Eco home part 1: keeping warm this winter

Natural medicine, vitamins and nutrition are some of the ways to keep colds and flu at bay in winter. Another way is the often forgotten old housewife’s recommendation to keep warm, and it has proved its merit over the centuries.

Keeping warm with clothes is one option, the other is to warm your house. That said the day of an oncoming flu or cold has often pointed out to us just how cold and draughty our home can be. The natural recipe of making sure one is snug and warm during winter within our four walls, has been forgotten. How can we ‘avoid that our house catches a cold” clocking up not medical bills but electricity bills?

our homes are not designed for warmth

Most homes in South Africa favour one season only, the Mediterranean to tropical climate. Many homes are therefore poorly designed with regards to heating and cooling. In fact, due to infinite and cheap electricity supply, builders and architects alike have often dismissed traditional building layouts and insulation features for the benefit of good looking designs, large open plan living areas double volume spaces and most of all low building costs.

To avoid catching a cold inside, one has to quite simply keep the cold out of the house and the warmth inside the house. Not really a secret, but a science. Once these scientific principles of how hot and cold air move around are better understood, keeping warm is really simple and saves money.

Natural energy patterns move hot and cold air around inside a house. We can’t see it, but we might feel it. Any home is practically a microclimatic zone and features natural air movements through convection, conduction and radiation. These ‘In-house weather” patterns collaborate in many ways:

stop the chimney effect

The classic ‘chimney effect” is hot air rising and cool air falling. We all know that a balloon filled with warm air will rise. Since hot air expands and thus has more volume than cool air, it is lighter and therefore rises up. This natural chimney effect is no different in a home and is more prominent in a double volume or double storey home. Any warm air downstairs rises either directly toward the ceiling or upstairs leaving the occupants below in the cold despite the hard working heater. By moving up a draught is created which in turn draws lower and cooler air. If you stick your hand under a door with a gap, you can feel a cold draught coming in.

Some of you might now wonder about a fireplace chimney? Up to 75% of the heat generated by an open fireplace is drawn up through the chimney by the ‘chimney effect” in the same fashion any heat would rise. And it gets worse: an oxygen hungry open fire will draw so much more fresh oxygen from wherever it can, a crack in the window, a gap under the door. The result is a constant supply of fresh cool outside air into your rooms. Warmth has little chance to build up. The place in the whole home that really feels warm is only right in front of the fireplace.

The remedy for convection:

• close doors to upstairs unless you want the warm air to flow upstairs to the bedrooms
• reverse ceiling fans to bring warm air which has risen up to the ceiling down again
• close doors to unused rooms
• close up the chimney of an unused fireplace for there is a perfect ‘chimney” to draw up any warmth from the home. One can use a chimney balloon.
• ensure all windows in the home are closed
• cover vents during colder times
• eliminate cracks and gaps in doors and windows using weather strips and door brushes
• close any holes in the ceiling, watch out for unused down-lighter shafts.
• close open keyholes

use insulation to increase resistance

In scientific terms conduction is the transfer of thermal energy between neighbouring molecules in a substance due to temperature gradient. It always takes place from a region of higher temperature to a region of lower temperature, and acts to equalize temperature differences. In home terms, warmth that builds up just below our ceilings, because of the ‘chimney effect”, will then move through the ceiling boards to equalize with the colder temperature that sits in the attic. How quickly the warmth will get through the ceiling boards and into the attic depends on the resistance of the material, the so called R-value. Like our bodies which need fleece and thick warm cotton jumpers, our homes also need insulation to increase the R-value of the materials that separate colder from warmer areas. Remember, warmth will always try its best to escape to colder regions.

The remedy for conduction:

• Ensure there is plenty of insulation above all ceiling boards, the thicker and fluffier the better
• Close curtains on windows and glass doors
• Close French or American shutters outside your windows
• Plaster walls
• Install double glazed windows

use the greenhouse effect

Radiation is when a hot object emits electromagnetic waves. These short waves deposit their energy by heating materials which in turn then emit the energy as long waves in form of heat. The biggest and most effective radiator we know is the sun. Quite different from many other countries, winter sun here in South Africa is not only a common sight but also a relatively long one: our shortest day is 10hrs long.

Have you noticed that your usually super hot car in summer is now just so snug and warm in winter? The heat building up in your car is classically called the greenhouse effect. And why not harvest it in one’s home, too? All we need to do is capture the warmth that the sun shining through the windows onto our floors and furniture has caused. We can harvest the warmth these materials give to the air in our home as long as there is no way for it to escape through convection or conduction. Ever heard of a winter garden? On a cold but sunny day, a well constructed winter garden with open doors into the rest of the home can act as a great source of warmth for the whole house. Of course, not only a winter garden can contribute warmth, but any closed window pane facing the sun.

Remedies to capture radiation:

• Let the sunshine in!
• Open curtains and blinds, but not windows
• Cut back trees which cast shadows on northern windows
• Rather have deciduous trees near your house and windows than evergreens as these allow sunshine to come through your window when you need it in winter
• Have a well insulated winter garden or a conservatory
• Do not drain hot boiling water from your pasta or potatoes into the sewerage. If you keep it in your sink it will radiate some warmth into your kitchen.
• And last but not least: sit by the window in the sun.

Remember that these three natural forces work hand in hand with any artificial heating method, such as wall panels, under-floor heating, fan heaters etc. In fact they make your heating system more effective and therefore more environmentally friendly by maintaining the warmth where you want it. Well managed, together these ‘weather patterns” are certain to keep any cold at bay and save you not only money on utility bills but possibly on medical bills as well. Always keep in mind, if you give warmth the chance to move out, your cold will move in!

When it comes to summer, think the other way round: let the heat escape from your home! Just before summer, I’ll let you know how to keep your cool!

By Martina Gluckman

Martina is a residential eco auditor and an expert in turning existing homes into energy and water efficient households whereby substantial savings on utility bills and carbon emissions can be achieved. She teaches residential eco-auditing through environmental education leader Global Carbon Exchange. Her company ‘Tiptoe – leave no footprint” is an eco consultancy which specialises in the residential sector offering energy-, water- and eco audits. The service is designed to help identified and eliminate inefficiencies in a home, and promote change to a greener more sustainable lifestyle for the owner.