What is the Passivhaus Standard?
The Passivhaus standard is a very demanding energy efficiency standard. It combines high indoor comfort, in winter and summer, with very low energy consumption. This is achieved by taking the utmost care of the building envelope through high levels of insulation, high performance carpentry and glazing, and a controlled ventilation system.
It has been applied since 1991, when first houses were built with this system in Central Europe. As of today there are more than 15,000 built examples of all types and functions around the world.
This standard does not presuppose any specific types of products or materials, nor does it require any certain architectural style. The small energy requirements that your buildings need can easily be covered by renewable energies, usually achieving in that case a type of construction with zero heating and cooling energy cost for the planet. Taking into account the savings potential of this system and the increasing scarcity of resources, the Passivhaus Institute in Darmstadt and IN&AR Infrastructure Engineering are working to further develop and make this type of efficient building more widespread.
We are certified Passivhaus-Designer and Tradesperson by the Passivhaus-Institute in Darmstadt, Germany.
The five basic principles of Passivhaus
1. Thermal insulation.
Very good thermal insulation for exterior walls and roofs is beneficial in both winter and summer. Low thermal transmittance of the external envelope also reduces the energy demand of the building. Depending on the climate, the thickness of the thermal insulation can be optimized until the tipping point is reached, after which the increase in thickness is of little relevance for the improvement of energy efficiency in view of the increase in cost.
2. Absence of thermal bridges.
The transmission of energy (cold and heat) occurs not only in general elements such as walls or ceilings, but also in corners, shafts, joints, etc. Thermal bridges are places of linear or point geometry of the exterior enclosure where the energy flow is greater with respect to the "normal" surface of the enclosure. These thermal bridges impair the energy efficiency of the building element. By following a few simple rules it is possible to eliminate the effects of thermal bridges:
• No interrupting of the insulation layer.
• Regarding the joints of the construction elements of the building, the insulation layer must join and fill them.
• If interrupting the thermal insulation layer is unavoidable, use a material with the highest possible thermal resistance.
• Thermal bridges reduce the surface temperatures of the inside face of walls in winter, which increases the risk of mold and mildew formation.
• Eliminating thermal bridges is generally a cost-efficiency issue, which boils down to reducing transmission losses or the transmission of heat loads. Through proper application of insulation in Passivhaus, the linear thermal transmittance is reduced to values below 0.01 W/mK.
Holes in the building envelope cause a number of problems, particularly during the coldest periods of the year. Air flows from the inside to the outside through cracks and holes have a high risk of causing condensation in the building. Cold air infiltration also causes users to feel uncomfortable. Since in most climates a Passivhaus building requires mechanical support for the continuous supply of outside air, the building envelope must be very airtight. If the building envelope is not sufficiently airtight, the air flow will not follow the intended paths and heat recovery will not work properly, resulting in higher energy consumption: it is important that a single airtight layer covers the entire building. The airtightness can be checked by the so-called Blower-door-Test (pressurization test). It consists of a blower placed on an outside door or window creating a pressure difference of 50 Pa. The external building envelope must have a pressurization test result according to EN 13829 of less than 0.6 air changes per hour (tightness value 50 Pa).
4. Forced Ventilation with heat recovery.
It consists of recovering a large part of the energy that goes out, when we renew the used air (with bad hygienic characteristics) to pre-condition the fresh air (with good hygienic characteristics). To minimize the energy demand of the building, an hourly air renewal of approximately 1/3 of the volume of the spaces is established (according to EN 15251). With this fresh air flow, we can bring about 10 W/m2 of heat, and 7 W/m2 of cold into the building. This amount of energy needed to condition the spaces is not very large and is sufficient to dispense with a conventional system of radiators or underfloor heating, with the corresponding economic savings that this entails. For Passivhaus buildings, a limit on heating and cooling demand of approximately 15 kWh/m2a is set.
5. High-Performance Glazing.
As these are the "weakest" elements of the envelope, great attention must be paid to their correct location and execution. Double or triple glazed windows (argon or krypton filled) are used, depending on the climate, and the carpentry must be insulated. The glass used is low emissivity, to reflect the heat inside the house in winter and keep it outside in summer.