1. Define priorities and set objectives
Doing this can help with the selection of your design team because you’ll be able to evaluate their ability to respond to your requirements. After you have engaged a designer, you can review those objectives and targets together and discuss the best way to approach them. It is likely that your designer will have valuable feedback based on experience from previous projects. Objectives and targets can inform decision making during the design process and will act as reference points for consultants and suppliers.
2. Decide if a rating tool or certification is right for you
If you’re using rating tools, their objectives and strategies will also need to be incorporated early in the process as they might dictate the way the design is approached. For example, if a tool sets a temperature range and a maximum heating load to achieve certification, it will be key to incorporate passive design strategies, as well as improvements to the house’s envelope, from the start of the process.
3. Prioritise and test design
Design will play a key role in achieving your comfort and health objectives. The way the house is positioned on the site, its size and its shape will all have a long-term impact on indoor air quality, the temperatures of each room, and noise levels. Passive solar strategies such as eaves and shading elements on the north, east and west, narrower and more compact building shapes, cross-ventilation and increased thermal mass can contribute to a house that is more comfortable by reducing heat loss in winter and allowing fresh air to circulate, preventing overheating in summer.
In addition to estimating your energy use, an energy model is a key tool for verifying the performance of your home in terms of comfort. Modelling is usually done by a sustainability consultant and will allow you to evaluate performance early in the design process by understanding impacts of design decisions such as orientation and shape. An early start will increase the model’s cost-effectiveness as optimisations derived from results can be made with little or no cost implications and will help the project achieve greater long-term savings.
As the design evolves, the model can predict indoor temperature ranges achieved passively as well as the required heating and cooling requirements for your home to remain at desired temperatures. Additionally, it will allow for different scenarios to be tested and determine if internal comfort can be improved through, for example, changes in insulation levels or window sizes.
4. Use systems and products to optimise the design
Choices around the house’s envelope can potentially have the greatest impact on internal comfort. The envelope’s role is to let the right amount of heat into the house and to keep it in once it’s there. An envelope that is designed and built properly will help you maintain healthy and comfortable temperatures, prevent excess moisture and reduce air leakage. A good designer will be able to interpret your objectives into specifications and a construction system that deliver your outcomes instead of just using materials and details from previous projects.
- Regardless of your preferred construction system, details and specifications will be key to improving the performance of your home. For example, if using a timber frame, you can research alternatives for reducing thermal bridging and increasing the space for insulation. If using concrete blocks, you can review if adding internal or external insulation can increase comfort. Different projects need different solutions, there is no one size fits all. Consulting with your design team and suppliers can ensure chosen products and details are the right ones for your house.
- Windows also play an important role in internal comfort. In the winter, efficient windows will help you keep the sun’s warmth inside the house while inefficient ones will let it out too quickly. The Window Association of New Zealand (WANZ) has developed the Window Energy Efficiency Rating System (WEERS) to assess the performance of windows which can increase certainty about the products you are using. Fitting security latches on windows will allow you to leave them open when you leave the house so that air can circulate.
Another important factor for improved indoor air quality is the selection of the materials used on your house. If you have defined products and substances that should be avoided during construction, you will need to invest some time finding substitutes for some of the materials typically used in the industry. Selecting products with a third-party certification such as Environmental Choice New Zealand
for paints, textiles, plasterboards and timber laminates is a simple way to ensure healthier material selection.
Remember that choices made around furniture, cleaning and personal care products will affect air quality as they also emit VOCs.
Systems should be considered only after improvements to the building envelope have been made. This is likely to result in a more holistic approach and in increased efficiencies. The selection of heating (and cooling) systems can be guided by the results of the energy model and should be made in accordance with your objectives around energy and comfort and health.
In addition to passive design strategies, most homes will require a heating system to maintain comfortable indoor temperatures, especially in the colder months. Heating typically accounts for 34% of your energy bills in winter4
and therefore the efficiency of the system you choose, in addition to the quality of the envelope, will be crucial. A more efficient system can help you reduce those bills while providing a healthier indoor environment. The right heating system for your project will depend on your location, personal preferences and your house’s specific conditions. Further guidance on alternatives can be found at the Smarter Homes
Houses in Auckland shouldn’t require active systems to control overheating. The city’s mild weather has traditionally allowed warmer temperatures to be regulated using passive means via openable windows and shading devices. At the same time, however, it is important to consider this issue during the design process and include strategies to avoid it such as eaves and shading elements on the north, east and west, and moveable screens on the east and west. Health and comfort issues associated with overheating include sleep deprivation, heat cramps and reduced productivity.
