There have been some pretty dramatic changes made over the last decade or so to how we build our homes. Good changes. Energy ratings have made a big difference, and more of us understand the value in building houses that require less energy to heat and cool these days. Especially important as energy prices become more frightening, and as the need to deal with carbon emissions becomes more urgent.
To understand why, you first need to get your head around how all of the emissions associated with the entire life of your house tally up. The basic equation looks something like this:
Building carbon = materials + construction + operations + decommissioning
“Building carbon” refers the total carbon emissions produced throughout the entire life of your house – obviously, the lower this is, the more “efficient” the house is considered to be.
The “operations” bit of this equation refers to the energy we use on a daily basis for things like heaters, air conditioners, hot water systems, iPads, electric toothbrushes and the like. “Operational energy” has traditionally (in recent history, anyway) accounted for the lion’s share of the total emissions across the life of your house.
As people become more energy-conscious though, and as star ratings and other regulated energy efficiency measures begin to take big bites out of emissions related to things like heating, cooling and appliance use, the volume of carbon emissions associated with the “operations” bit is shrinking.
As Edge Environment’s report explains, what this means is that the emissions related to the materials you build your house with now account – relatively speaking – for a much bigger slice of the whole “building carbon” pie. In fact, emissions related to the production of materials already account for up to half of lifetime emissions, in some cases.
This means that if you’re looking to make more of an impact on your home’s carbon footprint, choosing the right building materials is a good way to do it.
Life cycles and embodied energy
A proper assessment of a building material’s environmental impact is known as a lifecycle assessment (or LCA). A lifecycle assessment is a cradle-to-grave account of how much energy is required throughout the life of that particular product – part of which involves its embodied energy.
The embodied energy of the product accounts for all of the energy associated with the extraction of the raw materials used, and the energy used to manufacture and transport the product.
Some materials, by virtue of the fact that they’re considerably less energy-intensive to produce, compare pretty favourably in terms of their embodied energy – but obviously it’s a matter of looking at the whole package. There’s no point building a house from materials with a super-low embodied energy if it’s not possible to create a design that minimises things like heating and cooling loads.
The best choices to reduce embodied energy in materials will depend mostly on how the house is designed, and what sort of climate you’re building in – there’s no single material (or set of materials) that’s always gong to be the ideal choice.
How to choose the right materials
«It’s about optimised design and fit for purpose material selection rather than selecting silver bullet low impact materials,» explains Edge Environment.