BACKGROUND
Why do we need the Superhome Movement?
We need better houses, for our people, our environment, and our future...
The international Energy Agency (IEA) has commented that New Zealand is significantly behind other OECD countries when it comes to energy efficiency and building standards should be updated. Political paralysis has prevented the pressing and urgent changes required to improved building standards. Improved standards to facilitate healthy homes will also transition the industry to low-carbon built environments, with superior energy efficiency, reduced resource use and positive environmental effects.
The New Zealand Building Code is used by over 95% of the industry as the standard to achieve rather than the legal minimum requirement. *1 (BRANZ housing quality research). Furthermore, almost all homes delivered to consumers do not reach W.H.O. (World Health Organisation) standards. Accepted research identified many years ago, the relationship between poor housing standards and serious health issues in New Zealand. Philippa Howden Chapman https://www.bmj.com/content/337/bmj.a1411. Our poor building standards are contributing to unhealthy living environments and some very sobering health statistics. Respiratory diseases are directly linked to cold, damp and mouldy homes. Studies have found that Code compliant new housing is too cold 60% of the time and in addition this housing is a breeding ground for dust mites. There is a well-established link between mould, dust mites and respiratory disease
NZ has the highest childhood asthma rate in the world with 40% of our 8-year-olds having asthma. Additionally, we have the highest mortality rate from asthma of all high-income countries. As a nation, our healthcare costs for respiratory diseases alone exceed $6 billion annually.
https://www.asthmafoundation.org.nz/our-work/research/key-statistics
For more information https://www.superhome.co.nz/why/
What does the Superhome Movement do?
The Superhome Movement creates awareness and triggers behavioural change among homeowners, designers, builders and other industry participants to design and build better homes for improved health and wellbeing, happiness and comfort. Homes that not only live better, but last longer to reduce energy and other resource use. The fortuitous side effect being a huge reduction of environmental footprint and CO2 emissions that significantly contribute to climate change action.
The initial approach has been a grassroots movement doing real stuff from the bottom up. Educating and promoting industry leadership by example with demonstration projects open to the public and exemplar home tours linked to educational workshops, webinars and other events.
The Movement lobbies Government and Territorial Authorities to support the important changes urgently needed. Councils are supportive of the movement. However, the regulators have not been able to keep up with enforcing scientifically validated best practice; hence the community-led education and standard-setting approach. Successive governments appear to be paralysed by fear of changing the code due to the perception that improved quality will raise construction costs and be unpopular with constituents. Politicians take a short-term view and to date have been unable to act on this pressing and urgent issue for society.
It is financially positive to improve housing efficiency and sustainability. A key driver for improved building standards is to support the health and wellbeing of all New Zealanders, now and in the future. The Superhome Movement is dedicated to driving that change. Our goal is to raise standards by referencing and promoting international best practice design standards and techniques so that all New Zealand homes are healthier and more energy-efficient, while also promoting environmental, economic and socially sustainable practices.
Our Current Legislation
Building Act 2004
The Building Act (2004) provides the mandatory framework for the building control system to be followed when undertaking building work in New Zealand. Its stated purpose is covered in section 3 of the Act:
(a) to provide for the regulation of building work, the establishment of a licensing regime for building practitioners and the setting of performance standards for buildings to ensure that:
(i) people who use buildings can do so safely and without endangering their health; and
(ii) buildings have attributes that contribute appropriately to the health, physical independence and well-being of the people who use them; and
(iii) people who use a building can escape from the building if it is on fire; and
(iv) buildings are designed, constructed and able to be used in ways that promote sustainable development:
(b) to promote the accountability of owners, designers, builders and building consent authorities who have responsibilities for ensuring that building work complies with the building code.
Building Code
The New Zealand Building Code is contained in Schedule 1 of the Building Regulations 1992 which sets performance standards all new buildings must meet under the following headings; Stability, Fire safety, Access, Moisture, Safety of users, Services and facilities and Energy Efficiency.
The Building Code does not prescribe how work should be done, but states how completed building work and its parts must perform.
The Building Code consists of two preliminary clauses and 37 technical clauses. Each technical clause has three levels that describe the requirements for the clause and is listed below.
