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July 31 2008

 Guide to Green Buildings and Saving Energy

So you want to build an eco home (or maybe convert an old building)? We may know about the political pressure to ‘save the planet’, but possibly have little experience of the project planning and technical changes that are developing to address environmental impacts, so here are some hints and tips

Basically, buildings should provide occupants with a comfortable environment that is neither too hot nor too cold and protect them from the elements. When weather conditions change, modern buildings adapt by using air conditioning or central heating systems. They were developed when energy was cheap and plentiful, but as energy costs rise and as the relationship between this energy use and global warming has become more evident we need to look at alternatives. You can now obtain grants to enable you to install these

The UK Climate Impacts Programme (UKCIP) and the Intergovernmental Panel on Climate Change (IPCC) predict that there will be higher levels of winter rainfall and warmer drier summers (although the summers may also be wetter in some regions). It is also predicted that sea levels will rise by between 10cm and 90cm over the next ninety years, with the south and south east of the UK most affected. Whether we agree with these predictions or not, if these are the best predictions available with current data, then we should bear them in mind when making plans to build or adapt a current building.

There are many complex aspects to design, and as a non-architect and non- engineer I will not attempt to give advice on these matters, but current research advises that we should encompass the following:


1. Use building materials that optimise the amount of energy they absorb. These materials include natural stone (like that shown here from Dunhouse), earth and dense concrete blocks and are called the thermal mass of the building (basically the ability to store heat gained passively from the sun during the day and then release it back into the home at night). Getting the thermal mass right reduces the need for other methods of heating and cooling the building.


2. There are four main design strategies that help prevent buildings from overheating in summer, and these are orientation, shading, thermal mass and natural ventilation. The best results will be achieved through a combination of all these strategies

Increased winter rainfall
If the IPCC projections prove to be correct, the UK will be subjected to
increased winter rainfall. There is also concern that the UK will suffer from
more intensive summer rainfall. Recent events (2007) in northern and
central England have revealed the vulnerability of buildings to this.

There are two potential consequences of increased rainfall for the built
environment:

1. Damage to buildings through water penetration
This can harm brickwork and structural elements such as supporting
timbers. Damp can also affect the performance of insulation.

2. Increased flash flooding
As more hard surfaces are constructed, rainwater will pass more quickly from them to the mains sewers. This increases the volume of water in the sewers when it rains and increases the chance of flooding.


Protection from rain is best achieved through sound construction
and good maintenance. Pointing and brickwork should be checked, together with guttering, downpipes and drains. The roof should also be checked regularly, with broken tiles repaired or replaced. For new buildings, further protection to walls can be given by designing roofs that extend beyond the line of the wall.

You can also slow down the journey of the rainfall by having a green living roof, and redirecting downpipe water to water tubs for use in the garden or possibly for washing machines or toilets.

On a larger scale, water can be diverted to areas in the landscaping where it can filter down more slowly, for example, through gravel or other permeable surfaces, down to planting areas. These are called SUDS (sustainable urban drainage systems)

To protect against the risk of flooding, the main design decisions should relate to the ground floors and basements of buildings located in susceptible areas. The Environment Agency recommends extending concrete footings to new buildings and adding a waterproof membrane to the foundations. It also notes the benefits of a raised damp proof course. Wherever possible, ground and basement floors in flood-prone areas should be constructed from water resistant materials such as dense block work, concrete or brickwork.

The Environment Agency also recommends that all meters, panels and sockets are located at least 900mm above ground level, and that drains and sewers should be installed with anti-backflow valves to stop contaminated floodwater backing up into the property.

But what about areas suffering from drought?

Drought
If summer droughts do occur with greater frequency, as the IPCC predicts,
rainwater harvesting and water economy will become increasingly important.

Other ideas include installing taps that turn off automatically, using gravity rather than pumped water pressure for showers, and having spray taps that aerate water to create the impression of water volume.

Heating and Ventilation

Heat (that you are paying for with energy bills) can be lost through the building or through ventilation. Eco-friendly insulation, like Earth Wool,  will help, and ensuring that windows are airtight. The frame of the window should also reduce heat loss (aluminium will allow heat to escape much easier and so would not be very efficient)

A basic form of heat recovery system would involve a fan pull old air out of
the building over a metal plate, and as fresh air is drawn into the building it passes over the metal plate and some of the heat is transferred back inside.

(In an old building, the only solution is to improve insulation and have more efficient heating systems, such as passive solar heating and combined heat and power. Combined heat and power means that the heat generated during the production of electricity is recaptured).

Reduce electrical energy consumption
As well as lowering running costs, reducing electricity consumption will reduce greenhouse gas emissions.

Lighting
The simple way to reduce the need for lighting is to increase the amount
of natural light entering the room. Where rooms can’t be located near
windows and roof lights are not an option, you may want to use sun pipes. Where you do use artificial lighting, it is important to install a low energy type.

You can also install daylight sensors, occupancy detection and switch timers

Appliances
If you are purchasing electrical appliances for your development, you should
ensure that they are A or AA rated.

Waste and Recycling
When building a new home on the site of an old building, the least environmental impact will always be to reuse what you have, asking the following questions:

• do we really need to demolish and replace this building?
• can we re-use or recycle any old building materials
• how can we ensure new building materials have a low environmental impact?

The BRE has published the Green guide to specification which rates building materials from A to C (A having the least environmental impact). However, using A-rated materials will not result in an environmentally friendly building unless it is a sustainable and airtight construction.

It tends to recommend the use of less-processed materials, like slate roofing tiles rather than composite concrete tiles, timber rather than UPVC windows, and timber frame rather than a concrete and steel frame construction.

In addition, at the design stage you can ensure that there is adequate space
for both recycling and waste facilities on site.


Carbon neutral?
There has been a lot of press coverage recently about the ‘carbon neutral’ building, but what does it mean?

The simple answer is that, to be carbon neutral, a building must produce as much energy as it consumes.

This is quite complex and you would need to take advice before construction, but basically, after the construction process, attempt to use fuels other than fossil fuels (like windpower, solar power and underground heat pumps), turn off lights and install those suggested, and use general common sense.


Payback times
Renewable energy technologies are often criticised for their long ‘payback’ time. This refers to the time it takes for the cost savings of producing.

Grants will shorten the payback period, but remember to take into account the fact that our bills from fossil fuels are going to rise and rise before you dismiss renewables as being too expensive because of the initial outlay.

Tax breaks

This isn’t really related to green homes, but in green terms generally you may find these facts interesting! Cycle mileage to meetings is now an allowable expense against your income. Check that your tax code reflects this.

There is also a tax efficient cycle purchase scheme run by the government
that enables employees to purchase bicycles through their employer

Employers can also offer their employees a free or low-interest season ticket
loan up to £5000 per year. There is no tax or national insurance to pay on
the loan, provided the full amount is repaid to the employer.

What about the Ecology of the area?

Shrubs and hedgerows can function as natural breaks against prevailing winds (usually south-westerly in the UK), so reducing ventilation heat losses. Deciduous trees can be planted in front of south-facing elevations to create shade in summer, while still allowing winter sun through as leaves are shed.

Provided brickwork is not compromised, climbing plants can also provide added insulation and weather protection.

If site boundaries need to be well defined you might want to consider a mixed hedgerow rather than a fence. This will absorb CO2 and provide excellent food and shelter for wildlife. It is always be better to choose plant species that are native to the area if you do decide to take this option.