Metricon Homes builds its first Zero Net Carbon display home

Published: 2 November 2020

Challenges

  • Delivering energy efficient features that meet the ZNC Homes specification for a builder with more than 100 different home design options.
  • Delivering a ZNC home that resonates with the buyers.
  • A southerly orientation of the main living areas, which featured large windows to allow natural light to flow into the areas throughout the year, but did not make the best use of orientation opportunities (refer details below).

Home snapshot

Name of the home: Delta 29MR

Estate: Kaduna Park Estate

Address: 4 Mortlake Drive, Officer South

Retail pack: Energy Saver Plus pack

Home builder: Metricon Homes

Land developer: Parklea Developments

Size of home: 232m2

Retail cost (as displayed): $364,265

Energy and cost savings

Estimated annual savings: $1522

Estimated cost to consumer: $21,150 (aluminium windows) – $28,090 (timber windows)

Estimated annual greenhouse gas savings: 105% or 7tCO2-e

4 Mortlake Drive, Officer South, if it were a 6 star home 4 Mortlake Drive, Officer South (ZNC) Savings (%)
Energy use p.a. 59,749MJ -1637MJ 103%
tCO2-e emitted p.a. 5.7tCO2-e -1.4tCO2-e 105%
Annual energy bill $2617 $1095 58%

Table 1: Annual energy and carbon emissions savings of 4 Mortlake Drive (ZNC home)

Ratings

NatHERS rating: 6.6 Stars

Victorian Residential Efficiency Scorecard: 7

Carbon status: zero net carbon

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Introduction

Metricon Homes opened their first ZNC home on Sustainable House Day in September 2019, a four-bedroom 232m2 home, the prototype for an entire new range of home upgrade offerings. Metricon, Australia’s largest residential volume home builder, joined Sustainability Victoria’s ZNC Homes program to get support for the design, construction and marketing of high-efficiency, low-emission homes.

“Metricon’s consumer research has showed us that homebuyers are willing to spend a little more for a home that is more energy efficient, more comfortable and helps reduce their energy bills. We worked with Sustainability Victoria’s ZNC Homes Pilot Program to modify some of our home inclusions and are really pleased with the outcome, the Energy Saver Plus pack, which makes these types of homes accessible to new home buyers in Victoria,” said Peter Langfelder, Metricon’s Victorian General Manager and Director.

Metricon’s display home in Officer South, Victoria was designed to run on a combination of electricity and gas, with the homes emissions fully offset by renewable energy generated on-site.

The home was a vital step in Metricon now offering their Energy Saver Plus pack, a ZNC upgrade, to most home designs they offer in Victoria. Metricon’s move shows that you do not have to choose between good design and sustainable inclusions.

“At Metricon, we are always looking for ways to innovate and meet market demand for change," he said.

Working with Sustainability Victoria has allowed us to test home inclusions that when bundled together, not only offer our customers cost savings, but are also a win for the environment.
Peter Langfelder, Metricon’s Victorian General Manager and Director

Home design

Metricon’s Delta 29MR home was an existing design, which was modelled for an increase to the NatHERS rating from 6 to 6.6 stars. The home was then modelled for ZNC. The aim was to create an affordable and comfortable zero-emissions home.

Upon joining the ZNC Homes program in late 2018, Metricon developed its Energy Saver Plus pack with assistance from Sustainability Victoria, using the ZNC Modelling information.

The 232 square-metre home includes four bedrooms, two bathrooms and two living areas and is the perfect home for a family of four. The retail price of the display home including the upgrade package with timber windows is $364,265. The ZNC upgrade cost represents 7.7% of the total home cost.

The display home achieved a 6.6 stars NatHERS rating, which is 0.6 stars above the National Construction Code’s minimum star rating for new homes. This makes the home cheaper to run as well as more comfortable to live in.

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Due to other site constraints, one challenge for this home was that it had a southerly orientation of the main living areas, which featured large windows to allow natural light to flow into the areas throughout the year as well providing access to an outdoor living area.

A southerly orientation is a challenge because it reduces the amount of sun that comes into the home during the winter months. Analysis showed that the difference between simply having the living rooms facing north rather than south for this home design made a difference of 0.3 stars in terms of the NatHERS rating. The challenge was solved with extra insulation in the roof, double glazing to most windows and extra insulation in the walls.

Apart from ensuring that the home had a comfortable thermal performance it also was built with attention to air tightness, LED lighting, energy efficient fixed appliances and a roof solar PV system.

The building shell design includes:

  • doubled glazed windows to maintain a comfortable internal temperature
  • wall and roof insulation with a high R value that maximises thermal comfort and keeps energy costs down.

