Santorini 32 by Metricon Homes
Santorini 32 with Nordic façade. This stylish display home features a 7-star NatHERS rating and is net zero emissions thanks to the choice to upgrade to efficient all-electric appliances with solar PV. Consistently one of Metricon’s most popular floor plans the Santorini 32 is a versatile design able to achieve 7 stars across all orientations.
Feature home snapshot
Builder: Metricon Homes
Location: 10 President Road Sunbury – Villawood Redstone Estate – NatHERS Climate Zone 60
Design: Santorini 32 with Nordic Facade
Description: Single storey, 4 bedrooms 3 bathrooms 2 living areas
Size: Total area: 299.19m²
House area: 239.71m²
Garage: 36.23m²
Outdoor room: 18.3m²
Portico: 4.95m²
NatHERS energy rating: 7 stars*
Whole-of-home assessment: All electric with solar PV
*This home has been rated using FirstRate5 5.3.2b under NCC 2019.
Energy and cost savings
Using Sustainability Victoria’s Whole of Home Pilot Tool, the estimated annual energy use, emissions and energy bill amounts were calculated for this home and compared to the same home built to 6 stars with typical mixed fuel appliances. Thanks to its 7-star NatHERS rating, the selection of all-electric appliances and Solar PV the new owners of this home are expected to save $1,893 annually on their utility bills.
| 10 President Road, if it were a mixed fuel 6-star home | 10 President Road, 7-star (as built) | Savings [%] | |
|---|---|---|---|
| Annual energy use | 61,987 MJ | -9,748 MJ | 116% |
| tCO2-e emitted p.a. | 6.15 | -2.72 | 144% |
| Annual energy bill | $2,577 | $684 | 73% |
Table 1: Predicted annual energy use, emissions and costs, including supply charge for the Santorini 32 under a business as usual and as built scenario.
Home features
| Feature | Santorini 32 6-star | Santorini 32 7-star (as built) |
|---|---|---|
| NatHERS rating | 6 stars | 7.1 stars |
| Design orientation | North-east to the street | North-east to the street |
| Insulation - ceiling | R4 batts to ceiling | R6 batts to ceiling |
| Insulation - external walls | R2.0 to external walls | R2.5 to external walls |
| Insulation - internal walls | R2 to all internal wet area walls | R2 to all internal walls |
| Glazing | Single glazed aluminium | Single glazed aluminium to sliding doors in family, front door, and laundry; Double glazed aluminium everywhere else |
| Hot water | Solar hot water system - gas boosted | Heat pump hot water |
| Rooftop Solar PV | Not required | 6 kW Solar PV system |
| Heating and cooling | Gas ducted heating, no cooling | Ducted reverse-cycle |
| Lighting | Maximum 5 W/m2 | 2 W/m2; energy-efficient LED lighting |
Home design
The Santorini 32 in the Redstone estate has street frontage on the north-east side of the block and its garage located on the northern corner, aspects of the design which greatly limit its potential for higher NatHERS ratings. To achieve the uplift to the new NCC2022 thermal shell performance requirement of 7 stars, this home required both insulation and glazing upgrades. The following analysis looks at what it takes to uplift this home from 6 to 7 stars across all orientations:
-
This home does not have an ideal orientation, with the street frontage on the north-east side of the block. However, with only a 0.3 star difference between its best and worst, orientation has limited impact on possible NatHERS ratings. This is due to locating the garage on the same side as the main living spaces, shading caused by the alfresco/outdoor room and a lack of eaves. Without changing the overall design or specifications, the Santorini 32 is able to achieve 7 stars on blocks in most orientations (except north to the front or rear) by simply flipping the floorplan to ensure the living areas are on the north, north east or the north west side of the home. Achieving 7 stars on blocks with north to the front or rear can be as simple as upgrading the remaining single glazing, however optimizing solar passive design elements means this home can achieve up to 7.4 stars with a mix of single and double glazing.
Shading caused by the alfresco/outdoor room significantly limits the ability for this home to achieve higher ratings. On blocks with poor orientation or where shading caused by neighboring homes is a concern, a potential option to improve the NatHERS rating would be to remove the alfresco/outdoor room. This decision could increase the design rating from 7.0 to 7.2 and the range of possible ratings from between 6.9 and 7.2 to 7.0 and 7.4 stars. By removing the alfresco, this display home could achieve 7 stars across all orientations without further insulation or glazing upgrades. Cost will be a major factor in this potential design change and alternate solutions such as a louvred pergola would be required to maintain the indoor-outdoor living function of this design. While removing the alfresco from this design may not be practical, builders struggling to achieve 7 stars are advised to look carefully at the placement of alfresco/outdoor rooms to avoid negative shading impacts in heating dominated climate zones.
Adding eaves to the design doubles the number of orientations this home can achieve at least 7 stars and removes the need to flip the floorplan for some orientations.
