When building an extension, be mindful of the overall carbon footprint of your home.  

bifold open plan extension - how to reduce the carbon footprint of your extension - extensions - granddesignsmagazine.com

Image: Unique Home Stays 

Planning and building an extension is a lengthy process and it's important to consider what effect it will have on the environment as well as the overall carboon footprint of your home. The Grand Designs magazine team spoke to Adam Knibb of Adam Knibb Architects on the best ways to aim for a low impact build that is carbon aware. 

Zero carbon

Zero carbon refers to both embodied energy, which is used in the manufacture of the building materials, and operational energy, which is used to heat, cool and power an extension. If the entire building isn’t being upgraded, then even if you deliver a zero-carbon extension the overall house will still have the same carbon footprint. In theory, the extension could be below zero, generating energy sufficient to power the house, but I haven’t heard of anything like this being done before. 

wrap around extension - how to reduce the carbon footprint of your extension - extensions - granddesignsmagazine.com

Image: Mulroy Architects

The foundations

Concrete is still the industry standard for foundations but it has high embodied energy. You can reduce the embodied CO2 of foundations through different cement mixes or use of limecrete, but not offset it completely. One of our new timber-frame houses is set on a compacted gravel trench foundation, using aggregate from the previous demolished house with mechanically compacted layers, topped with limecrete to bind it all together. 

Read more: The Green Homes Grant hub

Timber frame

Build using timber frame, which has low embodied energy; all buildings ideally need to be constructed this way to minimise the environmental damage. Modern solutions such as SIPs (structural insulated panels) and CLT (cross-laminated timber) are best for reducing the carbon footprint. 

Traditional materials

Cob or straw bale could be used but it’s important to think holistically about the building. They don’t lend themselves to airtightness so additional membranes to reduce leakage will be needed.

kitchen island concrete extension - how to reduce the carbon footprint of your extension - extensions - granddesignsmagazine.com

Image: Simon Whitehead Architects

Be mindful

Follow the energy hierarchy: Be Lean – select the highest standards for materials. Be Clean – keep emissions low. Be Green – include renewables. Design your extension with good insulation, airtightness and building orientation in mind, then go for renewables such as air source heat pumps. The house will become more sustainable, with a lower carbon footprint, over time.

    

For more project inspiration, read Grand Designs magazine digitally for free now by registering your details

read a free issue of grand designs magazine

MORE ARTICLES

5 of best self build projects using timber 2020

Kitchen extension ideas to improve your home

Eco friendly ideas for home building in 2021


Kevins Column

Top self build highlights at Grand Designs Live 2019 hosted by Kevin McCloud

Find top experts, specialist exhibitors and a wealth of inspiration for your self-build or renovation project all under one roof.
visit-award-winning-grand-designs-live-hosted-by-kevin-mccloud

 
 

inside-a-re-imagined-london-maisonette-with-a-sunken-garden
Extensions

Inside a re-imagined London maisonette with a sunken garden

By excavating the garden, these homeowners were able to reimagine their homes internal space.

colourful-exposed-steels-uplift-this-modern-kitchen-extension
Extensions

Colourful exposed steels uplift this modern kitchen extension

This kitchen extension design uses exposed bright yellow steel beams to create an uplifting atmosphere.
how-to-plan-and-budget-for-a-basement-extension
Extensions

Planning a basement extension: what you need to know

A basement extension can be costly and difficult, but it also provides amazing opportunities for increasing the space your home has to offer.
indoor-outdoor-kitchen-spaces
Extensions

4 real extensions that blur the lines of in and outdoors

These modern extensions have design features that emphasise the space opening out onto glorious gardens.
proctor-shaw-floating-extension
Extensions

A two-storey extension with an optical illusion 'floating' pod

Explore this creative two-storey extension which uses an exterior cladding as a decorative finish inside.
period-property-extensions
Extensions

Period property extensions: how to blend old and new

Enhance the special character of an old home with a beautifully designed extension