Winter has arrived in Australia. The steps we take to keep warm are often an energy intensive exercise. For example, a CSIRO study in 2000 found that up to “5.5 million tonnes of firewood were burned in Australian households” each year. Warren McLaren reports on how to stay cosy during winter, without undue burden on our planet.
Glazed over
Double glazing has long been a niche industry in Australia, but its broader adoption would help cut down much of the energy we waste, not only on summer air-conditioning bills, but also winter heating. Fenestration can be measured for its conductivity (movement of warmth through an object). Windows are ascribed a star rating for their efficiency. Double glazed windows have roughly half the conduction rating of single panes of glass. This is noteworthy as windows can lose up to 20 per cent of a building’s heat. If the void between panes is filled with transparent argon gas, then performance is further increased. The choice of frames is also important: timber or plastic frames conduct much less than aluminium. Initial higher costs are recouped over time via much diminished heating bills. Retrofit options like Magnetite, MagicSeal and Clear Comfort allow existing windows, with all their existing embodied energy, to be retained whilst still achieving superior performance to plain glass windows.
A lot of hot air
Air is one of the best insulators we have. Bulk insulation is the best way of keeping it still because the tangle of fibres slows the transit of air. Insulation is scored for its thermal resistance, noted as an R-value, with higher being better. Climatic conditions across the nation require differing degrees of insulation. For an alpine region, say, the R-value for the ceiling is almost double that of a house in the tropics. Retrofits should at least insulate ceilings, because nearly a third of all heat loss escapes in this direction and any insulation is better than none. The available selection includes fibreglass, mineral wool, sheep wool, cellulose fibre (paper), polyester and even sheets of expanded polystyrene. With new constructions and renovations, floors and/or walls might be protected with many of the aforementioned insulation, but also others such as aerated concrete, strawbales, polyurethane foam and extruded polystyrene sheets can be called into service. Reflective foil and reflective foil foam laminate also insulate against radiant heat loss. The Federal Government will also install ceiling insulation in up to 2.9 million homes.
It’s curtains for you
There is another way homes can reduce heat loss through windows by about 40 per cent — the inclusion of thermally efficient curtains or drapes. Ideally, the curtains should be made from a heavy fabric and lined on the glass side with a similarly dense backing (being reflective will help reduce summer heat gain). The gap between the two also provides some additional insulation value. To be really effective, the air between the curtains and the window needs to be contained so it can’t move about. This is best achieved with a pelmet or fixed box covering the top of the curtain. Some pelmets are mostly decorative to hide curtain tracks, but for heat loss control they need to have a solid top. Curtains should also be wide enough and deep enough that they fit close to the wall, floor and beyond the window frame.
Save the seals
Unfortunately, up to a quarter of building heat loss occurs via air leakage. Weatherguards, rubber or foam adhesive strips, liquid silicone and caulking are just some of methods employed to seal doors and windows. But there are also often forgotten holes in the building shell. In old houses the high wall vents can be sealed closed. Likewise, with exposed floorboards all the rage, air leakage through the boards themselves and skirting boards should be investigated and plugged. Fireplace chimneys are another notorious heat loss point (especially when a fire is burning), but so too are the more modern bathroom exhaust fans. Baffle lidded covers, like the Draftstoppa, can be placed over these. The Isolite Downlight Guard performs a similar function for halogen downlights, which normally can’t have insulation nearby as their intense heat might ignite it.
Space wars
Heat loss occurs in a variety of ways. One is by convection, or air movement. Clever building design, or adaptation, can significantly reduce the unwanted passage of air. Smaller spaces are much easier to heat. Discrete internal doors or screens that can contain the vastness of open plan living areas allow heating appliances to perform at their optimum. Similarly, designing entry spaces to a home, such that they function like a spacecraft airlock, ensures that heated air is retained inside the building shell, whilst chilled external air is kept outside. Spaces like wet rooms, entrance hallways and laundries all provide this feature, whereby someone can enter the house through an outer door, remove coats, wet shoes, umbrellas, etc, before moving through an inner door into warmed living spaces. Automatic door closures can be useful if house inhabitants are neglectful of maintaining a closed door regime.
Fan the flames
We all know that hot air rises. Which is a shame, because we don’t spend much time near the ceiling. How then to get that air back down to us? A ceiling fan, of course. Most modern fans have a ‘winter’ switch which reverses the direction of the fan. This agitates all the hot air gathered between the height of the fan and ceiling, forcing it outwards and down a room’s walls to where it is actually useful. It is important, though, to select fans with the appropriate blade length and pitch angle for the intended room. Speed control is also a salient feature. Slower revolutions are better in winter because you don’t want too much of the warm air underneath being disturbed. It has been claimed that with the right fan, heating costs can be lowered by 10 per cent.
Passive mass
Contrary to its name, passive solar actually involves quite a degree of hard work, but mostly in the design phase, for once implemented, it largely runs itself — with a little help from the sun. With carefully prescribed glazing and interior materials, the winter sun, which sits much lower in the sky than in summer, can be enticed inside a residence. Once in, it should be encouraged to rest upon materials with thermal mass. These in turn store the sun’s heat. After the sun has passed, the thermal mass releases that radiant heat. Should the building have aforementioned insulation and glazing, along with curtains and pelmets, the released heat warms the room — no machines or running costs required. Thermal mass normally refers to extra dense materials like masonry products, ie, concrete, brick, tile, slate. These can be used as part of internal walls or floors so long as the winter sun can reach them, in conjunction with a judicious use of eaves, so the summer sun cannot.
Getting heated
Wood-fuel heaters are carbon neutral and cheap to operate, but older models are not overly efficient. With the particulate pollution they can generate, some jurisdictions have buy-back schemes to move households to cleaner burning heaters. Heat shifters (fans with ducting) transfer excess heat through ceiling spaces to other rooms. One form of low emission wood burning heater is the pellet stove. Inexpensive pellets (compressed sawdust waste) are fed into the electrically boosted heater by a measured hopper. They have very efficient heat results from the high temperature combustion, but with such low particulate they’re US EPA smoke testing exempt. Portable unflued (bayoneted) gas heaters are economical, but not allowed in some states due to indoor air quality issues with uncombusted gas. Flued gas heaters are the fixed location alternative. For central heating, hydronic heaters are available that pipe hot water to in-slab coils or wall mounted panels. Some use gas boilers. Others operate via heat pump technology — essentially like an inside-out fridge — gathering energy from the atmosphere into a sealed refrigerant coil around a heat-exchanger.
