Insulation Basics
| Insulate: To prevent the passage of heat, electricity, or sound into or out of, especially by surrounding with a non-conducting material. |
Why Insulate?
There are many reasons to have your home professionally insulated. For most people, reducing winter heating costs will quickly spring to mind, but there are many other benefits and some may surprise you.
Professionally installed insulation will create a home that's evenly heated, free of hot and cold spots, free of drafts and generally more comfortable. Heating and cooling equipment in a well-insulated home will have a lighter workload and may require less maintenance and repair work. Furthermore, thermal insulation has sound absorbing properties which can result in a quieter home and, some forms of insulation are resistant to fire and vermin.
You may be eligible for Government Incentives to help with the cost of improving energy efficiency.
Heat Migration
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The primary function of insulation is to prevent heat migration. This means keeping heat inside your home in winter and keeping it out during the summer. Heat can escape or enter your home via conduction, radiation, convection and air leaks.
Here's how these processes result in heat migration in your home:
- Convection is the movement of heat in a gas or liquid. As air gets warmer it gets lighter (technically it becomes less dense) and rises. Hot-air balloons demonstrate this effect nicely. In your home, warmer air carries heat up to your ceiling or roof.
- Conduction is the transmission of heat through a medium. Metals are very good conductors. Anyone who has touched a hot saucepan knows that heat conducts through metals very efficiently. In your home, heat can be conducted through walls, floors, windows, doors, ceilings and roofs.
- Radiation is how heat jumps between two separate objects. This is how heat from the sun crosses space to reach us. The sun can heat your roof, which then radiates heat into your attic and heats your ceiling, which in turn, radiates heat into your living spaces.
- Air leaks allow heat to hitch a ride on air which can sneak in or out of your home through gaps, cracks and crevices. A common culprit is gaps around door and window frames which may not fit snugly into the cutouts provided.
All this heat migration costs you money. Winter heat loss results in your furnace working harder and burning more fuel in order to keep you warm, while in summer, your air-conditioner slogs away to keep you comfortable.
How Insulation Works
Insulation drastically slows the migration of heat with thermal barriers and air seals. A thermal barrier prevents heat from traveling through walls and ceilings, often using materials that trap air to resist heat conduction. This resistance to conduction is known as R or R-Value. A higher number indicates better resistance (see below for a detailed explanation). A brick wall will have an R-Value of approximately 4, while a 26.6cm (10.5) thick layer of cellulose will achieve an R-Value of 40, the minimum standard set by the Ontario building code.
Air sealing prevents the movement of air though gaps and crevices. Air sealing is particularly important around doors and windows where gaps may exist between frames and wall structures. Such gaps allow air to leak in and out of your home, carrying heat along with it. Skipping air seals would be like leaving windows open.
R Value
R Value, or Resistance Value, is used to define a material's thermal resistance and allows easy comparison of the performance of various insulation products. The value is determined by measuring the amount of heat energy able to pass through a material. surface area of a material at a given temperature differential. Higher numbers indicate more resistance to heat migration and, therefore, better insulation. A material with an R-Value of 20 allows half the heat flow of a material with an R-Value of 10.
If you're into algebra, the actual equation for R-Value is R = A x dT ÷ Q, where R is resistance value, A is surface area in square feet, dT is the temperature difference in Fahrenheit and Q is the heat flow in BTU per hour.
RSI is the metric measurement of thermal resistance. To convert R to RSI, you must multiply R by 0.1761. To convert RSI to R, you must divide RSI by 0.1761. The Ontario Building Code minimum standard of R-40 is equivalent to RSI 7.0.