So what is passive solar design, and how can it help to overcome a chilly winter abode or summer hot box? Essentially, solar passive design is about creating an internal environment which maintains a consistent, comfortable temperature throughout the year, utilising the free resources of the sun, wind and a considered design. It can vastly reduce reliance on mechanical heating and cooling, not to mention reduce your energy bills.
Designing for your location and climate and creating a thermally comfortable interior does not have to be expensive either. Australia has eight different climate zones and, as such, architecture should not be generic but designed to suit each zone. Today, I will share with you the basic principles of passive solar design and how they could make a difference to your comfort inside the home.
In the vein of a real estate agent, an architect’s catchcry would have to be orientation, orientation, orientation. It is critical to consider the placement of your home on the site for its particular climate to take advantage of the sun and prevailing winds.
Ideally your living areas should be located to the north, except in tropical climates. This design by Melbourne Design Studios, which rated an eco-friendly 10 stars on the Nationwide House Energy Rating Scheme, has been orientated due north with the living zone (ground floor) and bedrooms above allowing maximum exposure to the sun and easy shading of walls and windows in summer. Utilitarian spaces not benefiting from passive heating have been positioned to the south including bathrooms and the laundry.
The majority of Australian houses fall within the climate that benefits from passive solar heating. This is where you can capture the warm winter rays inside your home, naturally heating it. This can be achieved as the sun is lower in the sky over winter, allowing the sun’s rays to penetrate deeply into your home, especially on the north-facing facade, as is the case in this abode. The dwelling has extensive north-facing windows in the lounge and living room taking full advantage of the sun’s heat.
Direct sun onto your windows can be your home’s largest source of unwanted heat gain in summer. But by understanding the sun’s angles you can minimise heat being drawn into your home over the warmer months. Consider correctly proportioned eaves, awnings and pergolas which will shade the windows (and walls) in summer but not in winter, thus creating a comfortable internal temperature and reducing the need for air-conditioning.
Shading from trees and vegetation can also contribute to a passive solar design. Consider how you lay out your garden and the planting of tall trees which can improve the performance of your building. Planting deciduous trees, which have lush foliage over summer, can create beautiful shade to outdoor spaces and your home. Then when these trees shed their leaves in winter, the filtered sunlight can warm all the way into your living area.
BONUS TIP: Plant dense vegetation on the western side of your home to shade the walls and windows from the setting sun. The afternoon is the hottest part of the day and is impossible to block unless you use a vertical device – trees are a natural answer.
From my perspective glazing is a no-compromise element in the design of a home. I recommend you install the very best glazing system you can afford. Glass has the single largest impact on the transmission of heat and can represent more than 40 per cent of heat loss to the outside and up to 87 per cent of heat gain.
Careful consideration should be given to both the size and orientation of all windows for the particular climate zone you’re in. The windows featured in this living room are double-glazed uPVC, which make the home more energy-efficient and are a great choice in a harsh coastal environment such as Lorne, Victoria, where this house is situated.
The techniques employed for natural cooling vary across Australia from the tropical climates up north to the more temperate environments in the southern regions. Depicted here is a prefect example of how a home can take advantage of the air outside – the rectilinear living space is proportioned to capture the breezes across the short breadth, from the large opening of the bi-fold doors to the high louvered windows opposite. Cooling is improved by the installation of a Haiku bamboo ceiling fan to gently circulate the air.
Materials with thermal mass are dense and can store heat within and include concrete, masonry, stone and rammed earth. The capturing of heat in thermal mass is best suited to regions with sunny days and cold nights. The thermal mass acts as a heat bank, storing the warmth from the sun during the day. In the evening, as the temperature drops, the heat is gradually released maintaining a comfortable internal temperature and reducing the need for mechanical heating. This house, designed by Swell Homes, utilises reverse brick veneer (RBV) and an exposed concrete slab for thermal mass. RBV is where the inside wall is brick and the outside is clad in another material such as fibre cement, timber or render. RBV is a very effective, thermally efficient wall system when coupled with appropriate insulation and external cladding.
Insulation is a barrier to the flow of heat and makes a vast difference in the comfort and temperature of your home. If you live in a old house it is worth installing ceiling and underfloor insulation. There are also companies that can retrofit wall insulation to an existing house by making small holes in the plasterboard and inserting/blowing insulation into the cavity. The wall cladding used in the renovation of this house creates the external weatherproof barrier and the insulation in the one system. Made from lightweight polystyrene foam it is a high-performance form of insulation with great thermal resistance. Extra insulation can also be added to the cavity in a stud frame wall, effectively doubling the performance of a timber-framed house.
Weather sealing your home is one of the upgrades that can be easily performed on an existing home or renovation. It is well worth considering as you can lose up to 20 per cent of heat through small openings around doors and windows. Installing curtains with pelmets, as featured here, can help to reduce unwanted drafts and retain the warmth inside your home, too.
A great passive solar design will consider all of the nine principals mentioned to create a unique home to suit the climate zone it is situated within. It will also reduce or eliminate your reliance on mechanical heating and cooling, which is better for the environment and your hip pocket.