What is sustainable design?
The design of new builds, extensions, refurbishments or renovations should all have the same aim - to minimise energy use and reduce carbon emissions.
JMP Architects aim is to fulfil our client's aspirations with minimal impact on the environment. We can design buildings, which will use less energy, using materials with less embodied carbon. The most significant factor in sustainable design is the building envelope. If a building is well insulated and built to a high standard it will use less energy to heat. It is far more cost-effective to save energy than to generate it.
Why design sustainably?
We are now facing a climate emergency. The earth is heating up. The evidence is there. Land and ocean temperatures are increasing, sea levels are rising, ice at the Earth's poles and in mountain glaciers is melting. We are experiencing more extreme weather such as hurricanes, heatwaves, wildfires, droughts and flooding.
Scientists agree that cutting greenhouse gas emissions, which causes the heat from the sun to become trapped in the atmosphere, will stabilise rising temperatures. It is acknowledged that buildings are a major contributor to carbon dioxide(CO2) emissions and global warming.
In the average UK home, 87% of the energy used is for space heating, hot water and for cooking. Our homes use four times as much energy in the form of heat as in the form of power. We can make a significant impact on global warming by reducing our CO2 emissions if we reduce our energy demand for heating or cooling our buildings. We can do this by improving our building's fabric.
Low Energy Building Standards
In December 2015 the United Nations signed the Paris Agreement to substantially reduce global greenhouse gas emissions to limit the global temperature increase in this century to 2°C and pursue efforts to keep it to 1.5°C. It is now widely agreed that we must limit the global temperature rise to 1.5°C. To achieve this the European Commission aims to be "net-zero" by 2050.
Unfortunately the current UK Building Regulations Standards are not in line to achieve net-zero by 2050.
2022 - The proposed Building Regulations update aims to ensure that all new homes will produce 31% less carbon emissions compared to current standards.
2025 - The governments proposed Future Homes Standard aims to ensure that all new homes built will produce 75-80% less carbon emissions compared to current standards.
Association for Environment Conscious Building (AECB) Design Standard and certification - this is voluntary standard which aims to promote sustainable building and reduce carbon emissions by 70% compared to current standards.
AECB Retrofit Standard - aims to ensure good thermal performance and comfort in existing buildings.
Passivhaus - Passivhaus is a voluntary low-energy standard and is the most energy efficient standard there is. A Passivhaus will use significantly less energy, up to 90% less for heating and cooling compared to the existing building stock.
EnerPHit - is the Passivhaus low-energy standard for retrofitting existing buildings.
The only way to achieve net-zero by 2050 is to build to the Passivhaus Standard now.
All buildings in the UK, new build or existing, need lots of insulation in the floor, walls and roof to keep the internal environment warm. If the building is well insulated it will use less energy to heat and you will save money on heating bills and reduce carbon emissions.
The insulation needs to be continuous, with no gaps or “thermal bridges”. Gaps in the fabric insulation can cause cold spots which can lead to condensation forming.
Windows and doors are unavoidable gaps in the continuous insulation but high performance windows can reflect warm air back into the building. The surface temperature of the inside of windows needs to be similar to the internal walls to avoid feeling a draught, only high performance triple glazing can achieve this.
The more airtight the building envelope is, the less warm air can escape. A continuous airtight membrane is required around the internal envelope of the building. Any gaps in the airtight layer can cause cold spots.
Think reuse first, and new build second. Retrofitting and repurposing an existing building can radically reduce carbon emissions compared to demolition and rebuild.
We can also reduce the amount of CO2 produced in the building process by using Low Carbon materials which are natural and locally sourced.
Low Carbon Materials
Buildings are a major contributor to global warming because the materials we use to build with release CO2 created during extraction, manufacturing, transportation and during the construction process. All the materials used in the building process will have embodied carbon. Embodied carbon also includes the CO2 produced in maintaining the building during its lifetime and then its demolition, transport of waste materials and recycling.
Concrete is the most abundant human-made material in the world, cement production creates approximately 7% of the worlds CO2 emissions and is the largest contributor to embodied carbon in the built environment. But we can use alternative materials.
Reused, re-purposed, local materials or natural materials will reduce the embodied carbon in a building. We can look at many different options for building materials which have lower embodied carbon levels: such as timber frame, wood fibre boards, Cellulose insulation, timber cladding, etc.
1. Timber frame; 2. Straw bale construction; 3. Timber I-Joists; 4. Wood fibre boards; 5. Cellulose (shredded paper) insulation; 6. Sheep's wool insulation; 7. Limecrete floor slabs
All buildings need to be designed to create comfortable environments, this includes the air temperature, air movement, humidity and lighting. We aim to design sustainable, well insulated buildings that provide good thermal comfort.
Build tight, ventilate right - well insulated airtight buildings need ventilation to allow fresh air in for our comfort. The best solution is Mechanical Ventilation with Heat Recovery (MVHR), which provides continuous fresh air into the building but also warms the air as it comes in past the stale air being extracted. If the fresh air coming into the building is warmer, less energy is required to warm the internal spaces.
Orientation - we need windows to allow daylight and fresh air into our buildings and for our wellbeing. By designing buildings with large south facing windows we can also capture the warmth from the sun, “solar gain”, which will warm the internal air.
Horizontal shading over south facing windows will prevent over heating in summer but still allow the sun to reach the inside when it is at a lower angle in winter.
Renewable Energy Systems
The energy used associated with heating, hot water, ventilation and lighting represents between 40% and 65% of a buildings whole life carbon. In the context of the climate emergency there is an urgent need to reduce buildings energy use. Burning fossil fuels to heat your home and hot water is the largest use of energy and producer of CO2. But there are alternative heating sources which will reduce carbon emissions:
Air Source Heat Pumps (ASHP) - absorb heat from the outside air and supply heat at a relatively low temperature (between 40C and 50C) to an underfloor heating system or large radiators. ASHPs use electricity to run but they are an efficient heating source if a building is well insulated. If you change from a gas or oil fired boiler to an ASHP without improving the building fabric your energy bills will increase. Think Fabric First.
Ground Source Heat Pumps - use pipes buried in the garden to extract heat from the ground. GSHPs can be used to heat under floor heating or radiators and hot water.
Solar Thermal Panels - use the heat from the sun to warm domestic hot water stored in a hot water cylinder. In the UK solar thermal systems can typically supply half a dwellings annual hot water energy demand, with no emissions at all!
Reducing the energy demand from buildings will not only help reduce CO2 emissions and the environment but will also reduce the demand on our National Grid system. We use energy in our buildings for heating, hot water lighting and ventilation but we also use electricity for cooking, to power appliances, TVs, computers, etc. We can look at on-site renewable electricity generating systems:
Photovoltaic panels - will produce electricity during daylight hours, the stronger the sunlight the more electricity is generated. Electricity can be fed back to the National Grid or stored in batteries inside the building to be used later.
Wind turbines - are a highly efficient way of creating electricity for the home. The stronger the wind the more energy is produced, therefore wind turbines are probably more suited to rural areas.