Our planet has been suffering from global warming for years and the effects of climate change have become more than evident in recent years. The construction industry also contributes to this problem, and the energy needed to make buildings comfortable, whether by heating or cooling, needs to be reduced drastically.
In 2019 the Spanish Building Code (CTE or Código Técnico de la Edificación) was updated to be in line with new European-Union wide regulations on energy consumption in buildings. According to the new regulations, any new buildings constructed after 2020 need to comply with the definition Near Zero Energy Building or NZEB (in Spanish ECCN or Edificio de Consumo Casi Nulo). This means new buildings need to be highly energy-efficient, with a very low demand for heating and cooling, which in turn needs to be covered largely by renewable strategies such as solar panels.
NZEB versus Passive House
One step further than a Near Zero Energy Building are the so-called Passive Houses. The main difference between certified Passive houses and Near Zero Energy Buildings is the level of energy efficiency. NZEB regulations specify that a building cannot consume more energy for heating/cooling than 40 to 86 kWh/m²·year (depending on the climatic region), whereas Passive House compliant buildings cannot exceed 15 kWh/m², wherever the building is situated.
As a result, a building designed and constructed according to the Passive House standard has a heating and cooling demand that is much lower than Near Zero Energy Buildings and therefore also a much lower heating and cooling bill. Comparative studies have verified that the reduction in energy consumption of a Passive House compared to an NZEB can be up 85%.
For these reasons, at ZEST Architecture we are in favor of increasing energy efficiency well above the existing norms of NZEB, if the client is happy with this, and we prefer building Passive Houses, which have a proven energy efficiency and therefore much lower energy costs, a great benefit for the client for the entire lifetime of the building.
What is the PassivHaus standard?
The international PassivHaus standard is the most rigorous standard with regards to energy efficiency. It is a performance based standard (which means you either pass or fail) with proven low energy consumption and superior interior air quality while dramatically decreasing greenhouse gas emissions. In some cases, Passive House compliant buildings can be constructed entirely without heating or cooling installations.
The entity that emits and controls the certificate that proves that a building is indeed a Passive House construction is called Passive House Institute (PHI). The PHI is an independent research institute founded in 1996 in Germany by Dr. Wolfgang Feist. This institute has played a crucial role in the development of the passive house concept. It is the only internationally recognized certificate that proves energy efficiency performance.
The criteria for a Classic Passive House are:
- Heating energy demand inferior to 15 kWh/m²·year
- Cooling energy demand inferior to 15 kWh/m²·year
- Primary Energy Demand (PER): 60 kWh/m2year
- Airtightness n50 inferior to 0,60 renovations/hour.
If the building has a renewable energy installation which generates at least 60 kWh/m2·year, this is called a Passive House Plus. If it generates 120 kWh/m2·year or more and feeds the excess energy back into the network, the building gets the Passive House Premium certificate.
The extreme energy efficiency of a Passive House is achieved by a simple strategy: the entire building envelope is thermally insulated, the building has high quality windows and doors with triple glazing, there are no thermal bridges (places where structural elements perforate the insulated building envelope which may cause problems with mold), the construction is extremely airtight and the building has mechanical ventilation with heat recovery. Shading devices make sure the building never heats up, while careful dimensioning of windows provides passive warming in Winter.
Can I open the windows in my Passive House?
A common misunderstanding about Passive Houses is that people think they do not allow users to open the windows. Passive House is a performance-based certification that focuses on limiting total energy use and increasing the interior air quality of buildings. Because the building envelope is so well designed and airtight, it is important to provide natural ventilation to every space, which is done by an Energy Recovery Ventilator, which makes sure the fresh air let into the building will have the same temperature as the stale air taken out*. As a result, the indoor air quality of a Passive House is far superior than that of any other building. Outside the heating and cooling season, you can open the windows as often as you like, but in Summer and Winter, although you can still open them as often as you like, you would be increasing your cooling/heating bill and there really is no need; you will have fresher air in the room without.
*This is achieved by letting the stale air that is extracted from the room pass on the heat (or coolness) to the fresh air, without mixing the air, by passing through a thing called a Heat Exchanger. So in Summer you won’t be letting in ultra-hot air when ventilating, the air inside remains nice and cool, but it is refreshed all day. Similarly, in Winter you won’t lose the warmth, because the cold air from outside is pre-warmed.
