INSULATION 49
hen Britain began its post war building boom, coal was king and energy was relatively cheap, so little thought was given to heat loss, and few buildings were constructed with any meaningful level of insulation. Now 70 years on, the world is very differ-
W
ent. With sky-high heating costs and a greater focus on the need to reduce energy consumption, builders, landlords and homeowners all take the insulation of their properties much more seriously. But before we look at insulation solutions, it’s important to understand exactly why it’s required. Insulation in a building is introduced to provide resistance to heat flow. The more heat flow resistance the insulation provides, the lower the likely heating (and cooling) costs. Good levels of insulation not only reduce heating and cooling costs, but also improve comfort.
HOW INSULATION WORKS To understand how insulation works it helps to understand heat flow, which involves three basic mechanisms: conduc- tion, convection, and radiation. Conduction is the way heat moves through materials, such as when a spoon placed in a hot cup of coffee conducts heat through its handle to your hand. Convection is the way heat circulates through liquids and gases, and is why lighter, warmer air rises, and cooler, denser air sinks.
Radiant heat travels in a straight line and heats anything solid in its path that absorbs its energy – think about sitting in front of a roaring open fire and how you feel warm on the side facing the fire but less so on the other!
Insulation materials work by slowing conductive heat flow, and to a lesser extent, convective heat flow. Regardless of the mechanism, heat flows from warmer to cooler areas until there is no longer a temperature difference. In a typical home this means that in winter, heat flows directly from all heated living spaces to adjacent unheated roof voids, garages, cellars and, particularly, to the outdoors. Heat flow will also move indirectly through interior ceilings, walls, and floors, wherever there is a difference in temperature. To maintain comfort in winter, the heat lost must be replaced by heat from a central heating system or other means. Adequate levels of insulation will decrease this heat loss by providing an effective resistance to the conductive flow of heat.
HOW CAN WE INSULATE EFFECTIVELY? Retrospective insulation – that fitted after the construction of a building – has tradi- tionally taken the form of thick layers of glass or mineral fibre placed between rafters in the roof void, or blown in cavity
A MORE MODERN ALTERNATIVE IS SPRAY FOAM INSULATION, WHICH IS APPLIED USING A PRESSURISED GUN SYSTEM
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THE HIGH PERFORMANCE ALTERNATIVE
Paddy Leighton of Icynene takes a look at heat loss in buildings, and how new, high performance insulation systems can improve comfort levels in both retrofit and new-build applications.
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