1. Objective: Social objectives the building must achieve.
2. Functional Requirement: Functions the building must perform to meet the Objective.
3. Performance: The performance criteria the building must achieve. By meeting the performance criteria, the Objective and Functional Requirement can be achieved.
Compliance Paths
Compliance with the Building Code can be demonstrated using various pathways.
The diagram below illustrates the hierarchy of New Zealand building controls, including the various compliance paths. The top three tiers of the pyramid (the Building Act and Building Regulations) show mandatory building legislation that must be followed. The rest of the diagram shows various paths that may be used to demonstrate compliance with the Building Code. Compliance with the Building Code must be demonstrated using one or more of the paths and the applicant can choose which path(s) to follow. With the exception of alternative solutions, the paths illustrated below must be accepted by the building consent authority as meeting the performance requirements of the Building Code.
It is these acceptable solutions and verification methods that need to change as they are leading to unacceptable outcomes. Industry practitioners continue to follow the acceptable solutions as they do not want the risk and liability of specifying something different to the standard approved details. One example of this is the very poor thermal performance and condensation risk of windows details in E2/AS1 of the NZBC.
Note that Sections D1, D2, E3, F2, 4-9, G1-3, 5, 11 & 15 all have no Verification Methods. E2's verification method is expensive and therefore only carried out by large suppliers / manufacturers. It is difficult to comply if there is not a verification methodology to comply with.
For more information https://www.building.govt.nz/assets/Uploads/building-code-compliance/handbooks/building-code-handbook/building-code-handbook-3rd-edition-amendment-13.pdf
This design guide will be an alternative solution in the hierarchy shown above, with the aim of one day making it an acceptable solution. This guide will show at least one exemplar solution for each of the Building Code clauses.
Residential Tenancies (Healthy Homes Standards) Regulations 2019
The healthy homes standards became law on 1 July 2019.
The healthy homes standards introduce specific and minimum standards for heating, insulation, ventilation, moisture ingress and drainage, and draught stopping in rental properties.
All private rentals must comply within 90 days of any new or renewed tenancy after 1 July 2021, with all private rentals complying by 1 July 2024. All boarding houses must comply by 1 July 2021. All houses rented by Kāinga Ora (formerly Housing New Zealand) and registered Community Housing Providers must comply by 1 July 2023.
Landlords are responsible for maintaining and improving the quality of their rental properties. These standards will help ensure landlords have healthier, safer properties and lower maintenance costs for their investments.
For further information:
http://www.legislation.govt.nz/regulation/public/2019/0088/latest/whole.html
https://www.tenancy.govt.nz/mi/healthy-homes/about-the-healthy-homes-standards/
These standards set a low bar in some areas and exceed the Building Code in others, so that you could build a house to the standards required by the Building Code for owner occupation, but it may not comply with the Healthy Homes Standards if you were to rent it out.
Exemption for certified passive buildings
(1) The main living room need not comply with regulation 8 if the tenancy building is a certified passive building.
(2) A building is a certified passive building if –
(a) one of the following applies:
(i) the building has been certified as a passive house under the Passive House Standard of the Passivhaus Institut, Germany:
(ii) the International Living Future Institute has issued one of the following in respect of the building:
(A) a Living Building Certification:
(B) a Petal Certification that includes a heating related requirement:
(C) a Zero Energy Certification; and
(b) that certification has not lapsed, expired, been cancelled, or otherwise ceased to be in force.
How we compare
Energy efficiency is one area where the current acceptable solutions are lacking the required information. Appropriate thermal performance of the building elements, together referred to as the building’s thermal envelope, is one of the essential requirements for energy efficient buildings. “R” Values can be used to measure and specify the thermal performance of building elements.
Below comparisons show New Zealand standards are significantly below other places with similar climates. Los Angeles, for example, has approximately triple the thermal ratings of New Zealand and it is not as cold there. As a comparison, Vancouver has an almost identical climate to Wellington.
