The Home Performance Index: Measuring the sustainability of our new homes
12 June 2018
More than 170 new residential schemes are launching in 2018, and all claim to be A rated homes – based on compliance with building regulations. Yet, there will be a gulf in the sustainability or quality of the different schemes.
For the Irish Green Building Council (IGBC) it was essential that home buyers should be enabled to make more responsible choices. So, the IGBC developed the Home Performance Index – HPI, to help them do just that.
But why do we need a sustainability rating system with advent of the Near Zero Energy Building (NZEB) standard? In the next two years, NZEB for dwellings will require an improvement from an A3 to an A2 rating. This represents an overall carbon saving for a typical semi-detached home of approximately half a tonne per annum. Not bad. But the NZEB standard only tells a small part of the story.
The other impacts of home construction
Inefficient use of land for home construction leads directly to degradation of habitats and fragmentation, an increase in pollution, and soil sealing. This, in turn, releases carbon from soil, eliminates future potential for carbon sequestration, increases precipitation runoff and alters the terrestrial water cycle. Lower per capita carbon emissions are more related to urban density than home energy efficiency, as development sprawl drives larger home size and car dependency.
Avoiding the need for a household to own a car will save up to a tonne of carbon a year, from the embodied impacts of the car’s manufacturing alone. This is before it is driven a single kilometre. The fuel to drive it, will add between 0.5 and two tonnes of carbon.
A poor location means two cars, so double these numbers. Just one bad decision and we are already down several tonnes. This will never be recovered by either home energy efficiency or by swapping petrol for electric vehicles. Not to mention, it imposes the costs of two cars on a household, a whole second mortgage, and the health implications of not integrating exercise into daily activities.
The embodied carbon of a medium sized home can amount to 100 tonnes, or a tonne per year for a 100-year life cycle. A large house of 200 to 300 square metres will double this.
Add substantial carbon and resource consumption impacts each year for repainting, furnishing and repairing larger homes, and additional carbon for inefficient infrastructure such as longer access roads and an elongated water system needed to service the sprawl. Use of illegally logged tropical hard woods, and inefficient water fittings will keep compounding this horrendous carbon bill.
NZEB, or passive house, will get us part of the way towards a low carbon future. But 90 per cent of potential carbon savings for households are through the creation of walkable, sensible medium density development (at least 75 to 100 dwellings per hectare), built with low carbon construction materials, and which enable healthy, low resource consumption lifestyles. What is good for the environment is also good for us: building low carbon communities will make us richer and healthier.
Certification tools LEED and BREEAM
This is one of the reasons for the development of more holistic assessment systems such as LEED and BREEAM, that look at land use, location, life cycle assessment, water consumption and ecology.
These have educated the commercial building sector that it is no longer acceptable to locate an office on an inaccessible greenfield site, floating in a sea of car parking, and that creating healthy green buildings creates a more productive workforce.
If this is important in the commercial sector, then it is much more important for the residential sector. This is why, a similar type of assessment system was developed for use on residential construction.
Development of Home Performance Index
To develop the Home Performance Index, the Irish Green Building Council carried out a study on all the existing sustainability assessment systems including the UK’s Code for Sustainable Homes, Sweden GBC MiloBygnnad (Swedish for Green Building), Germany’s DGNB system and LEED for Homes.
These have the same broad approach, a collection of criteria and indicators for measuring the different impacts, using weightings to suit the relative importance of the issue in the country. From these, the most useful criteria for Ireland were selected.
What does it measure?
The Home Performance Index was designed to be easy to apply and fully integrated with Irish building regulations to avoid duplication. It was piloted in 2015 on a small number of developments and brought to market in 2016 with some funding from the Environmental Protection Agency.
It is divided into five categories: environment, health and wellbeing, economic, quality assurance and sustainable location, each containing a set of indicators. The environment category measures the full environmental footprint of the homes, including land use, density, water consumption, embodied impacts of materials, energy use, sustainable sourcing and so on.
