Passive & Active Design in Green Homes
Last week, we wrote an article about easy solutions for you to improve your home performance without undertaking major work. Today, we are going to develop this wide subject we just addressed. In fact, if you are interested in building or renovating your own home, here is what you need to know before starting.
Indeed, to develop an energy efficient home, one must think not just about passive or active strategies but to the combination of the two.
You surely first wonder: What is the difference between the two?
A passive design uses natural “unpowered” systems to provide heating/cooling and ventilation in the house.
For example, the selection of the material, insulation, the orientation, and the form of the building will be important. Passive strategies will optimize and conserve the use of potential energy without first converting it into electricity.
An active design uses technologies such as solar panels, heat harvesting systems or wind turbines to convert energy into electricity. These systems are called powered, because they use electricity.
In climates which require cooling and heating, the use of thick walls matters to ensure a strong insulation and avoid using active heating or cooling systems. In fact, the thicker the wall the less heat or coolness will dissipate. The material used for the insulation also matters, in the same way as the thickness, the higher the thermal resistance, the lower the heat flow.
To conclude, this solution reduces the energy losses by reducing heat dissipation in winter and heat gain in summer, thus reducing the use of electricity in a second phase (active features).
High Albedo Roofing
Having a high albedo roofing reflecting sunlight limits the heat of the house. In fact, in order to reduce the gain of heat in the house as for the insulation you can also use roof materials or paint reflecting the sunlight to avoid using electricity to cool your home.
Using passive solar means installing windows and for example verandas to allow the sun heating a space in winter. For the summer or tropical zones, it’s important to also install sunshade, blinds and double or triple-glazed windows.
In the same way as solar heating, thanks to windows and skylights you can light your home without using electricity during the day.
This passive system is called natural cross-ventilation because it uses windows and doors openings to let air enter and exit through the building. Thanks to these systems you can cool your home without first using electric ventilation or air conditioning.
As we said in the last article, you can collect rainwater for tasks where the use of drinkable water is not needed: watering, toilet flushing or car and clothes washing.
As in every construction, using recycled, local and reused materials is the simplest and most effective way to reduce embodied carbon.
Green Roof & Vegetation
To finish with passive features, you can also improve the insulation of your home by installing a green roof and walls, it also allows you to renew the air and to reduce the amount of carbon released in the atmosphere, through photosynthesis. As we also said last week, planting deciduous trees to hide the house from the sun in summer and allow it to be heated in winter is a major solution. It’s also a good water retention for tropical countries.
Solar Electric & Thermal Energy
In addition, of all the passive systems enounced before solar panels convert solar energy into electricity for example to light your house during the night, heating or cooling your home if needed, or cooking. You can also use a solar water heater to heat water thanks to the warmth of the sun.
The use of heat pumps is also important. You can read the last article to better understand, but to sum up this technology can either capture the calories in the outside air or into the ground and transmit them inside to heat a room or capture the calories in the room and reject them outside to cool it.
HVAC systems are electronic systems that can Heat, Ventilate & Air Condition a room. Thanks to renewable energy such as solar through photovoltaics, you can, if passive features are not enough, use these systems.
Greywater is the water not used from showering, dish washing, hand washing or from the kitchen sinks. This reuse includes the treatment and filtration for toilet flushing, watering or clothes washing. In fact, you may prefer using first rainwater harvesting but if these solutions do not cover every task you can use in a second stage greywater.
As a conclusion, the use of passive devices is preferred first hand by maximizing it before using powered systems, with renewable energy.