Buildings in the United States consume 68% of the electricity generated in the country and 37% of the energy. If we consider our sources of energy, the political, economic, and environmental consequences of obtaining and using this energy, we immediately realize we have a problem. We do not yet have an unlimited of energy. The energy needs of our country are increasing. There are drawbacks to most energy sources. The logical approach is to develop and refine each track in the most benign possible way, and to be more efficient in our use of energy. This last phase needs to be underscored, understood, and undertaken. By becoming more energy savings , or efficient, much energy, political expenditure, money, etc., can be conserved. How do we become more efficient?
One building or house built efficiently, will not answer this problem but it is a start. Each one is built inefficiently is an addition to the overall problem. We already have a number of tools which will cut down considerably on the energy usage in buildings. Unfortunately, most builders, architects, and designers choose to ignore the most important of these. This is the use of efficient insulation. Preventing heat loss across a material is the job of insulation. Heat loss can be by convection, conduction, or radiation. Convection requires movement of a gas, usually air. Conduction usually occurs through a solid material, such as a frying pan. Radiation is the reason you feel heat from a hot metal roof overhead in the summer.
Here is a list of insulating materials and comments. Please see Wikipedia on R value and qualities of various insulators.
- Fiberglass. Average. It settles over time, losing space between fibers, allowing more conduction and airflow or convection. Inexpensive.
- Cellulose. Settles. Can be flammable. Inexpensive. Cold bridges.
- Icynene spray. Expensive, messy, good, but cold bridges remain from stud construction.
- SIPS, Moderate cost. Good insulation. No settling. Strong. Forms relatively airtight envelope around living space with less than 1/10th the airflow through a fiberglass stud-wall building.
- Vacuum Panels. Excellent. Expensive. Fragile.
Years ago, most thoughtful timber frame companies settled on insulated panels or SIPS which significantly reduce the airflow through building walls and roofs. The USDOE in studies at Oak Ridge National Laboratory has shown in whole walls (including window and doors) that equally R-rated SIPS or panel insulation compared with fiberglass batt insulation has only 10% of the airflow through the structure. Accurate records show that it costs half as much as to heat, cool,and power a SIPS insulated building than a fiberglass stud-wall building with the same R-ratings. Over a period of years, in a fiberglass stud-wall building, these differences in air flow along with settling of the fiberglass, consume large amounts of wasted energy energy into a much more expensive building, and long term costs to the owner and our country.
Here is the key. Stud walls keep a poor insulator, wood, as a bridge every 16 or 24 inches to decrease the insulating efficiency of the wall or roof. SIPS maintain a tight membrane.
Here is the bottom line. One must rate an insulating system by measuring its performance over a lifetime of a building.
Users and manufacturers of insulated panels have known for years the efficiency of panels and have documented these monetary savings. Sadly, they are still a well kept secret.
A timber frame house, 1,800 sq. ft., heated with an electric heat pump, in Western, North Carolina has cost an a monthly average $50 to heat, cool and power, for the past four years.
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