Health and wellbeing deals with all the issues that impact on the wellbeing of the occupants, such as daylight, indoor air quality, acoustics, VOCs and walkability of the neighbourhood. The economic section deals with the running costs of the homes from the costs of transport to energy costs.
Quality assurance measures the quality of the design and construction team, air infiltration, and other testing measures that ensure a rigorous approach to the design and construction process. Sustainable location looks at the accessibility of schools, shops, parks, services, public transport, walking and cycling paths.
The indicators required the development of a series of tools. For example, a whole infrastructure for measuring embodied carbon as part of full Life Cycle Assessment of Homes was developed. This includes a full environmental product declaration programme, databases, training and calculators such as One Click LCA. In many cases, it was simply a case of using existing calculators such as the one provided by the European Water Label, or working with the Centre of Excellence for Universal Design to develop a checklist.
Mandatory and voluntary criteria
To avoid cherry picking of the criteria, mandatory requirements are set in the most important areas, such as water efficiency, ventilation, thermal bridging, and enhanced air tightness. For example we set a maximum air infiltration level of 3m³hr/sqm/50pa as opposed to seven in the current building regulations but also insist that a properly designed and commissioned ventilation system is also installed.
It also sets a maximum annual heat demand, encouraging builders to provide the most efficient building fabric first rather than achieving a higher rating through renewables. This is based on the view that the fabric cannot easily be improved afterwards whereas additional renewables can be retrofitted.
There are three levels of certification. Certified indicates means that a basic set of criteria that go beyond building regulations are met. Silver demonstrates that additional non-mandatory criteria are met. Gold is for those who want to show real leadership.
Evidence must be provided for each category and this is fully audited by the Irish Green Building Council. The full technical manual can be downloaded at www.homeperformanceindex.ie.
Certification is already happening
The Irish Green Building Council has already certified a number of public and private housing developments and are in the process of certifying more with early movers like Dublin City Council, Sisk and Durkan residential. The system seems set for take-off in 2018 with some very large housing developments intent on certification.
Furthermore, it is already possible to see its intended effect in getting design teams to consider issues beyond energy efficiency such as embodied carbon.
Home Performance Index and the Well Building Standard
Home Performance Index is already gaining international recognition. Recently, the ‘Engineers Journal’ published an article on the first Well Certified office in Ireland: Arup in Cork.
The International Well Building Institute has also developed a community rating system for planning high-quality mixed-use communities that build in health and wellbeing. The Home Performance Index in one of only six global green rating tools alongside LEED, BREEAM and Greenstar that can be used to achieve credits in the system.
Therefore we hope to see dual certification in the near future with HPI certifying the homes and Well certifying the community they form a part of.
Benefit of rating tools
For the first time, Ireland has its own sustainability system for new residential construction on a par with BREEAM or LEED. This means that real data can now be captured to inform public policy formation and planning decisions.
It is hoped this can provide a single number summing up the carbon impact of many individual decisions. This, in turn, should allow for better co-ordination between policies such as planning, tax and transport, and empower Irish people in our transition to a low-carbon society.
If you are interested in registering a housing development under the Home Performance Index or receiving training, see www.homeperformanceindex.ie
For more information on EPD Ireland: www.epdireland.org
For more information on buildings life cycle assessment: https://www.oneclicklca.com/construction/carbonheroes/
For more information on IGBC events and education: www.igbc.ie.
Author: Pat Barry is the CEO of the Irish Green Building Council, which he co-founded in 2010. He is an architect with over 20 years of experience in Ireland, Europe and South America. Barry holds a master’s degree in environmental design of buildings from University of Cardiff and he is a qualified Passivhaus and DGNB consultant.http://www.engineersjournal.ie/2018/06/12/home-performance-index-measuring-sustainability-new-homes/http://www.engineersjournal.ie/wp-content/uploads/2018/06/a-hpi.jpghttp://www.engineersjournal.ie/wp-content/uploads/2018/06/a-hpi-300x300.jpgCivilBREEAM,building regulations,SEAI,sustainability