21 November 2022
Considerations for Designing Net Zero Houses
Climate change stories are incomplete without the big, bad villains – homo sapiens. Of all the nasty things we do, the process we use to build our dwellings and shelters is particularly nasty to the environment. According to United Nations reports a few years ago, the energy used to construct, operate and maintain buildings contributes to 40% of global carbon dioxide emissions. That’s a big bite of the pie, and governments, environmentalists and builders are scrambling to find ways to go on a much-needed diet.
Among multiple approaches to improving sustainable construction initiatives, enter the net zero house, or a house that uses energy that it has generated by itself, resulting in a net zero emission of carbon dioxide. A net zero house generates as much energy as it uses, so it produces as much renewable energy, both on and off site, as it needs. This becomes a self-sustaining building, which is also carbon-neutral. They can also be referred to as zero carbon buildings or net zero energy buildings.
A net zero house needs fresh thinking, accurate and effective building construction processes, energy-saving methodology and the use of modern technology. These houses do not use fossil fuels, such as natural gas and propane, at all, but rather uses electricity to power lights, cooking appliances, washers and dryers, for heating and cooling, hot water, electronics, etc. They can use tight, highly insulated building envelopes that need minimal energy for heating and cooling. An array of solar panels and solar hot water collectors help buildings generate its own power.
Features of a Net Zero Home
Solar photovoltaic panels are active solar power generators, as they actively generate electricity.
- Building design that considers the sun’s position to maximise heating or cooling is known as passive solar design. In warm to hot climates, large overhangs on windows for shading can be included in the passive solar design.
- Similarly, in cool to cold climates, large south-facing windows let in the sun’s heat to maximise indoor temperatures in winters.
- Regardless of the climate, insulation will help maintain the ideal inside temperature, reducing energy use for heating or cooling, with the extent of insulation required dependent on the climatic conditions of the region.
- For a net zero home, a comprehensive modelling of the house’s energy use is required, and special approaches, such as walls of double thickness may be used to allow greater insulation volumes.
- Houses typically lose heat when air leaks through gaps around doors and windows, porous plywood sheathing and other sources.
- Net zero homes need to ensure an airtight building envelope with careful attention to detail, sealing all gaps and considering wall porosity.
- Building ventilation needs to eliminate excessive moisture inside and prevent mould, bringing fresh air into an airtight building.
- Systems must be installed to bring outside air in and take stale air out, while recovering energy spent on heating and cooling previous air, such as a heat recovery ventilation (HRV) or energy recovery ventilation (ERV) system.
- Installing systems that are heat exchangers means that during winters, heat from warmed inside air will be retained before it is vented out, so occupants can have fresh air without wasting energy.
Heating & cooling
For a net zero home, energy used must be generated by the house.
- An electric heat pump can be used so that solar panels can supply electricity for heating and cooling. Heat pumps use the air or ground as a heat source, and they can work as an electric heater in the winter and an air conditioner in the summer.
- If heat pumps cannot work due to very cold outside temperatures, electric resistance heating (such as used in space heaters. hair dryers, etc.) can be used.
So, what do net zero homes look like? Do solar panels and other net zero equipment mean that such homes will look unpleasant?
- It is possible for a net zero home to look like any other type of house from the outside; some can even appear traditional.
- It is also possible to prefabricate a net zero home in a factory and transport it to the site. Units can be of different geometric shapes, such as squares, triangles and rectangles.
- Net zero homes using solar hot water collectors and photovoltaic panels can also have provisions for collecting rainwater for organic gardens.
- The advantages of using prefabricated net zero homes are that quality control, constructing with the exact tolerances required for net zero homes and adding precise window overhangs is easier.
- Windows, walls, rooms and even porches can be constructed with structural insulated panels (prefabricated walls using insulation foam between oriented strand board layers). These walls fit together easily on site.
- Not just individual homes, an entire neighbourhood can be constructed of net zero homes.
When It’s Good to Be Passive
- A passive house takes energy efficiency to a level where no mechanical cooling or heating systems are required.
- Using extreme insulation, passive solar characteristics and thermal mass – thick walls and floors that can absorb heat – a passive home stays at a comfortable temperature throughout the year, without a furnace or air conditioner.
There’s a nasty rumour about smart homes getting in the way of net zero goals. If the house is more connected, or more ‘smart’, or ‘smarter’, does it mean energy bills become overinflated? Packed with intelligent security, intelligent heating/cooling systems and other high-tech gadgets, does the home guzzle power?
- Well, it’s all about connections. If different devices are inter-connected by means of a centralised, inter-operable power management system, then they can all play nice and use less power than they do when installed separately.
- Smart homes can lead to safe homes, with automatic alert systems for electric wiring problems can help occupants switch to backup power.
Now that we know what they are, how they benefit both occupants and the environment, how do we design them?
Designing Net Zero Houses
Design for net zero houses requires a large amount of data and multiple processes, which is why it’s imperative professional support to supply comprehensive net zero home design services. In addition to the architect’s input, many net zero projects have an energy consultant, to build a model to view building performance, and a mechanical engineer to design HVAC systems with the greatest efficiency. It’s important to have a series of integrated design meetings with both design and construction teams for everyone to be on the same page.
- Detailed research and analysis of the local climate, sunlight hours, wind patterns, precipitation patterns and temperature ranges must take place first, This will guide the overall net zero strategy.
- Orientation comes next. The building orientation must take fulll advantage of natural breezes and the movement of the sun, for shading and lighting needs, helping design an efficient building envelope.
- For sites in the Northern Hemisphere, solar panels are most effective when facing south, so the roof must be designed to accommodate them.
- Efficient building envelopes needs to be airtight at the right places. Air must enter and exit through intended openings, not undesirable gaps.
- Triple-glazed windows, efficient insulation and special façade details can seal up any cracks.
- Low-energy HVAC systems, appliances and fixtures must be included in the planning stages.
R&R (Renovations & Retrofits)
- It may be more complex to renovate or retrofit a home for net-zero goals, as an existing house cannot be reoriented, and it is expensive to reverse-engineer a building envelope.
- In addition, walls must be insulated, cracks sealed up, efficient new mechanical systems and a rooftop solar array must be installed.
The energy model must be consulted to calculate the amount of electricity needed to offset the renewable sources being used, through solar panels or wind, geothermal or hydropower on-site power generators.
Project monitoring through post-occupancy studies and adjustments that result from them are crucial to the net-zero design process.
The 2030 Challenge, an architectural initiative to have all new buildings and renovations be carbon neutral by 2030, may seem like an impossible goal. Promoting sustainability design approaches and net zero housing can make it seem slightly more possible. However, along with needing experienced sustainable design consultants, it is crucial that architectural design services deliver accurate residential design drawings, residential construction drawings and other residential drafting services. Net zero homes may soon be the new normal.
XS CAD has valuable experience providing architectural design services and residential design drawings for general contractors and design consultants. Our range of services for building design firms across the world include residential drafting services, residential modelling and residential construction drawings, and we offer retained teams when required. We create these models, drawings and renderings by using Revit, AutoCAD, Illustrator and BIM 360 Design for cloud collaboration.