10.3.1. Reduce Energy Losses and Energy Consumption

There are many ways in which we can insulate our homes but first we should consider how to minimise heat loss from our buildings. In poorly constructed homes, the amount of heat loss varies according to the source of exit from the structure. For example, we are squandering heat through external walls (40%), the roof (25%), windows and doors (20%), the ground floor (10%) and finally via draughts (5%).

To draught-proof our home, we should block up any unwanted gaps (with the exception of ventilators) that let cold air in and warm air out. This is the cheapest and most effective approach to save energy. There are various inexpensive ways of preventing draughts, e.g. self-adhesive foam strips for doors and windows, a letter box brush, chimney cap and silicone fillers around pipework. It is also important to make the house airtight as far as possible by replacing glass windows and external glass doors with double glazed units.

It is easy to follow a number of energy saving, common sense actions including the following suggestions:

• Install a smart thermostat and set it at the desired temperature and timings.
• Install a smart meter to monitor energy consumption.
• Use energy efficient appliances.
• Choose energy saving LED electric bulbs.
• Turn off standby appliances and computers when not in use.
• Be smarter about hot water usage, for example, shower rather than running a long bath.

Most newly built homes are fitted with loft insulation and older homes can save up to 25% of potential heat losses by investing in loft insulation. This insulation will last over 40 years and the pay-back period is about two years. Mineral and wool sold in rolls like a blanket is the most common loft insulation material.

The most effective method allowing protection against heat loss from walls is so-called cavity wall insulation. This involves injecting an insulation material into the void between the inner and outer layers of brickwork. It works in the same way in which a thermos flask keeps a drink hot, by creating a layer around the house. Most newly built homes have cavity wall insulation as standard but older houses (such as those built before 1920 in the UK) do not have cavity walls. Here a possible solution is external solid wall insulation. There are many insulation materials (such as aluminium composite panel or rain screen cladding) which can be used for cladding external walls. However, following a number of fire tragedies (e.g. Grenfell Tower, UK, 2017), it is an essential prerequisite that cladding materials conform to building regulatory standards.

Appropriate floor insulation materials (e.g. expanded polystyrene sheets, polyurethane spray) can be used to insulate floorboards on the ground level of houses and to seal the gaps between floors and skirting boards. It is also important to insulate water tanks by using approved cylinder jackets and water pipes by polyethylene foam insulation.

10.3.2. Replace Fossil Fuel Boilers and Water Heaters

Heating systems in residential homes come in two parts – one section is for the supply of hot water to bathrooms, the kitchen and washing machines, while the other aspect is for hot water radiators. Many homes in the UK and rich countries are provided with a central heating system, which serves both hot water and heating. The supply of energy in this system comes from fossil fuel boilers. There are two types of fossil fuel boilers. Firstly, combination or ‘combi’ boilers provide hot water on demand for domestic use as well as central heating, and are a good choice for smaller homes. With the second type, a heat-only boiler (also known as a conventional boiler system), the hot water is stored in a hot water cylinder or storage tank. This system is suitable for a larger home with greater demand, where several people frequently need to use hot water at the same time. They also require space for a cold water feed tank, usually housed in the loft.

During July 2021 I interviewed 12 UK suppliers specialising in replacing fossil fuel boilers to find cost estimates for different possible scenarios. It should be noted that the figures that follow are indicative only.

In order to replace fossil fuel boilers and water heaters we have different options depending on the type and size of households. If the household is a one- or two-bedroom apartment then a simple solution could be to install a stand-alone electric water heater with a hot water cylinder for domestic hot water supply and plug-in electric convector heaters or electric storage heaters. A typical cost for this solution for a small apartment is around £3,000 in the UK.

For a medium-sized household with three or four bedrooms fitted with a fossil fuel central heating system, an energy saving alternative could be to replace the fossil fuel boiler with an appropriate electric combi boiler. As shown in Figure 10.1, this solution has the advantage that it will retain the existing radiators and can be retrofitted in the existing space. The cost of this type of solution could be £4,000 to £8,000 in the UK.

Retrofitting an electric combi boiler is a simpler solution but it is limited to smaller properties and at present the running cost of a gas boiler is more economical. It is envisaged that a longer-term green energy solution for households is likely to be electric heat pumps.

A heat pump is either air sourced or ground sourced. As shown in the schematic diagram in Figure 10.2, an air source heat pump works rather like a reverse fridge. The heat pump is installed outside and outside particles of air are blown over a network of tubes filled with a refrigerant to turn it into gas. The gas then passes through a compressor. The compressed hot gases pass into a heat exchanger surrounded by cool water in order to heat this water. This is circulated around the house to provide heating and hot water. Then the refrigerant condenses into cool liquid and starts the cycle again.

An air source heat pump (ASHP) costs from £8,000 to £18,000 to install in the UK. A Renewable Energy Incentive scheme is also operational in some countries including the UK. It works both as a heater or an air cooler. Air source heat pumps have key advantages: energy bills are lower than comparable gas heating systems, and they are known to work efficiently in severely cold countries such as Canada. However, an ASHP also poses drawbacks, including its noisy operation and a requirement for larger radiators.