A building’s thermal performance is not just about the level of the R Values. R Values are a snapshot in time and just one of many considerations. Insulation is achieved by creating still air. Insulation performance is affected by wind or draughts, so if your building assemblies, i.e. floors, walls, windows or roofs, are leaking air or insulation is exposed to draughts there will be a dramatic drop in overall thermal performance. If you consider the analogy of a woolly jumper; out in the wind, a woolly jumper will keep you much warmer if you have a windbreaker jacket over top. Likewise, an airtight construction with an airtightness layer with no air leaks in the overall building envelope will have a significant influence on performance. There are other important considerations in relation to airtightness, including moisture control. New Zealand has no standard for airtightness or how much leakage occurs through the external building envelope. See BRANZ article https://www.buildmagazine.org.nz/issues/show/building-better#feature-4094 Page 51 table 1 & 2.
Build tight and ventilate right
The standard for ventilation (G4), relies mostly on passive ventilation with outside air moving through open windows. This is not effective because it is reliant on the weather and occupant behaviour. Extraction fans in bathrooms and kitchens have been introduced but they need to be installed corrected and used appropriately. In addition extract ventilation does not control where the incoming air is coming in from. Proper whole building ventilation is essential as outlined in Ventilation and Air Quality.
No one else builds like this and construction standards in New Zealand are 30 years behind equivalent countries in the Northern Hemisphere.
Where we are heading
The first New Zealand Model Building Bylaws were introduced following the Napier earthquake of 1931. Originally documentation was prescriptive and regional but this later changed to a national performance-based approach with the introduction of the 1991 Building Act. After the Leaky Building Crisis of the late nineties, the Building Act was updated in 2004.
Compliance validated by outcomes, measured by monitoring buildings in use, is the future of compliance, instead of the current situation where compliance is approved by review of design predictions from plans and specifications or theoretical modelled performance. Currently, all that BCO’s (Building Consent Officers) can do is confirm that design documentation submitted illustrates predicted compliance with the New Zealand standards. Conversely, monitoring confirms the quality of the build as well as the design.
This includes the quality of the workmanship. BRANZ research found that 75% of insulation is poorly installed in NZ buildings. This is important as even small gaps in insulation have a dramatic effect on overall performance. BRANZ have shown that just a 4 mm gap results in a reduction of 12-15% in R-value due to convective air movement. In practice there are often much larger gaps along with compressed and creased insulation. Issues also include poorly fitted or absent insulation around installed services (pipework and wiring etc). This means the actual performance is significantly less than the minimum design standard in NZ. https://www.buildmagazine.org.nz/assets/PDF/BUILD117-68-Research---Poorly-fitted-insulation.pdf
Poor detailing means there are typically lots of thermal bridges present in standard NZ. A thermal bridge directly connects the inside to the outside and transfers heat past insulation through the building material itself. Uninsulated concrete, steel, and aluminium (windows) are easy examples to spot. As you’ll see in the windows section, aluminium is an exceptional conductor of heat, and terrible for windows unless the thermal bridge is broken (thermally broken aluminium). Other materials can avoid thermal bridging too, mostly with simple design considerations.
In practice, building inspections aiming to confirm compliance don’t adequately verify the quality of insulation installations and ignore serious thermal bridging issues.
A BRANZ research study in 2020 has revealed that there is much higher thermal bridging present than previously assumed. There is on average a 34% ratio of timber to insulation and in some cases much more. This is significantly more than the 14-18% framing content generally assumed by regulators and the building industry.
Full Research Report available here: https://www.branz.co.nz/pubs/research-reports/er53/
Advanced Framing Solutions workshop webinar recording link 15th October 2020
Recent articles from BRANZ and the Government's consultation on Building For Climate Change Legislation show we are thinking about making progress. http://www.buildmagazine.org.nz/articles/show/airtightness-of-apartments.
Monitoring of built performance will provide a feedback loop where design and construction can be adjusted to improve performance. See Section on Monitoring.
CARBON FOOTPRINT
What is a LOW CARBON HOME
All houses should operate within the carbon budget. Performance is made up of Upfront emissions and Lifecycle emissions
In order achieve our carbon obligations, all buildings should achieve its carbon budget. A lifecycle analysis will tell you if you are within your carbon budget.
Climate Change and Healthier Living Environments
Climate change is one of the biggest environmental challenges of our time. The health of our homes is critical to get right now so our buildings, which are designed to last for 50-100 years, are not harming occupants and the environment by leading to high carbon climate change. Super design is affordable and required for our obligations and future.
