Green Services Direct

Steps you can take to boost its eco-credentials

With ever growing concern about climate change, people are increasingly looking at ways to live more sustainably and minimise their carbon footprint. So, how can you add valuable living space to your home that is automatically planet friendly while kind to your wallet? See below for some top tips and ideas.

What is a carbon footprint?

First, a quick refresher on the jargon. There are two terms commonly used to describe a building’s carbon footprint. The ‘embodied carbon’ refers to the energy used during the manufacture and transport of building materials when CO2 is released into the atmosphere.  Meanwhile the ‘operational carbon’ relates to the heating, cooling and power requirements of the building when in use.

When planning your extension, ask your architect how to reduce its carbon impact. For example, concrete is still the industry standard for building foundations, though it has high embodied carbon (link to article). There are, however, greener alternatives, such as limecrete. Scot Masker of Masker Architects explains: “Concrete is an accepted and good way of building and that’s why everyone uses it. You can use greener products, such as limecrete, but be prepared to provide extra justifications to building control inspectors to make sure they are happy as it’s an alternative construction method.”

Greener building materials

In construction, greener materials are generally those that are natural or reclaimed and which can be sourced as close to the building site as possible. Masker explains: “Locally sourced materials are also likely to be suitable for the context in which the building is located. For instance, if flint, stone or slate can be sourced locally then it’s likely to be reflected in local building traditions.”

Choosing timber frame construction is one way to reduce the embodied carbon impact of your project. Wood is a renewable resource and using it for framing reduces reliance on more energy intensive materials like steel or concrete. Look for certifications like FSC (Forestry Stewardship Council) to ensure the timber is responsibly sourced. “It’s all about a careful balance between sourcing, travel distance and energy used to produce the material,” said Masker.

Cob and straw bale buildings have low carbon footprints and excellent insulation properties but can be quirky looking. Masker explains: “You will end up with thick walls and small windows, which is very energy efficient and green, so you need to be prepared to accept the limitations of these traditional craft construction methods.”

Consider also using natural insulation, such as hemp, wood fibre or sheep’s wool. On the topic of insulation, Masker said: “We generally recommend Rockwool, a sustainable, stone wool which is better than fibreglass insulation which is basically spun plastic. Specialist insulation, such as sheep’s wool, requires greater thicknesses to reach the same level of insulation and so will need thicker walls.”  Other options include innovative Porotherm Clay Blocks, that fulfil the requirements for thermal insulation with no additional insulation necessary.

Fabric first

If you want your extension to be as green as possible, you really need to follow the ‘fabric first’ approach.” This prioritises the energy efficiency of the materials that make up the building fabric itself rather than relying on renewable technologies, such as solar panels or heat pumps.  Buildings designed and constructed with a fabric first approach prioritise reducing the space heating demand and energy consumption. This includes taking great care to ensure the building is as airtight and highly insulated as possible. Plus, choosing building materials with a high thermal mass, such as a concrete or a stone floor, which can store and distribute heat effectively.

Ventilation

Avoiding gaps in the structure of the building means better heat retention, but it can also lead to the air indoors becoming stuffy and stale. Good ventilation helps prevent the build-up of stale air, moisture and potentially harmful pollutants. Good ventilation can be achieved by opening windows and incorporating ‘breathable’ materials. For example, lime mortar or sheep’s wool insulation, can deal with moisture by mopping up any free water and releasing it into the atmosphere.

An alternative, “more hermetically sealed” approach relies on whole house mechanical ventilation systems that include heat recovery.  The ventilation system provides a consistent supply of fresh outside air to the inside without any unnecessary heat loss. Masker said: “The downside is people don’t live like machines and like to open windows and doors and the system has to react to those changes whereas a more organic house might be better.”  

Passive solar design

Solar panels on the roof are not the only way to harness the power of the sun to heat your home. A low-tech passive solar home collects heat as the sun shines through south-facing windows and then releases the heat during the evening. Large, double or triple-glazed windows, often floor to ceiling, capture as much sunlight as possible and warm the inside via a greenhouse effect. Insulation will help to trap the heat in the building and reduce summer overheating as it regulates temperature. A roof overhang or shades or louvres at the top of a south-facing window is essential to prevent overheating in summer. 

“The size and orientation of your windows needs to be carefully controlled as it makes a massive difference to the amount of heat gained or lost inside a home,” explains Masker. Extensions have more site constraints than a new build, so it may not be possible to have south-facing windows. Nevertheless, the glazing needs to be carefully considered. Strategically placed windows and skylights minimise the need for artificial lighting during daylight hours, saving on your energy bills.

Reuse not landfill

One of the biggest ways to reduce your carbon footprint is to reuse materials that would otherwise go to landfill. When demolishing any structures that need to be removed, consider reusing those materials elsewhere in your project. Reclaimed bricks, clay tiles and slates are examples of materials that can be used again, minimising waste and the need to produce more.  Crushed aggregate is another. “If you want a truly sustainable extension, you need to consider the entire lifespan of the materials and if the component parts can be broken down and re-used rather than end up in landfill,” said Masker.

Don’t forget renewables

When people plan an eco-extension, thoughts soon turn to incorporating renewable technologies such as solar panels or heat pumps, though, a fabric first approach is greener. That said, planning a new extension is a good time to consider upgrading the boiler in your existing home whether it’s fitting a modern condensing boiler or switching to a heat pump. Seize the opportunity to make your whole house more eco-friendly. Extensions usually involve more service requirements whether its heating or hot water for an additional living room or bathroom, An upgrade will allow you to increase the capacity of your system.

Improving the insulation and airtightness of your existing house is important. There is little point going to a lot of trouble building a super-insulated, airtight extension if heat is leaking elsewhere.  Think twice before installing a log burner. While popular, these stoves pump out carbon emissions through the chimney.

Green roofs and VOCs

Incorporating a green roof into the architectural design can help in a lot of different ways, said Masker. A sedum roof can increase the insulation of the building and biodiversity and be attractive to look at which is important if the roof is easily seen on a single-storey extension. “Plus, a sedum or grass roof can add to a sustainable drainage solution and help to reduce problems like flash flooding,” said Masker. Finally, sustainability can also be considered in your finishes and décor. There are many different types of eco-paints on the market now as well as sustainable flooring and furniture.

When planning to build an extension there are numerous ways to make it more eco-friendly. Building an extension with green credentials is an investment, providing long-term benefits in terms of reduced energy bills and increased property value.