Despite persistent low energy prices, building energy efficiency continues to improve, at least partly due to regulations, such as the European Buildings Directive, which will require “Nearly Zero-Energy” buildings starting in 2021.
The Passive House approach to building superinsulated, high-efficiency buildings is also making inroads, and makes building a net-zero building or nearly-zero building easier.
According to the Passive House Database, nearly 3,500 buildings have been certified worldwide. That is a small number, certainly, but it is growing as builders become more familiar with the techniques and materials that allow Passive Houses to reduce energy consumption by up to 90 per cent, according to the Passive House Institute (PHI). The remaining energy demand can be met with renewable energy, resulting in a nearly-zero or net-zero building.
In 2015, the Passive House Institute introduced two certification standards, Passive House Plus and Passive House Premium, that joined the original standard, now called Passive House Classic. The new standards further reduce energy use, while also requiring energy generation. The standards recognize both on-site and off-site energy generation. According to PHI, “If a building plot is unsuitable for on-site generation, then investment in new off-site renewable energy installations can also be taken into account.”
Requirements for Passive House certification remain at 15 kWh/(m²a) for heating demand. The primary energy demand, however, is changing. According to PHI, “the overall demand for renewable primary energy (Primary Energy Renewable) will be used instead of the primary energy demand, which was previously used.”
Here’s how the three standards compare:;
- Passive House Classic buildings must not exceed 60 kWh/(m²a) for primary energy renewal (PER)
- Passive House Plus buildings must not exceed 45 kWh/(m²a) for PER and must also generate at least 60 kWh/(m²a) of energy in relation to the area covered by the building
- Passive House Premium energy demand is limited to 30 kWh/(m²a), with at least 120 kWh/(m²a) of energy being generated
The first Passive House Plus was certified in 2015. The house in Ötigheim, in southern Germany, employs standard Passive House techniques to ensure energy efficiency, such as a high level of insulation, triple-glazed windows, airtight envelope with minimal thermal bridging, and a heat-recovery ventilation system. Heating demand is 13 kWh/(m²a), the total demand for renewable primary energy comes to 28 kWh/(m²TFAa) using the PHPP design tool. A 64 square metre photovoltaic system on the south-facing roof generates electricity, resulting in a total production of 76 kWh/(m²a) of renewable primary energy. According to PHI, 10 Passive House Plus buildings have been certified to date.
"This building proves that creating an infrastructure based completely on renewable energy is already possible today for every building owner," said Dr. Wolfgang Feist, director of the Passive House Institute. "The considerably improved Passive House energy efficiency allows the issue of seasonal discrepancies between generation and demand and the resultant storage problems to be overcome with minimum effort."
The first building to be certified as Passive House Premium was also certified in 2015, this one in the town of Kaufbeuren, in Bavaria. The 900 square metre structure is a mixed commercial and residential project for building services company Airoptima, officially known as the “House of Energy”, with a heating demand of only eight kWh/m²a. A 250 square metre photovoltaic system on the roof produces renewable energy.
According to PHI, standard energy-saving features contribute to the miniscule energy usage of the building. In addition, a ground-source heat pump covers the any remaining hot water provision and heating demand. The photovoltaic system provides for domestic electricity and auxiliary energy, with the surplus fed into the electrical grid.