by Douglas Barnes
I am currently in the process of designing a home for myself and my wife. Living in Canada, the number one priority is warmth. To solve that problem, we must focus on energy capture and energy storage.
To capture energy, the house will be oriented with the long side facing the sun. This side will be fenestrated to allow the entry of solar energy from the sun (which, strikes the Earth with over 950 Watts per hour per square metre before any loses come into play). The energy needs to be stored once it has entered the home or the house will heat up nicely in the daytime but become quite cold in the evening. In this case, the main storage will be a monolithic concrete slab floor. In addition to this storage, there will be a masonry fireplace, whose massive brick structure will hold energy, and earthen or lime rendering of the walls will also help.
Windows are good. Too many windows are bad. So, fenestration will be reasonable. We will match percentage of window area with our latitude. We’ll be building in Southern Ontario at about 45o north latitude, so we’ll have around 45% window area on the southern wall. Too many passive solar homes in Ontario have nervously designed what amount to glass walls on the south side thinking that if a little is good, a lot is better. The result is over-heated homes. While there are some who might not mind 30oC temperatures inside in January, they certainly don’t like the over-heating that will occur at other times of the year.
The Canadian Housing and Mortgage Corporation recommends making thermal mass (the dense material that serves as heat storage – concrete, brick, and mud in this case) be around ten times greater in area than the area of sun-side fenestration.
General layout of the rooms recognizes at what times the rooms are used during the day. The first place people go in the morning is the kitchen. It therefore makes sense to place the kitchen on the southeast side of the building (northeast if you are in the southern hemisphere). In this way, light and solar heat is available first thing in the morning. From there, other rooms follow the sun according to the usage of the room. The exception is the dining room which is placed next to the kitchen for practical reasons.
With this information, it is possible to design a building that performs brilliantly from an energy perspective. However, there is no guarantee that the house will be even remotely livable inside. To make the home a place that I actually want to live in and keep for the rest of my life, I am using Christopher Alexander’s A Pattern Language to design the home.
Another advantage to the passive solar layout is that it creates a nice pattern in the home. A long, thin home has a series of rooms one after another. This helps create privacy in the home and avoids giving the house an overcrowded feeling.
In too many modern homes these days, visitors immediately have full view of the private areas of the home as soon as they enter, and sometimes as they approach the main entrance. There needs to be a gradient of intimacy from public to private areas of the house.
The interior space must have a natural flow that takes into account the uses of the space inside. Hallways and corridors have been avoided as much as possible. Rather, movement flows through rooms making some areas very social and inviting to people moving through the building.
The common area of the home is at the heart of the building that intersects with all the major traffic flows throughout the home.
There is a sequence of seating spaces in the home that offer different levels of intimacy. The living room has a main seating area that is very social. It’s on the main path through the home, in a sunny place, and centrally located. Just off this main space are two other seating options ranging from semi-private to private. There is also a sunny nook off the kitchen. An additional seating space will be available on the second floor (which is currently being revised).
While this does not include every pattern I used in the design, it highlights the main ones that had the most influence in guiding the layout of the interior spaces.
1. The optimal thickness for thermal mass storage is 4 inches thick. Any thicker and diminishing returns start. If it is too thin, it will heat up and cool down too readily rendering the mass less effective. (For example, tile on subflooring heats up and cools down so fast as to have no appreciable effect in storing energy.)
2. This is Bill Mollison’s rule of thumb, and I have checked it out with a local architect and friend, Steve Hilditch (hilditch-architect.com), who has designed passive solar homes. Steve agrees that Mollison’s ratio is appropriate for this area.
3. I have a number of friends that have built many homes for themselves in the same area. After each one is build, they find that the house was not what they really wanted, so they sell and build a new place, hoping that it will be the right one. The error is that the layout of the home was not approached with a recognition of what problems one faces in designing a space. For example, when designing the entrance, it needs to be readily apparent what the entrance is; there needs to be a transition from the inside to the outside; and there needs to be some sort of an entrance room that creates a public space for visitors that is separate from the private areas of the home. This is just one example of many problems in design that must be addressed in the layout of the house.
For more design information, please see Designing a Livable Passive Solar Home