What is a Passive House?
The passive house is a term denoting a building’s energy consumption per unit area is very low and ideally offset by solar gains and internal gains. There are already long as engineers and architects have focused on the design of passive houses using various methods and technologies to achieve a reduction in the consumption of heating and cooling a building.
Many examples of experimental projects are found in the literature [ 1 ] and the problems they have encountered in operating mode illustrate the difficulty of meeting the needs of thermal comfort of building occupants throughout the year with minimal heating or air conditioning while respecting the essential supply fresh air quality and pollutants discharge internal needs.
These experimental houses left from some well-known since ancient times, such as orientation of facades enjoying large windows, natural ventilation, thermal inertia of the heavy and dense materials (clay, stone, brick principles, adobe, water …) and protection against the sun in summer with shade.
But an inherent flaw in the vast majority of technical was fluctuating internal climate, with temperatures varying from 11 to over 27 ° C, resulting in a loss of comfort and enjoyment for the occupants.
Moreover, many concepts require human intervention (opening / closing of vents, shutters or insulating blankets, etc.), requiring constant vigilance on the part of occupants to adapt to prevailing weather conditions first and second internal gains.
In 1988 a new concept emerged from a conversation between Professors Bo Adamson of Lund University in Sweden and Wolfgang Feist of the Institute for Housing and Environment, Germany.
Their concept was developed with many research projects funded by the State of Hesse, resulting in a first building of four homes townhouses built in Darmstadt (Germany) in 1990, this concept allowed a saving heating 90 % relative to local standards of the time. In 1996, Mr. Feist founded the Passivhaus Institute in Darmstadt also.
Construction “Passivhaus” contrasts sharply with the old concepts.
This is a construction standard that promises unparalleled comfort, both thermal and in terms of air quality and noise levels, and without any human intervention, with some electronic controls reliable mechanical systems.
The thermal inertia so prized by traditional designers is not so much the result of heavy materials strategically in the house but the fact of extreme tightness coupled with the thermal envelope insulation unusual.
In addition to allowing this high level of comfort, Passivhaus house promises a 85% reduction in heating costs of a building in relation to Novoclimat® requirements, which means a load of heating so low that conventional heating system is unnecessary for this type of construction.
Principles of Passivhaus home
The design of the house Passivhaus, as specified by the Passivhaus Institut in Darmstadt, Germany, which manages the certification is based on the following six principles:
- A very high thermal insulation of walls and windows of the highest quality
- The elimination of thermal bridges
- Excellent air tightness
- A comfort ventilation with heat recovery
- Optimized capture (but passive) solar energy and calories soil
- Power consumption limited to appliances.
Technical definition of a Passivhaus home
Passivhaus house requires both components with very high performance and great care during the construction phase. These components would normally meet the following requirements:
- The elements of the outer casing must have a U-factor lower than 0.15 W / (m2K) (R factor greater than 37.8).
- The envelope must be achieved without thermal bridges.
- The tightness of the envelope must be verified by a blower door test and air leakage shall not exceed 0.6 CAH under a pressure of 50 Pa (in both directions).
- All the windows must have a U-factor of less than 0.8 W / (m 2 K) (R greater than 7.1 factor) and a Coefficient Solar Heat Gain (SHGC – English SHGC) of at least 50%.
- Windows must have a total U-factor (including frame and spacer junctions) of 0.8 W / (m 2 K) (R greater than 7.1 factor).
- The ventilation system must have a heat recovery efficiency of at least 75% and a power consumption of less than 0.45 Wh / m3 volume of supply air.
- Generation systems and distribution of hot water used must produce minimal heat losses.
- A very efficient use of electricity in the household is essential.