Ventilation not only reduces overheating (especially at night), it is also one of the key means of achieving good indoor air quality. Your design approach should ensure that fresh air enters the house and effectively circulates through it, and that excess moisture is removed from wet areas. A well-designed natural ventilation system should provide cross-ventilation and effective air movement throughout the house, but active systems are needed to remove moisture from wet areas. They are also useful if you want good air quality with little manual control.
Systems and products to discuss with your architect or designer include:
- Finishes such as paints and coatings
- Insulation (thermal and sound)
- Heating and cooling systems
- Ventilation (just for wet areas or for the whole house)
5. Build well
The quality of the construction process will be key to ensuring objectives and targets incorporated in the design process will be accomplished. Some of the important aspects to pay attention to when building a new house are:
- Weathertightness. When the wind blows, air leaks into your house through cracks, openings and gaps in the envelope, bringing cold and moisture in from the outside. If the house is not properly built, water might also penetrate its structure. Water and air leaks can cause serious problems such as structural damping, increased spread of fire and smoke, and increased noise levels. Good specifications and quality construction will increase the weathertightness of your home and the opportunities to achieve a healthy and comfortable indoor environment. For more information on this topic check out the Weathertight website developed by BRANZ.
- Thermal bridging. The detailing and construction of the envelope significantly influences the house’s ability to retain heat. Thermal bridging occurs when a poorly insulating material allows heat to easily escape from the building. As more energy – in the form of heat – leaves the house, more energy must be introduced to keep it at comfortable temperature levels. Bridges usually happen where studs and nogs intersect, in aluminium joinery, and in places where insulation has not been properly installed. A standard 90mm frame has 16% thermal bridging from the studs and nogs. To reduce thermal bridges, design should minimise breaks in the insulation for both walls and ceilings. Additionally, when bulk insulation is being installed, no gaps should be left between the insulation and the framing, and segments should be carefully cut to match the size of the frame, avoiding folds.
Building inspections will ensure your building is Code compliant but they will not ensure your house is built to an acceptable level of quality. Engaging someone who has a proven track record to manage your project will be the best way of getting the results you expect from the construction process.
Asking upfront about tests and quality control procedures they may undertake to ensure the building’s construction quality will be essential when making decisions about the project team. One commonly used test they may use to understand the airtightness of your home is the blower door test. With all the windows closed, a fan tightly fit to a door sucks air out of the house, simulating the effect of wind and allowing an auditor to measure how much air is leaking in. The results allow you to find and eliminate leaks, and to compare your house’s performance to acceptable standards of airtightness.
6. Use your home intelligently
The way you live in your home will play a key role in achieving a sustained healthy indoor environment over time. A house that has been designed with sustainability outcomes in mind will also need to be used in a conscious and intelligent way to avoid further comfort and health issues or increased running costs to maintain that comfort. For example, having an airtight home and not allowing fresh air in can increase the concentration of CO2, which creates stuffy rooms and health problems. How you use your home will have an impact on aspects such as moisture levels, internal temperatures and air quality. Everyday actions like the ones listed below can help you achieve an indoor environment that is more comfortable and healthy:
- Using extractor fans when cooking or showering will prevent the accumulation of excess moisture in kitchens and bathrooms.
- Leaving windows open when you leave in the morning (if security permits) will dilute toxins in the air and allow fresh air in.
- Closing curtains at night, especially in winter, can help to keep the warmth in.
- Drying your clothes outside or in a drying cabinet will prevent around 5 litres of moisture per load being released indoors and will also prevent mould growth and deterioration due to excess moisture.
- Using flued gas heaters will be safer and will prevent the release of moisture and gasses into your home. Unflued gas heaters should never be used in bedrooms.
In addition to using you home intelligently, maintenance will be essential to achieve a healthy and comfortable environment in the long term. Wall cladding and coatings, for example, will need regular maintenance to ensure they are able to resist the elements. A maintenance schedule will be a useful tool to ensure you are always aware of aspects that need to be taken care of. You can create your own with the help of designers and suppliers or you can use an online tool developed by BRANZ