The fixed appliances include:

  • Chromagen solar hot water system – gas boosted
  • Actron ESP plus 23KW ducted reverse cycle air-conditioner to the whole house (ACOP and AEER 3.4)
  • gas cooktop and an electric oven
  • IC4 rated LED lights throughout.

Comparing design features with a standard home

Comparing the ZNC home design to the standard Delta 29MR home design, the benefits include superior build inclusions, increased comfort, less environmental footprint and reduced energy costs.

The table below compares the Metricon ZNC home design with a standard home design:

Feature Standard home design in Climate Zone 6 4 Mortlake Drive, Officer South home design
NatHERS rating 6 stars 6.6
Design orientation Variable South-facing
Insulation R4.0 batts to ceiling R5.0 batts to ceiling
Insulation R2.0 external walls R2.5 to external walls
Insulation None (sound proofing only) R2.5 to internal walls of wet areas
Insulation R1.0 ductwork R1.5 ductwork
Windows Single glazed aluminium Double-glazing to most windows, timber framed single-glazed to the large south facing windows
Hot water A Chromagen solar hot water system – gas boosted A Chromagen solar hot water system – gas boosted
Roof-top solar PV Not required 6kW PV system
Air-tightness 10m3/hour m2 at 50Pa (not verified) 4.63m3/hour m2 at 50Pa (verified)
Heating and cooling Any compliant product on the Australian Market 23kW reverse cycle ducted cooling with an ACOP and an AEER of 3.4
Lighting 5W/m2 4W/m2. Energy efficient LED lighting IC4 rated and feature lighting

Comparing construction features with a standard home

Standard homes with a 6 Star NatHERS energy rating, insulation meeting only basic NCC requirements, no double glazing and no post construction ABV testing, are often colder in winter, hotter in summer, noisier, more draughty and more likely to allow dust and pollen into the home, making these homes much less comfortable and healthy to live in.

By comparison, the indoor ‘feel’, temperature/conditions of 4 Mortlake Drive, Officer South is comfortable no matter what the weather conditions outside the house. Modelling data also shows that the home, if left unheated and cooled would have less hours outside the comfort range between 18–26°C.

During the launch of the home in September, no heating had been provided overnight and the home still felt comfortable when staff arrived to set up.

The build

Metricon’s display home in Officer South was constructed over a six-month period.

Care was taken in construction of the building shell to produce a high level of air tightness, so that occupants are less reliant on using energy for heating and cooling, which accounts of up to 60% of home energy use.

To produce high levels of air tightness, extra care is taken during to install the insulation to realised air leakage, in particular around the window frames and the openings for services such as the air-conditioning. Silicone sealing between the slab and frame was applied and a sisalation wrap was installed with care taken to realised tears and gaps.

Additionally, draught sealed exhaust fans and weather strips were installed for further draught proofing. Finally to ensure that moisture would not build up in the wet-areas, these areas operate automatically measuring when moisture builds up and releasing the moisture directly to the outside.

All venting from the kitchen and the wet rooms vent directly to the outside rather than into the roof cavity – further avoiding the risks of mould and mildew.

As-built verification assessment

To verify that the Metricon display home met the ZNC Homes standard, an independent As-built verification (ABV) check was undertaken to ensure that the original design intent had been realised in the build.

This verification check included two checks:

Sales and marketing

Research shows that when marketing a sustainable product there is a substantial amount of customer confusion in the market and it is not clear to the customer what the benefit is to them. Metricon has shown a clear understanding of their market segment by communicating clearly what the consumer benefit is. The display home therefore contains plaques that show what the benefit is for the customer and not necessarily for the environment.

Conclusion

By building the ZNC home and offering this product as an upgrade to any design they have on the market, Metricon has shown that it is ready to lead the volume home construction market in the future and that they are ready to meet the challenges a carbon emission free future may pose.

“We have seen an enquiry and purchase trend emerging in our regional Victorian business which is interesting. Arguably this customer is more aware of Victoria’s extremes in temperature and the effect a thermally efficient home has on living quality and utilities bills. We will be looking to strengthen knowledge of the Energy Saver Plus pack and its benefits across all of our Victorian consumer markets in 2021", said Peter Langfelder.

Metricon has opened a second ZNC display home in Mickleham in Melbourne’s North, and ran a competition to provide the upgrade to three lucky winners of the Energy Saver Plus packs. The competition received 200 applicants, demonstrating that there is an interest in the product.

When the Delta 29MR was launched it attracted media attention with a reach of over 2 million. This home has started a conversation around the creation of an environmentally conscious product that can be offered to the mass market and essentially becomes an easy option. Metricon and Sustainability Victoria have done all the thinking so the customer doesn’t have to make the difficult choice between good design and a comfortable home – it is all done for them.