Conference PaperPDF Available

Nearly Zero Energy Building (nZEB) in Latvia

The 9
International Conference “ENVIRONMENTAL ENGINEERING”
22–23 May 2014, Vilnius, Lithuania
eISSN 2029-7092 / eISBN 978-609-457-640-9
Available online at
Corresponding author: Agris Kamenders. E-mail address:
© 2014 The Authors. Published by VGTU Press. This is an open-access article distributed under the terms of the Creative Commons
Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and
source are credited.
Section: Energy for Buildings
Nearly Zero Energy Building (nZEB) in Latvia
Agris Kamenders, Rihards Rušenieks, Ruta Vanaga, Claudio Rochas, Andra Blumberga
Riga Technical University, Riga, LV1010, Latvia
The main question studied during this study was what does it takes conversion of conventional building built according minimum energy
efficiency requirement by existing building code to nearly zero energy building (nZEB). The aim of this study is to work out technical
requirements to reach nZEB level in Latvia and test them in real building project.
Real energy consumption data and indoor climate conditions have been analysed to understand building energy performance after
construction. At the moment no official low energy building guidelines exist how to reach very low energy standard in Latvia climate
conditions. This study also helps to identify challenges and future development needed for building components to reach nZEB level.
Keywords: Nearly Zero Energy building; energy modelling; energy and indoor climate monitoring.
1. Introduction
Building regulations have been developed setting requirements for nearly zero energy building definition as European
Parliament set targets that all new buildings in EU must be nearly zero energy by 2020 [1]. There are different definitions
what has bee understood by term nZEB. In general and now most widely used definition of nZEB is given by Energy
Performance of Buildings Directive (Directive 2002/91/EC,EPBD) and nZEB is defined as building that has a very high
energy performance and that energy required should be covered to a very significant extent by renewable energy sources. In
many cases net zero energy building term is used. Word “Net” is used what appoints a balance between taken energy from
the energy grids and supplied back over a period of time indicating the idea of energy-efficient systems and insulation
materials of building to lower heating and electricity demand combined with renewable energy systems like solar thermal
and photovoltaic (PV) systems for space heating and covering hot water productions [2], [3], [4]. Acquisitions from each
option depend on characteristics of building and conditions, however currently on-site options are accepted in most cases
because of possibility to cover energy consumption of building by a significant part of renewable energy [5], [6]. The most
common renewable on-site technologies for reaching net zero energy goal are photovoltaic (PV) and solar thermal panels in
combination with other technologies like ground source heat pumps [5], [6], [7]. However dependency only on on-site solar
energy in the northern Europe deals with obstructions like mismatching between the energy production and consumption
[8], [9] and the restricted area of roof and façade [9]. Abundance of local energy variables like biomass in Finland serves as
a solution, where it can be used for micro and small-scale biomass-based combined heat and power (CHP) systems and can
even reduce dependency on on-site solar energy [10]. In Denmark considering the dense city areas, weather conditions and a
large number of wind turbine co-ops, the solution for optimal energy could become off-site renewable energy supply
options [5]. In addition analysing current price levels for renewables like PV installation it is considered that investment in
energy efficiency is more cost-effective than investment in renewable technologies [11]. It is harder to reach Net ZEB level
by renovation than by transposing efficient technologies in new buildings however some examples like multi-family social
house building in Montreuil (France, built in 1969) which has been renovated in 2001 fulfils the passive house standard
[12]. Innovative technologies can help to improve energy efficiency like improvement of insulation, implementing phase
change materials, establishment of innovative shading devices, use of advanced sensors, zone heating and cooling and
monitoring systems in order to improve energy performance level [7]. Different techniques reduce energy from economy
perspective and optimize cost performance of ZEBs (around 20 kWh/m
a in Denmark) [5]. Even when elaborating building
design to accomplish net-zero energy level in technical effectiveness it is not verified that it can also gain effectiveness of
economic resources. [2], [13], [14].
2 A. Kamenders et al. / The 9
Conference Environmental Engineering. Selected Papers, Article number: enviro.2014.263
Current Latvian building codes LBN 002-01 set minimum requirements for U-values of building components and
building airtightness. There are no clear guidelines what U-values and what technologies should be used in Latvia to
achieve nZEB level. The aim of this study was to find out what does it takes to redesign conventional building built
according minimum energy efficiency requirement by existing building code to nZEB level. The requirements for building
envelope and ventilation were defined by help of energy modelling. After that single-family house has been designed, build
and achieved results measured.
2. Climate data
Climatic data play a significant role in building energy consumption therefor good understanding of climate conditions is
very important. Latvian climate is characterized by cold climate with very mild summer temperatures. The yearly average
temperature is typically around +6 °C. Usually heating season is 211 days long with average temperature +0,4 °C and
minimum design temperature – 21 °C. The software Meteonorm and Latvian building code LBN 003-01 was used to
generate climate date for energy calculation. In the Figure 1 monthly average values of the outside temperature and solar
irradiation on the horizontal as well as on the four main sky directions – north, east, south and west are showed.
