We have previously discussed our involvement with the Howgate Close project. However, a lot more has developed since then! As such, we are bringing you an updated look at the project, with a particular focus on some of the data carefully collected by Dr Chris Parsons and Dr Jerry Harrall. The project is a fantastic proponent of passive solar design, and as it stands, is the most energy-efficient housing development in the UK.
We also entered the project into the Regional Energy Efficiency Awards for the East Midlands. You may have guessed, we won! The project submission is currently going through further work to be submitted for the National Energy Efficiency Awards.
The principle of passive solar design
The passive solar design takes advantage of the sun’s energy. It also incorporates local climate characteristics to provide natural heating and cooling in a building. It can significantly reduce energy costs and create a more comfortable, sustainable environment. Howgate Close’s passive solar design does not use mechanical or electrical devices, such as fans or pumps, to distribute the solar heat.
- Orientation: A building should be oriented so that its main windows face the sun’s path. For instance, this means facing south in the northern hemisphere, while in the southern hemisphere, it means facing north.
- Windows and Glazing: Proper window selection is critical. South-facing windows should have a high solar heat gain coefficient (SHGC) to allow the winter sun in, while north-facing windows (in the northern hemisphere) should have a low SHGC to minimize summer heat gain.
- Thermal Mass: This refers to materials that store heat and release it over time. Brick, stone, and concrete are examples of materials with high thermal mass, which can absorb solar heat during the day and release it at night to help moderate indoor temperatures.
- Insulation: To maintain the indoor temperature, sound insulation is crucial. Insulation helps prevent heat loss in winter and heat gain in summer.
- Ventilation: In summer, natural ventilation can be used to cool the building at night. In cooler seasons, heat recovery ventilation systems can use the heat in the stale exhaust air to pre-warm fresh incoming air. Howgate Close can ventilate throughout the property.
- Shading: During warmer months, shading devices such as overhangs, awnings, pergolas, and trees can help prevent overheating by blocking high-angle summer sun.
The numbers behind Howgate Close
Dr Chris Parsons, a retired GP and second-generation farmer in Eakring, conceived a project named Howgate Close to resolve local multifarious issues like affordable rural housing shortages, diminishing biodiversity, and environmental impact.
The project covers 10 acres of previously intensive arable farmland. This now hosts nine rented homes, 60KW solar panels, and over 10,000 newly planted trees and hedgerows. It has helped address issues like rural housing shortages, climate change, soil restoration, carbon sequestration, biodiversity, water management, and community cohesiveness.
The Return On Investment (ROI) of Howgate Close is 4.6%, with a 15-year payback period. The site mitigates 16 tonnes of carbon emissions annually from its renewable energy generation. It also sequestrates an additional 9 tonnes of carbon annually due to rewilding efforts. The average energy bill for the first 10 months was less than £1 per day across all nine homes. This demonstrates its affordability and energy efficiency.
The homes were designed by the local Hockerton Housing Project (HHP) using principles such as southerly orientation, high thermal mass superstructure, super-insulated envelope, and renewable energy. They achieved the highest As-Built SAP Ratings in the UK, ranked in the top 0.01% of 12 million registered EPCs. This made them among the most energy-efficient dwellings in the UK.
The construction of the homes was notable for what wasn’t included. For example, features like no ground source heat pumps, air source heat pumps, cavity walls, roof trusses, or traditional foundations. The buildings have silicone render external walls, ceramic tiled floors, and 220mm prestressed concrete plank roofs.
Despite facing initial opposition, the project set a legal and planning precedent when it gained planning permission after an appeal. The total project cost was £1.5m, with build costs of £2,100 m². It compares favourably with the costs of building a conventional dwelling (£1,800 m²) or a Passive House (£2,200-2,400 m²).
Residents in the development come from a mixed demographic. As such, it is seen to embed a strong sense of community, a safe living environment, and a future model of post-hydrocarbon neighbourhoods. The rental model allows the properties to be sold after 15 years. Crucially, the initial and future selling prices are pegged at 80% of their open market value.