John and Isobel Mackenzie had always been very eco-conscious, but when their first grandchild was born a few years ago, reducing their carbon footprint became a priority. To heat their house they’d been running an oil combi boiler for the last ten years which used over 1200 litres of oil per year. This meant every shower and bath, and every time they turned on the central heating or made a cup of tea had an impact on the environment. They just couldn’t sit back knowing this and decided to make some changes to reduce their carbon footprint.

Many people don’t realise but oil and gas heating systems are huge polluters. The average UK household emits 2.7 tonnes of CO2 each year from heating their house. In fact 14% of UK greenhouse gases come from houses, which is a similar level to car emissions.

Knowing what a big polluter their old combi oil boiler was, the Mackenzies decided to replace it with a renewable energy alternative: a Ground Source Heat Pump.

What is a Ground Source Heat Pump? 

Ground Source Heat Pumps pump a mixture of water and antifreeze around a loop of pipe, which is buried underground in your garden. These pipes are housed in the ground either horizontally or vertically, in boreholes. Heat from the ground is then absorbed into the fluid and passed through a heat exchanger inside a heat pump which lives in a plant room outside your house. (This is typically an external building like a converted garage). The heat energy is then effectively concentrated and used to heat your house.

First impressions

This was new territory for the Mackenzies. Their first impression was that Ground Source Heat Pumps looked complicated and expensive. It was difficult to understand how 100 metre deep boreholes connected to a heat pump, which looked like a giant fridge, could produce enough renewable energy to heat their house. Talking to the right specialist was critical to understanding the process, installation and benefits.

Choosing the right supplier

To manage the installation, they chose borehole and Ground Source Heat Pump specialists, Nicholls Boreholes, working directly with Design Engineer Skye Tansey, who led the installation process.

There were six key steps which took just under a month:

1. Nicholls Boreholes’ team dug three vertical 100 metre boreholes spaced evenly apart in the garden.
2. A separate groundwork team then dug two one metre deep by one metre wide trenches for pipework which would connect the borehole heads to the plant room and then from the plant room to the house.
3. Nicholls’ team then installed and tested the pipework connecting the boreholes to the plant room.
4. Nicholls’ plumbers and electricians installed the heat pump, exchange equipment and water tanks in the plant room.
5. A plumber removed the oil boiler and then connected the equipment to the existing heating and hot water system.
6. Nicholls’ team then installed and tested the pipework connecting the plant room to the house.

Project management

To keep costs down, the Mackenzies took on a key part of the project management and enlisted their own builder and electrician to support on various tasks, including:

• Drawing up a detailed diagram of the garden to help map out where the boreholes would be placed.
• Digging the two trenches: one from the boreholes to the plant room and the other one from the plant room to the house.
• Converting their garage into a plant room.
• Installing a high powered electricity supply to the plant room to power the heat pump.
• Ensuring there was a water supply to the plant room. This was done with a single water pipe going one way from the water metre to the plant room. Then two pipes coming back, supplying hot water for heating, and a supply of water for hot water. These were then insulated to keep them hot.

Renewable Heat Incentive

The Mackenzies qualified for the Government’s domestic Renewable Heat Incentive (RHI), a UK Government scheme set up to encourage the uptake of renewable heat technologies by providing financial incentives. The domestic RHI was launched on 9th April 2014 and covers England, Wales and Scotland. It provides financial support to the owner of the renewable heating system for the first seven years.

As a result of the RHI, the Mackenzies will be reimbursed approximately two thirds of the overall cost of their Ground Source Heat Pump.

Reducing their carbon footprint

Now their Ground Source Heat Pump is up and running, it provides perfect heating and hot water all year round. It could also save them up to 70% off their fuel bill, in comparison to their previous oil boiler. They also have peace of mind that they’re making small steps towards helping to reduce air pollution, slow climate change and safeguard the planet for future generations.