The five principles
The 5 principles of a
Passive House design
Contrarily to that of traditional houses, the envelope of a Passive House is a continuous one, an air barrier which is wrapped uninterrupted around the entire house. Thus, this kind of envelope could be thought of as a type of ‘coat’: a very useful ‘coat’ that is continuous and joined up to form a complete loop. This means that there are no unintended gaps in the building envelope that allow uncontrolled air to leak in or out of the building.
2. High-quality windows and doors
In winter, solar radiation warms up the house. In summer, passive cooling methods block it to prevent overheating. All these measures ensure a natural and pleasant indoor climate all year round.
3. Thermal bridge-free
In order to avoid these problems, the structures of Passive Houses are carefully designed to guarantee the airtightness of the house. This way, energy loss and points of condensation are avoided while ensuring greater energy efficiency.
4. Thermal insulation
Energy loss through facades, glazing, floors and roofs is minimal. The thicknesses double or even triplicate the ones used in conventional houses to guarantee thermal comfort for the inhabitants of the house by maintaining temperatures around 20º C even on the walls’ surface. It is precisely this continuous insulation that “wraps” the whole building’s thermal envelope of the building that avoids air leaks. Therefore, all the conflictive points susceptible to air filtration are protected. The high-quality insulation contributes to the house’s energy efficiency by allowing you to keep your home at a constant temperature at the same time that contributes to greater acoustic insulation.
5. mechanical ventilation with heat recovery
The fact that you do not need to open the windows to ventilate is an advantage, especially during winter. Natural ventilation can be used during the whole night to dissipate the heat that has accumulated throughout the day (in the summer). The ventilation system works in a simple way. On the one hand, the system uses filters installed in the air inlets and outlets (located at strategic points in the house) to purify the air coming from outside before it enters the house. This guarantees genuinely clean indoor air.
On the other hand, depending on the season of the year, the system carries out a heat exchange between the air coming into the house from outside and the air inside the house in order to save energy to heat it up or to cool it down. For example, during winter, when the outside temperature is colder than the one inside the house, the system recovers the heat from the inside air before expelling it from the house and transfers this heat to the outside air so that it enters the house already heated. In summer, the system works the other way round: it recovers the cold from the indoor air and transfers it to the outdoor air so that it enters the house cooler.
How does a Passive House work?
A Passive House is a house that has been designed and built in such a way that it requires very little energy to maintain a constant, pleasant temperature. In this sense, such buildings need hardly any active heating or cooling to stay comfortable year-round.
More specifically, Passive Houses use 90% less energy than traditional ones to reach a comfortable temperature all year round. Thus, conventional and highly-energy-consuming heating and cooling systems are rendered unnecessary.
A Passive House is heated and cooled off “passively”, with minimal energy consumption.
During winter, the house makes the most of the climate conditions making efficient use of the sun, internal heat sources and the heat recovery carried out by its ventilation system to heat up and keep a temperature never lower than 20° C.
During summer, it makes use of passive cooling techniques such as strategic shading or pre-cooling of the air supply to keep it comfortably cool. This way, the temperature never surpasses 25° C even at the hottest of summers.
A simple example to understand how a Passive House works is through the simile between a coffee machine (traditional house) and a thermos flask (Passive House).
The coffee maker will keep our coffee hot only as long as it is connected to the power supply.
On the other hand, the thermos flask will keep the coffee hot without needing any active external energy source thanks to its airtight and thermal insulating properties.
A Passive House uses higher-quality thermal insulation, glazing (double or even triple glazed glass windows) and insulated frames in order to:
- Retain heat and cold in depending on our needs and stopping them from leaking out.
- Prevent the outside air from entering the house uncontrollably (either hot or cold).
Even before it is built, each house is designed to take full advantage of the particular climatic and geographical conditions of its location.
In a privileged Mediterranean climate, such as that of Mallorca, sun’s rays shine at a lower angle in winter while, in summer, sun’s rays strike the earth’s surface almost perpendicularly. This means that the best orientation for a house in the northern hemisphere is south.
With all this in mind, we design south-facing facades with large glass windows directed towards the sun that let in natural light throughout the day and act as solar collectors and natural radiators in winter.
In summer, we can avoid excessive solar radiation by using overhangs, designing shaded areas such as porches, cornices, canopies, awnings and pergolas or taking advantage of the natural shading of vegetation (such as trees or creeper plants).
These shaded areas (used in combination with the use of the external breeze) will prevent too much heat from the sun getting into the house and will keep it cool during the summer.