A Well Designed Sustainable, Solar Passive Home will Add Vitality to Your Life

Healthy Homes

We live in a world where we are surrounded by man-made chemicals

Some are quite harmful, others less so. Minimizing our contact with chemicals on a daily basis has proven health benefits. A great deal of chemicals are used in the construction of a modern day home. To remove some of these chemical products from the internal construction of a home can be quite straightforward and can have plenty of health benefits. Removing a lot of VOC’s (volatile organic compounds) from inside of the home for example is as simple as selecting the correct paint or cabinetwork. VOC’s have a high vapour pressure at ordinary room temperature which is a result of the chemicals having low boiling points. Harmful molecules are given off into the atmosphere that we then breathe. Formaldehydes which evaporate from paints have a boiling point below -18 degrees Celsius. It’s easy to see that at room temperature a lot of formaldehydes would be given off into the atmosphere.

Energy Efficiency

What is an energy efficient home?

An Energy Efficient home should engage all of the principles of a Solar Passive home with the addition of energy producing or energy saving devices. For example solar power system, heat pumps or solar hot water systems will all contribute to lowering the homes reliance on the mains supply ultimately reducing its carbon footprint.

Simply put, an energy efficient home is one that uses minimal energy to run. In that regard the home uses natural resources such as the sun and wind to warm the home, provide power, hot water and so on. We are very lucky in Perth as we have plenty of beautiful sunshine all year round and in summer great afternoon and evening breezes. It is also very fortunate that our sun shines in from the north and our summer breezes blow in from a southerly direction. As a designer you could not ask for better conditions to be able to design a home that requires minimal energy to run.

Solar Passive Design

What is solar passive design?

A well designed solar passive home will invigorate its occupants. Have you ever been on holiday and stayed in a nice bright beach house? Did you feel more alive? Did you feel more relaxed? It has been proven that sunlight adds vitality. It’s a big part of the reason many people from all over the world settle here in Western Australia. We have great sunshine and it makes people feel good. So why do we build homes to keep the sunlight out? Is it because we have hot summers? A well designed home can be cool in summer but still be nice and bright. More importantly we want that beautiful sunshine to come into our homes in winter. Why not live in a home that makes you want to get up in the morning and enjoy the day. Why not live in a home that makes you feel alive!

Designing your home around a few key principles will maximize its comfort and efficiency. Follow these principles and you are well on your way to achieving a home that will not require artificial heating or cooling and will just make you feel good living there.

  1. Orientation
  2. Glazing
  3. Air Flow
  4. Building Fabric
  5. Thermal Mass

Orientation

Locate rooms that you use most to the northern side of the home. Maximize winter sunlight into these rooms to heat up thermal mass.

Glazing

Maximize glazing to the north to gain as much winter sun into the home as possible. In that regard no eaves work best in winter. Provide sufficient shading to northern glazing in summer to minimize heat penetrating into the home. Retractable horizontal blinds or adjustable horizontal louvres that shade 4m or more is best practice. Specifically designed eaves for the home are next best.

Do not design windows into the east or west elevations if possible. Shade them well with vertical screens if they are needed. Minimize southern glazing but ensure enough operable windows for airflow.

Airflow

Locate glazing and internal wall openings to maximize air movement through the home in summer. Good roof design will aid in drawing air through the home. 

Sliding windows are generally not the most efficient option for a southern wall as only half the window is operable.

Building Fabric

When we talk about building fabric we are generally referring to the main construction of the building. We consider the floor structure, walls, windows, external doors, ceiling and roof frame to all be a part of the building fabric. The building fabric is the key structure of the building and it keeps the heat out in summer and heat within in winter. It is important that the building fabric performs well to reduce ongoing energy costs and comfort for its occupants. By keeping the building square or rectangular will reduce the surface area of the building further improving the performance of the building fabric.

Thermal Mass

Locate thermal mass in the home to stabilize the homes temperature. Products such as concrete and masonry will absorb and store heat. Heat will always move from a warmer material to a colder material until both are stabilized at the same temperature. Getting sunlight onto a concrete slab during the day will warm it. When the air temperature in that same room cools in the evening, the concrete will release its energy into the room stabilizing it. A slab acting as a thermal mass body will also aid in cooling a home in summer as it absorbs heat out of the room.

It’s interesting to note that water has four times the thermal mass of concrete or masonry so by looking at ways to store water in a home is good way to stabilize its temperature.

