First, let’s define what a 'net-zero energy home' is. In a nutshell, it is a home that produces as much energy as it uses over the course of a year. In order for a home to be able to achieve this goal, there are a number of things to consider at the initial planning stages of your build (ideally even before you choose the section!)
1. LOCATION Ideally, the location for the home would be in a site that is flat, north-facing (so that it receives unobstructed sunshine for most of the day), and has little exposure to the elements. If achieving a direct North facing site isn’t possible, you can still achieve a high performing home via clever design, but it is more complicated. If the house is oriented 20 degrees East or West of true North, there is very minimal loss in performance. Trying to find such a site that ticks all of these boxes may be quite a challenge, so be sure to prioritise sun exposure. The more you can achieve in terms of ideal location, the less likely you will spend on energy bills.
2. SIZE When it comes to achieving net-zero energy, the smaller the house, the smaller the carbon footprint. They cost less to build and heat and are therefore also kinder on the wallet. Smaller may also mean being able to spend a little more on better energy efficient items such as ventilation systems, insulation and appliances.
3. SHAPE A smart house design would incorporate a more straightforward shape, rather than one broken up with smaller parts within it. An open-plan space will cost less to build, insulate and heat or cool.
4. THERMAL ENVELOPE
The thermal envelope of a home is the separation between what is inside and outside the liveable space. At Green Abode all our concrete slabs are fully insulated underneath and around the edges (most of your heat loss occurs around the edges of a concrete slab). If you are building with Structural Insulated Panels (SIPS), the entire envelope of the house is also highly insulated.
5. ROOF OVERHANG
If you can calculate at what times of the year and day the sun needs to be minimised from the house to avoid overheating in summer and when it needs to be maximised in winter, this can significantly affect your energy bills. A roof overhang can be worked into the design of the house to make the most of the sun.
An R-value is a measure of how well a barrier (i.e. a window, insulation, door, etc.) resists the conductive flow of heat. Generally speaking, the higher the R-value, the better the insulation.
R-values need to be appropriate to your local climate. New Zealand building standards require that R-values start at R0.26 for windows and work their way up to R3.3. With Green Abode homes, however, our R-values start from R2.8 and finish at R9.4.
When homes are built with energy efficiency in mind, they are more tightly sealed than an average home. This makes it crucial to ensure proper airflow through the house through a central ventilation system. A good ventilation system will ensure the removal of stale air, allergens and other unhealthy particles from the home and replace it with fresh air regularly. Be sure to include all mechanical ventilation equipment and ducts into your plans. As much as possible, try to specify all the efficiency ratings on the plans.
8. HEATING + COOLING
To meet the net-zero energy goal, reducing the energy required for heating and cooling a home is essential. The ventilation systems that Green Abode install also acts as heating and cooling units.
9. SOLAR ENERGY
Solar photovoltaic (PV) panels are the most cost-effective renewable energy source for most net-zero energy homes. If you plan to use PV panels, ideally, the location of the house would have unobstructed sunlight between 9 am and 4 pm. Be sure to consult a solar contractor early in the process to identify any key design issues.
Some companies offer free installation for a 20-year contract. This option is worth investigating if you don’t like the idea of paying such a large amount up-front.
A tool that is highly recommended for the design phase of a net-zero energy build is energy modelling. Energy modelling is a virtual assessment of the way energy is used in a building. It focuses on energy consumption, utility bills, and life-cycle costs of various energy-related items such as heating, air conditioning, lights, and hot water. Energy modelling can be done right at the design stage, once the plans are drawn up with dimensions, elevations, windows, and doors. They can help steer you in the direction for such things as the best layout of the house, most suited R-values and whether to use solar panels or not, among other things. The plans can then be adjusted so that the project will reach the net-zero energy goal at the lowest cost possible.
We would also suggest conducting an air blower door test before ceiling plasterboard and insulation installation to identify possible air leaks. Doing the test at this stage will ensure that any leaks can be resolved before the build has progressed too far.
If you would like to book in an energy modelling assessment or an air blower door test or would like more inflation about either service, please get in touch with us via the contact form on this website.