The Inside Scoop On Insulation: Zones, Ratings, Alternatives

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Have you ever wondered what prevents the temperature in your house from matching the temperature outside? Whether it’s keeping the heat in or keeping it out, the energy efficiency of your home is determined by the quality of the insulation within its walls. 

Insulation Facts-R values and zones

The type of insulation required for a home greatly depends on what climate zone it lies in. In the continental US, there are 7 zones and each zone calls for different R-values for insulation. R-value stands for “thermal resistance” and its number is based on how well the insulation keeps energy (heat) from escaping your home. The higher the number, the more dense the insulation is, and the better it is at regulating temperature and minimizing energy loss. 

Starting with Zone 1 at the tip of Florida to Zone 7 up in Maine, as you go north, the R-rating requirements for insulation increase. This is because climates are colder as you increase zones, thus requiring thicker, denser insulation. 

The r-value needed also depends on the area of the house being insulated.

  • Walls

When it comes to insulating walls, the size of boards used in framing determines the R-value of the insulation used. For 2×4 studs, every zone uses R13-R15, and for 2×6 framing, R19-R21 is used. The difference is the width and density of the insulation. R21 is more costly, but it’s more dense and more energy efficient, which means less heat can escape through the walls.

  • Attic

Most attics use blown in insulation with a lower R-value over the top of fiberglass batting to achieve a value ranging from R-30-R60.

  • Floors and Crawl Spaces

Floors and crawl spaces use thinner insulation and often have multiple layers to achieve an R-value between R13-R30.

Types of Insulation

There are four main types of insulation commonly used in residential construction. What type you use often depends on the area being insulated and each type has benefits and drawbacks.

  • Blanket

Blanket, or rolled insulation is constructed of fiberglass, mineral wool, plastic fiber, or natural fibers and is most commonly utilized in unfinished walls (such as garages) and attics. It is relatively inexpensive and can be installed easily. The drawback to using this type of insulation is that it is itchy and hazardous to breathe in. 

  • Foam Board

Foam board insulation is typically used in basements and is applied to the interior of concrete walls. They are thinner and denser, and are used in conjunction with other forms of insulation (such as concrete blocks) to increase the R-value. The foam is made of polyurethane or polystyrene. The benefit of using foam boards is that they offer significant heat retention for their size but they require the addition of a fireproof gypsum board overlay to meet building codes.

  • Loose-fill and Blown-in

This type of insulation, made from cellulose or fiberglass, is used to add to the existing R-value. It is commonly used in attics. In cellulose form, it is the most environmentally friendly type of insulation and is made from newspapers and other recycled paper products. In fiberglass form, it poses the same dangers as blanket insulation. 

  • Spray Foam or Foam-in-place

Spray foam insulation is one of the most effective forms of insulation. It not only has a 35% higher R-value and decreases airflow, it’s also a great noise barrier. This insulation can be sprayed in, injected, poured, or blown in on top of existing insulation. Due to its high energy efficiency and ease of application, it’s a preference among its class. 

Alternative Insulation Options

For people who wish to be more environmentally friendly, there are a handful of “green” fiber and foam options to choose from.

  • Wool

Sheep’s wool, to be exact. This type of insulation is both water and fireproof. It is formed by pressing wool fibers together to form a dense layer of insulation that keeps moisture out and prevents condensation. 

  • Cotton

If you’ve ever wondered what happens to old jeans, here’s your answer. Denim is the most common form of cotton recycled for insulation. It’s natural, renewable, and eco-friendly and can be manufactured into roll form for ease of installation. While it is significantly more expensive than fiberglass, there’s no risk of inhaling airborne particles. It is also manufactured with borate, making it fireproof. Cotton is also a natural insect repellent.

  • ThermaCork

This product is made from compressed oak bark. It is free of toxins, renewable, biodegradable, recyclable, and acts as a noise barrier. 

  • Nanowood

Nanowood is still being tested but researchers have found a way to bleach wood and compress it to form an insulation denser and more eco-friendly than classic styrofoam. It isn’t available commercially as of the time of this writing, but scientists are hopeful newer methods of manufacturing can bring the price down, making nanowood more cost-effective. 

Whether you’re a contractor or completing your own home improvement projects, it’s important to understand climate zones and insulation ratings to make your home as energy efficient as possible. 

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