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Choosing The Right Type Of Attic Insulation

May 8, 2015

Which Insulation is Right for your Home?

Insulation is like your home’s favorite sweater in winter and shade tree in summer. Choosing the right type of insulation not only affects your comfort, but also determines your home’s utility bills and overall energy efficiency. Let’s take a look at how insulation works and the best type of insulation for your home.

Insulation and Heat Flow

Heat flow is the main reason you might feel uncomfortable in your home. It describes the natural tendency for heat to move from warm objects to cooler objects. In the summer, heat flow causes the hot air from outside to leak inside. In the winter, the warmth in your living spaces moves to unheated basements, attics, garages, and outdoors.

Heat flow involves three basic mechanisms:

Conduction is the way heat moves through objects, like how heat from coffee moves through the mug to your hand.

Convection describes how heat circulates through gases and liquids. It’s why cool air sinks and warm air rises.

Radiant heat describes heat that travels in a straight line, warming anything solid in its path.

Most forms of insulation operate by hampering conductive and convective heat. Insulation’s resistance to conductive heat is measured by its R-value. The higher the R-value, the greater the insulating effectiveness.

Batt Insulation

Batt or blanket insulation is the most common form of insulation and comes in large rolls or chunks. Batts are made from flexible fibers, most commonly fiberglass and cotton, though you can find blanket insulation made from:

  • Mineral wool
  • Plastic fiber
  • Sheep’s wool

As effective as batts can be, they often have trouble filling a space. Insulation works best when it completely fills a space. Gaps, compression, voids, or otherwise incompletely filled areas are equivalent to air leaks in your walls or around your doors. Batts also don’t do well when they have to compete with other things inside the walls—framing, wires, exhaust fans, electrical junction boxes, lighting.

Blown-in Insulation

Loose-fill or blown-in insulation comprises small particles of foam, fiber, or other materials. Thanks to the smaller form, blown-in insulation can conform to any space without disturbing the structural foundation. The most common types of materials include fiberglass, cellulose, and mineral wool made from rock or slag, all of which are made from recycled waste:

  • Fiberglass contains 20-30% recycled glass
  • Cellulose comprises recycled newspaper
  • Mineral wool is produced using 75% post-industrial recycled content

Of these, cellulose tends to have the higher R-value per inch, meaning you’ll ultimately need less of it.

This form of insulation is installed via a hose that blows the particles into the attic empty space—hence, blown-in insulation. This method allows you to fill in any gaps and create a complete layer of insulation that ensures full protection from heat flow.

Spray On Insulation

Sprayed foam insulation comprises a liquid compound that expands and hardens as it dries to create an effective barrier against heat flow. The most common types of liquid foam insulation include:

  • Cementitious
  • Phenolic
  • Polyurethane
  • Polyisocyanurate

These foaming agents don’t contain CFCs (chlorofluorocarbons), HCFCs (hydrochlorofluorocarbons), or other chemicals that can damage the earth’s ozone layer.

Sprayed foam insulation can have twice the R-value per inch of traditional batt insulation, but the real advantage comes with the method of installation. The consistency of the foam allows it to fill even the smallest cavities. As it cures, the foam compounds conform to the shape of the cavity, creating an effective air barrier to prevent leakage.

Determining what type of insulation is right for you involves several factors. Where do you want it installed? What R-value do you want to achieve? You also have to take into account overall lifecycle costs, impact on indoor air quality, and ease of installation. If you’re not sure, get some professional advice from a Bob Jenson Air Conditioning & Heating.


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About The Author

Bob Jenson

For over 45 years, Bob Jenson has been providing quality heating and air services to the San Diego community.


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