| Home Energy Savings -- Ventilation and Insulation Basics |
From "Home Energy Savings"
episode HES-103 |
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Segments in this episode of DIY's Home Energy Savings workshop cover such topics as how to evaluate the ventilation in your attic, deciding on the right type of insulation, installation of fiberglass insulation and the insulation alternative of blown-in cellulose. Poor insulation and improper ventilation in your home's attic could be the cause of needless expenditures -- both for heat and air conditioning. Attic Ventilation Basics Insulation and ventilation work together, and you need to properly utilize both to ensure that your home is energy efficient. In winter, attic vents (figure A ) allow cold air to flow into the attic, preventing ice dams and keeping moisture from building up. In summer, ventilation allows hot air in the attic to escape. You want to make sure that the ventilation you do have is adequate. If you don't have enough ventilation, you may need to add more. Following are some examples of attic ventilation:
- Soffit vents along the edge of the roof allow air into the attic between rafters.
- Box vents (figure B), or a ridge vent, allow air from the attic to escape through the roof. A ridge vent can be challenging to install in an existing home but is highly recommended for new home construction or if you're replacing an old roof.
- Gable wall vents (figure C) are located on the gable ends of the attic. These allow air to flow in and out of the attic, depending on the season.
Proper ventilation will create a healthier environment in your home and help with its energy efficiency. Fiberglass Insulation Basics Before you choose the insulation for your project, it helps to be familiar with "R-value" (figure D). The R stands for "resistance to heat flow" -- thus, the greater the R-value, the greater the insulating ability. Requirements vary depending on where you live and what you'll be insulating (for example, an attic needs a higher R-value than a wall). Check with your local building inspector to learn the minimum R-values required in your area and for your application. Fiberglass is the most common material used for insulation. It comes in the forms of batts and blankets. The difference between a fiberglass batt and a blanket is that a batt is precut and a blanket is one continuous roll. Insulation also comes in a variety of R-values. Here are some factors to keep in mind when selecting the proper R-value for fiberglass insulation:
- R-13 is 3-1/2" thick and is appropriate for 2-by-4-stud wall cavities. In older homes, this grade of insulation may be found as insulation in attics but, according to the Department of Energy, R-13 (figure E) is no longer considered adequate for attic insulation.
- R-19 is 6-1/4" thick (figure F) and is used in 2-by-6 wall construction and in attics.
- R-30 (9-1/2" thick) and R-38 (12" thick) (figure G ) are made specifically for attic insulation. R-30 is adequate for most parts of the United States. R-38 meets the minimum requirements for the northern tiers of the U. S. and Canada -- which experience harsher winters.
Insulation is available either with our without a vapor barrier . A vapor barrier (figure H) keeps moisture from migrating into the insulation and condensing. Vapor barriers are always placed on the warm-in-winter side of the insulation -- i.e., toward the living space. As mentioned, fiberglass insulation comes in both batts and blankets. The R-25 blanket (figure I ) shown in our demonstration is designed specifically for reinsulation in attics. A cost-effective alternative to fiberglass is cellulose insulation, which comes in bags (figure J). Cellulose insulation, made from at least 75 percent recycled material, is easy to install: it's blown into the space using a specialized blower that can be rented from home stores or rental centers. If you're insulating a basement wall or an exterior wall before you apply siding, consider rigid foam board (figure K). It typically has a higher per inch R-value than fiberglass, and it's easy to work with.
Proper techniques for the installation of various types of insulation are covered in segments that follow in this episode.
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