Passive design vs. Sustainable design – what’s the difference and can we help you achieve both?
10th May 2021
Building design and construction professionals are increasingly looking to design & deliver buildings in a more environmentally friendly manner. The UK government recently set an ambitious target to reduce emissions by at least 68% by 2030, compared to 1990 levels and the ultimate goal set out in the Paris agreement – endorsed by 197 countries around the world – is ‘net zero by 2050.’ Construction needs to play a significant role in this if buildings of the future are to help realise this scenario.
There are a number of approaches to this, and several types of design that could potentially assist in reducing emissions and reducing a building’s impact on the environment both locally and as a whole.
Design approaches that contribute to reducing emissions
Passive design works to maximise the use of ‘natural’ sources of energy. This includes harnessing environmental conditions such as solar radiation, cool night air and air pressure differences to drive a comfortable internal environment without the need for mechanical or electrical systems. It also includes any other natural resources available.
Examples of this might be larger windows placed strategically to make the most of natural light and heat on the building at times when it is most used, or the harvesting of rainwater to flush toilets.
Other examples are the use of thermal mass and insulation.
Thermal mass is the ability of a material to absorb and store heat energy. A lot of heat energy is needed to change the temperature of high-density materials such as concrete, bricks and tiles – materials said to have high thermal mass. Lightweight materials such as timber have low thermal mass, whereas insulation acts as a barrier to heat flow and is essential for keeping your home warm in winter and cool in summer. Different design decisions will be relevant if insulation is predominately needed to keep heat out, keep heat in, offer soundproofing, or help eliminate moisture problems.
Thermal mass does not provide an alternative for insulation. Thermal mass stores and re-releases heat, while insulation stops heat flowing into or out of the building. Insulation must work alongside other passive design principles for it to achieve the desired results.
Farrat – as Certified Passive House Component providers – have been working specifically with Passive House to advise structural engineers and designers on how to specify carefully to eliminate thermal bridges in buildings and structures, using experience gained through projects including The University of Salford. Find out more on how to benefit from this specialist advice in Passive House+ Sustainable Building Magazine here.
Active design makes use of active building services systems to ensure comfortable conditions within a building, such as boilers, mechanical ventilation, electric lighting, and so on.
However, active design features aren’t limited to those that rely on less ‘green’ sources of power and can actually be used as a way of making a building more environment friendly. An active design element of this kind might be electric lighting powered by the harvesting of wind, wave or solar energy instead of by the main grid.
Buildings will generally include both active and passive design measures.
Sustainable design in construction – sometimes also called environmentally conscious design or eco design – is the philosophy of designing a built environment to comply with the principles of ecological sustainability. In essence, it aims to eliminate the negative environmental impact that a building generates.
The difference between passive design and sustainable design is that sustainable design can be made up of both active and passive design: It is not exclusive to the passive design methodology of using what is available naturally. It can also include actively increasing sustainability by generating energy. It can also look at other aspects of design such as energy conservation and use of sustainably sourced materials.
It is potentially a more holistic approach that meets more needs than passive alone. However, the more active design aspects mean you have a greater the need for materials and infrastructure, so you might argue that the more you rely on passive design, the greater sustainability you achieve.
Commonly used areas of sustainable design:
- Energy efficiency. Making sure that the energy a building uses isn’t wasted is the biggest no brainer and is one of the oldest forms of sustainable design – dating back to the 1940s and made popular in the 1970s-1980s.In 2021 and beyond, for more ambitious constructions this goes beyond loft insulation! Architects and engineers are looking at every aspect of a building to identify areas where they can minimise the loss of energy, and this includes external and internal materials. At Farrat, our structural thermal breaks are frequently used for this very reason, as the most efficient and responsible way to thermally separate structural connections and prevent heat loss in the building envelope.
- Using natural energy to generate of power. Wind, solar and even wave power generation is on the rise and there are whole buildings or even cities powered in this way. For example, Adelaide’s municipal operations have been powered entirely by renewable energy since July 2020. At Farrat, we are working with responsible companies across the world to design and manufacture bespoke industrial vibration control solutions to isolate renewable energy power plants, such as hydro-electric power dams. Generating your own power comes with its engineering challenges. In addition to ensuring the optimal construction and placement of the equipment itself, ensuring there are not adverse side effects to energy generation is essential to the comfort and security of buildings in habitants. An example of this might be ensuring that the impact of any vibrations caused by a window turbine is reduced with Building Vibration Isolation.
- Rainwater harvesting. Desert climate cities led the way is the use of rainwater in building design. For example, Madurai is a city in India of over 1 million people where 83% of buildings use rainwater harvesting.
Closer to home there are central buildings where it has been added to the design. For example, the Museum of London was built in the 1970s but in 2011 they rolled out their new rainwater harvesting initiative, with a 25,000-litre tank that both flushes the toilets and irrigates gardens. Rainwater harvesting is now a passive design being introduced at planning stage, such as at the new sustainable food facility and vertical farm planned in the Midlands.
Given the expected significant changes to the climate over the coming years, new homes need to be as climate responsive and energy efficient as possible. Construction professionals are actively acknowledging their responsibility to utilise and combine best practice principles from across passive, active and sustainable design to futureproof buildings, and the role of suppliers in this value chain is critical. We must ensure that the building materials we supply are fit for purpose and meet the highest of standards when it comes to sustainability, such as PassiveHaus, BREEAM and LEED.
At Farrat, we’re committed to the delivery of sustainable communities and will continue to work with developers, contractors, architects, structural engineers and consultants to develop engineering solutions that help to reach environmental targets and ultimately make lives better.