By optimizing solar passive design principles, small, cost-effective changes such as optimising the design of eaves increases the thermal comfort of this home and allows for code compliance in more scenarios.
-
At 6 stars the design can achieve compliance with single glazing (U = 6.70, SHGC = 0.57) throughout. To uplift the home in its current orientation a combination of single and double glazing was used:
- Single glazing to the front entry, laundry and main sliding doors between the living space and outdoor room,
- Argon filled double glazed aluminium (U = 3.79, SHGC = 0.6) to all other windows.
If north is to the front or rear, upgrading the main sliding doors to double glazing ensures the home can not only achieve 7 stars in its worst orientation but increases the maximum possible NatHERS rating from 7.2 to 7.4 stars. While it is possible to achieve 7.4 stars with a mix of single and double glazing combined with the removal of the alfresco, upgrading to double glazing throughout is the best option to maintain thermal comfort and reduce issues associated with condensation on single pane glass while keeping the additional living space provided by the outdoor room.
-
To achieve a 6-star NatHERS rating the Santorini 32 only requires R2 insulation in external and internal wet area walls and R4 insulation in the ceiling. To achieve its 7-star rating:
- external wall insulation has been upgraded to R2.5
- ceiling insulation has been upgraded to R6.
- Internal wet area walls remain insulated with R2
- all other internal walls also received R2 insulation.
-
Upgrading from 6 to 7 stars and including all-electric appliances with solar PV means the residents of this family home will be saving 73% or approximately $1893 annually on their energy bills. Appliances upgraded in this home include ducted reverse-cycle heating and cooling, heat pump hot water and induction cooking. Additionally, a 6kW solar PV system ensures the owners get a net zero outcome and the maximum benefit of an all-electric home. The combination of efficient all-electric appliances and solar PV ensure this home is net zero for operational emissions and will achieve compliance with the NCC2022 Whole-of-Home energy requirements.
Santorini 32 interior showing single glazed sliding door unit to outdoor room. Home construction
Through their collaboration with SV, Metricon homes have developed strategies to ensure consistent installation of insulation and better air tightness outcomes. In order to achieve its designed 7-star rating, it is crucial the builder takes care to ensure the Santorini 32 performs as intended. Standard Australian construction practices often result in draughty and poorly insulated homes. The construction process for this home involved some additional steps ensuring quality built outcomes.
- Additional care has been taken when installing insulation, ensuring coverage is continuous and free from gaps. This includes around windows, at external corners and wall junctions and inside bulkheads which are commonly missed.
- A plaster airtightness strategy has been employed, this includes caulking of plaster to the concrete slab, caulking service penetrations and caulking and sealing around cavity slider doors.
- The ducted heating return air plenum has been sealed internally – this is not commonly done. Proper installation of ducted return air plenums significantly reduces air leakage and draughts in the home and increases the efficiency of ducted heating and cooling systems.
- All exhaust fans and the kitchen rangehood are fitted with in-line dampers and are vented externally under the eaves. This prevents draughts and reduces issues with condensation associated with extraction fans venting into the roof cavity. Quality exhaust fans ensure a healthy indoor environment.
As-built verification
Santorini 32 undergoing blower door testing as part of the 7 Star Homes Program. Sustainability Victoria engaged an independent as-built verification assessor to ensure that the home was built to meet its intended energy efficiency targets. The verification check included a blower door test to measure air leakage, a thermography test to check insulation coverage and visual inspections of glazing, ceiling insulation, extraction fan vents and appliances.
-
The home was blower-door tested to determine the air leakage rate. The home passed the blower door test with an air-permeability of 5.86 m3/h/m2 @ 50Pa, which is good result and well below the 7 Star Homes program requirement of 10 m3/h/m2 @ 50Pa.
-
This test uses a thermal imaging camera that can ‘see’ heat, enabling the assessor to inspect the installation of insulation, by looking for hot spots and cold spots in the ceilings and walls. The inspection is passed if no more than 5% of insulation is missing in the walls, floors and ceilings.
The home passed with only an impressive 0.64% deficit in ceiling insulation.
Summary
Metricon’s displays in the Villawood Redstone Estate in Sunbury demonstrate how 7-star homes are light, bright and comfortable. The Santorini 32 is able to easily achieve 7 stars despite a less than ideal block orientation and neighbouring properties. The uplift from 6 stars has been achieved by upgrading select windows from single to double glazed units along with insulation upgrades. No reduction in glazing has been required.
Significant thermal performance improvements are gained by upgrading the large expanses of sliding doors to a double-glazed alternative. This upgrade results in the Santorini 32 achieving between 7.1 and 7.4 stars across all orientations. The choice to build all-electric with solar will save the occupants of this home 73% on their annual energy bills and ensure compliance with upcoming whole-of-home requirements.