Sunday, May 18, 2008

Choosing the Proper Home Insulation

Of all the energy-saving, utility bill-cutting approaches that are employed in the modern home, insulation is the best publicized. Why? It's the cheapest method of making your home energy efficient. Attic insulation, wall insulation, floors and crawlspaces, it's all recommended. But which type is the best for the job? The answer, it turns out, is, "It depends".

Which Kind of Insulation is Best?

This depends on:
  • Your budget - How much will you spend VS how much you'll save on utility bills.
  • What's available locally - This can affect how much you'll pay for material.
  • The area to be insulated - Different areas of the home have different needs.
  • How much insulation needs to be installed - How much square footage will be covered?
  • Method of application - Will you roll it out? Will an insulation contractor spray it?

R-Value Considerations

An insulation's R-Value is it's resistance to heat flow (out in the winter, in during the summer). The higher the number, the better. The insulation's data sheet or packaging will give you a number, but there are other factors to consider.

For example, fiberglass batts installed between exterior wall studs will give you a certain R-Value, but heat will still flow through the studs. This is an example of thermal bridging. Little can be done here except using insulating sheathing or using an alternative framing technology such as SIPs (Structural Insulated Panels) or ICFs (Insulated Concrete Forms).

Density also has an effect. For example, fiberglass batts will only give the rated insulating value if they are normally "fluffed out", not compressed into a smaller space than they were designed for.

Types of Insulation

  • Blanket insulation - This may be purchased in either batts or rolls. In areas such as attics, rolls are easier to install. Batts work well in walls between studs. The paper tabs are stapled to the studs to keep the batts from settling down over time, victims of the force of gravity.
  • Blown-in loose fill insulation - This is usually rock wool, cellulose, or fiberglass. It works well in attics and requires pneumatic equipment. Either an insulation contractor can be hired or you can rent the equipment and DIY.
  • Foam insulation - This can either be open-celled or closed-celled. This type is also sprayed on. The open-cell insulation allows for moisture to move through it but has a lower R-Value than closed cell.
  • Radiant barrier - This can either be a powder that is mixed with latex paint or a radiant barrier foil product. The radiant barrier paint can be sprayed on the underside of the roof sheathing or rolled/sprayed onto walls. The foil is claimed to work better on the roof sheathing in the attic but some claim that it interferes will cell phone reception.

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