A healthy home is built by implementing healthy design elements. Building science principles should be applied in choosing appropriate low-toxic building materials and effective construction techniques. An integrated whole-house ventilation system should be incorporated to help eliminate air pollutants. Additionally, the home should be constructed with a great emphasis on resistance to water penetration and on humidity control – humidity levels should ideally be maintained between 25 and 55%.
The majority of Americans spend well over 50% of their time in their homes in what they believe or hope is a healthy and safe dwelling. However, the Environmental Protection Agency has reported that the internal air quality of homes can be much worse than the outside air; many times containing levels of pollutants that are two to six times higher than the outside air. All of us at studio26 are dedicated to doing our part in addressing this air quality concern.
There are many types of possible pollutants in the internal air of homes, and they may come from various sources. The three main origins of pollutants are from the building structure, the home furnishings and activities inside, and the outside environment. Builders need to be selective in the techniques and materials that they use during construction to limit the air pollutants that can be generated from the building itself. They also need to be concerned about how their homes can effectively minimize, dilute, or exhaust air pollutants. Common pollutants that can affect internal air quality are numerous and include: dust, mold, carbon monoxide, nitrogen oxide, formaldehyde, volatile organic compounds (VOCs), radon-gas-related compounds, smoke, micro-organisms, pet dander, and other allergens.
Local building standards and codes normally don’t address enough of these air quality concerns. However, a healthy indoor environment is a primary concern in the design and construction of your studio26 home, particularly since much can be done for relatively little added cost.
Standard Features – Some standard features that studio26 will include in most of our future homes are outlined below:
Our homes are built with an extremely tight envelope to greatly improve energy-efficiency. This tight enclosure is also designed to block air infiltration and water penetration from the exterior while allowing any possible water vapor to transfer when needed for drying purposes to either the inside or outside. Details of our Demonstration Home’s envelope design can be found in the November 2006 issue of Green Builder Magazine [hyperlink to new window PDF here]. In homes, mold can be a serious pollutant that must be controlled. There are numerous kinds of mold that can grow in many places within the home. In fact, mold can be found almost anywhere that both water and their food source are located. For example, mold can easily grow in the walls of a home if water or dampness is present, since wood can be a food source for mold. We pay serious attention to our moisture management plan including the installation of an effective drain plane within the wall to help manage water penetration into the envelope from the exterior side. However, since we never assume that water can be completely controlled 100% of the time, we also design the wall section to allow moisture in the form of water vapor to escape and ultimately dry to one or both sides of the building envelope.
Heating, Ventilation, & Air Conditioning
Since our homes are built very tightly, studio26 has the advantage of designing and implementing – without compromising energy-efficiency – a sophisticated HVAC system that provides fresh, conditioned air evenly distributed throughout the entire home. To help avoid the harsh climatic swings through the seasons, both the HVAC equipment and the ductwork are ideally located inside the conditioned building envelope. The system’s ductwork is almost exclusively constructed of galvanized sheet metal (compared to the common practice of installing fiberglass duct board) to help maximize airflow due to less resistance inside the duct and also minimize the possibility of harboring any undesirable airborne particles. Both supply and return ducts are typically insulated and efficiently designed to run as short as possible to help ensure that the temperatures at the diffusers/registers within the rooms of the home are extremely close to the air temperature at the central air handler. This helps provide even temperatures within a room and also among rooms around the home. Furthermore, duct airflow rates are designed and air sealed with a special mastic to not only sufficiently maintain the appropriate room temperatures throughout each season, but also to maintain a positive pressure inside the house even when any spot ventilation is operating in the kitchen or baths. Due to the home’s ultra-tight building envelope, our homes are also equipped with energy recovery ventilator (ERV) units to help exhaust stale air and bring in fresh air with very little heat loss. This fresh air is then sent to the central air handler where it is first filtered and then distributed throughout the various zones of the house. Through programmable thermostats, microprocessor-controlled zone heating and cooling is utilized to enhance the versatility of the whole-house HVAC and increase overall occupant health and comfort.
As a critical component of the HVAC system, all of our high-performance homes are equipped with an effective filtration system that delivers cleaner and healthier air within the home. In fact, depending on the specific needs of the project, we often install a whole-house air cleaner capable of removing up to 99.98% of airborne particles and allergens from the filtered air. Since the unit is located at the variable-speed central air handler, air is able to circulate through the filters at the lowest effective level, meaning more thorough air cleaning. Depending on the specific unit installed, the manufacturer reports that the filtration system removes sub-micron particles with high efficiency and is several times more effective in removing fine airborne particles than any HEPA filters.