But we know this already; just like we know that climate mitigation requires the construction and operation of low carbon buildings.
What you might not know is that BRANZ have calculated a carbon budget for residential dwellings in New Zealand. The is the amount of carbon that each newly constructed house can afford to emit in construction AND operation if New Zealand is to meet its climate change aspirations and help the world avoid ecological catastrophe.
This budget is 279 kgCO2eq/m2 over a 90 year building life. You can see from the below graph that the majority of the carbon in our residential buildings (60%) is emitted through the energy used while we live in them.
This is where we need to target our initial efforts; reducing the energy use of buildings. Closely following, this is reducing the upfront carbon in the materials that we choose to build from (25% from materials used in initial construction and maintenance).
We also need to do everything we can to support biodiversity. This can be through the materials we choose to build from to what we plant on our site. The following sections of this document will lead you on a journey on how you can change the way you design and build today to deliver healthy, low carbon homes.
Designing homes with a lower carbon footprint
New Zealand has committed to reduce net emissions of greenhouse gases (except methane from plants and animals) to zero by 2050. https://www.mbie.govt.nz/have-your-say/building-for-climate-change-transforming-operational-efficiency-and-reducing-whole-of-life-embodied-carbon/
Recent calculations suggest that the built environment accounts for up to 20% of New Zealand’s greenhouse gas emissions. Both new and existing buildings will need to produce fewer emissions to help meet the net-zero carbon target set in law.
Houses built today must have a lifespan of at least 50 years, so they will obviously be part of the net-zero carbon world after 2050. A 2019 study by Massey University and BRANZ scientists calculated how much carbon dioxide new 3-bedroom homes can emit in their lifetimes to meet climate targets. Based on research to date, New Zealand home construction and operation currently produces too much carbon dioxide by several multiples.
This chapter sets out some guidelines for how houses can be designed and constructed to have much lower carbon footprints.
Consider the carbon footprint early in the design process
Reducing carbon in home building requires attention to every area of the project, but mainly:
● Site selection
● Thermal performance/comfort
● Materials selection
● House size
● Construction waste
● Specification of appliances/services
The key is to start considering these issues at the very earliest stages of planning. Everyone – client, designer, builder, subcontractors, and materials suppliers – needs to understand the goals.
Site selection
The two key features of site selection from a carbon footprint perspective are location and solar access:
A site should be within walking distance of shops and other services and/or regular public transport. This reduces the likelihood of high energy consumption from long or frequent car journeys.
A site should have good solar access and be of the size and shape that allows a north-facing home to be built with minimal winter shading. Good passive solar design can then reduce the need for purchased energy for space heating.
Thermal performance/comfort
The energy used by the occupants’ accounts for the biggest contribution to greenhouse gas emissions made by a house over its service life. Designers need to do a thermal model early in the design process, to better understand the home’s year-round performance and whether it meets set energy targets. For many parts of New Zealand, a well-insulated north-facing home can provide comfortable internal temperatures year-round. Supplementary heating/cooling would only be needed on just a few of the days of the year.
There are several good sources for assisting the design of thermally comfortable houses. These include: www.level.org.nz and www.yourhome.gov.au. However, these provide more ‘rules of thumb’ rather than specifics, such as:
● Amount of time comfort is achieved year round.
● Proportion of time a specific bedroom is too cold from a health perspective.
● The effectiveness of various external shading devices on controlling overheating.
● The performance of the house using predicted climate changed climates for a particular year.
Only through applying thermal simulation which leverages hourly climate files for the specific site and location, can these types of issues be examined with confidence. These tools usually require a skilled operator to use.
Although space heating needs can be minimized, choosing a low carbon space heater is still an important part of the equation. The lowest carbon space heating forms are: efficient double burners using sustainably sourced wood; pellet burners; and high efficiency heat pumps. The worst space heaters are un-flued LPG gas heaters, diesel and coal burners.
