Zero Carbon Buildings – 101
Who wouldn’t like to live in a home that was not only was affordable to buy or rent, and that is cool in summer and warm in winter, but also has no energy bills, and doesn’t contribute towards global warming through its heating or cooling?
We often hear about ‘net’ zero carbon, and carbon ‘neutral’, and indeed it may be important to include these offsets in certain circumstances. However, this article refers to real zero carbon buildings, i.e. the buildings generate more power than they use.
“The built environment is responsible for 47% of UK carbon emissions, excluding embodied carbon”, according to Oxford University. The UK Committee on Climate Change found that “Energy use in homes increased between 2016 and 2017.”
When we also consider that the way new homes are built, and existing homes retrofitted often falls short of stated design standards, there is little doubt that action is needed to change the design specifications, materials used and the construction process, in order to ultimately improve the quality of buildings and their impact on the environment.
“Emissions reductions from the UK’s 29 million homes have stalled”, according to the UK Committee on Climate Change in 2019, but buildings can achieve zero carbon using today’s technologies, and in an affordable way. This can be achieved using efficient and renewable technologies.
- Step 1: insulated and airtight building fabric (i.e. walls and roof).
- Step 2: efficient and renewable energy system.
It is important to take a ‘fabric first’ approach so that the energy requirement for the building is known, and from which plant and equipment required to deliver thermal comfort, can then be accurately sized. Of most significant importance is airtightness, and second to this, the insulation. It is easier to achieve airtightness when there are fewer component parts to the building (and therefore less parts to install incorrectly!). For example, structural insulated panels (SIPS) can be used, and when specified with good thermal properties, and installed with high-quality tolerances, can achieve excellent airtightness and insulation.
Renewable energy system
There are many technologies on the market, and new technologies emerging each year. It is important to select technologies that not only deliver the efficiency and carbon properties required, but are also simple to operate and can be maintained by mainstream, local companies. A sensible approach is therefore to use proven technologies, rather than those at the ‘bleeding edge’.
When designing and building homes an integrated team approach is essential to ensure that the whole team has aligned thinking and incentivisation in the following areas:
- Materials selection – specifying the building method to be used, for example SIPS, so that designs can be orientated to the (various) panel sizes.
- Design – integrating the architectural designs and structural properties with the size and structural properties of the SIPS panels, and with the M&E (mechanical and electrical) systems, for example optimising roof-space and orientation for solar collectors, and allowing internal space for heat-pumps and batteries.
- Construction – on site, quality and detailing is important, for example, panels installed incorrectly could create an air-gap and decrease airtightness, the wrong type of screws can create a weakness in the thermal performance of the fabric (known as ‘thermal bridging’). The fewer component parts that are installed on site, the easier it becomes to achieve high-quality.
- Post occupancy - performance testing to monitor the in-use performance of the building and identify any deviance from the designed energy use, and sharing of data to speed and encourage industry-wide learning and improvement.
Case Study – Corby
The Corby project at Priors Hall Park is a development of 31 houses and 16 flats, all of which are zero carbon. We selected an off-site manufactured panel system that has significant practical and technical benefits, including that it can be used to construct 11 storeys without any external support, and is a soundproof 185mm wall panel with an amazing 0.15W/m2k U value that gives outstanding insulation, and also provides excellent air tightness.
The renewable energy system combines proven elements into a new, unique, but simple system. Each home collects free energy from the sun using PV-T (photo-voltaic thermal) panels and stores surplus summer heat in the soil within foundations of the building in an earth energy bank, and surplus energy in a battery. The stored low-grade heat, is then withdrawn for use within the building via a heat pump which raises the temperature to a level that can be used for space heating and domestic hot water.
“We want to share knowledge and performance data with others so that these solutions become commonplace in mainstream housing projects” said Anthony Morgan, Director at Carbon Free Group
This simple system is affordable, and saves home owners on average £1,500 p.a. compared with the average 4 bedroom house, and protects them against energy price increases. If fuel poverty is an issue, this is eliminated as there are no fuel bills. The homes also emit zero carbon to the atmosphere through their operation, thus helping to mitigate climate change when compared to a traditional house.
Further information: firstname.lastname@example.org www.carbonfreegroup.com
Please note: the views expressed in this blog are those of the individual contributing member, and are not necessarily representative of the views of IEMA or any professional institutions with which IEMA is associated.
About the Author
Greg is the COO at Carbon Free Group.