Building Envelope
In Auckland we are lucky enough to have a temperate climate, making energy efficient building design fairly simple. A house that is comfortable all year round can be achieved with reasonable levels of insulation, reduced thermal bridging, summertime shading features, and ventilation.
The building envelope of a house (walls, roof, floor, windows, and doors) is a very important element of the design as it can have a huge impact on the energy performance of the building. Thermal modelling of our preliminary design shows that with adequately insulated walls and high performance windows we should be able to avoid the need for heating the house for the vast majority of the year.
The high insulation levels will result in uncomfortably high temperatures in the summer without adequate ventilation and shading which we will address through opening windows, eaves and other shading devices.
In Zero Energy Building Envelope we introduce the topics covered in the Structure section and discuss GreenStuf insulation, ClimaGuard N70 glazing from MetroGlass, and Viking Roofspec's Enviroclad green roof membrane.
Benefits of a high-performing Building Envelope
A building envelope that avoids heating or cooling gets us 30% towards the Zero Energy goal.
The building envelope separates the inside of the house from the outside, protecting inhabitants from the elements. Constructing ours to avoid the need for heating or cooling gets us 30% towards the Zero Energy goal, as the average home utilises this much of its energy consumption in space heating.
There are cost and health benefits to living without the need for heating or cooling:
- We don’t have to worry about paying for heating as electricity prices go up in winter, and year-on-year.
- We don’t need to worry about the maintenance of mechanical units.
- The entire house is warm rather than having warm areas in heated living areas and cold pockets in bedrooms.
- We get fresh air, because we can open windows in winter and the house will still be warm.
Incorporating passive design
Designing a building envelope with passive solar gain in mind is one of the most cost-effective ways to make a building perform.
A building envelope can't achieve high performance through products alone. To maximise its effectiveness it is important to design the building envelope with passive solar gain in mind. This is also one of the most cost-effective ways to make a building perform; taking this approach during the design phase won't actually cost any more money. We have a full page on passive heating & cooling achieved through design; some of the key methods used were:
- Facing windows towards the north, and designing their size to allow the right amount of passive solar energy into the house.
- Placing living areas like the lounge, dining, and bedrooms on the warmest side of the house (the north) and spaces less lived-in such as the kitchen and bathrooms on the south.
- Placing the kitchen at an eastern corner to take advantage of morning sun.
- Designing the size and shape of the first floor overhang to provide shading to living areas in the summer, but allow a lower winter sun to penetrate and heat the concrete thermal slab.
With the building envelope designed, we used a number of products and methods to help control the temperature inside, most of which are shown in the concept markup below.
Concept markup of building envelope features. The section shows the building when viewed from the east.