How does insulation work?

Heat flows from warmer to cooler via convection, conduction and radiation.

Heat flow through a ceiling is an example of all 3 types of heat transfer:

Bulk insulation such as cellulose works by having sufficient density to effectively prevent convection through the product but still low enough density to avoid conduction.

The optimal density of cellulose means that for a given thickness you will obtain the highest R value. Also as cellulose has a constant and low thermal conductivity for all practical installation densities and temperature differences the R value can always be verified by simply measuring the installation thickness.

Insulation with an R value does the following:-

  1. Limits the flow of heat for a given temperature difference. Heat flow is energy which costs money.
    The density of heat flow rate in W/m² is given by:
  2. The total power to heat the space in W is given by:

See energy usage.

  1. Maintain a temperature difference for a given flow of heat and take advantage of winter sun or other heating or cooling.
    The temperature rise in K (or °C) is given by:
  2. Reduce the day to night variation in temperature, in conjunction with the specific and latent heats within the building.

See temperature variation: Q1|Q2|Q3|Q4

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