High Performance Case Study - New Build
New Build
Stone Pine Court, Thirteenth Beach
Project Brief:
The brief is for a new 4 bedroom home including; second living area, 2 car garage and space to park a golf buggy. The new family home should be optimised to take full advantage of its lush views and include a swimming pool with visibility from all aspects of the home. Externally the building should present well to the street but be simple in architectural form. From the outset the client would like to avoid a gas connection and expects solar and heat pump technology will be required to achieve this.
Site Conditions:
The site is located at Thirteenth Beach, a new subdivision surrounding the 13th Beach golf course facilities. The new home will have great access to Barwon heads and surrounding beaches and amenities. The site itself is flat with N-S orientation and views of the existing practice fairway.
Design Strategy:
All electric home with no gas connection
Solar heated swimming pool centrally located to allow north facing windows into living area. Maximise visibility of the pool where possible
Living spaces oriented for fairway views and green outlook. Provide solar control through deciduous trees strategically planted on adjacent land to provide solar control.
Garage to act as a thermal buffer to the dwelling
Zoning of living and sleeping zones
Steps
The first step is to analyse the existing design if constructed to 6-start minimum requirements. During our initial assessment we decide what sequence of modifications will attain best ‘bang for buck’ for the project, ie maximum energy reductions with minimal additional construction cost.
Our first identifiable issue was the concrete slab and its connection with the ground. By decoupling this with an insulative layer of XPS board the transmission heat loss was almost halved. It appears that the benefits of insulating a concrete slab is grossly undervalued as it is common practice to avoid this as it can be difficult if not planned out correctly.
Secondly we addressed the transmission heat loss through the windows by replacing the aluminium frame with timber.
We then completed the improvements to the thermal envelope by increasing our walls to a 140mm stud frame, which allows for the installation of R4.0 insulation batts.
Lastly we addressed our ventilation heat loss improving our airtightness from 10AC/h to 5AC/h. This would involve taping all external membranes, around windows, penetrations and an air blower test to ensure the quality of workmanship.
As shown in the right hand column on the table below, Specific annual heat demand.
Summary of features
Envelope:
Floor: 100mm Concrete Slab on ground, 30mm XPS insulation, 80mm screed
Walls: 140mm Frame with R4.0 batt insulation
Roof: Truss roof R5.0 batts, Vaulted ceiling to living area R5.0 batts throughout
Windows:
Timber framed double glazed
Airtightness:
5 Air changes per hour (blower door test to ensure quality)
Airtight passage door to garage
Mechanical heat recovery ventilation unit (ensure high air quality and avoid sick building syndrome)
Energy required for annual operation of the building: 56.22 kWh/m²*
This diagram shows that we conducted 4 tests after our baseline was established, highlighting the sequence of our sequencing for this particular project.
The diagram below shows the final test results directly compared with the standard construction baseline;
Results:
Additional Construction Costs: $87,100**
Annual Energy Savings: 31,177.2 kWh (80% reduction)
Annual Carbon Reduction: 32.71 Tonnes***
Annual Savings: $9,353.2
Payback Period:9.31 years
Conclusion
Although still far from a Passive House performance (we’d need to get down to 15kWh/m2 & 0.6 ACH) there are some huge benefits from a high performing house, especially at this scale, which we would t-shirt size as a large house.
We found that by implementing some pretty simple strategies there are some serious economic benefits that can be expected. A payback period of only 10 years shows the significance of the operating costs of a building this scale. This makes sense from an economic perspective and the additional benefits listed below can be enjoyed by the occupant from day 1. Given that this is a family home, these added benefits of high performance construction would also continue to contribute to future generations.
A reduced carbon footprint of 36 Tonnes per year is significant in my book. In fact, it’s the equivalent to 26 Rhinos!
We all know that it’s no longer business as usual. By improving our designs and how they perform we can have a long lasting effect on the planet’s well being as well as our own.
Additional benefits from High Performance Building Method:
Indoor air quality, pollen and dust free
Comfortable year round climate (20-25C)
Balanced indoor temp (no hot or cold spots and draft free)
Extremely low energy bills
*Our software makes the following assumptions; a baseline airtightness of 10 ACH; a thermal comfort level of 20-25 degrees is maintained 24/7; energy supply cost of $0.30/kWh; assume all energy supply is via electricity and not gas.
**We are not builders or quantity surveyors, this is an estimate only
***Carbon emissions calculated as per Carbon Calculator