Passive Solar Heating and Cooling

PASSIVE SOLAR HEATING & COOLING
and energy saving ideas.

By John Helm


These days all the talk is about saving energy and there are a lot of new as well as old systems to take advantage of the sun for heating and even cooling. Since my years in university I have been aware and have studied the various ways to take advantage of this free source of energy. The problem is that while the suns energy is there to be taken and used for free, the actual ways that we collect it and turn it into a form which is useable are generally not free and sometimes very expensive.

Over the years I have made many proposals to my architectural clients to implement various ideas into their projects. For the most part when the costs came in they resorted to the time tested and much less expensive standard forms of heating and cooling. The initial cost of the equipment can take many years to pay for itself and in the US at least where people tend to move often they don’t consider it a wise investment.

Therefore, in this short article I will restrict my comments to the things that we can do in our existing homes that require little or no costs and then I will discuss a few things we can do in our new homes to maximize the collection of the sun’s energy for heating and turn that around for cooling.

Existing Homes
We will start this little journey at the front door. Do you know that just putting a good door mat outside and a rug inside the exterior doors can save energy? Yes it can. Approximately 80% of the dirt we bring into our homes comes from our shoes. So just cleaning them before entering saves the extra time we would have to use the vacuum cleaner. Taking off the shoes and putting on house shoes or slippers will save even more.

Now I’m going to tell you some things you probably already know but I bet you don’t do them. Since I said no extra expense, I will stick to the things we can do just to maximize heating or cooling and minimize heat gain or loss without spending any money. The windows are generally the major tool here. They represent a hole in our walls when it comes to energy gain and loss. So they need to be managed. Assume you have curtains and better yet shutters that open and close. In the morning when the sun is out in the winter, open the south facing curtains or shutters while keeping the windows closed to let in the solar energy and open the doors of those rooms to the rest of the house. Keep the others closed until the outside air temperature warms up or you just can’t stand having them closed. As the sun passes reverse the process. At night shutter everything up.

If you have a fireplace, close the flue when you are not using it. Heat rises the open flue sucks the heat right out. On the subject of heat rising remember that it will rise to the upper floors on a two story house. If those floors contain the bedrooms, close the door leading to the stairs if you have them during the day or if no stair doors close the bedroom doors. There is no need to heat rooms not in use.

In the summer we reverse the above. Keep the south facing windows shuttered. Open the flue and open second floor windows that don’t face south.

Also keep in mind that hard surfaces such as tile and concrete absorb heat. This function can be used in winter and summer. If you have a tile floor for example expose it to the sun in the winter it will heat up a radiate the heat back out in the evening. In the summer protect it from the sun; you might even cover it with a rug but only in the summer. In the summer we can open all the windows in the night to cool the house and then promptly close them in the morning.


New Homes and Remodels
The most cost affective way to minimize energy use in new homes, when we remodel or make additions is to use the things we would build anyway in a way that is energy use conscious and does not add any or little to the cost. As before we start with windows for natural light north facing windows are great but that’s the worst location for heat loss or gain. They don’t see the sun. So it’s best to minimize them unless we are building an artists studio or they face a beautiful view. South facing windows are the one’s we want with hard surface floors facing them and concrete walls inside the house to absorb the heat to be radiated out in the evening. Skylights that can be opened bring in natural light and when opened in the summer allow the heat to rise out of the house.

Those big south facing windows are great in the winter as long as the sun is out; they are not so great when it’s not. So we should make some provision to cover them and of course they should be double glazed as should all the windows, even triple glazed in harsh climates. And what do you do about them in the summer? In the summer they must be shaded. This can be done several ways. We can shutter them, put up louvers or roll up awnings. Permanently shading them will eliminate their use for heating in the winter so don’t do that. One way we all know is to plant deciduous trees near them. Those trees will shade them in the summer and allow the sun to shine in during the winter as well as provide a nice appearance in the view and the yard.

Fireplaces can be a good source of heat if properly designed using outside air for combustion and some form of providing circulation of the heat generated. Glass doors allow radiant heat to pass while minimize the amount of heated inside air that rises up the flue. In the summer open the glass doors and the flue to allow the heat to flow out. Fans can be placed in the attic at little expense to draw out additional heat.

Let’s also not forget insulation, perhaps the very most important addition. Blanket insulation made of fiberglass is the least costly and in fact adds little to the overall cost. If one objects to the glass fiber there are also natural products made of wood and recycled cotton. Increasing the thickness of walls in wood frame construction allows increased insulation but at added cost though not that much in the overall picture. Another item to consider is using one of the modern house wrap products instead of the conventional tar paper. They seal the walls, but allow moisture to pass from the inside to the outside.

Finally let’s not forget the lighting. Windows, skylights and solar tubes can minimize the amount of lighting we need to turn on during the day. Proper placing of lighting for general purpose lighting as well as task lighting is important to minimize electrical usage. The use of fluorescent light wherever possible can reduce energy use by 2/3rds and as they become less expensive LED lights will bring consumption down even more.

So I have just touched a bit on the overall subject perhaps you, your architect and your contractor will be encouraged to use these ideas and think of more on your own.

Copyright 2009 by John Helm may not be reproduced in any form without the permission of the author.