Heat Reflecting Membranes The technology explained WORLD DISTRIBUTOR Long-life Heat Reflecting Membranes (HRM’s) made from a various sheet materials were conceived by NASA space scientists to protect orbiting craft from solar radiation. This heat control technology has spawned a variety of terrestrial applications. These include the famous “space” blankets that keep athletes and accident victim’s warm, heat-reflecting sheaths for water tanks, air- conditioning ducts, heat-sensitive equipment and even Formula One racing car components. Colin Hawkes, Apollo’s MD explains why his company’s HRM’s are a further development where mass production techniques have provided tough, cost-effective membranes for use within domestic, commercial and industrial buildings. Introduction There are many types of insulation available that reduce heat gain and heat loss. Some materials provide greater resistance to heat transfer than others depending on the mode of heat transfer: radiation, conduction or convection. The concept behind a Heat Reflecting Membranes The primary function of a Heat Reflecting Membrane (HRM) is to block infrared energy radiating across air spaces. Infrared energy (radiation) converts to conducted heat when it strikes a surface such as a wall or roof. The energy transmits through materials, molecule to molecule, until it reaches the next air space where it then radiates from the surface to the next object. The molecules of air touching the solid surface warm, so energy can also leave the surface as rising convective air currents. A HRM works either by reflecting back most of the radiating infrared energy striking its bright non-tarnish surface (reflectance) or by not radiating heat (emittance). Emissivity is a measure of the amount of heat a surface can either absorb or emit. For instance, an emissivity value of 1.0 represents a perfect absorber or emitter of infrared energy. Typically, most building materials have an emissivity value of between 0.85 and 0.95 (see table overleaf). Membranes from Apollo have an emissivity of only 0.05, so 95% of the radiant heat is blocked. Whether stated as reflectance or emittance, the performance is the same; an HRM effectively blocks the passage of infrared energy through structures. To act as a radiant barrier the HRM is installed within a structure facing at least one air space, usually 19 to 25mm. Heat conducting through the structure and crossing the air space as infrared energy is then blocked by the membrane. Eliminating infiltration and air leakage It is generally accepted that air leakage and infiltration through a building have a detrimental effect on energy efficiency and the comfort level of occupants. In temperate climates during winter, warm air can be literally blown or sucked out of building’s and be replaced by cold, damp air. In tropical climates, moisture-laden air entering a structure will certainly have a negative effect on air quality and a building’s general performance. Apollo membranes incorporate layers of aluminium film and vacuum-metallised polymer so they are easily moulded around adjacent framework (see photograph) and once positioned will not spring back. Apollo’s aluminium-faced, self-adhesive tape is then used to seal joins between sheets of membrane, around doors, windows and other fittings, obviating the need for many of the mastics usually employed. Assuming outer doors and windows are of adequate specification to stop unwanted draughts, by sealing the envelope of the building, factors for air infiltration and leakage may be eliminated from the energy calculation. In addition, the flow of ventilation air through rooms is easier to control as it is not disrupted by unwanted draughts or stack effect where buoyant air in the building can draw in outside air. This is good news for the builder and HVAC engineer who needs only to calculate for the ventilation required. Used in floor construction, the system can also restrict the ingress of methane and carbon dioxide from landfill sites and the movement of airborne radon from subsoil into the building. An excellent vapour barrier With low moisture transmission rates, Apollo HRM Systems, also act as excellent vapour barriers, halting moisture migration into the building’s other insulation layers. The systems ensure “mass” insulation materials keep dry and maintain their performance. Housing applications Attic room example Colin Hawks explains, “Our Thermo-Foil® system used to line an attic room will reduce the thickness of the soft insulation required, substantially reduce energy needs and improve comfort for occupants. The membrane eliminates excessive heat gain caused by incoming solar radiation yet can keep the room warm during cold weather. No matter the season, room temperatures are far easier to control”. “Normally, solar heat striking a roof will conduct through the tiles and insulation layers crossing any air spaces as unwanted infrared energy, eventually warming the plasterboard and over heating the room. HRM in warehouse roof Thermo-Foil being installed in a living area prior to fitting plasterboard Thermo-Foil being installed in an attic room prior to fitting plasterboard