Passive Design is energy efficient design
Brick walls add character to any room, providing a textured backdrop that complements other design elements. Exposed brick walls can make an otherwise boring space feel warm and inviting, not to mention unique!
The atmosphere of this rustic clay brick home south of Johannesburg, is not only authentic and appropriate for the semi-rural area, it’s also practical.
I’ve spent most of my life in the construction industry,” admits proud homeowner, Mariana Lamont. “As a woman of course my home is where my heart is. I have a real appreciation for craftsmanship.
“The bricks I chose have that handmade feel. Each has its own hues and shades, such character. In a world of steel and glass and shiny plastic, clay brick is 100% natural. It’s the perfect contrast to smooth and reflective metal surfaces and it brings out the colour and softness of textured fabrics. It also supports local South African manufacturers and construction workers.” Mariana explains.
“There’s just something magical about the late afternoon sunlight dappling a wall of natural brick. I took this photo of the rainbow – it illustrates how my home makes me feel protected and blessed.
“My home is totally liveable. My kids can play, my dogs can be dogs. My clay brick walls can handle the toughest abuse, and still look great. And now that I am working from home, I can confirm these walls are also a great insulator against noise!
Harnessing free energy – without a solar panel
People think of passive design as something new and trendy,” Mariana says.
“Actually passive design is just energy efficient design. It harnesses free heat from the sun, and natural night time cooling, to make my home more comfortable. It reduces my heating and cooling bills. Incorporating passive design into my house did not add to construction costs, because it was taken into account during the design and construction stages.
While passive solar heating is still very desirable in cold climate, cooling is more of a priority in South Africa. This Highveld house needs to deal with both extremes, making the choice of clay brick as a building material more important.
Passive design for the Southern Hemisphere considers:
- The movement of the sun across the sky, with seasonal changes
- Temperature ranges, both seasonal and day–night
- Humidity ranges
- Direction of cooling breezes, hot winds, cold winds, wet winds
- Impact of local geographic features and adjacent buildings
Thermal mass in building design
Thermal mass is the ability of a material to retain heat energy when subjected to thermal temperature differentials. Clay brick has relatively high thermal mass.
As executive director of the Clay Brick Association of Southern Africa, Mariana Lamont has easy access to facts and figures comparing building materials. The CBA is known as one of the top sources of research on energy efficiency in buildings.
“My walls are double-leaf clay brick with a cavity. In summer, my walls absorb the heat energy from the sun. Because it’s a dense material, this process is slow. Brick is able to absorb a large quantity of heat energy before it radiates to the inside of the house.”
Maximum external air temperature is usually reached between noon and 2pm. A lag of 6 hours - typical for clay brick walls - means the brick reaches maximum heat around 7pm, just as outdoor temperatures are falling. The brick releases its heat back outside, not inside.
In summer, heat energy on the surface of a west wall is 700-900W/m² . But thanks to the insulation, only 5-6W/m² of heat energy on average passed through to the internal space. What that means, is a lovely cool house in summer.
“Now it’s winter, the opposite happens and insulation traps the heat inside,” Mariana concludes “These walls don’t just make my lounge LOOK warm and cosy, they trap the heat well into the evening.”