BUILDING IS VERY CARBON INTENSIVE
25% of the UK's greenhouse gas emissions come from the built environment - the construction, running, and demolition of buildings.
A material's 'embodied carbon' is the entire carbon footprint of extracting, processing, delivering, and installing it. Generally, it is not a legal requirement in the UK for projects to use low-carbon construction methods or materials.
Carbon Emissions In-use
'In-use' carbon is usually that which is emitted by non-renewable energy use to heat, cool, and power a building. There are some regulations around how much energy buildings can use. However, it is possible for many buildings to be adapted to emit no carbon, or even better, to generate more energy than they use (making them 'carbon negative').
THE 'FABRIC FIRST' MANTRA
'Fabric first', is industry jargon for reducing the energy required to run a building before addressing how it is powered or heated.
In practice, this means we always seek to insulate a building as much as possible before spending money on 'green' energy sources like solar panels or air-source heat pumps.
When the energy required to run a building (its 'energy demand') is reduced to as low as possible, it is far easier to create a building which has a low carbon footprint and is cheap to run. When we create a building with low energy demand, the amount of equipment (e.g. photovoltaic panels) required to run it also reduces.
Passivhaus is an energy performance standard for buildings. Passivhaus is synonymous with the best all-season comfort coupled with the lowest running costs for your building. Clean air and comfortable room temperatures all year round.
In the UK we typically achieve Passivhaus by:
First, accurately modelling the building in its real geolocated environment using up-to-date weather data which returns expected heating and cooling needs, and the possibility of overheating;
Installing very high levels of insulation - like putting on a very thick, warm coat, but with the opposite effect in summer where the additional insulation slows the transfer of heat into the building;
Specifying triple-glazing, which also reduces the amount of noise pollution getting into the building;
Making the building airtight - this means sealing up all the little holes accepted in conventional building world. In an average 1960s house, air leakage is responsible for about 25% of all heat lost!
Installing an MVHR (Mechanical Ventilation with Heat Recovery). This 'magic box' keeps the building supplied with fresh air, filtering out pollutants and pollen, and recapturing at least 75% of the heat from the stale/humid air it extracts.
Designing out 'cold bridges'. A cold bridge is any building element where heat can easily travel from inside to outside. A common example is roof joists which can 'bridge' the inside and outside of a house and so heat is easily conducted through them.
Despite the name, the Passivhaus approach can be applied to any building, not just houses. Existing buildings can be brought up to the similar but slightly less onerous EnerPHit standard.
There is also PassivHaus 'Classic', 'Plus', and 'Premium' - these standard range from 'very low' operational carbon to carbon negative buildings.
OUR APPROACH TO REDUCING CARBON EMISSIONS
Different materials performing the same function can have wildly different carbon footprints. For example when building a floor, rather than casting a concrete slab and foundations, 'screw pile' foundations with timber floor joists, can reduce the carbon footprint of the floor by 90%.
Every project has different requirements and pressures, but where feasible we will:
Specify timber instead of steel for structure (e.g. beams);
Specify non-petrochemical insulation, for example wood fibre insulation;
Specify internal finishes which have no- or low-formaldehyde content, and no VOCs (Volatile Organic Compounds) - which both contribute to poor air quality;
Aim to exceed the performance requirements of the Building Regulations with our detailing;
Avoid specifying products manufactured by companies known to have been involved in the refurbishment of Grenfell Tower.
Sometimes, due to technical constraints, compromises are unavoidable. There is a cost implication of the above approach, unfortunately, but we will take this approach unless you advise us otherwise.
There are lots of construction and household products which contain VOCs (Volatile Organic Compounds) and which 'off gas' into the air we breathe, with potential health implications.
We try to use only low- or no-VOC materials in the construction of our projects. Due to VOCs' proliferation, this is a huge challenge and off-gassing can occur from many products, including loose furniture, which we often don't have so much control over in our projects. As such ventilating homes (like with an MVHR) is even more important!
Not only does the MVHR system re-capture heat, but it runs continuously helping to maintain good air quality and a healthy environment. This also keeps a building's internal carbon dioxide and humidity at healthy levels, reducing concentrations of unwanted airborne chemicals and the potential for mould growth.