Building an eco-friendly house may be simpler than you thought

Thankfully, building green has cast off its once hippy image and now is widely used and incorporated within architecture, helped by spiralling energy costs and increased ecological-awareness. With the introduction of homes now coming with an energy rating,building green is not only planet friendly, but is a major marketing tool should you ever sell your property.

There are now numerous natural avenues to wander down if you’re building from scratch or renovating. One of the hardest things about building an eco home is deciding exactly what ecological factors are most important to you.

• Do you want low energy bills?
• To create a natural environment or just want a smaller carbon footprint?
• Or just what is the most ecological and environmentally friendly way of building?

This is where it gets impossible to quantify, and it’s often simpler to strive to keep the embodied energy of your home, its energy use and environmental impact as low as possible.

Some of the most well-insulated building techniques – structural insulated panels (SIP’s), insulated concrete formwork, etc – score highly on low energy use and high insulation, but use manmade materials, with a high embodied energy. Below we will explore a range of natural building techniques and materials.

Planning your house

The most important consideration when planning your green build is design, and using your plot to make maximum use of natural resources. Positioning and layout are crucial: for example, to make the best use of the heat from the sun, make sure your house sits on a north/south axis for maximum solar gain, which could cut around 5% from your heating bills. Existing trees, hedges and hills on site can be used as protection from wind and rain so your house won’t have to work as hard to keep the cold out. Once you are ready to draw up plans, make sure it’s done with the help of an experienced green architect or consultant who can advise you how to build an airtight, thermally efficient building, on the best possible orientation.

Techniques and materials

Man-made building materials such as bricks and concrete have a high embodied energy: that is, use a great deal of energy in production, and even more once transport to site is taken into account. If used in abundance, they will give your house a large carbon footprint before it’s even built. By using local natural materials, you’ll not only have a low carbon footprint but a healthy living environment, too. There is a huge variety of materials and methods to choose from, depending on the final look you are trying to achieve, the amount of work you want to do yourself and what materials you can find locally or from a reputable source.

A more sophisticated technology, this enables collected water to be used  inside the house, directing rainwater from the roof (first check your roof is clean and not made from toxic metal or aesbestos) into an underground storage tank installed close to the house. From here, a submersible pump supplies the toilets, washing machine and dishwasher on demand.

There are two types of system: a gravity-fed version that needs a header tank, or a direct system that pumps filtered rainwater straight to WCs and appliances. The latter will deliver water at mains pressure, but has the disadvantage that if your electricity supply is cut for any reason, you’ll be left without a rainwater supply, too. With this sort of system it might be wise to leave one toilet on mains water, just in case.

There are three sizes of domestic tank – 3,500 litre, 4,700 litre and 6,500 litre –  your selection will depend on the size of your roof, average local rainfall and the household’s estimated consumption.

Is the water clean?
Before entering the tank, the water first passes through a filter to remove any surface debris, then a water-smoothing inlet so it doesn’t disturb the sediment at the bottom of the tank.

The tanks are designed to overflow two or three times a year into a soakaway or storm drain to sweep and scum from the surface, which also cleans the filter. And to avoid drawing surface scum into the system, water is drawn off via a floating filter from just below the surface. As the water is kept dark, cool – below 18°C – and well oxygenated, no harmful organisms can grow.

In remote areas, rainwater can be upgraded to fully drinkable standard using non-chemical ultra-violet sterilisation.

What happens in a drought?
During dry spells, when the rainwater in the tank gets low, a sensor is activated and either mains water is drawn in to top up the tank, or the system switches over automatically to mains water supply.

A one-way valve ensures that the liquid in the tank cannot back up into the mains water system.

What are the regulations?
Building Regulations cover the installation itself, siting of the tank and pipe runs. You are required to use separate pipework for the rainwater-fed appliances, using a different colour or otherwise making them easily identifiable, and you must inform your water supplier if your system uses back-up from the mains.

Planning permission isn’t normally required. In fact, some councils suggest that including a system as part of a new home scheme can help with planning applications.

Installation and maintenance
Systems can be retrofitted in existing buildings, but it’s far easier to fit them when building a new property or extension, as the installation of the tank and piping won’t cause too much disruption.

According to Ecozi, fitting a system in a new build is pretty low cost, as most of the tasks required to install a rainwater harvesting system – digging drains, installing plumbing, etc – have to be done anyway. The largest additional task is excavating the tank hole, the cost of which will depend on what you plan to do with the spoil.

The tank itself is made of very strong recycled polyethylene and is typically guaranteed for 15 years, but should last indefinitely. Being underground, it is not affected by frost. The electronic control system and pump are typically guaranteed for two years.

As for maintenance, the only regular chore you’ll need to stay on top of is to check the filter every quarter, and flush it through with water from your garden hose.

How much will it cost?
The outlay for the initial system will be between £2,000 and £3,000 for a good quality domestic version, depending on the size of the tank.

