Simple modifications to existing homes can help reduce greenhouse gas emissions Derek Wrigley explains.

If you want to reduce your household costs and greenhouse gas emissions, the key is retrofitting.

But what does this mean and how does it help?

Derek Wrigley, the author of Making Your Home Sustainable, explains:

What is retrofitting?


It is a way of modifying an existing house to take advantage of the abundant natural energy which is all around us but insufficiently recognised by homeowners and, unfortunately, most builders.

A retrofitted house can produce very significant and worthwhile savings in annual running costs.

Why should people retrofit their homes?
1. To reduce electricity usage as much as possible unless it comes from a green renewable source. The installation of Photovoltaics (which converts light into electricity) is the best way - I pay no electricity bills.

2. To save all rainwater on site and re-use it as much as possible before its release to drainage systems. Install tanks, (but) this does not stop flow to our rivers, it only delays it.

3. Install a vertical buoyancy air-flow system to eliminate the need for airconditioning - it's much cheaper, more effective and less polluting.

4. Install southern reflectors to southern windows to heat cold, southern rooms in winter. Up to 7kWh of heat and glorious sunlight can be acquired every sunny day in a well-designed house.

What are your tips to retrofitting a bathroom to reduce water consumption?

Train your fingertips to reduce flow, (you can clean your teeth in an eggcup-full of water). Install low-flow shower heads, dual-flush toilet cisterns or modify the cistern mechanism to supply only what is necessary - easy.


What household items can we source greywater from?

You can source it from wash basins, showers and washing machines. Avoid dishwashing machines unless outflow is captured safely - care is needed.

How can we identify which solar hot-water system is best for our style of home and our needs?

The usual black plate absorbers (of solar energy) required optimal placing in regards to the sun's path during the day, but the evacuated tube absorbers allow a little more flexibility and can be more effective.

The latter is more frost-resistant but is more expensive. The heat-pump systems are much more flexible as they absorb their heat from the surrounding air and can be placed indoors, so do not affect roof designs. They are, however, not quite as efficient in their use of electricity, but nevertheless are effective converters of ambient heat into useful domestic heat.

What is solar access, what are the benefits and how can homeowners increase it?

It is the ease of access of solar radiation to a house or building so that the energy impinging on it can be used in an effective way.

Trees and other buildings can block solar access and most buildings up to recent times have not been designed efficiently so that radiation can be effectively used in the house.

This includes daylight, sunlight (psychological value), sunlight in the form of infra-red heat energy and ultra-violet radiation, which can be used to purify polluted water.

What are the options for shading our homes and keeping them cool in summer and warm in winter?

Good orientation of the main rooms is an essential start. External shading of sunlit windows is much more effective than internal shading measures such as curtains and blinds.

External shades should prevent infra-red heat radiation from reaching windows but should permit daylight to penetrate the window so that electric lighting is not required in the daytime. Such shading should be adjustable to shade in summer and permit the winter heat radiation to pass through.

Fixed eaves that are good in summer are often ineffective in letting the heat through in winter, so northern eaves must be adjustable.

East and west windows require more careful design as the sun is lower in the sky.

What are "silent consumers" around the home?

Unnecessary lighting which is not being utilised, stand-by lights on appliances, clocks on ovens and microwave ovens; opaque external blinds shading the windows in winter causing the electric lights to be on inside.

How important is insulation in reducing energy usage and how can we determine which type of insulation is best for our home?

Insulation is essential in winter to prevent expensive heat loss from inside to outside and vice versa in summer.

Bulk insulation (soft and fluffy) is best to resist heat flow (by conduction) through walls, floors and ceilings and reflective insulation is better where radiant heat is flowing (up or down).

Reflective foil, however, needs an air space on the shiny side if it is to work effectively and horizontal foil (shiny side up) over the ceiling can be ineffective because dust settles on top.

* Making Your Home Sustainable: A Guide to Retrofitting by Derek Wrigley is published by Scribe, available online.