Each building component of your building will contribute, either negatively or positively, to the energy efficiency of your home. While all components need to work together to result in an energy efficiency home, it is important to understand the role each plays.
The floor of your house is significant, as an energy efficient floor can help reduce your energy costs and raise your star rating. Concrete slab on ground works the best as the ground temperature can help moderate the temperature in your house. If this is not possible, enclosing the entire perimeter of your elevated floor helps the house to stay a moderate temperature by using the ground temperature to keep the sub floor at a consistent temperature. Insulation is important to ensure heat and cold do not move through the floor. Insulation needs to be matched to your house design as more is not always better in floors.
Floors between levels
A floor between levels does not contribute much to the energy efficiency unless it is concrete, allowing thermal mass into the house, or if it is a floor over a garage – which should be insulated for better energy efficiency.
Windows are the most important factor in an energy efficient house because windows are holes in the fabric of your house. They are the worst performing construction element thermally, however improving a windows thermal performance can reduce greenhouse gas emissions and energy costs. It is extremely important to balance the heat and cold that enters your house, since up to 40% of a home’s heating energy can be lost and up to 87% of its heat gained through windows. The biggest mistakes we see with windows are too much glazing, not enough glass on the northern side, too much glass on the east and west or too many fixed windows. If you are having windows - make them opening windows to help heat escape!!
Eaves and Shading
Eaves and shading are very important especially on the northern side. Not enough shade and your home wil be filled with hot summer sun. Too much shade and all the winter sun will b blocked making your home cold. As a rule of thumb, homes in Perth and surrounds, shading width should be equal to half the measurement of the window sill to the bottom of the shading.
There are two items in walls that will help with your energy efficiency – thermal mass and insulation. Thermal mass is the ability of a material to soak up heat and then dispense this heat later, reducing temperature fluctuations. Materials such as brickwork and concrete can soak up heat in the day and release it when the sun is gone, especially on warmer days and cooler nights. The other important item is insulation. External walls should be insulated to reduce conducted, radiant and convected heat transfer – within stud frames, cavities or the inside/outside of solid walls. Insulation is less important in walls that have thermal mass (such as cavity brickwork) and very important in lightweight or framed walls. No matter what walls your project has, insulation is an important factor to consider for an energy efficient house.
Ceiling insulation is the most important insulation in your house as it greatly reduces heat gain and loss. Our research has shown that including ceiling insulation of R4.0 can increase the energy efficiency rating of your house by up to 4 stars, when compared to houses with no ceiling insulation. This means that if you do not have adequate ceiling insulation your house WILL NOT be energy efficient.
Roof insulation is installed to reduce radiant heat gain within your house. While it is not as effective as ceiling insulation, it still assists with the energy efficiency of your home. The most common insulation for steel roofs is a foil faced insulation such as ‘Anticon’. Tiled roofs usually use a sarking product to protect from water that can also act as insulation. for more about roofs see Nina's post about energy efficient roofs here: Cool Roofs
Skylights are a great source of natural light and can supply more than three times as much light as vertical windows the same size, ensuring less electricity use, contributing to energy efficiency. If you have skylights make sure they are best quality - preferably double glazed - to ensure minimal heating and cooling are lost through them. They can also be used as a ventilation stack if they are opening – allowing heat to escape.