Sustainable Housing Group
Home Last updated: 23 March 2009 |
You are here:Home > Housing The Aberdeenshire Environmental Forum Housing Group exists to promote an “eco-friendly” approach to housing and planning. Our aims are firstly, to create a market for greener housing by informing the general public of the benefits. We aim to promote issues such as energy saving within existing homes as well as in new developments and water conservation in the home. Secondly, we aim to influence planners and developers to adopt a more sustainable approach to development, not only looking at the positioning of new developments, but also the materials and technologies involved in their construction. Comparing Insulation Values The basic principle of heat flow is that it travels from areas of higher temperatures to lower down a gradient like water flows down a hill. When it meets a solid material it travels through that material by conduction. Some energy is reflected back by the surface. Most insulation works by reducing the conduction. Heat does not travel through small pockets of air as well as it does through dense solid materials, so most insulants incorporate lots of air and are therefore relatively light. Some work by also reflecting the energy. Conductivity Most data given on thermal properties is given in terms of their Thermal conductivity k or ? Units W/mK (1 Watt =1joule/second) This represents the amount of heat or thermal energy in Watts that will pass through 1m2 (one square metre) of material 1m thick when there is a temperature difference of 1K between the faces. (Within normal temperature ranges assume 1K is similar to 1 degree centigrade)  The higher the conductivity the faster heat will flow through the material Sometimes the resistivity (r) is given (just to be confusing) Resistivity is the inverse of conductivity i.e. 1/k Units mK/W (watch those units) Resistance Units m2K/W Is the resistance to the flow of heat of a given thickness of a material. This is obtained by multiplying the thickness by the conductivity - the higher the resistance the slower the heat transfer. For insulation purposes the higher the resistance the better. ‘U’ Value; Thermal Transmittance. Sometimes rather misleadingly insulation packages give ‘u’ values which is not strictly correct. Units w/m2 K This is the inverse of all the resistances of all the materials and surfaces of your wall or roof (say) added up. For example, the resistances of the external surface+slates+felt+sarking+cavity+insulation+plasterboard+ internal surface divided by 1 So in brief when comparing insulations
You don’t have to play the Generation Game The latest ‘must have’ is your own mini wind generator whizzing round giving you loads of free electricity. You can buy them from one of the leading DIY stores, and even David Cameron, the leader of the Conservative Party, has one on his house in London. The theory is that you produce electricity from the wind – a renewable source – instead of it being made by the burning of fossil fuels which releases carbon into the atmosphere. Not only that, but you don’t have to pay for the electricity either and can save money into the bargain. Sounds great in theory, but the wind would need to blow constantly at 12 metres a second, or around 27 miles per hour, to give a 1kW output from one of these domestic wind generators, saving you a mere £60 a year in electricity costs. Try driving your car at 27 m.p.h. and stick your hand out of the window and see just how strong the wind would need to be! It is far better to consider conserving energy rather than creating more to use! If the wind were to blow around your house constantly there would be greater conduction of heat from the walls, roof and windows, and through draughts. Make sure your insulation is sufficient, and this does not mean just up to building standards. Our standards fall well below those in other northern European countries, and it is about time that our politicians accepted the fact that Scotland is indeed a very cold country in the winter and cannot just be lumped together with the warmer southern parts of England and Wales. Put another layer of insulation in your loft – after all, heat rises and this is where there is greatest loss. See how quickly the snow melts on the roofs of some new houses during the winter. Open the curtains on south-facing windows in the daytime and close all curtains as soon as the sun goes down. Turn down the thermostat on your central heating. After all, it is very unhealthy to go from a hot house into the cold outside air – you can always wear something a little warmer in the house to be nice and cosy. Don’t forget to switch off the radiators in unused rooms. Reduce the temperature of your hot water by a couple of degrees, and as the adverts say, use your washing machine on a cooler programme. In the kitchen, find out how much water you need to boil in the kettle to fill your teapot and fill it to that each time. Boil just enough water for a mug of coffee, never just fill the kettle and switch it on. Open the fridge door as little as you can, and make sure food is cold before putting it in the fridge. Defrost frozen foods in the fridge, and let them do the cooling! When cooking, use a steamer and steam your green vegetables over the pan your potatoes are boiling in – this will save you using another hot plate – even if you did this each time you cooked in a year, you would probably save the energy you could expect to ‘make’ with your wind generator in that year. And then of course, there are the energy-saving light bulbs. These use a fraction of the energy used by conventional light bulbs – a lot of their energy goes to making heat. Get used to turning lights off in empty rooms, and don’t leave appliances on standby. Most of them use almost as much energy on standby as they do in use. We tend to think now in terms of saving the planet by reducing carbon output, but on a personal level we can all make good financial savings too. And save ourselves the expense of buying a mini wind generator too! |