Ground source heat pumps (GSHP) are also good low carbon heating systems, and they have higher efficiency rates and lower running costs than ASHPs. A GSHP makes use of the ground's constant temperature and uses that to both heat up homes and supply domestic hot water. A GSHP absorbs low-grade surrounding energy from the ground and then compresses and condenses this energy to a higher temperature. Heat is transferred to the heating and hot water system of the house, as shown in a schematic diagram in Figure 10.3. The fluid from the heat exchanger then continues its circuit back to the submerged pipework to commence the cycle all over again.

By comparison with an ASHP, a GSHP has several advantages as it is not noisy and is both more energy efficient and cheaper to run. However, the main disadvantage of a GSHP is it very expensive to install (in the region of between £20,000 to £40,000 in the UK) and it requires a lot of ground space. Households in the UK would also require planning permission. Thus, an ASHP could be considered for a medium-sized house and a GSHP is more suitable for a larger property with available land. Heat pumps are more attractive in countries requiring both heating and air conditioning (e.g. USA, Canada, Japan).

10.3.3.Seek to Use Renewable Energy

A steady forward approach for a household aiming to attain lower carbon emissions is to switch to a renewable energy supplier. However, herein lies the problem. Some major suppliers in the UK (for instance, E-On, Centrica, Pure Planet) are claiming to be renewable suppliers, but while this may be true, their approach at present is likely to be offsetting carbon by planting trees all over the world. There are some suppliers (e.g. Octopus Energy, Ecotricity) who have a better reputation as truly renewable energy suppliers. Centrica have invested in EDF Energy's existing and future nuclear plants (e.g. at Hinkley Point and Sizewell in the UK) and aim to increase their share of nuclear source electricity.

The most genuine method of using a source of renewable energy for a household is to consider domestic solar energy. As explained in Chapter 7, solar panels, also known as photovoltaic systems (PV systems), covert the sun's energy into electricity that can power our households. The system uses semiconductor technology to convert energy from sunlight into direct current (DC) electricity. This current is then passed through an inverter to convert it into alternating current (AC). As shown in Figure 10.4, the system can be either grid-connected or stand-alone.

Grid-connected systems are linked to the local utility grid to ensure a continuous supply of electricity. When the domestic solar panel system generates more electricity than the household needs, the surplus energy can be exported back to the national grid. Likewise, if more electricity is needed the grid can supply this. Stand-alone systems are not connected to the grid, but instead charge a solar battery system. These batteries store the electricity generated by solar panels. The stored electricity from these batteries will be used to operate household appliances. Stand-alone systems are operated in areas with local utility grids and are typically more expensive to include the cost of expensive storage batteries. The average domestic solar panel system, without storage batteries, costs between £5,000 and £10,000 in the UK.

Solar thermal collectors do not have PV cells and use sunlight directly to heat up water that is stored in a cylinder. The hot water from the cylinder can then be used for domestic heating needs. Solar thermal panels are roof-mounted, just like solar PV panels, but look slightly different, as instead of cells they have multiple pipes to heat water.

10.3.4. Apply a Circular Economy

As defined in Chapter 3, a circular economy is aimed at eliminating waste and the continual use of resources. The approach is to reuse resources, repair defects, refurbish facilities, rebuild products to original specifications, and recycle wastes to create a closed-loop system. The outcome is minimising the use of resource input, wastes, pollution and carbon emissions.

The application of a circular economy can benefit all sectors of our economy. In the context of retrofitting buildings two specific areas will be discussed: the construction industry and household appliances.

According to a recent report (Retro-First, 2021), every year some 50,000 buildings are demolished in the UK, producing 126 million tonnes of waste and accounting for 10% of carbon emissions. RIBA (the Royal Institute of British Architects) has advocated that the demolition of buildings should be halted and buildings should be preserved and re-purposed. Materials should be salvaged and re-used whenever possible. RIBA argues that the construction of large buildings gobbles up fossil fuel–hungry materials (e.g. steel, cement, aluminium and plastics) and hence developers ought to be more considerate and should be obliged to refurbish. The Institute has requested that it should be allowed to force firms to calculate the total carbon impact of each project they wish to undertake. The Royal Institute of Chartered Surveyors (RICS), in partnership with RIBA and other organisations, is developing the first international standard for reporting carbon emissions across all areas of construction.

The campaign by these influential professional bodies is on the same page as the principles of the circular economy. The end goal of a circular economy is to retain the value of materials and resources indefinitely with little or no residual wastes. This requires a transformational change in the way that buildings are designed, built, operated and demolished. Government intervention in both taxation and legislation should help. For example, retrofitting could be tax-exempt like new constructions and all new build proposals should indicate how much carbon will be emitted during the manufacturing and construction process.

The principles of a circular economy should also be applied to the ‘replace or repair’ policy of home appliances (e.g. washing machines, dishwashers, cookers, fridges). Their suppliers should be obliged to produce and supply spare parts for, say, 10 years so that appliances can be easily repaired. Suppliers should also introduce an exchange plan and offer to take the customer's old item away when delivering the new one. As shown in Figure 10.5, the cycle of the circular economy can work well and to the benefit of both suppliers and customers.

The recycling of products also applies to electrical and electronic items (such as televisions or computers). The Waste Electrical and Electronic Equipment (WEEE) directive regulates the manner in which manufacturers and retailers in European countries should behave regarding recycling.