Building materials used during home construction certainly can and many times do contain toxins or pollutants. Examples of such materials commonly used today are: particleboard, hardwood plywood, engineered lumber, carpeting, sealants, and adhesives. We research the materials that are used in the construction of our homes, and indoor health to the future homeowner is an important factor in our material selections. For example, studio26 prefers to use lower formaldehyde-emitting products when possible. There are references to other specific low-emitting materials that we use during construction in several sections below.
Dry basements are very important because damp basements are a good source for mold and mildew problems.Our approach for a dry basement is to:
- Install a sub-surface drainage system, complete with crushed stone and filter fabric, adjacent to the footings around the perimeter of the entire foundation;
- To address a typically overlooked detail, apply an effective waterproofing membrane to the top face of the concrete footings prior to the pouring of the foundation walls, which will help ensure a critical capillary break to minimize the transmission of unwanted moisture and soil gases through the concrete
- Similarly, apply an effective waterproofing membrane to the exterior face of all below-grade foundation walls;
- During backfill, slope the ground near the house at 5 degrees or greater away from the house
- Inside, first install at least 2” of rigid insulation (R-10 or greater) board above the crushed stone in the basement area;
- Then install polyethylene sheeting (moisture barrier) over the rigid insulation board and bring it up the foundation walls before pouring the basement concrete floor;
- After the slab is poured, apply a penetrating top-coat sealer to the inside faces of both the foundations walls and concrete slab to further restrict the transmission of moisture and soil gases; and finally
- When possible, include the basement within the conditioned space of the house – that is, insulate and heat the basement.
Radon Mitigation System
Radon is an odorless, colorless gas that originates from naturally decaying radium and uranium. In certain parts of the country where radon is more plentiful, especially in Eastern Pennsylvania, it can seep into homes causing a serious health hazard over time. When the gas is present in the home, it can decay into radioactive products that can be inhaled and even cause lung cancer. Since we build homes in a radon susceptible region, we always install a radon mitigation system, which conforms to the U.S. EPA requirements.
Central Vacuum System
When possible, studio26 believes that central vacuuming should be incorporated so that pollutants are removed completely from the house, particularly when vacuuming carpet. In many of our homes, we provide an effective central vacuum system equipped with a powerful motor more than capable of servicing all of the rooms. As our standard practice and a critical healthy home detail, the vacuumed dirt and pollutants are not only collected in the system’s filtered tank, but also exhausted directly to the outside and not into the garage or basement as is often seen in homes.
A poorly vented combustion appliance such as a furnace or fireplace is a serious health hazard. A by-product of most combustion processes is carbon monoxide, which is an odorless, invisible, and toxic gas. As an initial barrier to a common source for carbon monoxide, the attached garage, we install polyethylene sheeting under the drywall in the walls/ceilings shared between the house and the garage. Additionally, our homes have UL approved carbon monoxide monitors/alarms on each level of our homes including rooms above the garage with a minimum of one near each sleeping area. For further protection against carbon monoxide, our installed fireplaces and combustible heaters (i.e. tankless water heater, etc.) are always sealed and direct-vented to the outside. In the kitchen, our homeowners often select an induction kitchen cooktop instead of a gas-fired unit. Gas-fired cooktops do have certain cooking benefits over conventional electric cook-tops such as speed and better control, however so do induction cooktops. In addition to eliminating the production of combustion by-products inside the house, induction cooktops are more energy-efficient and even faster than gas-fired units, which also help save dollars on your energy bills.
Paints and Finishes
The paints, stains, and other finishes that homebuilders use can greatly affect the internal air quality of the home because these products can release trace amounts of undesirable gases, such as volatile organic compounds (VOC), for a long time after a home is built and occupied. As a result, studio26 specifies environmentally friendly, zero-VOC paints, stains, and finishes wherever possible.
Generally, we try to install as many smooth surfaces as possible around the home simply because dirt, dust, common bacteria, and other household pollutants are easier to remove during cleaning. For flooring, we typically prefer surfaces such as hardwood, ceramic tile, natural stone, or slate compared to more cavernous surfaces such as carpeting.
We suggest the minimal use of carpeting not only because of its course surface, which can often harbor dust mites and other allergens, but also because it commonly emits unwanted VOCs into the air. As a result, many of our homes do not have carpeting. When carpeting is preferred by our homeowners in parts of the home, we recommend environmentally-friendly padding and carpets with a short pile and pile made of nylon, polyester, or wool. We also recommend selecting carpet with the Green Label / Green Label Plus certified by The Carpet and Rug Institute (CRI). Furthermore, we strongly prefer not to install carpeting in the basement, kitchen, and bathrooms where elevated levels of moisture are typically found in the home.