There are four primary principles related to heat flow:

• Heat flows from hot to cold
• Heat flows by conduction, convection and radiation
• Heat flow can never be stopped, it can only be slowed down
• Insulation resists heat flow and is rated for it's R value (RSI)

Energy (e.g. heat) moves from high concentration to low concentration, towards equilibrium. Equilibrium is a dynamic state (always changing depending on the conditions).

In the average house, heat moves whenever there is a temperature difference and moves out of a house in all directions during the heating season.

Modes of Heat Transfer

There are three modes of heat transfer:

CONDUCTION	CONVECTION	RADIATION

Illustration Source: Keeping the Heat In, Fig.2-2, Pg.10

A difference in temperature is the driving force behind heat transfer. The greater the temperature difference, the greater the flow from hot to cold. Heat can flow in three distinct ways (conduction, convection, radiation).

Why Control Heat Flow?

COMFORT	DURABILITY	ENERGY EFFICIENCY
Comfort benefits: Creates warmer surfaces and reduces chills and drafts caused by radiation and convection Prevents overheating due to excessive solar gains	Durability benefits: Eliminates cold spots that may cause condensation problems resulting in the growth of mould and mildew and the staining of structural components as well as finish materials	Energy efficiency benefits: Results in greater energy and dollar savings

Illustration Source: Keeping the Heat In, Fig.2-5,Pg.14

Not Managing Heat Flow Means…

• High heating bills
• Comfort problems
• Uneven temperatures - cold rooms / cold floors
• Frozen pipes
• Condensation - mould, mildew