Budgets for new house projects typically focus on the cost to build the home. In addition, objectives or principles can be discussed and agreed with the design team that incorporate the other aspects of lifecycle costing. For example:
- Targets may be set for operating costs for water and energy that guide selection of products and systems.
- A maintenance schedule and budget can be established at the beginning of the project and added to as products and systems are considered and selected.
- An expectation can be set as to the lifespan of the building that guides selection of products and impacts the maintenance schedule.
Priorities should also be set for each of the factors above as many decisions will need to be made throughout the course of the project that require trade-offs. A clearly defined and agreed set of priorities will facilitate this decision making.
2. Prioritise and test design
Decisions made during the design process will have cost implications. Your home’s orientation, for example, will probably impact future energy costs while material selection will affect the initial cost of the building as well as maintenance costs in the future. One of the key decisions in the early design stages that can have a dramatic effect on cost relates to the size of the building. The bigger your home, the bigger the impact on every type of cost within lifecycle costing:
- Cost to build will increase because more materials and time are required.
- Operating costs and heating costs in particular will increase as there will be a larger internal area to keep warm.
- Maintenance costs will increase as more materials used in construction results in more materials to be maintained over time, and more materials to be replaced at the end of their lifespan.
One cost-related figure that actually goes down as the size of a house increases is the cost to build per square metre. This is a figure commonly quoted when comparing different options, but it is important to remember it is only useful when comparing homes of the same size.
Cost savings through design
Like most sustainability outcomes sought in housing, the biggest gains can be achieved for the lowest cost at the design stage. The cost of changes increases as design progresses, and even more so as construction begins, so it is important that early design stages are guided by all the sustainability objectives for the project, especially those related to operating costs.
Some key considerations during the early stages of design that will reduce operating costs are:
- Placing and orientating the building on the site to make the most of the sun’s energy for heating and local wind conditions for cross-ventilation. This can reduce or eliminate the need for heating and cooling systems and the energy to run them.
- Designing a roof of the right size and pitch to maximise the performance of PV solar panels. This will result in more energy generated, thereby reducing ongoing electricity costs.
- Designing a roof of the right size to capture the volume of rainwater required. This can maximise the contribution of rainwater tanks and reduce the cost of mains water supply.
Engaging a sustainability consultant to test the design from its early stages will help to determine if targets set around energy, water and thermal comfort are being met. Optimisations resulting from these tests can significantly reduce the home’s future running costs.
3. Use systems and products to optimise design
As described in earlier sections, many products and systems related to sustainability outcomes will impact cost to build but can also reduce operating and maintenance costs. When selecting them you and your design team should refer back to the goals and priorities set at the beginning of the project to ensure the decisions made are consistent with your objectives.
Remember to consider products and systems holistically as they will often work in conjunction with other items in the home to deliver the outcomes you seek. There are many types of products you will need to consider throughout the course of your project. Some areas where holistic cost considerations can provide benefits are:
- Building envelope. Investing in a better-performing building envelope through improved glazing and insulation can reduce or eliminate the need for heating and cooling systems and their associated maintenance and replacement over the life of your home.
- Operating costs of systems. Some of the systems in your home will deliver a reduction in one type of operating cost but an increase in another. For example, a rainwater system to reduce water costs may also require a pump that requires energy to operate. It is important to consider both when determining the impact on operating costs.
- Maintenance costs of systems. The performance of systems in your home will diminish over time if they are not properly maintained. It is also important to factor in the replacement cost of systems and their expected lifespan within your home.
- Fittings. The fittings you install will impact the supply of energy or water to your home. For example, using LED lights throughout your home can reduce the size of the PV system required to meet your energy targets. Fittings related to hot water use (e.g. showerheads) can reduce not only the amount of water supplied to the home, but also the amount of energy needed for water heating.
- Finishings. Some low-toxicity finishes such as paint or untreated timbers may result in higher maintenance costs due to more frequent reapplication or replacement. Many low-toxicity products are available that are just as durable as more toxic options and maintenance information should be sought from suppliers.
4. Build well
Construction will be the most capital-intensive stage of your project. With the help of your bank you’ll need to schedule regular payments to the builder and subcontractors, as well as purchasing materials. In addition to these capital costs, the quality of the construction process will affect running costs of your house in various ways:
- Good construction will ensure your house performs as it was designed, especially in regard to thermal comfort. A house with acceptable levels of airtightness will retain heat whereas a draughty one will let it out quickly. If your house can’t keep the warmth in, your heating system will have to work harder to keep the house at comfortable temperatures, resulting in increased running costs over time.
- Periodic maintenance of your home will be necessary for systems and products to perform in the best way possible. If these are installed without following the manufacturer’s instructions they can deteriorate faster and will need to be replaced or serviced earlier than expected.
5. Use your home intelligently
The way you live in your home will play a key role in achieving your objectives and targets over time. Even a house that has been built with the highest sustainability outcomes in mind will perform poorly if used in an inefficient way. Everyday decisions about the way you use appliances and systems, for example the time you take to shower or water your garden, will be reflected in your water and energy bills.
In addition to smart use of your home, maintenance will be essential to ensure products and systems continue to perform efficiently over time. A neglected heat pump, for example, can use between 10% and 25% more energy than a well-maintained one.6 The maintenance cycle of each component of your home is likely to be very different. A maintenance schedule will be a useful tool to ensure you are always aware of aspects that need to be taken care of and can be created with the help of designers and suppliers.