WOODEN nZEB HOUSE
WHAT DOES A nZEB HOUSE MEAN?
nZEB stands for “nearly Zero Energy Building” and is part of Directive 2010/31/EU (“Energy Performance of Buildings Directive” or “EPBD”). According to the in 2020 republished Law no. 372/2005 on the energy performance of buildings, "the building with almost zero energy consumption is the building with a very high energy performance, where the energy requirement from conventional sources is almost equal to zero or is very low and it is largely covered by renewable energy, including renewable energy produced on site or in the vicinity."
Practically, from January 1 2021, all new buildings must meet this standard in order to be approved. We design and build to the nZEB standard by following the principles of a passive house.
WHAT IS A PASSIVE HOUSE?
A passive house has a superior thermal performance and consumes very little energy for temperature control. It is a strict standard which aims to optimize the thermal requirements of a building. This can be achieved by simple but rigorous techniques. The most important criterion for or a house to be passive is that the annual energy consumption for temperature control must not exceed 15 kWh/m2/year or the maximum thermal load must be less than 10 W/m2.
The most important criterion for or a house to be nZEB is that the annual energy consumption for temperature control must not exceed 110-141.2 kWh/m2/year depending on the climatic zone according to the calculation methodology MC-001/2021, and at least 30% of the energy must come from locally produced renewable sources or within a 30km radius of the building. The nZEB standard applies not only to residential but also to public or commercial buildings and is based on the five principles of the passive house, to which one is added one:
THE PRINCIPLES OF A nZEB HOUSE
Thermal envelope's heat transfer coefficient U < 0.15 W/m2K
Number of hourly air exchanges < 0.6 at 50Pa pressure
REDUCED THERMAL BRIDGES
Continuous thermal envelope without thermal bridges
HEAT RECOVERY VENTILATION
Centralized mechanical ventilation system with heat recovery with efficiency > 75%
The window frames and glazing must have the coefficient U < 0.8 W/m2K
At least 30% of the house's primary energy needs must come from renewable sources: solar systems and heat pumps
nZEB HOUSE IN A TIMBER FRAME SYSTEM
The timber frame system comes with two main advantages. First, wood is a natural, resistant, and durable material which has a low thermal conductivity compared to other structural materials. Second, the prefabricated load-bearing exterior walls containing sufficient thermal insulation have a relatively small thickness; this results in more usable area. More details on how to build nZEB in a timber frame below:
From January 2021, new residential buildings that do not comply with the nZEB standard will no longer receive building permits (a result of Directive 2010/31/EU of the European Parliament and of the Council of the European Union on the energy performance of buildings).
THE ADVANTAGES OF AN nZEB HOUSE
An nZEB house has several advantages.
First, it has low operating costs. The investment in energy efficiency measures means a reduction of 40-90% in monthly energy costs. From an investment point of view - given that a house is a a long-term investment - an nZEB house is a solid investment even though the purchasing costs might be relatively higher.
Second, with a negative fixed carbon footprint and a lower variable carbon footprint, the house has a less negative impact on the environment. Since the wood we use is a renewable material, the wooden house stores CO2 in its structure. See more information in this blog post. Additionally, the variable emissions are much lower due to the lower energy consumption.
Third, it has an efficient use of space. Within the wall thickness of 15cm there are both load-bearing walls and thermal insulation. This is possible because wood allows for a simpler approach to thermal bridges as it has a lower coefficient of thermal conductivity than conventional materials such as concrete, steel or brick. For example, in the classic 30cm masonry system, a minimum of 10cm of insulation is needed on the façade, which means a double wall thickness for the same level of thermal performance. The insulation makes it a warm house and reduces the noise.
DISADVANTAGES OF AN nZEB HOUSE
nZEB houses have some disadvantages. First, the initial investment costs of an nZEB house are higher compared to a house that is less energy efficient. However, with the new regulations, there is no option to build less energy efficient anymore. Strictly speaking about building with wooden structures, the cost can still be a disadvantage.
Second, a prefabricated nZEB house requires a more substantial budget in advance as it cannot be paid in staggered stages since the production and construction times are short, which means that more materials are required in a shorter period of time. Think about the thermal envelope elements - walls, floors, and roof modules - with cladding, insulation, membranes, windows and finishes.
HOW MUCH DOES A NZEB HOUSE COST?
A very good question. Without a project we cannot estimate the right price. Obviously, an nZEB house has a higher investment cost than a conventional one, but the investment cost is amortized over time, due to the monthly energy savings. It is very important that the process starts from the design phase. We have architect partners specialized in the design of nZEB houses and Passive House certificates, energy auditors and designers of specialized structures and installations. So, we offer you 2 options:
PREFABRICATED WOODEN HOUSES
MORE DETAILS ABOUT THE nZEB STANDARD
It has been more than a year since the nZEB standard became mandatory for all new buildings. We are part of the pRO-nZEB Cluster and support the development and implementation of this standard in our industry. In the video below we talked to experts in the field and our partners in the clusters about nZEB, what the challenges are and where at which level of implementation we stand.