Sat Kaur: Timeless Principles For Eco Homes

The Government’s new Green Home Grants scheme is now live. Low-income households and private homeowners are being offered vouchers of up to £10,000 and £5,000 respectively to ‘wrap up [their homes] for the winter’. Retrofit measures covered under the scheme are detailed here.

WHY RETROFIT IS NECESSARY

Domestic retrofit is a response to two primary issues: climate change and energy security. Around 84% of the existing English housing stock was built prior to the mandatory requirement for insulation and whilst statistics vary annually energy used in homes contributes to around 20% of annual UK carbon emissions. Around 62% of energy used in each home is attributed to space heating, which is why the Green Homes Grant focuses on insulation measures and low-carbon heating.

WHAT TO WATCH OUT FOR

Variation in regional and local climates mean that blanket application of high performing retrofit standards may not be a straightforward solution to long-term energy efficiency and thermal comfort in homes.

Studies conducted by the studio in conjunction with Oxford Brookes University have demonstrated that retrofit schemes employing superinsulation and airtightness measures can result in increased overheating risk, which could be exacerbated by warmer future climates.

The summer of 2018 may seem like a distant dream now, but experts claim its unprecedented global heatwave may be representative of forthcoming summers. UK climate projections illustrate hotter summers and milder winters for almost all regions. Projections for Southeast England indicate that in 2080 rising temperatures intensified by currently high-performing retrofit schemes could endanger the lives of vulnerable occupants and will require homes to refer to mechanical cooling which will result in a reduction of initial carbon savings. This is why adaptation strategies such as shading and natural ventilation need to be considered when creating climate resilient retrofits.

Though both are necessary, climate change mitigation and adaptation strategies can be contradictory. Calibrated dynamic simulation studies are a good way of testing combinations of both to provide energy efficient and climate resilient site-specific solutions.

DESIGNING FOR COMFORT AND ENERGY EFFICIENCY: A few pointers

1. Analysis of Context and Environment: It is important to evaluate homes in context to obtain a good understanding of how local environmental features affect energy use. Considerations should include exposure to wind, access to solar gain, access to daylight, and the effect of shading from neighbouring structures. Current and future climate data for temperature, windspeed and wind direction is freely available from the MET Office website and should be studied.
2. Orientation and spatial organisation: For energy savings, a general rule of thumb is to relocate infrequently occupied rooms such as utility and shower rooms to the north and living rooms and bedrooms towards the south. For wellbeing, rooms should be placed to support healthy circadian rhythms. Exposure to prevailing winds should be considered to minimise heat loss and optimise natural ventilation.
3. Insulation: The thickness, thermal conductivity, and location of insulation material can make a difference to how a building behaves. Insulation acts as a barrier to heat transfer. It is most efficient at limiting heat loss and heat gain if it is placed on the outside of a building.
4. Glazing: Installing Low-Emissivity coated double or triple glazed windows can help to reduce both heat loss and heat gain. However, the size and placement of glazing is as important when considering home extensions. Large south-facing windows will offer the most access to sunlight but lead to increased overheating risk.
5. Shading: Fixed and occupant-controlled shading can help to reduce solar heat gain in the summer and heat loss in the winter. Insulated external shutters can help to create comfortable internal environments if closed when outdoor temperatures are at their highest during the day in summer and lowest during the night in winter.
6. Natural Ventilation: If a site is located in an area with reasonably good air quality, then controlled natural ventilation is a fantastic free resource for cooling homes. The creation of ventilation pathways that capitalise on prevailing winds and allow for passive stack ventilation can help to provide comfortable conditions for occupants in the summer. Night purge ventilation is most effective in terms of cooling homes.
7. Surface colour and texture: Highly reflective light-coloured surfaces can help to reflect heat and keep homes cool in the summer. Application of white rendered external insulation, white walls and ceilings can all help. Care should be taken that floors are not too shiny to avoid glare.
8. Landscaping: Carefully considered planting can enhance biodiversity and contribute to better air quality and wellbeing. It can also offer opportunities to provide windbreaks. Deciduous trees can help to cool and shade homes in the summer whilst allowing in light in the winter. Distance and heights of trees must be carefully considered. Green spaces have been known to lower temperatures in areas suffering from the Urban Heat Island Effect. The inclusion of water bodies can contribute to evaporative cooling on dry summer days. Green roofs also provide cooling and insulation.

If this post caught your attention take a look at ‘101 Rules of Thumb for Low Energy Architecture’; A beautifully illustrated simple little pocketbook, by Huw Heywood. ‘Adaptive thermal comfort: principles and practice’ by Roaf, Humphreys and Nicol; this is a book for the science buffs!

Sat Kaur is a practising architect, associate lecturer, and the director of a little Architecture Studio ltd. She is passionate about designing low-impact homes that make people feel good.

“I decided to establish a little Architecture Studio because I want to make eco-friendly healthy architecture available to as many people as I can. Ordinary, everyday people like me.” – Sat Kaur