Home Insulation Basics

Radiation, Convection and Conduction are the three methods that moves heat in your home. Radiation is the transfer of heat energy by electromagnetic wave motion. Heat is transferred in direct rays. It travels in a straight line from the source of heat to a body. The closer you are to a hot object, the warmer you’ll feel. The intensity of the heat radiated from the hot object decreases as your distance from the object increases.

Conduction is the transfer of heat from one molecule to another, or through one substance to another. It is heat that moves from one body to another by direct contact. For example, heat is transferred by conduction from a boiler heat exchanger to the water passing through it. When you touch a suction line of an air conditioner and it feels warm, that’s heat energy moving from the warm copper pipe to your cooler hand by conduction.

Convection is the principle of warm rising and cold air falling. The transfer of energy by warming the air next to a warm object and then moving that warm air. As warm air rises it warms the air above and continues to rise. Some older furnaces used gravity to move heat throughout the house.

Air movement moves 98% of all water vapour in building cavities. Air will always move from a high pressure area to low pressure area by the easiest route available. Proper air sealing of a house will prevent this transfer of moisture into your cavities, voids and insulation.

The laws of physics govern how moist air reacts within various temperature conditions. The study of moist air properties is technically referred to as psychrometrics. A psychrometric chart is used by professionals to determine at what temperature and moisture concentration water vapor begins to condense. This is called the dew point. By understanding how to find the dew point, you will better understand how to inspect for and diagnose moisture problems in a house.

It is important that the air leakage pathways between the living spaces of the house and other parts of the building are stopped or sealed closed. Air leakage into a wall or the attic can carry a significant amount of moisture. If there is air leaking around electrical outlets or around plumbing lines in the wall, moisture can be carried along those same pathways.

Insulation in the form of batts, blankets, loose fill, and low-density foams all work by limiting air movement. The still air inside the insulation is an effective insulator because it eliminates convection. Still air also has low conduction, so heat doesn’t flow very well via conduction through insulation.

Don’t confuse insulation’s ability to limit air movement with air sealing. Insulation reduces air movement only within the space it occupies. It cannot limit air movement through other pathways nearby. For example, the insulation in the wall cavity does not affect the air leakage that may take place around a window frame. Adding insulation will likely not have the same effect as air sealing. Insulation’s resistance to heat flow is measured or rated in terms of its thermal resistance, better known as its R-value. Thermal imaging scans can detect hidden moisture and missing insulation in your home.

When buying a home in the Barrie area call Barrie’s Professional Inspection Services and how they can protect your investment. Barrie Home Owners should visit Barrie’s Home Owner Tips and Advice Blog

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