Indoor Environment Systems

Indoor Air Quality

Homebuilding has been evolving in North America for over three centuries. Starting with the log cabin, the American home construction industry has been heavily influenced by the vast availability of forest products. The entire continent is influenced by a "2x4" mental paradigm about how a house should be built.

During this period of evolution, improved products and methods have steadily advanced. And currently, energy conservation considerations are playing an important role in the building industry. Concurrently interest in environmental air quality has become a significant factor. One of the consequences of this interest is that houses are continuously becoming tighter, permitting less and less infiltration of fresh air into the interior envelope. This is true for all house construction and not necessarily just for the materials shown here. The use of a total concrete shell as described here assures a tight envelope.

We want fresh air coming in and stale air going out.

Occupants of tight houses are not only consuming oxygen, they are also contributing carbon dioxide (CO2) to the indoor atmosphere. In addition, pollutants and odors can build up. They include for example, paint and similar solvents, pet danders and wastes, cleaning chemicals, aerosols, radon, insect wastes, airborne viruses and bacteria, tobacco and fireplace smoke, and other indoor pollutants.

The heating, ventilating and air conditioning (HVAC) industry appears to have recognized this need and some have responded with improved equipment to address the need for fresh air in and stale air out. Some companies have developed specialized air exchanging equipment. Below is an illustration of a typical energy-efficient air exchanger. For a sense of size, it is approximately 3x2x1.5 feet in dimension.

Cut-away illustration of a typical exchanger.

Such devices are appropriate for buildings where the ambient weather conditions are not conducive to year-round natural ventilation from open windows and doors.

Ductless Heat Pumps

With the disaster-resistant structural systems demonstrated in this website, the necessity for constructing attic spaces is obviated. Energy-conserving insulation is installed as an integral part of the structural wall and roof systems.

In order to avoid installing air distribution ducting systems, the use of through-the-wall refrigerant-based heating and cooling devices becomes practical. Such devices are now readily available around the world with about 30 manufacturers. A very informative presentation about such systems prepared for the Northwest Energy Efficiency Alliance (NEEA) by Jeffrey Pratt is Ductless Heat Pumps [PDF].

Through the use of expanded poly-foam insulation of thicknesses sufficient to produce the code-prescribed R-Value for walls and roofs plus the availability of new highly efficient window systems now on the market, heat losses can be reduced exponentially in new house construction. The long-term annual savings in energy costs can offset the initial cost of installations by a considerable reduction in energy billings every year for the life of the structure. Costs of installing heat pump type environmental systems can be offset by the elimination of ceilings as well as forced-air ductwork during house construction. Duct energy losses may account for as much as 30% of the cost of energy for a typical house. Using the construction technology shown in this website seminar, house sustainability may exceed 200 years or more. Gross energy cost savings over that kind of time period can be substantial.

Ductless heat pumps are mounted on a small amount of wall space near the ceiling. These products fit seamlessly into nearly any home decor. Comfort is easily and precisely controlled using an infrared remote control. The ductless air conditioning systems, often called ductless high walls or mini-splits are also a quiet and efficient alternative to window air conditioners.

These ductless air conditioners (Mini-split Air Conditioners) have two main components: an outdoor condenser, and an indoor air-handling unit, containing evaporator and blower. Ductless mini-split air conditioners have numerous potential applications and advantages:

Use of the insulating form concrete construction methods described here also enables elimination of attic spaces and air duct systems. This not only saves money during construction but also project execution time. It also eliminates the need for several specialty trade subcontractors who sometimes compete with each other for workspace.

While the initial installation cost of a mini-split system may be somewhat more than conventional centralized HVAC systems, the savings in monthly energy costs will amortize this difference in a relatively short period of time. The long-term energy cost savings become appreciable with time. With the ever increasing cost of energy, this will be a significant factor in the future cost of living.

For additional details about this subject, see the U. S. Department of Energy's Ductless, Mini-Split Heat Pumps website.

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