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Office of Energy & Sustainable Development (OESD)
Office of Energy & Sustainable Development (OESD)

Insulating Your Home for Energy Efficiency and Comfort

Why Insulate? Properly insulating your home will help reduce your heating and cooling costs and make your home more comfortable. Insulation is a smart investment because it provides year-round comfort and savings. Heat flows naturally from a warmer to a cooler space.  In the winter, this heat flow moves directly from all heated living spaces to adjacent unheated attics, garages, basements, and even to the outdoors. Heat flow can also move through interior ceilings, walls, and floors—wherever there is a difference in temperature. Insulating keeps heat where you want it to stay.

Insulation is rated in terms of its thermal resistance or R-value. The “R’’ stands for resistance to the flow of heat and is a measure of how effective the installed insulation will be. The higher the R-value, the more slowly heat will move through the building exterior.

Heat Control Insulation helps a building stay warm when it is heated and stay cool when it is air conditioned by reducing the energy flow. To maintain comfort, the heat lost in the winter must be replaced by your heating system and the heat gained in the summer must be removed by your cooling system. Properly insulating your home will decrease this heat flow by providing an effective resistance to the flow of heat.

Sound Control Insulation reduces sound transmission by reducing unwanted noise from appliances, audio equipment, conversation and other sources of sound. Therefore, an insulated floor, wall or ceiling will have improved sound control. 

Moisture Control A vapor-resistant facing (commonly called a vapor retarder) can be purchased attached to a batt or roll insulation. The facing is used to decrease the possibility of moisture vapor condensing and being trapped within a building.  Insulation can help prevent the growth of potentially dangerous mold and mildew in your walls, air ducts and ceiling.

Types of Insulation:

  • Batt insulation is semi-rigid material used to insulate floors, walls and ceilings. Batt insulation can be made from fiber glass (spun melted sand and glass), mineral fibers (slag or other industrial by-products), or cotton fibers. These materials are processed into batt or roll insulation, with or without facings. Batts or roll insulation is specially designed to fit between studs, joists, and beams.
  • Loose Fill can be made out of fiber glass, cellulose or wool. Loose fill is best used in enclosed existing walls or open new wall cavities, unfinished attics, or hard-to-reach places. Loose fill is good for adding insulation to existing finished areas, irregularly shaped areas, and around obstructions. The installation process for loose fill insulation requires a blowing machine.
  • Foam Board or Rigid Foam is generally made out of plastic and is best used on unfinished walls, including foundation walls, floors and ceilings or on unvented low-slope roofs. Foam has a high insulating value for relatively little thickness.
  • Spray Foam starts off in a liquid state and then hardens once it is in place. Like loose fill, spray foam is best used in enclosed existing walls, open new wall cavities, and unventilated ceiling or attic roof assemblies.

Where to Install Insulation?

  1. Attic spaces (including attic access doors to unfinished attics and knee walls in finished attics)
  2. Ducts in unconditioned spaces
  3. Cathedral ceilings
  4. Exterior walls (and interior walls for sound control)
  5. Floors above unconditioned spaces (garages, crawlspaces)
  6. Foundations with conditioned crawl spaces or heated slabs
  7. Basements with habitable space
  8. Hot water piping

Permit Information:

Insulation installation (excluding blown-in wall) requires a Building Permit from the Building and Safety Division, except for retrofit projects adding blown-in insulation where wall finishes are not disturbed. Installing attic insulation can trigger the requirements for smoke and carbon monoxide alarms to be installed and hardwired with battery backup if the building has attic access. For more information, see the Smoke Alarm Flow Chart


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