Material selection
Construction materials have an impact on the environment for their entire lives, from extraction/manufacture to their final disposal. For many materials a large proportion of their emissions have been released before construction begins. This impact can be calculated through life cycle assessment or carbon footprinting. The graph below provides an illustration of the relative importance of greenhouse gas emissions due to materials, derived from carbon footprinting of case study houses by BRANZ. Here, ‘materials’ accounts for building material extraction, manufacture, use over the period and disposal; ‘energy’ accounts for space conditioning, water heating, refrigeration and entertainment but not that required to get water to and from the site – which is accounted for in ‘water’.
Household greenhouse gas emissions due to materials, operational energy and water over different timeframes.
Decisions around what materials to build with usually involves balancing different factors. As an example, concrete may involve a lot of emissions in its production, but if it is used to provide well positioned thermal mass for a building then it can reduce the building’s long-term energy consumption. Adding more thermal insulation to a house is technically increasing the material used in construction, but the extra carbon cost is low and again it can lead to reduced energy use. Timber can have advantages in net-zero carbon construction because trees capture and store atmospheric carbon dioxide as they grow. However, they must be sourced from sustainable forestry operations in which forests are replanted after trees are harvested (look for certification by FSC (Forest Stewardship Council) or PEFC (Programme for the Endorsement of Forest Certification).
BRANZ has developed some tools that can help designers to better understand the greenhouse gas implications of material choices. These include:
● BRANZ CO2NSTRUCT – a dataset of embodied carbon of different materials. This captures emissions from the manufacture of materials only. Available at www.branz.co.nz/co2nstruct.
● LCAQuick – estimates whole-of-life embodied carbon (including manufacture of materials, transport and installation, maintenance and replacement and end-of-life) and operational carbon (from energy and water use). Available at www.branz.co.nz/lcaquick.
House size
In general terms, the bigger the house, the bigger the carbon footprint. This can be true even for higher-performing, better-insulated houses – while they may consume less energy in space heating, they require more materials to build and upkeep, which means more greenhouse gas emissions. The best approach by far is to focus on more efficient design rather than larger size.
Construction waste
House construction today produces construction waste. Given that a lot of greenhouses gases have been emitted in the manufacture and transport of this material, reducing waste will obviously reduce emissions.
Designers can help reduce waste by:
● Setting an achievable waste target.
● Keeping the range of materials to a minimum.
● Using modular sizes in design to reduce offcuts.
● Specifying prefabricated materials where possible.
● Not be beholden to passing trends and fashion which cannot be easily renovated.
● Designing buildings for deconstruction, so materials can be reused or recycled rather than everything going in the skip.
Builders can help reduce waste by sorting waste and maximizing recycling. The REBRI website www.branz.co.nz/REBRI has a lot of practical guidance.
Specification of appliances
As noted above, the house occupants’ use of energy accounts for most of the greenhouse gas emissions from a house during its service life. With new-build homes today, incidental loads (mainly from a variety of appliances, and entertainment devices) and water heating are amongst the largest consumers of energy and therefore, can account for the largest proportion of greenhouse gas emissions.
With water heating systems, the most commonly specified electric storage cylinders and gas instant hot water systems account for several times more greenhouse gas emissions than other types of water heating. The systems with low lifetime operation-related CO2 emissions (not necessarily in order) are:
● Wetbacks on efficient double burners or pellet burners that use seasoned, sustainably sourced timber.
● Heat pumps with a CO2 refrigerant and a coefficient of performance > 2.5.
● Electric-assisted solar thermal or direct solar.
The New Zealand water efficiency label scheme (WELS) applies to tapware, washing machines, dishwashers, toilets (and urinals) and showers. Aim to purchase the highest star rating for your needs. As an example, specifying a 3-star showerhead with a flow of 8.5 litres per minute rather than a shower delivering 14 litres per minute could save a household around 47,000 litres per year.
Some key tools to help
There are many existing tools around that can help design and build houses with a lower carbon footprint. The WEERS tool for selecting windows and glazing and the WELS star rating for appliances and fixtures are two examples. For choosing energy efficient appliances, the www.energyrating.gov.au/label is a useful tool. Many thermal modelling systems used to optimise the thermal efficiency of a house design will also help to reduce its carbon footprint.
BRANZ has an extensive programme of work underway in this area. New tools and resources will be made available on the BRANZ website and announced in Build magazine.
Recommended Healthy Home guidelines for Carbon Reduction are set out in the table below:
