In an earlier post, I talked about Energy Efficiency & Net Zero Energy 2020 (NZE 2020). If you live in California and you want to build a new home, your home will have to produce as much energy as it consumes. In that post, I talked about Four basic parts of the building we can improve

  • Building Envelope
  • Attic Space
  • Lighting
  • Water Heaters

While NZE 2020 is for new homes ( you know it will apply to home remodeling projects in the future) there is a quick & easy way to improve the energy efficiency of your home. Insulation. I know it is not the sexiest topic, but one that you should check that you have the maximum amount of insulation in your own home. Do you have enough insulation?

Current Minimum Standards

In California, we have the California Energy Code (refer to as Title 24). This law states the minimum standards for floors, walls, & attics insulation.

  • Floors: R19 = 5 ½” – 2×6 Floor joist, minimum
  • Walls: R19 = 5 ½” – 2×6 Stud Wall
  • Ceiling: R30 = 9 ¼” 2×10 Ceiling Joists or Roof Rafters

The R-values listed represent the insulation quality of the product – higher the number the more energy efficient it is. If I was designing your home remodeling project in California these are the minimum insulation values I would use. There is a list of other things I would also include, but let us stay with insulation for this post.

What Type of Insulation Are There?

There are many different types of insulation, and more coming on the market every year. We are going to look at the top five insulation products available for you. I have provided a summary below. For a more detailed description and discussion see Department of Energy’s: Types of Insulation

Fiberglass Insulation

This is the most common insulation that is used in homes. It is cheap and widely available. It is made up of fiberglass strands which make air pockets and that air gap helps prevent heat loss and gain through the wall. Though it is widely used – it is being phased out because of the chemicals that are used to create the insulation. R-value = R3 – R4 for each inch of insulation—2×6 wall = R19.


Another type of insulation for your walls and ceiling. Rockwool is made from rocks. What?? Yes, you heard me right. Natural rock is heated until it is a liquid (about 3,000 degrees) and then exposed to high-pressure jets of air or steam and then spun at high speeds. Think of it like making cotton candy. Rockwool is typical contains between 75 to 90% of recycled materials, non-combustible and fire resistant, and has excellent sound-deadening properties. This insulation is double the cost of fiberglass insulation, without the chemicals of fiberglass. It R-value is higher 4-5 per inch (2×6 wall = R23) so you will save more money on energy costs.

Cotton Batts

Cotton Batts (aka Blue Jeans) is insulation made from denim. This denim usually comes from jean factories waste material. It can have other products with the denim. It is as easy as fiberglass insulation, without the itchiness. Though it is not as widely available. It is also cost 3 times the amount of fiberglass insulation for the same R-value; R-value is 3.5-4 per inch (2×6 wall = R19). So denim is more a lifestyle and environmental choice.

Foam Board or Rigid Foam Insulation

Rigid Insulation can be used in walls, ceiling, and outside of foundation walls. It is a dense package of insulation (usually in a thickness of ½” to 2”) and thus has a higher R-value, R-5 per inch of thickness. A 2 x 6 wall thickness will have an R-value of 27. Though you would best use this type of insulation in conjunction with batt insulation. The rigid foam over a wood stud wall (interior side) would reduce the thermal bridging between the wood studs and the exterior weather. A 2×6 wood stud wall with batt insulation is R19; adding 1 inch (R-5) of rigid insulation on the interior would increase the wall’s R-value to R24.

Spray foam insulation

Applying closed cell insulationLiquid foam insulation is insulation that is sprayed into wall cavities and it expands to fill all the nooks and crannies in the wall. This makes it an excellent wall insulation material. It R-value is 6 – 6.5 for each inch of insulation. There are two types of foam: Open-Cell and Closed-Cell. I typically will specify closed-cell because it is denser and does not absorb moisture as does the Open-cell. Spray foam insulation is most expensive of the insulation types presented here because this is a job for a professional installer. The other downside is if you need to add anything to the wall, like a new electrical outlet. The wall cavity is now filled solid with insulation. That insulation will need to be chipped out to put in the electrical box and wiring.


If you want to quickly improve the energy efficiency of your home, there is no better way that insulation. Adding insulation is a quick and relatively easy way to do just that. You have a variety of choices when comes to insulation.