An added bonus of Passive Houses is that the excellent Windows and glazing and the extreme airtightness also deliver amazing acoustic advantages, so that you won’t be bothered by street and traffic noise anymore.
How do I get a Passive House certificate?
Other than green standards such as LEED, Passive House is a performance based standard which emits an official certificate that proves that the building in question does indeed perform to the required low energy consumption criteria. In order to test the building’s performance, an independent official called the Passive House certifier, checks the passive house design and executes an airtightness test, in order to make sure the technical design is well executed. In order to pass this test, the Passive House criteria mentioned above (insulation, airtightness etc.) must have been taken into account from the start.
Development of a Passive House building starts in the concept phase, when the climatic conditions on site are carefully studied. The solar and wind orientation of the building are of the utmost importance. The largest Windows are preferably placed in the South façade, where they will be easy to shade in Summer when the sun is very high in the sky, while in Winter when the sun is low in the sky we can benefit from passive heating. The size and position of Windows are carefully calibrated in a Passive House, and all this needs to be done by a specialized Passive House designer, who is trained to validate the design by checking the composition of the building envelope, windows sizes and positions, but also the necessary heating and cooling, all using special software.
Co Govers, the founder of ZEST Architecture, is a certified Passive House designer, who makes sure that even buildings for which no official Passive House certificate is demanded by the client, are designed to meet the highest possible energy efficiency standards.
ZEST Architecture and Passive House
ZEST Architecture always designs buildings that are sustainable, energy efficient and comfortable for their users. For this reason, we pay a lot of attention to solar orientation, but also the relationship with the surroundings, the materials for the building etc.
House in Matarraña
A good example is our Project for a house in the Matarraña region which is currently under construction. Although this house will not be certified as a Passive House, it has been carefully designed to follow the Passive House design criteria. The house is in a location with stunning views, and also needed to be mostly on one floor, and on a narrow plot. So in the end we adjusted the shape to have mostly perfect climatic orientation, great views, but are also catching the cooling Summer breeze which specifically comes from the West.
For ZEST the choice of sustainable materials is also crucial, even though this is neither required for an NZEB nor for a Passive House. We look at the CO2 footprint of materials, but also at their provenance. In this case we are working with a wooden load-bearing construction, which is pre-industrialized and mounted into big panels in a factory under perfect circumstances, then moved to site and mounted. But we also use a large amount of material which can be classed as “0 kilometers”, because we are using the earth that has been excavated for the foundations and the pool to build a long Rammed Earth wall that runs through the entire house. Read here about how this is done.
Visualisation of completed house
Photos of the prefabricated timber-frame house under construction
The Z1 house grew from our desire to create a house with a luxury appearance and good materials, suitable for a difficult terrain. We felt that given the advances in the industrialization of construction (which by the way also help reduce waste on site) it should be possible to create a house that looks luxurious, while still being a Passive House. We studied the possibilities of prefabricating the timber load bearing construction, which would help us control better the building costs and delivery times. Since in general prefabricated and industrialized buildings usually assume a perfectly flat terrain, our aim was to also offer the possibility of constructing a house on a site with a gradient. This is how our Z1 House was born, a house designed in beautiful detail, yet adaptable and with the options to customize both distribution and size.
Visualisations of completed Z1 House
Z1 has been designed as a one-storey house with a wooden load bearing construction on stilts, which allow us to adapt the house to the gradient and orientation of the terrain. Depending on the version you choose, the façade is either render on exterior insulation or wooden slats (ventilated façade). The extreme simplicity of the design emerges from a strong spatial concept, creating a fluid living space without corridors, entirely oriented to the exterior and the views. The floating terraces have wooden slat shading devices either in the roof or as a vertical element, making the design flexible for different solar orientations.
All variations of the Z1 have been designed according to Passive House standards and can be certified as Passive House if so desired. Click here to read more about our Z1 House. When a client wishes, the entire procedure is carried out to obtain the Passive House certificate for the building, from the preliminary design to the completion of the work and obtaining the certificate. At ZEST we have a certified Passive House designer and we have the support of other trusted professionals to carry out the entire procedure.
Visualisations of completed Z1 House