Renewable Energy Sources for your self-build

Renewable energy is generated from natural resources such as the sun, wind and water.

Increasing numbers of people are turning to greener energy options owing to the rising costs of gas and oil, concern over carbon emissions and greater levels of awareness of the alternative solutions available. But how exactly do you build a more sustainable home at all levels of the build - in particular the heat sources and water supply?

Solar energy

Solar photovoltaic (PV) systems and solar thermal collectors use the sun's energy to create electricity and only require daylight, not direct sunlight, to work. By using photovoltaic panels with a battery, inverter and controller it is possible to start generating electricity for domestic units.

Thermal panels turn heat radiated by the sun into hot water. The liquid that circulates through these thermal solar panels is heated by sunlight, this then passes through a coil in the water tank which in turn heats the water stored in the tank.

According to the Energy Saving Trust, a typical home solar PV system could save around 1.3 to 1.6 tonnes of carbon per year (depending where you are within the UK).

Solar panels on a house roof
Pros

Reduces your electric bill and your carbon footprint.

Homeowners who install new rooftop solar panels from 1 January 2020 will be able to lower their bills by selling the energy they do not need to their supplier. The Smart Export Guarantee (SEG), which kicks off in 2020, will require energy suppliers to pay households for the excess/unused electricity that they export to the National Grid. This will allow homeowners to convert any unused solar energy into cash, providing them with an extra income on top of their energy bill savings.

Energy bill savings from solar panels depends on your lifestyle: how much electricity your solar panels produce, and how much of this electricity you use. To maximise your panels, you would need a south-facing roof. For example, if you are at home during the day, the more you are likely to save as you’ll use daylight to generate your electricity. According to the Energy Saving Trust (July 2019 stats) if you are living in London and at home all day you could save £390 a year (including SEG). This means you could earn back the installation cost in around 15 years.

Cons

Expensive to install. The average domestic solar PV system is 4kWp and costs around £6,200 (including VAT at 5 per cent)*

*Energy Saving Trust

Using the fabric-first approach in self-build design can produce a low energy, efficient home. So what is the fabric-first approach? Learn more here.

A timber frame

Ground Source Heat Pumps


These kind of pumps use solar energy naturally stored in soil, bedrock and groundwater as a heat source. They do require electricity to operate, but they efficiently convert this into five times as much heat energy for every unit of electricity used.

The pump performs the same role as a boiler in a central heating system. But it uses ambient heat from the ground, rather than burning fuel to generate heat. 

This kind of pump requires plenty of space for the system to be installed – plenty of room for digging machinery. How big the ground loop needs to be depends on how big your home is and how much heat you need.

A mixture of water and anti-freeze is pumped around the ground loop and absorbs the naturally occurring heat stored in the ground. The water mixture is compressed and goes through a heat exchanger, which extracts the heat and transfers it to the heat pump. The heat is then transferred to your home heating system.

Pros

It’s efficient – you need to use electricity to power the pump that circulates the liquid in the ground loop. But for every unit of electricity used by the pump, you get between two and four units of heat – making this an efficient way to heat a building. It also cuts costs – cheaper Economy 7 electricity tariffs can be used to lower the cost of electricity to power the heat pump.

It could lower your fuel bills, especially if you replace conventional electric heating or an old oil or LPG boiler. It could provide you with an income through the government’s Renewable Heat Incentive (RHI). It will heat your home as well as your water and it is low maintenance.

The payback period is difficult to predict. You have to take into consideration the type of system you're replacing, whether you qualify for RHI payments, how well insulated your home is and how you'll be using the heat generated from the pump. The Energy Saving Trust estimates that the maximum you could save with a ground source heat pump is £2,405 a year (with the RHI payment) which is a five-year payback period in the best case scenario.

Cons

It’s an expensive endeavour to install this kind of pump, typically around £10,000 to £18,000 depending on the size of the system you choose. This cost doesn’t take into account the time and costs involved in digging the groundworks and planning permission may be required.

