Around 75% of the energy used by the average household goes towards heating water and rooms. If you consider that our demand may soon way exceed Eskom’s capacity, that’s a high percentage. It warrants a complete re-think about how we heat and cool our homes.
Passive and low energy architecture (PLEA)
A plea to use common sense? If you’re in the fortunate position of being able to design your home, do so in a way that maximises natural energy conservation and diminishes the need for heating and cooling. This includes:
• north-facing windows to allow as much natural light as possible
• insulated roofs and walls
• overhanging eaves or a stoep deep enough to keep summer sun from hitting your windows in summer, but shallow enough to hit your windows in winter, or use shutters
• If you want to calculate this yourself – use SketchUp from Google to help you work out solar projections yourself
• thick walls – straw-bale or cob – or built out of materials like stone – these are highly insulative
Weathering the heat and the cold in South Africa means sealing windows and doors – better known as draft proofing. You can get insulation strips (rubber strips with a self-adhesive backing) or a tube of silicone caulk [what is caulk?] from your local hardware store to fill in the cracks on windows, doors or anywhere that a draft gets through. And for the space at the bottom of your doors, between the door and the floor, install a door sweep – it reduces airflow and is protection from water during heavy storms. You can also try adjusting the striking plate so that your door closes more snugly. And thick, full-length curtains pulled across windows at night will help keep the heat inside the home and prevent cold from getting in.
Insulating the roof
Insulating your roof is one of the easiest and most economical ways to cut down on your need for heating and cooling. An un-insulated home loses about 40% of its heat through the roof and ceiling and acts as a heat trap during summer. There are two major types of insulation materials for the roof – blanket and batt. Blanket-type insulation comes in long rolls, which you then cut to fit, and batts come in pre-cut lengths. These include Aerolite (fibre glass), Isotherm (polyester fibre made from recycled green plastic bottles) and Thermguard. (made from 70% recycled newsprint; said to have less impact on the environment than Aerolite and Isotherm)
Solar water heating
The merits of solar water heating are many, although the present cost – between R12 000 and R20 000 - means that the average home cannot afford it:
• if you properly install a solar water heater, it should last at least 25 years
• it can reduce your electricity bill by half
• it saves you about 95% of water heating costs
Government and business have already launched water-heating projects like that in Johannesburg recently, where 170 homes in Cosmo City received a geyser and solar panel each [joburg.org] Another project, launched in March 2007, offered incentives to install solar water heating systems to 500 households in Gauteng, KwaZulu-Natal and Western Cape [southafrica.info] And a similar project is anticipated after the Western Cape’s announcement of a range of incentives, tariffs and tax breaks for using renewable energy to feed back into the national grid. [urban sprout] A possible Cape Town bylaw may soon require all new buildings, including domestic residences, to have solar water heating systems. [eepublishers]
For local suppliers of solar water heating
Electric heaters use a lot of energy - even low-energy wall heaters (those rather unsightly squares attached to the wall) barely take the edge off the cold, and even though they claim to be energy efficient, still use electricity. Unfortunately, buying green energy, such as green renewable energy offered in places like the UK - where you can support energy sourced from wind, solar, combined heat and power and energy from biomass - is not yet an option in South Africa. Projects like the Darling Wind Farm and Amatola Green Power aren’t available to residential clients, making electricity very ‘ungreen’.
Gas heaters are a greener alternative – gas contains practically no sulphur and is clean and eco-friendly when burned. There is the portable kind of gas heater, which can be moved from room to room as you need them, or there are gas-fired grates that are a lot less work than traditional fires - which you still need to stoke and tend. However, this option wastes huge amounts of natural gas each year and is not a renewable energy source.
Depending on who you’re talking to, the wood-burning fireplace can be a more environmentally responsible form of warming your home. On the downside there is evidence that the emissions from wood stoves contain carcinogens – i.e. we’re smogging up the skies. On the upside: wood-burning, in combination with responsible reforestation, may well help the environment by reversing the green house effect [guardian] - although we’re not convinced.
The bottom line with wood burning:there is good wood burning and there is bad wood burning. Wood burning is only environmentally-friendly when your wood comes from well-managed woodlands and forests that are being replenished, and local is better. One should burn “sustainably harvested, properly processed and seasoned fuel in an advanced combustion stove or fireplace that is vented through a chimney that runs straight up through the building” [woodheat.org] Download this responsible wood burning factsheet and read two reasons why [the tree.org] advocates wood is an environmentally-friendly fuel.
Staying cool inside your home isn’t necessarily about air conditioning. Here are some alternatives:
• a foil radiant barrier in the roof (Enviro-tuff) – it’s stapled to the underside of the roof rafters and reduces heat by 25%
• install eco-insulation made from recycled paper
• coat your roof with ceratech coatings (air conditioning in a can)
• ceiling fans reduce a room’s temperature by 4˚
• window coating (sun control film) reflects up to 80% of incoming sunlight
• white window shades or blinds can reduce heat gain by 40-50%
• patio’s, retractable awnings or overhangs over north-facing windows
• hang tightly woven screens or bamboo shades outside north-facing windows
• plant deciduous shade trees and shrubs on the sunny side of the house
• grow vines on trellises outside your windows
Efficient air conditioners
One wouldn’t be wrong to consider the environment and air conditioners diametrically opposed. But there are ways to make air conditioning more efficient:
• if your air conditioner is old, consider replacing the outdoor compressor with a more recent, high-efficiency unit
• don’t air condition unused rooms
• provide shade for the outside unit – this will increase efficiency by 5-10%
• make sure that your air conditioner is the right size for your home, studies show that most are oversized
• set your air conditioner at 22-23˚ to save energy
Enter solar-powered air conditioning
A Chinese company called BROAD introduced the concept and supplied their first client in America two years ago, and have now sold in over 40 countries. They call them ‘absorption chillers’. Their intention is to commercialise the solar energy air conditioning system worldwide. Let’s hope they’re available soon in SA! [treehugger.com]
If you enjoyed reading this green guide, then you’ll also enjoy:
green your lighting
green your cleaning
green your personal care
green your baby
eating & shopping organic in Jo’burg
eating & shopping organic in Cape Town