Frequently Asked Questions

Energy, energy use, energy efficiency, and building science are all complex subjects. E-Star™ provides answers to many questions on these and related topics. The following is a compendium of questions submitted to E-Star. If you would like more information feel free to e-mail question to Matt Thornberry.

E-Star

What kind of organization is E-Star?
E-Star is a non-profit organization with 501(c)(3) status with the U.S. Internal Revenue Service.

What is the difference between E-Star and ENERGY STAR?
E-Star is a Home Energy Rating System (HERS) program that is certified by a nationwide program called the Residential Energy Efficiency Network(RESNET). E-Star’s energy rating program is a “yardstick” for measuring the energy efficiency of a home based on a 0-to-100 point scale. There are HERS programs like E-Star in virtually every U.S. state; however, E-Star is the predominant HERS program within the state of Colorado. ENERGY STAR^® is a program run by the U.S. Environmental Protection Agency throughout the entire U.S. and internationally as well. ENERGY STAR sets energy efficiency standards for a variety of consumer and commercial products. A product’s manufacturer may affix an ENERGY STAR label on a product when it meets ENERGY STAR’s designated level of energy efficiency. ENERGY STAR has established a level of energy efficiency for homes – 86 points or higher on an accredited HERS scale, such as the one used by E-Star. If E-Star runs the “yardstick” for energy efficiency, then ENERGY STAR is a milestone on the scale because any home scoring higher than 86-points is an ENERGY STAR home. A comparison of building programs further explains the differences between E-Star and ENERGY STAR.

Who manages E-Star?
E-Star is managed by an Executive Director who reports to the E-Star Board of Directors.

Construction and Building Science

What can water do to a home?
Water from rain, snow, and human sources can damage a home and cause harm to its occupants. This is because most homes are built with cellulose-containing products such as wood and drywall. When water comes into contact with cellulose, it provides a food source for mold. Mold uses cellulose as a food source and thereby destroys the structural members of a home. Certain kinds of molds can be harmful to people, particularly when mold spores are inhaled. For this reason, water and moisture management are very important considerations in the construction and maintenance of any home.

What are expansive soils?
Colorado is a rather unique area of the U.S. in that its geologic composition causes soils to expand. This can make it difficult to build homes in some areas of Colorado. Colorado builders sometimes use special foundations called structural wood sub-floors to counter the effects of expansive soils. However, these structural wood sub-floors can trap water or water vapor and allow mold to grow. This problem can be countered or eliminated by adequately ventilating the area beneath the structural wood sub-floor.

What is a house wrap?
A house wrap is put underneath the exterior siding of a home. It allows water that penetrates a home’s siding to drain and dry to the outside, rather than allowing the moisture to remain inside the structure where it could cause damage or promote mold growth. House wraps can be made of felt, plastic sheets, or even paper. Builders have used house wraps for decades.

Energy and Environment

What is the source of energy in homes?
Fossil fuels such as coal and natural gas are the source of most energy in homes. Natural gas can be used to heat water and warm living space. Sometimes electricity is used in place of natural gas for heating. Electricity is used by air conditioners to cool homes. Coal (and increasingly natural gas) is burned in power plants run by utilities to produce electricity used in homes. While renewable sources of energy such as wind power can produce electricity for homes, the vast bulk of residential energy still comes from fossil fuels that release pollutants such as nitrous oxides, sulfur dioxides, and mercury.

What is more effective for protecting the environment – energy efficiency or the use of renewable energy?
Both. However, for a variety of economic and socio-political reasons, renewable energy is more expensive than energy derived from fossil fuels. Therefore, the implementation of energy-efficiency measures is usually a more cost-effective and attainable method of reducing the impact of fossil fuels on the environment. In fact, some energy efficiency measures can pay for themselves within a relatively short amount of time and then go on to save money for a homeowner many years into the future.

Why are carbon dioxide emissions a concern?
Carbon dioxide is widely believed to contribute to global warming. Carbon dioxide traps heat from the sun and does not allow it to escape back into space from which it came. While a certain quantity of carbon dioxide in the atmosphere is necessary for the maintenance of life on Earth, increased levels may cause the polar ice caps to melt, rising sea levels, more severe storms, and other deleterious environmental impacts. Carbon dioxide is emitted when fossil fuels are burned. Adopting energy-efficient practices in homes can help to prevent global warming.

Energy Efficiency

What is a hot water heater blanket?
A hot water heater blanket can be purchased at hardware or home supply store. It is typically made of fiberglass adhered to a plastic sheet. The blanket is wrapped around a hot water heater and prevents energy from escaping through the sides of the tank. This increases the efficiency of the hot water heater. Use of a hot water heater blanket is often one of the most cost-effective means of increasing energy efficiency in a home.

Why is it better to build a home with 2x6 instead of 2x4 studs?
Wood is not a good insulating material. The vertical wood members of a home are called studs and are what holds up the walls of a home. The 2x6 studs are wider, and therefore stronger, than 2x4 studs. Therefore, fewer studs can be used when building a home with 2x6 rather than 2x4 pieces of wood. This allows more insulation to be put into a wall, thereby reducing the amount of energy that can escape from a home. Incidentally, 2x6 construction conserves natural resources by reducing the overall amount of wood required to build a home.

How does building orientation affect energy efficiency?
The orientation of a home can increase or decrease the energy efficiency of a home. The best way to orient a home is north-south, with adequate overhangs on the south facing windows to prevent the sun’s rays from penetrating the house during the summer months. Low-E glass on all the windows also prevents undue overheating of the home. However, a north-south orientation will allow for solar warming in the winter months when the sun is lower on the horizon and solar heating of the home is preferable. Homes that are oriented east-west do not promote energy efficiency since solar warming cannot take place in the winter and unwanted heat will enter the home through the west facing windows during the summer.