New government programs encourage people to make their home more energy efficient and green. Insulation is an important part of an energy efficient home, but more insulation is not always better. Adding insulation and installing insulation in previously uninsulated spaces may be a waste of money and can actually harm your home.
Additional insulation reaches a point of diminishing returns. Before the point of diminishing returns, every dollar spent increasing insulation yields at least a one dollar reduction in energy costs over a reasonable time period. After the point of diminishing returns, every dollar spent yields less than one dollar energy cost reduction over the same time period. An investment in additional insulation does not make financial and energy efficiency sense after the point of diminishing returns.
One place to begin looking for the point of diminishing returns is The International Residential Code (IRC) 2009. The IRC contains minimum insulation requirements for new homes. The IRC required insulation is not at the point of diminishing returns, but it is close. For example, IRC minimum attic insulation in warm climates is R-30. Increasing to R-38 approaches the point of diminishing returns. Exceeding R-38 may pass beyond the point of diminishing returns and may not significantly improve energy efficiency in warm climates.
We have simplified the eight IRC climate zones to three zones because the attic and crawl space insulation requirements are similar for some zones. Where insulation requirements in our zones differ from the IRC requirements, we use the higher requirement. Contact your local building official to determine the insulation requirements in your area.