Low-E glass has role to play in curbing CO2 emissions
Policy responses to the need to save energy in domestic housing often overlook the role of glass. Internal and external insulation, more efficient boilers and solar heating are all supported with grant aid from the Sustainable Energy Authority of Ireland (SEAI). Glass is excluded.
Yet the energy savings from replacing old, single-glazed windows with modern, Low-E (low emissivity) glass are considerable. A study by Dutch research institute TNO, commissioned by Glass for Europe, shows that, across the EU, over 90 million tonnes of CO2 emissions could be saved by the widespread use of low-e glass.
What is Low-E glass?
Low-E glass is specially treated with a microscopically thin, virtually invisible transparent coating on one surface. The coating reflects heat back into the building, thereby reducing the heat loss through the window.
It also reduces the heat transfer from the warm (inner) pane of glass to the cooler (outer) pane, thus further lowering the amount of heat that escapes from the window. The coating allows large amounts of solar energy to enter the building, thereby heating it.
This coating is used on glass in both double and triple-glazed units. The properties of Low-E insulating glazing mean that your windows can actually contribute to the heating of your home by (i) reflecting the house’s heat back into the room, and (ii) trapping heat from the sun inside the house (called “solar gain”).
Older double-glazed windows do not contain low-emissivity glass, and are therefore not energy efficient. Manufacturers of Low-E glass, such as Pilkington’s, recommend Low-E glass for rooms with a high proportion of windows and doors, for sun rooms and conservatories and for north or east-facing windows.
In the Dutch study mentioned above, researchers measured the number of Terajoules (TJs) that could be saved by installing Low-E glass. Terajoules are measurements of energy required for heat. For instances, one joule is the amount of energy required to heat one gram of cool air by one degree Celsius. A Terajoule is 1012 joules. A city the size of Dublin uses about 50,000TJ of energy a year.
If Low-E glass was (i) installed in all new builds in Ireland, and (ii) retrofitted to all existing buildings, it would save just over 6,000TJ of energy (equivalent to nearly 650 tonnes of CO2).
Find out what home energy saving grants are available from the SEAI Better Energy Homes Scheme: http://www.seai.ie/Grants/Better_energy_homes/homeowner/Step_1_Decide_on_work_to_be_done/
Information about types of glazing from the European glass manufacturers’ trade association, Glass for Europe: http://www.glassforeurope.com/en/issues/faq.php
Have a look at this video from the Corning Museum of Glass on how Low-E glass works: https://www.youtube.com/watch?v=sEtMGItzLHE