Design Choices and Embodied Carbon; a Case Study
Design choices made in the project planning phase have profound effect, not just on the time and cost of the build, but also on the embodied carbon of the project. These choices also last the lifetime of the building as choices made here can affect the thermal performance of the building, which in turn affects the heating and cooling costs and carbon output of the building for its lifecycle.
I’ve tried to keep technical terms to a minimum in this article, but here’s a primer for those I have used:
CO2e - Carbon Dioxide equivalent aka Embodied Carbon: the mass of harmful chemicals released into the atmosphere from a given activity, normalised to an amount of CO2
R-value: The rating applied to insulation
Specification
For example, Australian builders have had a love affair with brick veneer for several decades. This inefficient design has an embodied carbon of approximately 145kg of CO2e per m2. But the thermal performance of this wall system is only around 2 to 2.5 R-value.
While an insulated double brick wall is more expensive upfront, it has a lower embodied carbon rating of approximately 125kg of CO2e per m2 and can deliver an R-value of 8.7.
The difference in embodied carbon between these two types of construction is due to the embodied carbon for manufacturing vs transport for each construction type. See the charts below:
Manufacturing v Transport Costs
The R-value will have a significant impact on heating and cooling costs and the amount CO2 emitted powering the AC over this period.
An Example
When factoring some assumptions around Air Conditioning use, a 24m2 shed, with 60m2 of brick veneer external walls will emit 521.5 tonnes of CO2e over a 30 year lifecycle if powered by a coal fired power plant, such as those used in NSW. the same shed built from insulated double brick will emit 155 tonnes of CO2e, a 70% reduction.
The upfront cost for this wall system is about 25% cheaper than the insulated double brick, but over the 30 year lifetime of the building will cost close to 60% more in NPV terms.
Wall Type Comparison
Speak to Quantum Insights Advisory, or contact the author, about your Carbon Management Plan and how to optimise your projects cost and carbon inputs.
Some Notes and Assumptions:
All calculations are of A1 to A4 (Manufacturing and Transport) emissions and don’t factor in A5 (Construction) emissions.
Calculated for a project in Sydney NSW.
Energy and Carbon calculations are for operation of air conditioning only
AC calculated as being used for 8 hours a day with differing temperature differentials between inside and out for each season.
I’ve assumed all power will be provided by a coal fired power plant, though this hopefully won’t actually happen
Cost per kWh: 34c
Weight of CO2e emitted per kWh: 0.96kg
I’ve assumed and inflation rate of 3% (I can hope can’t I!)
