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Upgrading your insulation: Is net zero energy use possible?

Jeffrey Anderson | Improvement Center Columnist | March 7, 2014

Imagine never having to figure electricity or heating costs into your household budget again. Even better, how about living in a home that helps make the earth a better place? A net zero energy house is defined as a structure that gathers energy from the sun, wind, or earth to meet or exceed its own net demand. And the first step toward achieving this goal might be upgrading your home's insulation.

Net zero energy and your home's outer envelope

The typical home uses energy for heating and cooling, powering appliances and entertainment devices, and everyday tasks such as cooking and bathing. And according to the government's Energy Star website, about half of all that energy used by the average house is in the area of heating and cooling. Having an efficient HVAC system can increase energy efficiency, but to achieve peak performance, the conditioned air must be maintained at the desired temperature. This is why your home's outer envelope is so important.

The outer envelope of your home keeps warm air inside during the colder months and outside during the summer when temperatures can climb. The outer envelope of a typical house consists of:

  • The attic and roof system
  • Exterior walls on every level including windows and doors
  • The basement or crawl space

Each of these assemblies that make up the envelope is assigned an R-value that expresses its ability to prevent the transfer of heat. The total R-value of each assembly is arrived at by adding the R-value of each component used to create the system.

A typical exterior wall R-value may consist of the exterior siding, intermediate sheathing, insulation, and interior wall finish such as Sheetrock. Energy Star estimates that upgrading your home's outer envelope to their recommendations may be able to lower utility costs by as much as ten percent. And lower utility costs translate to less energy usage - the first step in becoming a net zero energy house.

R-value and the various types of residential insulation

So how do you go about using insulation to start your journey toward a net zero energy home? By understanding the various types, where they're normally used, and the protection they can provide. Here are a few of the most common types of residential insulation:

  • Fiberglass batts - Batt insulation is normally installed in exterior walls, around the perimeter of crawl spaces and basements, and between trusses or rafters in roof systems. It can also be placed between the floor joists in basements and crawl spaces. In most cases, the R-value batt insulation provides is determined by its thickness. The thicker the fiberglass, the higher the R-value. Many homes have 3.5 inch thick batts in their exterior walls that have an R-value of 13.
  • Blown-in insulation - The name says it all with this type of insulation - it's a loose fill material normally blown into place. Blown-in is used most in unfinished attics, but it can also be used to upgrade the R-value of exterior walls. Blown-in insulation is one of the easiest ways to beef-up the protection your attic assembly provides your home. The R-value provided by blown-in materials is normally determined by its depth.
  • Spray foam insulation - There are many different types of spray foam insulation that can be used to make your home more energy efficient. One thing they all have in common is that all are in a semi-liquid state during application, then harden during the drying process. Some spray foams can harden enough to increase the structural integrity of the home. Foam insulation can be used in just about any part of a house including exterior walls, finished or unfinished attics, and basements or crawl spaces. Small cans of the material, available at most home improvement stores, are ideal for closing up gaps around windows and exterior doors. The R-value of spray foam can vary depending on its composition and the depth of the application.

If you have an exterior siding project planned in the future, adding insulation boards or installing insulated siding are other ways to increase the energy efficiency of your home.

Insulation: Is it enough to achieve a net zero energy home?

While upgrading your home's insulation can be a great first step, it usually must be combined with a few other improvements to achieve the goal of a net zero energy home. However, Matt Grocoff's old house, considered the oldest net zero energy home in the country, is proof that the goal is possible regardless of your home's age or style. A few other improvements to consider:

  • Cool roofing materials
  • Solar panels
  • Low flow shower heads and toilets
  • Purchase Energy Star rated appliances
  • Consider a wind turbine
  • Get an energy audit

It may take a while before you produce more energy than you demand, but if every improvement you make in your home reduces the amount of energy you use, you'll be well on your way.

About the Author

Jeffrey Anderson has a Degree in English from V.M.I., and served as an officer in the Marine Corps. He worked in Residential and Commercial construction management for 25 years before retiring to write full time. He spends his time writing, remodeling his old farmhouse, and in animal rescue.

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