As pumping costs are estimated to be less than 10p a week, the UK Rainwater Harvesting Association claims that the payback period on domestic systems is between 10 and 15 years. The good news for those looking to install a system is that, as water bills are expected to rise 10% a year for the next five years, the payback period could be much shorter than that.

Green roofs offer an attractive, eco-friendly way to cover your home

Green roofs are not only attractive and vibrant eco-havens for plants and wildlife: they are are also superb insulators and heat regulators.In hot weather they help to cool the room below, while in winter they provide superb insulation and thermal mass, which by keeping heat in could lower your home’s energy bills considerably.

Their boost to energy performance means that green roofs can help you to meet the environmental targets of the Code for Sustainable Homes if you’re building a new home. Green roofs have an additional extra-important role to play when it rains as they act like a sponge to retain water, reducing the likelihood of flooding.

What’s more, these bio-diverse micro-environments for wild flowers, bees, birds and bugs can only take a few simple steps to install.

To all intents and purposes, a green roof is a carpet of vegetation that sits on a conventional flat or pitched roof. The carpet is made up of lightweight soil, planted with sedum, grasses, lichens and moss over layers of shale, gravel and crushed brick.

Intensive v extensive
Intensive roof
This is the typical ‘roof garden’ that usually comprises a thick soil, where a wide variety of plants, lawn or even trees can be planted. These usually require regular maintenance and need an artificial irrigation system for the plants to thrive properly. Not surprisingly, they are heavy and more usually found on weight-bearing concrete roofs of commercial buildings.

Extensive roof
This is the sort of green roof more likely to appeal to self-builders. Primarily installed for visual appeal and to reduce the environmental impact of the building, it is based on a shallow layer of soil and requires very little maintenance. It doesn’t create a huge structural strain on your building and is generally planted with grasses, mosses and alpine species known as sedum.

Both flat and pitched roofs can be suitable sites for a green roof. Most residential buildings can support the weight of an extensive green roof with little or no structural alterations, or you could even add one to your garage, garden or bike shed. Simple lightweight systems weigh between 60-150 kg per m2 – but remember that this will increase when the plants and earth are saturated with rain or snow.

Speak to a design professional before starting to work out the weight that your roof can take. If your roof pitch is more than 20° you will also need to seek professional advice, to make sure that the green roof does not slip.

Nature watch
Alpine sedum plants – used on many green roofs as a base for the growth – are used to living in harsh elevated conditions and thrive all year round with little maintenance.  To attract more wildlife, sprinkle in some wildflowers adapted for low-nutrient soils such as cowslip, rockrose, harebell, hawkweeds and thyme, associated with limestone and chalk environments. In no time, you will find your roof a home for moths, beetles and the many species of bumblebee.

If you’re a real wildlife lover, you could go one step further and create a ‘brown roof’, by incorporating crushed bricks and stones – perhaps left over from your build – which can help recreate natural habitats for birds, as well as insects. In fact, in urban areas, green roofs have been hailed as central to the reintroduction of birds, including the threatened black redstart.

The basic principle of a GSHP is very simple one, and the technology has been around for more than 50 years. Here in the UK, the temperature of the top 15 metres of the earth’s surface maintains a relatively constant 12°C throughout the year, due to the large thermal mass of the ground – that is, it retains the warmth of the sun.

GSHPs extract natural warmth from the earth to heat your home and provide plenty of hot water all year round. How? Simply put, a ground loop of polyethylene pipe is laid in trenches in your garden or land, about 2m deep. These loops are horizontal, vertical or a ‘slinky’ coil variation. The length of the ground loop depends on the size of your home and the amount of heat you need.

The pipe is filled with a mixture of water and anti-freeze, which circulates to absorb heat from the ground. The fluid then passes through a heat exchanger in the heat pump and the low-grade heat from the passing water is extracted and concentrated into a higher temperature. This continuous process brings heat to your radiators or underfloor heating.

Preparing the ground

If your garden is big enough, horizontal ground loops are the most cost-effective method. Where space is tight, vertical boreholes, including vertical ground loops of 25m to 150m deep, are a good option, although they’re expensive compared to horizontal loops.

Because of the disruption installation entails, ground source heat pumps are best suited to new build projects, as long as plans are included in the initial building design and installation is scheduled carefully with any other external works you have on the go. The excavation, installation, backfilling and commissioning of a typical GSHP with good ground conditions should take about three or four days. Costs range from £8,000 to £12,000, with new builds cheaper than retrofits.

This can be partially offset through the Department for Energy and Climate Change (DECC) Renewable Heat Incentives (RHIs), which are planned to replace the now-defunct Low Carbon Building Programme. Expected to be launched in April 2011, RHIs will provide financial returns through payments linked to the amount of heat you generate by renewable means.