Perth Home Design

What is wrong with the way houses are built and designed in Perth?

It’s interesting that for centuries all around the world humans have designed homes that suit their lifestyle and environments which for the most part are efficient in their own right.

Let’s look at a traditional Khmer house in Cambodia. They build out of timber, brick and thatch. The sleeping area of the home is on the first floor. It is built from local timbers. The first floor walls and floors are all timber. Their climate is tropical and their nights are warm. The timber structure does not gain heat during the day and allows the temperature inside the building to cool and equalize with the ambient air temperature. The ground floor kitchen area is often enclosed with brick and this is due mostly to the susceptibility to flooding.

Now let’s look at our English counterparts. It’s a cold climate so their priority has always been how to keep the heat in. Prior to the invention of double glazing in the 1930’s this was best achieved with small windows and heavy masonry walls. The masonry walls absorbed heat and provided good thermal mass radiating heat into the building as the external temperatures dropped in the evening.

In Perth we have a temperate climate. We experience hot summers and cold winters. When Europeans moved to Australia they brought with them their architectural design philosophies, none of which really suited all of our climate traditions.

We had adopted their practices in design and being so isolated from the rest of the world we just kept evolving these bad practices. Most of our housing in Perth (until 6 Star has forced our hand) had very little north facing glazing and when it did the designer stuck a big alfresco roof over it. No winter sunlight penetrated directly into the home forcing the occupants to crank the heater up in winter and turn lights on in the middle of the day. I’m certainly not against a good alfresco, but it needs to be located correctly to allow the home to perform.

Another bad practice has been our desire to construct out of double brick for so long. There are few if any temperate climates in the world apart from Perth where double brick is the main form of wall construction. Now with 6 Star rating it’s starting to show its weaknesses. The National Construction Code calls for cavity wall insulation to stop heat transfer through the wall when designing to deem to comply standards. A more efficient construction method in our climate is reverse brick veneer. This means brickwork on the inside providing thermal mass in winter and timber frame on the outside protecting the walls from adverse temperature on the outside. If you are building a two-story home then perhaps look at locating all bedrooms to the first floor. Construct this floor entirely of timber frame, insulate it well and it will be a much more comfortable, allowing the building to cool in the evening in summer just like the Khmer house in Cambodia. As timber is an insulator which means the building will not experience as much heat loss in winter to stay cozy and warm.

At Ecohabit Homes we are certainly not against double brick and we still design with it a lot, but mostly because of client demand. We always tailor the construction and design of the home to suit our clients’ needs. We provide our clients with all the information they need to make an informed decision on what is the best construction method for their home. You have to live in the home, it should be what you want and work the way you need it to.

How Solar Passive Design Works

Perth is a designer’s nirvana in which to design energy efficient houses. We have ample sunshine year round and great sea breezes. Our only Achilles heal is lack of water. Water issues can be overcome with rainwater holding tanks as well as grey and black water treatment systems.

The diagram above shows how some basic principles allow us to achieve good solar passive design in Perth.

Sun:

A) In winter we should allow sunlight to penetrate into the home from the north, heating up the concrete slab and walls during the day. In the evening as the internal temperature of the house starts to cool the slab and walls release their energy stabilizing the internal air temperature of the building. The result is little or no heating. requirements. Note: covering up thermal mass, which would otherwise be exposed to winter sunlight, with timber flooring, some types of tiles, carpet or furniture will negate much of its benefits.

B) In summer the eaves of the building protect northern windows and walls from the sun.

C) East and west facing walls should contain little or no windows. Walls and windows on these elevations should be protected by vegetation or other screening methods.

D) Bedrooms with south facing windows shall be exposed to summer sun in the early hours of the morning and late in the afternoon. This should be taken into consideration when placing these windows.

Wind:

E) Summer sea breeze is pretty consistent in Perth. It conveniently blows in from the south or southwest. Air flowing over the top of the home with a well designed roof will create a low pressure that will draw air through the home. 

What creates our sea breeze?

A little understanding on how a sea breeze is generated can go a long way in understanding how important it is to make the most of it. Air over a warm land mass heats up. That air rises and needs to be replaced. Heavier cool air is drawn in from the ocean replacing the warm air that has risen. That’s a sea breeze in a nutshell. Our sea breeze is pretty consistent during summer. Speak to a sailor or local kite boarder and they will tell you that there are not too many days during summer when they can’t rely on the Fremantle Doctor.

Article by – EcoHabit Homes