight was done not only to separate the living spaces from more toxic products, but also as part of the controlled environment for a whole house ventilation system.

In investigating other MCS homes, we discovered that the one universal aspect for every home was its air filtration system. Air quality plays a major role in the health of a building, especially with the high standards for tight, well-insulated buildings. While sensitivities may vary from person to person, the single most effective intervention for a healthier environment is a good quality air filtration system.

To achieve maximum air quality, several levels of filtration were installed. When the ventilation system is closed, and all the doors and windows are shut, air is brought from the forest edge side of the house, entering the attic through a heat recovery ventilation unit that preheats then pre-filters the air. The system also includes a whole house fan to keep the air filtered, circulating, and the interior space pressurized. The air filtration uses both hepa and charcoal filters to absorb microscopic pollutants and gases (such as formaldehydes). All exhaust is vented towards the garage and driveway. In addition there is a 3500 cfm whole house emergency fan to evacuate pollutants quickly should there be accidental contamination.

One of the major sources of formaldehyde pollution in today’s environment is fabric and clothing since virtually every piece of fabric, clothing, upholstery, drapes, carpeting, sheets and linens, bath towels, etc., are permeated with formaldehyde as a finishing agent. This is not an inert agent, but out gasses for an indefinite time. Because of our client’s sensitivities, and because both moisture and other solvents are problematic as well, the crawl space, closets, bathrooms, and utility room were also individually vented.