Air source heat pumps

ASHPs work in a similar way to GSHPs – this time converting energy from the air into heat – but not offering quite as much efficiency as GSHP. Generally ASHPs are faster and more straightforward to install. There’s no need for groundwork preparations, or miles of piping – just a unit mounted on an outside wall, which makes them a better bet for retrofit. A basic ASHP system can often be installed in one or two days.

One problem with ASHPs is the rather large box attached to your house, which can be noisy as well as unsightly. But this is changing. “Modern systems use advanced, inverter-driven compressor technology from the commercial air conditioning sector to produce high efficiency at low noise levels, says John Kellett, general manager of Misubishi Electric Heating Systems. “Models such as Ecodan run the compressor and fan when required. This helps make the unit efficient and keeps noise to a very quiet 49dBA.”

Payback

With such substantial costs and time involved, are heat pumps really worth the effort? “That depends on where they are being installed and what fuel they are displacing,” says John Barker-Brown. “For a new build people are reporting a seven-to-ten-year payback for a GSHP compared to an oil-fired system. With the proposed RHI the payback would be a lot quicker when replacing all fuels.”

When retrofitting, high-temperature renewable heat pumps can bring cost savings (depending on your personal domestic average use) of anything up to £750 to £1,000 a year. Installing a GSHP can also save 4.5 to 5.5 tonnes of CO2 per year.

ASHPs such as Ecodan deliver between 2.0 and 2.33kW of renewable heating energy for every 1kW of electricity used, can cut emissions by up to 50 per cent over gas boilers and reduce running costs by over 30 per cent. Even greater savings are possible in some retrofit applications with older gas or oil boilers.

What’s more, they can help new homes achieve Level 3 and 4 of the Code for Sustainable Homes.

Beneath the surface the ground maintains a relatively constant temperature all year round, even in winter. A ground source heat pump can extract this heat, by circulating a water/antifreeze mix through pipes buried in the ground, and then transfer it to heat water for domestic or space heating use.

Ground Source Heat Collection Methods include:

• Borehole, Closed Loop, where the heat transfer fluid is circulated through pipes set in a borehole, up to 100m deep.
• Horizontal, Closed Loop, where the collection pipes are laid horizontally some 1.5m to 2m below the surface.

The benefits…

Heat pumps have been in regular use for many years; over half a million units are operating worldwide and tens of thousands now being installed each year as customers recognise the many benefits that include:

• Space heating costs reduced by up to 50%
• Proven technology, which is easy to install.
• Reliable, low maintenance systems.
• Low installation costs.
• Grants available to help initial installation set up costs.

People been building homes using straw for centuries, thanks to its low cost and ready availability. There are two mains ways to build: using the bales to build load-bearing walls or as a highly insulating infill. When used to bear load, the bales are placed on top of each other in a stretcher or running bond with long wooden pegs driven through to connect layers. When used as insulation, the bales infill the walls of a timber frame structure. In both cases, walls are rendered with lime, as it’s flexible enough to cope with minor movement in the bales, and lets vapour pass through.

Properly built, straw bale houses are fire-resistant, waterproof and super-insulated. A modern version of this old technique is Modcell prefabricated structural panels, comprising a timber frame filled with straw bales, compacted, reinforced and protected with a render coat or timber fascia. They are made in ‘flying factories’ – the company works with local farmers to identify a nearby source of straw to reduce transport emissions. Panel sizes vary to suit project requirements, and as you can imagine are extremely heavy – up to 1.4 tonnes each – so you’ll need to get professional help for correct safe installation.

Solar thermal hot water (STHW) systems are one of the simplest and most widely installed of the renewable energy systems available, transferring the abundant energy from the Sun into hot water, even in winter!!. In the UK some top up from a secondary heating sources, such as your existing boiler or immersion heater particularly during the winter months, however, a correctly sized and installed solar thermal system should still provide up to 70% of your annual hot water requirements.

Many tens of thousands of solar thermal hot water systems are currently in use in the UK and the numbers continue to grow as more and more people recognise the many  benefits including;

• Quick and easy installation.
• Free generation of hot water, saving up to 70% of annual hot water costs.
• These are simple, reliable, low maintenance systems offering long component lifetimes.
• Government Incentives with Grants available
• A variety of installation methods are available including integration into roof.
• Low installation costs.

Quick Facts about Solar Photovoltaic Panels

HOW LONG WILL IT LAST?

The solar panels have a life expectancy of around 50 years with most systems having a 25 year warranty and little or no maintenance required.

WHAT ARE THE SAVINGS?

Savings can be considerable and a basic 2.4 kWp system could provide around 40% of a household’s annual electricity. The more it generates the more you save as any excess electricity can be sold back into the national grid.

Quick Summary…

• A basic 2.4kWp solar system could provide around 40% of a households annual electricity
• Reduce your carbon footprint as solar PV is a green renewable energy
• No maintenance costs with a life expectancy of around 50 years
• Qualifies for the Feed in Tariff (FIT) so providing an excellent return on investment