Home insulation is not a common item to upgrade in a house in San Francisco.  But if you’re renovating your house and opening up some walls, it might be an easy place to help lower your energy bills and increase the comfort level of the home.

Quick Summary of the Products Available:

  • Batt Insulation:
    • Made from fiberglass and comes in roll with a variety of thicknesses and widths.  The R-Value is between 3.1 – 3.4 per inch.
  • Blown Insulation:
    • Can be made of chopped up fiberglass or cellulose and is typically used in attics.  The R-Value is between 2.2 – 4.3 per inch for fiberglass and 3.2 – 3.7 per inch for cellulose.
  • Spray Foam – Closed Cell:
    • As the name implies, it is a liquid material that sprayed into the insulation wall or ceiling cavity that expands and hardens as the two chemicals react to one another (isocyanate and polyol).  The R-Value is between 6 – 6.5 per inch

Current Standards:

The San Francisco metropolitan area is classified as Zone 3 and requires insulation to be at least an R-30 value in the attic and R-13 or R-19 in exterior walls (depending on wall thickness).

 

Common Questions:

  • Should I insulate my attic?
    • Yes.  The cost benefits of insulating an attic can be huge, especially if you like your home nice and warm in the winter.
  • How much does it cost to insulate an attic?
    • It depends on the material that is used and how accessible the attic space is.  To install blown fiberglass with an R-30 Value in a 1,500 SF home with good accessibly to the attic space, can cost between $2,500 to $3,500 ($1.82 per square foot).
  • How much does Spray Foam cost?
    • Spray foam is about double the cost of a traditional batt or blown fiberglass insulation.
  • What are the advantages of spray foam (closed cell) insulation?
    • First, spray foam is an air barrier so it completely seals the home and prevents homes from being drafty. Second, it allows a higher R-Value in confined spaces like standard 2x4 wall framing.  For example, traditional batt insulation is limited to an R-13 value in a 2x4 wall. While spray foam can increase the wall R-Value to approximately R-18.
  • What is the best bang for your buck option?
    • The best option is to use a combination of closed cell spray foam and batt insulation.  Spray a ½” inch layer of spray foam to completely air seal the wall and then install batt insulation in the wall cavity.