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Energy Efficiency

Common Concerns: When to Invest in Energy Efficiency | An Efficient Home Functions Cohesively | Zero Net Energy Homes | Benefits of Energy Efficiency | Energy Efficiency can Pay for Itself

Overview

A properly functioning home should be a comfortable and healthy living environment. Perhaps surprisingly, the best home solutions for providing comfort and health are often quite energy efficient. This is because when the functional components of the home are considered together, they complement each other instead of working against each other. The basic components of the whole home system are:

Common Concerns: When to Invest in Energy Efficiency

It can be hard to know if a house is energy efficient by just looking at it. In fact, many people only start thinking about energy efficiency when they pay high energy bills or are uncomfortable in their home. Different energy uses can affect gas or electric consumption in different ways though, and targeting those uses can help find the efficiency improvements that will help save the most money in your house.

Typical homes built before the 1970’s are generally poorly insulated and inefficient so they offer the greatest opportunity for improvement and saving energy. Air (warm or cold) is lost through holes in the walls, roof, or floor (which together form an envelope ). Often these holes have the same effect as leaving a window or two wide open, which is clearly not helpful when you are trying to heat or cool your house! Houses with a “leaky envelope” need a lot more energy to stay at a comfortable temperature, leading to high utility bills. It may even be difficult to make such a house comfortable, despite spending hundreds of dollars a month on heating and air conditioning bills.

On the other hand, energy efficient homes use less energy to stay comfortable than inefficient homes. This is even more important for homes in extreme climates (hot or cold), because the greater the temperature difference between outside and inside your home, the more energy can be saved with energy efficiency. Most any energy efficiency improvement can pay for itself over time, but improving older homes or homes in very hot or cold climates can have the greatest impact on energy savings.

An Efficient Home Functions Cohesively

A well insulated and sealed home will require less energy for heating and cooling because the home will retain more of the conditioned air and be less influenced by outside weather. When a house needs less energy to stay comfortable, we say it has a smaller energy “demand”. Smaller heating and cooling demands can be matched with smaller, high efficiency HVAC systems. To maximize energy efficiency and minimize energy consumption, an appropriately sized high efficiency system should be big enough to heat (or cool) the house on the coldest (or hottest) day, but not too big for the more moderate weather the rest of the year. Planning efficiency improvements for the whole house, and not just one part (such as the furnace) can make the most of energy cost savings and pay for the improvements over the long term.

Zero Net Energy Homes

Insulating a house will help lower its energy demands, but it can even be possible to lower demands enough so that the remaining energy needs can be covered with renewable generation systems such as solar thermal heating and solar photovoltaic electricity. Such homes already exist and are referred to as “zero net energy.” A ZNE home is one that produces as much renewably produced energy over the year as it consumes. The ZNE home is the concept behind the Strategic Plan of the CPUC which has set up funding and goals to substantially increase the numbers of zero net energy homes (new and existing) over the next several years.

Great attention must be made in maximizing the efficiency of a home’s envelope efficiency and designing high performance HVAC systems in a well functioning ZNE home, before determining how much renewable energy to apply to the house. Doing so will minimize the home’s energy demand, so that less renewable energy is needed. When done out of order, making a home zero net energy becomes very expensive.

If you are interested in making your house ZNE, it is also important to keep in mind your household’s use of energy. It may be difficult or costly to cover the homes energy needs with renewables if:

the house is kept very warm in winter (or very cool in summer)
the household uses a lot of hot water
the house uses or leaves on appliances which consume a lot of electricity

Benefits of Energy Efficiency

The main benefits of energy efficiency in buildings are threefold:

Save Money: cost savings from decreased energy consumption
Mediate Climate Change: decreased CO ₂ emissions from residential building energy use, which are responsible for 21% of US emissions ^*
Expand Energy Independence: on a national scale, decreased energy consumption means less reliance on foreign energy

Since energy efficiency is a good investment for decreasing climate change and energy dependence, many tax rebates are available to defer the upfront cost, meaning pay off periods for home energy improvements can be shortened.

There is a lot of potential for saving money as well as for reducing greenhouse gas emissions through energy efficiency improvements throughout the U.S, as widely studied and published by the international consulting firm, Mckinsey & Co.