Passive House vs other green standards
As mentioned in our previous blog, ‘What is Passive House?’, Passive House is a globally recognised standard. Principally seen as a low-energy standard it also provides guaranteed high levels of internal air quality and comfort.
But why choose to build a Passive House, Certified or otherwise, when you could build a Nearly Zero Emissions Building (nZEB), or BREEAM rated building, or LEED, or WELL…. there are many alternatives, too many for a single blog. We will focus on three common UK alternatives and hopefully demonstrate why Passivhaus may be the best choice for your project: BREAAM, nZEBs and Life Cycle Assessments.
BREEAM is a well-known UK sustainability accreditation which covers 10 areas – management, improvement of health and well-being, energy efficiency, transport, water usage, use of materials, waste management, land use, innovation, and pollution. Because of these multiple criteria, BREEAM is seen as an all-round ‘sustainability’ certification. This may appear to offer a sizable benefit over Passive House certification but brings to mind the old saying "a jack of all trades and master of none". The energy efficiency criteria for BREEAM are limited, offering a maximum of 50% energy savings (for the highest standard *) compared to the minimum of 70% by Passive House. Also, more recently there have been examples of buildings being rated BREEAM ‘Good’ on the merits of pre-construction reports or exterior elements such as cycle stores and planting – which can easily be undone. This notional ‘checkbox’ approach, (often only implemented because of planning requirements) can leave clients footing the bill for unwanted ‘green’ features that do very little to improve the overall performance of their building and do not offer enough tangible benefit.
Because BREEAM is a well-known standard the costs of implementing it have been reduced and construction teams are often well-versed in what needs to be done and when. But this becomes a double-edged sword as people are less ‘Wowed’ by the lower, more common ratings, particularly when they know they have been achieved by focusing on the ‘cheap’ credits and doing the minimum possible to achieve the target rating
So, nZEBs could be an alternative. Nearly Zero Energy Buildings are a growing type of green building. This mathematical calculation aims to ensure that the energy used by the building is almost zero. Often this is achieved by using smart or renewable technologies such as Air source heat pumps and solar panels. This does mean that the building's energy use is offset in some situations rather than reduced. Furthermore, some nZEB calculations don’t include what is known as unregulated energy such as equipment or appliances. Finally, and unfortunately, there is no nationally prescribed standard yet – the UK Green Building Council is working on this. The Passive House standard effectively creates an nZEB by having an energy demand as low as possible. Furthermore, you can then add energy generation, gaining a higher standard of Passive House Plus or Premium, and having a truly Zero Energy building.
Finally, Life Cycle Assessments, or LCAs, are another mathematical calculation to determine the carbon used in the construction, use and demolition of the building. This ensures that materials used can either be recycled or have a low impact on the environment. There are also some energy reductions whilst in use, but these are not always quantifiable. There is also some debate as to how helpful carbon is as a measurement. The more the grid or transport is de-carbonised the less carbon the manufacturing and subsequent transport process uses – and this varies on an hourly basis!
So why Passive House? It is a scientific method that has repeatedly guaranteed that what is designed will be delivered. It significantly reduces the energy used whilst promoting green energy use – by way of the Primary Energy Renewables criteria. Furthermore, because the standard is a fabric-first approach the benefits last for the entire life span of the building. But this standard can also be used alongside the other certification methods discussed. The main criticism of Passive House is its lack of material standards and it’s true you can use as much energy or carbon to create a Passive House. However, this can be mitigated by employing both the Passive House standard and an LCA.
Furthermore, the list of “soft” comfort criteria that a Passive House meets ensures that the building is healthy. For example, the strict ventilation criteria ensure that the building has filtered fresh air all year round. Any concerns of users finding the mechanical ventilation too noisy are avoided by the strict noise criteria for all MVHR units installed in Passive Houses. These ventilation standards added with minimum surface temperatures almost guarantees that mould does not grow.
We think the Passive House standard provides the best starting point for all projects. For those looking for an even greener building we can discuss what additional criteria can be used to make your building more sustainable for your budget, and how you might be able to achieve up to 90% energy savings over a typical project.,
*As BRE advertise in the ”What makes a BREEAM-certified home better?” leaflet https://tools.breeam.com/filelibrary/BREEAM%20Refurb/KN5266_-_Benefits_of_BREEAM_to_householders_final.pdf