The pandemic has made it clear the importance of mitigating the effects of climate change. The built environment is one of biggest offenders when it comes to the climate change crisis. In 2018 according to the latest United Nations environment program the energy used to build and operate our buildings accounted for nearly 40% of the world’s carbon dioxide emissions.
We release 55 giga tones of green house gasses into the atmosphere every year, in order to stop global warming we have to get our green house gases down to zero. To start tackling this we need to start building net zero structures. To put it simply net zero means for every molecule of green house gas we put into the atmosphere, we also take one out making our net emissions zero.
Going net-zero is important as we can tackle climate change by reducing global warming.
How can this be achieved? Architects and designers now have the power to advocate for change for the new built environment. One increasingly prevalent strategy is in the design of net-zero-energy homes, something that architects & designers can begin implementing in the initial stages.
What is a Net Zero home?
A net-zero home is designed and built for the conservation of energy; using renewable energy systems to generate the energy they need, these homes produce as much energy as they consume, without using fossil fuels. As long as the annual net-energy consumption is zero, a home can be called net-zero.
Features to consider when building a net zero energy efficient home.
Rammed earth walls for the structure.
The process of building with rammed earth walls creates a very low carbon footprint. Unlike building with conventional building methods i.e. concrete this uses around 10-20% cement which in itself as a material goes through a process and contributes greatly to air pollution and global warming. With rammed earth construction, materials are sourced locally and doesn’t go through a process in order for it to be suitable to build with, it is simply extracted from the site, add a little water to create a damp mix and then its ready to use. Rammed Earth walls have a high thermal mass absorbing heat energy through the day and releasing it into the building as temperatures fall at night. Experiments have shown that rammed earth walls can actually reduce daytime temperatures by 4 or 5 degrees, there leading to less energy consumption to keep your homes cool.
Positioning of the home.
Positioning of the home must be planned carefully as well as the sizing and placement of windows.Lets look at Ghana for example. Ghana is a few degrees north of equator, this means that few windows should be placed on the east and west of the building, as the heat from the sun is unwanted when the sun rises and sets. Shading by overhangs is important on the north and south sides of the building.
Roofing
Clay roofs are very effective in reducing cooling loads and alleviating overheating in countries with high temperatures. The thermal properties of this material used for the roof can have a major influence on the surface temperature and in turn the amount of heat conducted through the surface of the building.
Windows
With Ghana being a few degrees north of the equator, windows facing north or south will absorb the least heat. In warm tropical climates like Ghana, a louvered window is one of the best types of windows for natural ventilation. Louvered windows have many advantages in tropical regions. They offer energy-efficient ways to light and cool a home in warm climates naturally.When fully open they allow for almost up to 100% ventilation. Today louver windows have come a long way from how they were 50 years ago, modern louvered windows offer a more sophisticated locking mechanism also some have solar on the blades to help capture energy for your home.
Rainwater harvesting
Put simply, rainwater harvesting is the technique of collecting filtered water that falls on the roof of a building and storing it in large tanks ready for re-use. With water shortages on the continent becoming common and the continually increasing demand for water consumption, more and more households are realizing the benefits of harvesting rainwater.
Wastewater harvesting
Grey water harvesting is a process where we can reuse used water in home, for example collecting shower, sink or washing machine water and reusing it to flush toilets.
Passive cooling
Geothermal cooling is a renewable energy system that moves heat from your home underground, thus using below the earth’ s surface under your home like a heat sink. Geothermal energy cools air by moving hot air through a geothermal heat pump, therefore moving heat from inside your home to the cooler environment 20 feet under the earth's surface. Thermal heat pumps are low in energy when connected to the grid or can be solar if you want to go completely off grid with your cooling.
Due to the mass of the earth below, geothermal systems can cool even extreme heat, great for cities like Accra. Another environmentally friendly element of geothermal cooling systems is the hardware. The below ground loop can last for generations, and the above ground equipment for decades.
Renewable energy
Solar energy uses the sun’s light and heat to generate renewable or ‘green’ power. The most common form of solar energy is harnessed by solar panels. You’ll also see them on top of houses and other buildings. The cells are created from semiconductor materials. When the sun’s rays hit the cells, it loosens electrons from their atoms. This allows the electrons to flow through the cell and generate electricity.
Adopting low waste practices in your home.
Grow your own food
Producing food is big business. To grow, make, transport, store and cook our food is an energy intensive process and one, which generate greenhouse gas emissions that contribute to climate change. Food production is estimated to account for 31% of greenhouse gas emissions worldwide. By growing your own food you can cut down on food miles, trips to the market and wasteful packaging, all of which generate harmful emissions that contribute to climate change.
Get into composting
Composting is a great way to reduce food waste going to landfill that does not break down as easily causing harmful gases like methane in the atmosphere. When composted in the garden, waste can break down properly as it remains above ground with access to fresh air, within a year you have natural fertilizer to use for your garden and plants.
Solid waste
More than ever it’s important to do our bit for the environment and to adopt ways in the home of how we can reduce our waste significantly. Simple things like choosing products with minimal or no packaging when you next go to the supermarket or market. Buying reusable airtight containers to store and preserve food for longer to help reduce food waste. Investing in reusable items such as shopping bags, rechargeable batteries, if you have infant’s reusable diapers, reusable water bottles.
The market for building net zero sustainable homes is something that is very new on the continent, we believe over time it will become something that new homeowners will insist on and with people becoming more environmentally aware, architects and designers will design taking into considering these carbon positive features.
