Considering Passive Design
Lots are getting smaller and the ability to design a house that incorporates passive design is becoming progressively difficult. It has been noted that there are several core factors in the design process that are to be considered, there is orientation, materialistic factors such as thermal mass, ventilation, insulation, shading and glazing to be well thought out. However the chosen lot to build on can make it hard for a designer or architect and will have to work with its given location and orientation. The appropriate attention provided to each of these factors can vary according to the location of a proposed building, for instance a building up north of Australia will require different attention to each of these factors compared building in a more southern climate.
Effective materials for harnessing and distributing that solar energy is appropriate, such as the right window treatments, adequately insulated walls and ceilings, windows, and roofs and high thermal mass materials . Other factors to consider is ensuring that there are no draughts and that all external doors or windows are to be sealed.
Starting from the appropriate floor plan, if possible, it is best to have a decent setback of at least 3m to the neighbouring residence from the East, North and West boundary to minimise the possibility of being in a neighbours shadow and receive maximum solar energy during winter.
The recommended key zones to channel this solar access is into the Living Rooms. The Living rooms should be the first point of contact to receive that winter solar energy only to then distribute that energy to the remainder of the home.
It is important to consider that a room that receives five hours of efficient solar heating on a clear day will have nineteen hours of fluctuating heat loss.
To insulate in one sense of the term is to quarantine. Insulation is effective in reducing the transfer of unwanted sounds as well as thermal energy, providing an adequate amount of comfort within the home and together with maintaining that comfort within the home. Insulation is manufactured in all forms of materials according to its purpose, insulation is made for cavity wall, framed walls, ceilings, roofs, floors and windows.
The right amount insulation is measured on a case by case basis, so as stated before If you live in a naturally ventilated home in the northern areas of Australia, the aim of insulation is to reduce the amount of heat getting in without restricting the hot air escaping. Reflective insulation under the roof and in walls that are not permanently shaded should work well.
High thermal mass materials such as clay bricks are materials that have a thermal lag by holding on to and releasing the heat for longer when it is needed, slab on ground ,if not on the ground consider insulated floors or enclose the under floor space encouraging a connection with the ground temperature. Good passive design uses thermal mass to absorb excess heat from within a house during a summer day and dump it to cool night skies. In winter, solar energy heats up the mass during the day, then it is able to re-radiate that heat into the residence at night. It is critical that thermal mass is well insulated from external temperatures and that it is exposed to winter sun in cooler climate zones.
Windows and Glazing
The glass to floor percentage has a large influence towards achieving your thermal comfort. Glazing is both the biggest source of heat loss and heat gain. It has been noted that the ideal window design is where 30% of your window sill to eave height is where you have should have the top of the windows setback to your eave line. While this is not exactly practical it is important to ensure that your windows are adequately shaded in summer and not overly shaded in winter. Additionally ensure that your windows are not excessive of 30% of you floor area and that they follow the rules of correct orientation.
External shading can provide a path of solar energy to enter your home as well as limiting its amount. The right approach can block up to 90% of the unwanted direct sunlight hitting your windows during summer. There are two common forms of shading to select from, either fixed shading devices such as the continues eaves of your existing roof line, or verandah like shading and there are those that are adaptable to seasonal changes. Fixed devices such as eaves and pergolas are the more common and well known approaches to the provision of shading, however these can be designed to allow the winter sun to enter but exclude the hot summer sun.
There is a lot to consider when designing a passive design, it best to consider these factors thoughtfully before proceeding to the final design. A good solar passive design is achievable (especially orientation and location of rooms) when these principles are established to begin with. It is a common misconception that good insulation and top of the range products will fast track a building to becoming a good passive design building.