1 2 3 4 5 6 7 8 9 10 11 12
kWh/ (m²*month)
Fig. 1. Climate date
Intensity of the annual available solar irradiation is between 900 and 1000 kWh/m
, which is comparable with other north
European cities, like Stockholm (<1000 kWh/m
), Oslo (<900 kWh/m
) and similar to Copenhagen.
3. Design and calculations
In the beginning building was designed according to the requirements Latvian legislation in terms of energy efficiency. The
main characteristic of the building:
Building Type: Two storey single family house
Location: Latvia, Gipka
Architect: Ervīns Krauklis, “Krauklis Grende” Ltd
Heated floor area : 191 m²
Renewable energy used : PV panels
Ventilation: “Paul” Thermos 300 recuperation system
Heating and hot water: “Vaillant” heat pump
The building was redesigned to reach very low energy performance level by using PHPP (Passive house planning
package) energy calculation programme. Building design followed the main design principles of the very low energy
building [15]:
Minimise losses and consumption;
Optimise gains;
Substitute the remaining energy need with environmental friendly energies.
The changes needed and difference between minimum requirements of existing building code LBN 02-01 and nZEB are
summarized in Table 1.
3 A. Kamenders et al. / The 9
Conference Environmental Engineering. Selected Papers, Article number: enviro.2014.263
Table 1. Building elements
Building elements Conventional building defined nZEB values
Roof U value, W/(m
K) 0.194 0.05
Walls U value, W/(m
K) 0.291 0.06
Ground floor U value, W/(m
K) 0.242 0.1
Windows U value, W/(m
K) 1.745 0.8
Ventilation Natural ventilation 0.3 h
0.3 h
Effective Heat Recovery Efficiency
Infiltration n
, h
0.93 0.43
During building redesign process many important solutions for walls, foundation, and roof structures had been found.
Elements were carefully redesigned, insulation thickness was optimized, mitigation and minimising of thermal bridging
were done. The redesigned building to achieve nZEB performance level shown in Figure 2.
a) building according Latvian building code b) Redesigned building to achieved nZEB level
Fig. 2. Building cross-section
Two different energy calculation programmes were used for energy calculation to define changes needed:
PHPP 2007 (passive house planning package);
TRNSYS 16 simulation program (Transient System Simulation Tool);
With help of PHPP and TRNSYS calculation tools building energy consumption was calculated to optimize building
envelope insulation thickness and to define technical requirements what should be fulfilled to reach nZEB level. It was not
possible to change building orientation, building shape and building aesthetics. Connection details were designed to
eliminate thermal bridges and to assure building airtightness. Construction was made to minimize thermal bridges.
According PHPP 2007 calculation space heat consumption for conventional building is 127 kWh/(m
a) and for building
redesigned according passive house concept 33 kWh/(m
a) with means 75% of savings of heat each year. The real energy
consumption has been evaluated during first heating season.
4. Measurements and monitoring
To understand real building performance the work for this study includes energy and the indoor climate data monitoring.
Monitoring consisting of the following long term measurements:
Indoor air temperature in all rooms of the building;
Outdoor air temperature;
Relative air moisture in the living room and bedroom;
Level of CO
in the bedroom;
Start up and shut down of ventilation equipment’s antifreeze circulation pump;
Heat consumption for heating and hot water.
Blower door test was carried out for the construction (see Fig. 3) to clarify important elements like building air tightness
and thermal bridges.
4 A. Kamenders et al. / The 9
Conference Environmental Engineering. Selected Papers, Article number: enviro.2014.263
a) Blower door test during construction b) Blower door test after construction works
Fig. 3. Blower door test during and after construction works
First Blower door test shown very good results n
= 0.43 h
with were used for space heat calculation. After all works
during the heating season second blower door test where conducted and with showed worse results n
= 0.81 h
. The
results are summarized in Figure 4
y = 7.3908x + 109.12
= 0.9902
0 10 20 30 40 50 60 70 80
Fig. 4. Blower door test results
During Blower door test fan is used to blow air in or out of the house. Figure 4 shows pressure difference between inside
and outside and y axes shows flow through the Blower Door fan. Blower Door test has been used to measured airtightness
of a building. According to the existing Latvia building code 002-01 for the airtightness calculation the results obtained at
50 Pa are used. Pressure as 50 Pa is chosen to minimize stack-induced airflow and wind-driven airflow effects.
The results where calculated according Eqn (1).
0.81, ,
= = = (1)
– building volume;
V’ – fan output (m
Consumed heat energy was measured with help of heat energy meter. Since the amount of used energy for heating
depends from outdoor and indoor temperatures, these temperatures were monitored during heating season. For
measurements HOBO loggers where used see Figure 5.