Choosing your own materials is arguably one of the most important stages of a self-build, they will affect the performance, efficiency and sustainability of your home. Learn more about the importance of choosing your own materials here.

Isover insulation

Air Source Heat Pumps (ASHPs)

ASHPs convert the energy created by the outside air into heat, giving a comfortable temperature inside the home - reducing heating costs.

An air source heat pump is usually placed outdoors at the side or back of a property. It takes heat from the air and boosts it to a higher temperature using a heat pump. The pump needs electricity to run, but it should use less electrical energy than the heat it produces.

As well as heating, these pumps work in reverse to provide cooling. Many products are available for different sizes and types of building and heating requirements. They can be used with radiators but work better with underfloor heating. They can also provide full heating and hot water without a back-up system.

Pros 

Easy to install and energy efficient. 

Cons

ASHPs can be noisy due to the condenser units which blow out colder air to the immediate environment. They’re not cheap – the Energy Saving Trust estimates that the cost of installing a typical ASHP system ranges between £6,000 and £8,000. These also require enough space to install a condenser unit (which looks like an air conditioning unit). However, according to the Energy Saving Trust, the potential annual savings of installing a standard air source heat pump in an average sized, four-bedroom detached home in England, Scotland and Wales is between £1,341 to £1,586 (including RHI payments).

Our quick overview of building an energy-efficient home gives low energy options that you can incorporate in your self-build design. Read more here.

Glass panels

Biomass heating

Wood-fuelled heating systems, otherwise known as biomass heating use organic material such as wood pellets, logs or chips to generate heat. They are environmentally friendly and CO² and sulphur-free when burning.

A stove burns logs or pellets to heat a single room - and may be fitted with a back boiler to provide water heating as well. A boiler burns logs, pellets or chips, and is connected to a central heating and hot water system.

Pellet costs depend on the size and method of delivery. If you have room for a large fuel store that will accept several tonnes of pellets at a time, delivered in bulk by tanker, this can help to reduce your costs. Logs can be cheaper than pellets, but costs depend on the wood suppliers in your local area, as they cost a lot to transport. If you are lucky enough to have room to store more than a year’s worth of logs you can save money by buying unseasoned logs and allowing them to ‘season’ for a year.

Timber in a wood pile
Pros

According to the Energy Saving Trust, there are significant energy savings to be had. You could save up to 14.3 tonnes a year in carbon dioxide emissions when a wood-fuelled boiler replaces a solid (coal) fired system. Financial savings are more variable - if you replace an older liquid petroleum gas heating system with a wood-burning system you might save up to £1,205 a year, but if you are replacing an old electric heating system you could save as much as £960 per year.

Cons

Biomass needs more work than traditional gas and oil boilers because you will have to supply the system with pellets or chips.

Wind turbines

The modern wind turbine is quiet and available in different sizes, depending on the required output. A small unit can attach directly to the roof, or larger units will have their own support post. Energy is generated when the wind blows the blades, the blades rotate a shaft. A generator converts the energy from the rotating shaft into electrical energy.

There are two types of domestic-sized wind turbine. A pole mounted or free standing turbine has a generation capacity of about five to six Kilowatt (kW). Building mounted systems can be installed on the roof of a home where there is a suitable wind resource. Often these are around 1kW to 2kW in size.

Wind turbine in the countryside
Pros

You could slash your electricity bills and cut your carbon footprint. Wind electricity does not release any harmful carbon dioxide or pollutants.

Cons

The cost of a system will depend on the size and the mounting method. Building-mounted turbines cost less to install than pole-mounted ones, but they tend to be less efficient. For equipment and installation, with VAT at five per cent, the Energy Saving Trust estimates that a 2.5kW pole-mounted system costs between £9,900 and £19,000 and a 6kW pole-mounted system costs between £21,000 and £30,000. The wind speed required to generate a profitable amount of electricity using a domestic turbine is around six metres per second. Location is a key factor as there aren’t many locations in the UK that regularly reach this wind speed, so even with a more expensive pole-mounted system, you may struggle to break even.

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