Home Design that Makes Solar Sense 0

Riverbend Passive Solar Home

Riverbend Passive Solar Home

People do some strange things.  Like building a house that’s well insulated against the winter cold but shuts out the sunshine – the sunshine that warms up everything it touches.  Then adding a big heating system to keep the house warm.

Whatever happened to common sense in home design?  Why not have windows to invite in the warmth and light of the sun in the winter when you need it?  Then shade them in the summer so your house stays cool without needing an air conditioner?  Does this make sense to you?

Passive Solar Design

This idea, called passive solar design, has been around for ages but most people have never heard of it.  It’s called “passive” solar because it doesn’t need any solar hardware, like solar panels, to make it work.  It’s all in the design of the house, a design method that can save you up to 70% in energy costs – for heating, for cooling and for lighting.

How It Works – Window Design

So how does it work?  The idea is to let the sun shine into the house as far as possible all day long during the cold winter months.  The result of accomplishing this?  Your house will be at room temperature when it’s minus 30 degrees Celsius outside, just from the sun shining into your home!  I know, because I live in such a house and that is what happens.

My Passive Solar House in January

My Passive Solar House in January

This is how it’s done.  You make the long wall of your house face south (unless you’re in the southern hemisphere – then you want to face north).  Put plenty of energy efficient windows, that are manufactured for solar gain, on that south wall.  You don’t need to overdo it.  Take the area of the south facing glass and divide it by the floor area of your house and multiply by 100 – this gives you your percentage of south glass.  The ideal is to have this somewhere between 5% and 15%.

Passive Solar Home at the Winter Solstice

Passive Solar Home at the Winter Solstice

In the winter the sun is low in the sky and shines directly into the home as you can see in this 3D view of a passive solar design at the winter solstice.  All south facing windows are completely unshaded and the sun will shine directly against the back wall of the south facing rooms.  On sunny days, this will give you enough heat to totally heat your home.  However, the days are short and the nights are long in the winter and the sun doesn’t shine every day.  For those times you will need some kind of heating system.

Passive Solar Home at the Summer Solstice

Passive Solar Home at the Summer Solstice

How It Works – Overhangs

In the summer the sun is higher in the sky and the roof overhangs prevent the sun from shining into the windows on both levels.

It looks like the sun is shining into the taller windows on the lower level but, due to the depth of the window opening, very little light actually enters the room.

How It Works – Thermal Mass

Passive solar energy is so effective that you need heat absorbing materials in the southern rooms of the house to store some of the heat from the sun.  This is partly to keep the house from getting too hot  and partly to store heat for overnight so that the indoor temperature drops more slowly.

It’s hard to imagine that the temperature inside the house would get too hot on a minus 30 day with only the sunshine for a heat source, but we actually had a chance to experience this in our own home.  We were building our home during the early part of the winter and were working inside on the drywall on a cold, sunny December day.  The fire in the woodstove had gone out hours ago and we had no other heat source but it got so hot in the house we had to open the windows and doors.  This system seemed to work too well!

The next year we were sitting at our kitchen table on another sunny December day and noticed that we were perfectly comfortable – no need to open windows this year.  That’s because the home was finished and now included heat absorbing materials called “thermal mass” in passive design jargon.  Thermal mass can be something like a concrete or tile floor or brick or stone facing on the wall where the sun will shine on it.  The amount of thermal mass you need depends on the south facing window area that you have.

Stone Thermal Mass Wall in the "Island Rose" Passive Solar Home, designed by Suncatcher Solar Ltd.

Stone Thermal Mass Wall in the "Island Rose" Passive Solar Home, designed by Suncatcher Solar Ltd.

Use a Solar Friendly Floor Plan

Once you’ve gained and stored all this free solar energy you want to make the most of it by having an open floor plan that allows the warm air to circulate throughout the house.  Use ceiling fans if you have cathedral ceilings and leave your room doors open unless you want to close some of them, to keep your bedroom cool, for example.

Passive solar design makes perfect sense to save cents whether you are in a cold or a warm climate.

Interested in a Passive Solar Home Design?  Contact Suncatcher Solar for a custom design or a Ready-to-Build plan.

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