Building an Energy Efficient “eco” home – Part 1
Using nature to create a comfortable house
Not building a house which takes advantage of passive solar design and thermal mass is like not putting the bin out on garbage night because you just couldn’t be bothered. It only takes a week for you to regret your decision and wish you had spent the extra time to make things right.
The same principle applies to not designing your house to take account of passive solar design principles. You will regret your decision on the first hot or cold day when you crank up the electricity to compensate for the inclement climate costing you money and using unnecessary resources.
Not creating an energy efficient house will feel the same as watching the flies rise up around your stationary garage bin – you have visible evidence that your original decision absolutely stinks.
What can an energy efficient house offer?
An energy efficient house is designed to create a moderate internal temperature throughout the year regardless of the outside temperature. This will create a house that is shaped to the natural environment to make it comfortable to live in while reducing heating and cooling expenses.
In fact, an energy efficient house can offer up to 90 per cent savings on energy bills on old houses and 75 per cent savings on comparable new houses according to Passipedia, a group that encourages people to adopt these principles into their homes.
Early planning means houses are orientated to make use of the best breezes, let in natural light, seal in heat loss through better design, use the sun to heat a home and keeps it warm throughout the night, or keeps it cool in the day letting you beat the heat and the crippling air conditioning bill.
Although a house can be retrofitted to add to its efficiency, it is best to begin building a low impact house from the outset of the design.
After all, according to Peter Graham from the University of NSW, “The decisions we make when we design, build and run our homes affect our health as well as natural environments far beyond the physical state of construction.”
Creating an energy efficient house through passive solar design should not be a big sell; the benefits of it should be so obvious that it should be something that is clamoured after.
Passive solar design is all about making a house more liveable, and best of all, it is free.
Talk the talk
Passive solar design has its own specialised jargon. Get familiar with it to sound like a pro.
Energy efficiency: Using a reduced amount of energy to create the same end.
Heat transfer: The movement of heat in and of a house.
Insulation: Material within the walls and roof to improve heating and cooling.
Low impact: Creating a lower carbon footprint.
Orientation: Facing the house towards the equator to catch the best winter sunlight. Homes face north in the southern hemisphere and south in the northern hemisphere.
Passive Solar Design: Making use of the sun for heating and cooling the home.
Shading: Shading by trees or architectural structures to reduce the sun and heat in summer periods.
Thermal Mass: A large surface such as a concrete flooring that will capture the heat in the day and release it during the night.
Vents: Additional air spaces to allow heat transfer.
While the definitions leads to the answer of what you need to do, life is usually more complex than that.
We've added these to our glossary for easy future reference - Editor
There is nothing more Garfield-like than a delicious lick of sunshine streaming into a sunny nook where a well-positioned chair offers a very comfy place to have a coffee with friends, challenge your favourite adversary to a game of chess, read a picture to a child or just grab some ‘me’ time.
A correctly orientated house has all the main living areas facing towards the equator with larger windows to capture the winter sun. In the southern hemisphere living areas should be placed on the north and garages, bathrooms and bedrooms should capture the full summer sun on the west or the cooler southern side. In the northern hemisphere the house should face south.
There are set calculations to determine the height of the sun in summer depending on the home’s distance from the equator. The further from the equator the lower the sun’s direction in summer and eaves can be measured to length to compensate for the hottest time of the year.
While it sounds easy, there are a million reasons why the house and the block you have chosen will not fit exactly, and that ability to adapt to the given restrictions has been one of the reasons that passive solar design has not become a mainstream practice especially in the project home market.
It can be problematic when home orientation compromises on aesthetics, view and privacy. In these cases you can add compromising details such as courtyards, semi-transparent glass or plantings to create privacy. Any gains in passive solar design will be appreciated in extreme weather conditions and early adjustments will make the final design more liveable.
Shifting the heat
Heat will always make its way into a house, once it’s in during the summer months the best way to manage it is to move it straight out. Based on the principles of hot air rises, you can place vents in the ceiling to reduce the heat load in the ceiling cavity.
A turbine vent in the ceiling helps move the hot air out of the house and can be powered through wind, solar power or electricity depending on the level of technology. It is possible to have a system that not only draws out hot air but recirculates filtrated night air back through the home for additional cooling.
Heat can also be shifted through low-tech ceiling fans. Select a fan with curved blades, variable speed and a reverse function to move the greatest amount of air. Not only with this cool the house during the summer, but it can also be reversed to recirculate trapped hot air from the roof area.
The joy of winter sun can be lost when it is blasting full strength through the same windows on a hot summer’s day. Passive solar design is about using the sun wisely and making the most of it in the winter and blocking it out during the summer.
Taking time around a new building site can help you decide whether you need to keep any existing trees on the west side that will bring welcome relief on hot afternoons.
Not all homes can have western tree shading so a creative outlook will create a range of options for homeowners. Verandas and outdoor living areas are an excellent way to increase the versatility of your home while simultaneously cutting the amount of hot summer sun access.
Most obviously, window treatments on the inside or shutters on the outside can add style and texture to your home while also reducing heat, noise and softening internal sounds. Window treatments will also act in the same manner as insulation and will trap winter heat inside the home.
Other shading options include incorporating angled veranda slats which are positioned to cut the harsh summer sun but allow the mild winter sun or using deciduous vines to achieve the same aim.
But wait, there’s more
Whole books have been written on passive design and this article is the first of several that will look at specific aspects of major design principles that are worthwhile incorporating into the design process of a new build.
Keep a watch out for information on ventilation, glazing, thermal mass and insulation in Part 2.