Home buyers benefit from reading the eco-scorecard.

Household energy efficiency ratings (or star ratings) tell you how comfy the temperature of your home will be throughout the year.

“Most people wouldn’t know the star rating of their house,” says Matt Fisher, from the Association of Building Sustainability Assessors. “But the stars have a dollar value in terms of the price and running cost of the home – that will become better understood as a lot more houses advertise with their star rating.”

So how are the ratings figured out?

Energy assessors plug the details of your plans (or existing building) into a nationally accredited software program, such as FirstRate5 or AccuRate. The program analyses the home’s layout and orientation, and the construction of the roof, floor, walls and windows.

This information is matched with the local climate to calculate how much heating and cooling you’ll need. “It’s a very sophisticated model,” Mr Fisher says. “Using climate data collected over many years, it calculates [the home’s temperature] for every hour of every day of the year. It works out the amount of heat or cooling energy necessary to keep the house comfortable.”

Homes can score between zero and 10 stars. At zero stars, the building does next to nothing to protect against temperature outside; at 10, it will be comfortable all year round without artificial heating or cooling. A five-star home is good, but far from outstanding.

Last year, state and federal governments agreed to lift the residential standard from five to six stars. The states must bring the rules into effect by May 2011, at the latest.

“It’s a step in the right direction, but we need to go further,” says Liz Minchin, Age journalist and author of new eco-book Screw Light Bulbs. She argues the regulations should have been more ambitious, by adding a timetable for even higher standards and factoring house sizes into the ratings.

“The five-star regulations helped slow down the increase in emissions from Victorian homes, but those emissions are still growing – largely because houses are getting so much bigger,” she says.

“Bigger homes typically take more energy to keep cool or warm – and that costs everyone money in rising energy bills, because we need to build more expensive power generation to cope with spikes in electricity use.”

The good news is that the governments have agreed to another change that should push household energy efficiency higher. Homeowners and landlords will soon be required to declare the energy, water and greenhouse performance of a house when they put it up for sale or lease.

It means that buyers and renters will be able to compare the environmental impacts and ongoing costs of different homes. Even though the full details and start date aren’t set (it will be phased in from May next year) the plan is relevant immediately – especially for people considering renovations.

Ms Minchin says a similar mandatory disclosure scheme in the ACT has shown that energy-efficient homes attract higher prices. A study for the federal government found that in 2005, lifting the energy rating of a median-priced house in the ACT by just half a star added about $4,500 to its value.

“Buyers are becoming more conscious of climate change and energy prices,” Ms Minchin says. “Real estate agents say people are asking about energy ratings more and more.”

Compost toilets save water, energy and nutrients.

We flush nearly one quarter of our household water down the toilet. “At the moment there’s this silly situation where we use high-grade water to flush our toilets,” says planning expert Professor Patrick Troy from the Australian National University. “To cut down our consumption of potable water, we need to change the way we manage human body wastes.”

Professor Troy, editor of Troubled Waters: Confronting the Water Crisis in Australia’s Cities, says composting toilets work with little or no water, and are suitable for suburban and even multi-storey housing. “They can be fitted into standard bathrooms so they look just the same, except they don’t have cisterns and flushes.”

The many different designs – both commercial and owner-built – fit into two broad categories: continuous or batch composting. Continuous systems, such as the Clivus Multrum, use one container. The material decomposes slowly and emerges as finished compost that can be safely dug into your garden. Batch systems, such as Rota-Loo, use two or more containers. Once one is full, it is replaced, sealed and set aside to compost. Commercial systems cost from $800 to $8000, depending on the model and size.

The Environmental Protection Authority accredits commercial composting toilets before they can go on sale. The authority’s code of practice for onsite waste management permits them to be used in both sewered and unsewered areas.

Hamish Skermer runs Natural Event, a business that provides composting toilets for festivals and events around the world. “People can have confidence that these systems meet rigorous standards,” he says. “Composting toilet technology can work anywhere on any scale. If we can do it for 18,000 people at the Falls Festivals, then a family of five can do it in their home.”

Even so, householders often find it difficult to get council approval, usually based on perceptions rather than substantive health issues. But those attitudes are changing: Natural Event has already provided toilets for community events run by a number of Melbourne councils.

Unlike conventional toilets, compost toilets require some maintenance – at the least, to distribute the finished soil conditioner. “They all have to be managed, because it’s not a flush system where it’s taken away and it’s someone else’s problem,” Mr Skermer says. The toilet should not smell. If it does, it’s a sign that something isn’t right. But he says that householders can easily fix any issues by attending to the drainage or ventilation, or adding cover material such as sawdust.

He argues that pee and poo shouldn’t be even referred to as waste. It’s the line of thought most recently popularised in The Humanure Handbook, by American writer, Joseph Jenkins. “We have to understand that shit ain’t shit,” Mr Skermer says. “Waste does not exist in nature. The mere concept of a toilet being ‘waste management’ is a backwards thought.”

Compost toilets not only dramatically reduce water consumption, but also cut the energy required to pump sewerage (currently powered by heavy-polluting brown coal) and return valuable nutrients to the soil. “Our food contains nutrients in the form of nitrogen, potassium, phosphorous and all the trace elements,” Mr Skermer says. “We eat and then pee and crap into the sewer system and a large amount of these nutrients are pumped into the ocean. We’re removing ourselves from the cycle.”