News
Passive House
Passive house, otherwise known as PassivHaus. Originated about 3 decades ago in Europe. Based upon the premise that adopting a few key design principles can enable the creation of buildings with healthy, dry indoor spaces that require little or no heating or cooling.
Passive House buildings are designed to be resilient to temperature peaks and be comfortable all year round.
The term can be misleading because the concept is not only applied to houses, but all dwellings. Across the spectrum, certified Passive House buildings have one thing in common: an exceptionally high level of energy efficiency and comfort.
Passive House principles are not detrimental to design but rather enhance it. They are usually light filled with high ceilings in main living spaces, featuring large windows in specially targeted areas to enhance the feel of the home.
The Key principles
Passive House is designed and built in accordance with building-science principles:
- Orientation
- Airtightness
- Natural or shading devices
- Natural heating
- Thermal mass and insulation
- Mechanical ventilation heat recovery
- High performance windows
- Thermal bridge free construction
1. Orientation
It is critical to consider the placement of your home on the site for its particular climate to take advantage of the sun and prevailing winds. Ideally your living areas should be located to the north, except in tropical climates.
2. Natural heating
Most Australia's regions benefits from passive solar heating, which is the natural winter sunlight inside a dwelling, naturally heating it. Typically clear glass is ideal with a high Solar high Gain Coefficient (SHGC).
3. Shading
By understanding the sun’s angles you can minimise heat being drawn into your home over the warmer months. Correctly proportioned eaves, awnings and pergolas, even trees and surrounding shades will protect the dwelling in the warmer seasons.
4 Thermal mass
Materials with thermal mass are dense and can store heat within, such as concrete, masonry, stone and rammed earth. The capturing of heat in thermal mass is best suited to regions with sunny days and cold nights. The thermal mass acts as a heat bank, storing the warmth from the sun during the day. In the evening, as the temperature drops, the heat is gradually released maintaining a comfortable internal temperature and reducing the need for mechanical heating.
5. Insulation
Insulation is a barrier to the flow of heat and makes a vast difference in the comfort and temperature of a dwelling. measured in Resistance (R) value, usually from R1.5 to R2.7, the higher the value the greater the protection. a dwelling is similar to a boat, the more elements that are shielded the greater the protection from the outside elements. floors, walls and ceilings, each element must be insulated to be airtight. the insulating one element more and leaving out the other will not suffice just as a boat needs to be sealed in all places for it to float. Insulation offers the best performance per dollar compared to glazing and it should not be compromised.
6. Glazing
Glass has the single largest impact on the transmission of heat and can represent more than 80 per cent of heat loss to the outside and up to 87 per cent of heat gain through its transparency. a standard double glazing unit is equivalent to R0.25 which is 10% as efficient as standard insulation. triple glazed units offer closer equivalent to the heat loss protection as insulation.
Thermal bridging is the movement of heat across an object that is more conductive than the materials around it. The conductive material creates a path of least resistance for heat. Thermal bridging can be a major source of energy loss in homes and buildings, leading to higher utility bills.
A significant thermal bridge can be created in residential home construction by the studs in the walls, which could account for 10-20%. As the insulation is put in-between the studs and are not continuous as per image below.
Thermal bridging is not accounted for in most energy rating software‘s. Resulting in dwellings achieving a greater star rating by a factor of 10-15% than in reality, a home rated at 6 stars is actually 5.5 stars.
To combat the problem of thermal bridging, the studs must be covered with continuous insulation such as a high quality wall wrap or foam. Either can be installed in the inside or outside side of the stud wall. (refer to diagram on the right in top image)