5 A. Kamenders et al. / The 9
Conference Environmental Engineering. Selected Papers, Article number: enviro.2014.263
a) Temperature logger b) CO
and relative humidity logger
Fig. 5. Temperature and CO
For the measured energy consumption data to be comparable with calculated data, they were adjusted, assuming that
climate conditions are uniform and the indoor temperature t = +20 °C. Adjusted energy consumption data are shown in
Figure 6 on a monthly basis.
1 2 3 4 5 6 7 8 9 10 11 12
mon th
Heating Tem perature
Fig. 6. Adjusted energy consumption data per month
The total energy consumption for the building in 2010 was 6719 kWh, or 35 kWh/m
a. In Figure 7, calculation results of
the model are compared with measured data and data from the dynamic model.
Measured Calcul ation TRNSYS
kWh /m
Fig. 7. Comparison of energy consumption – measurements versus calculations
As is shown in the Figure 7, the calculated energy consumption accurately represents energy consumption in the
building. Weather normalization of energy consumption data have been done to compere them with calculated data during
design phase.
5. Results from monitoring and conclusions
First real nZEB have been build according passive house design principles in Latvia. Work conducted for this study
includes measurements of energy consumption data and of comfort decision criteria from Latvia’s first nZEB.
Measurements proved that it is possible to build a private house (heating area 191 m
) in Latvia whose energy consumption
6 A. Kamenders et al. / The 9
Conference Environmental Engineering. Selected Papers, Article number: enviro.2014.263
for heating does not exceed 35 kWh/(m
a). According to the passive house design principles heating should be provided
only with ventilation what limits the heating peak load to 10 W/m
. From experience gained during design and construction
of the one of the first nZEB in Latvia it seems very hard to meet required peak load (<10 W/m
) in case of small single
family houses with reasonable effort and costs, based on an internal heat gains 2,1 W/m
. We see that to achieved nZEB
performance level better windows should be developed and used in cold climates. Some problems have been detected with
roof windows and windows where PV cells are mounted.
The following technical indicative properties could be used for Latvian climate to reach nZEB performance level:
walls, roof, coverings <0.08 W/(m
windows <0.65 W/(m
mechanical ventilation with heat recovery >85%;
building air tightness n
<0.4 h
maximum utilization of solar energy in a passive manner;
maximum compactness.
To develop cost effective nZEB in Latvia future research and development are needed:
Airtight and well insulated doors;
User friendly low temperature heating systems;
Low costs widows and window installation systems;
Low costs and user friendly indoor climate and energy consumption monitoring system;
Sealing and airtightness products;
Low costs high efficiency recuperation and ventilation systems with simple control;
Inexpensive automatic external shading systems.
[1] Hernandez, P.; Kenny, P. 2010. From net energy to zero energy buildings: Defining life cycle zero energy buildings (LC-ZEB), Energy and Buildings
42(6): 815–821.
[2] Kapsalakia, M.; Leala, V.; Santamourisb, M. 2012. A methodology for economic efficient design of Net Zero Energy Buildings, Energy and Buildings
55: 765–778.
[3] Cellura, M.; Guarino, F.; Longo, S.; Mistretta, M. 2014. Energy life-cycle approach in Net zero energy buildings balance: Operation and embodied
energy of an Italian case study, Energy and Buildings 72: 371–381.
[4] Thormark, C. 2002. A low energy building in a life cycle—its embodied energy, energy need for operation and recycling potential, Building and
Environment 37: 429–435.
[5] Marszal, A. J.; Heiselberg, P.; Jensen, R. L.; Nørgaard, J. 2012. On-site or off-site renewable energy supply options? Life cycle cost analysis of a Net
Zero Energy Building in Denmark, Renewable Energy 44: 154–165.
[6] Panão, M. J. N. O.; Rebelo, M. P.; Camelo, S. M. L. 2013. How low should be the energy required by a nearly Zero-Energy Building?, The
load/generation energy balance of Mediterranean housing.Energy and Buildings 61: 161–171.
[7] Kolokotsa, D.; Rovas, D.; Kosmatopoulos, E.; Kaliatzakis, K. 2011. A roadmap towards intelligent net zero- and positive-energy buildings, Solar
Energy 85(12): 3067–3084.
[8] Sartori, I.; Napolitano, A.; Voss, K. 2012. Net zero energy buildings: a consistent definition framework, Energy Build 48: 220–232.
[9] Fong, K. F.; Lee, C. K. 2012. Towards net zero energy design for low-rise residential buildings in subtropical Hong Kong. Appl Energy 93: 686–694.
[10] Mohamed, A.; Hasan, A.; Siren, K. 2014. Fulfillment of net-zero energy building (NZEB) with four metrics in a single family house with different
heating alternatives, Applied Energy 114: 385–399.
[11] Marszal, A. J. M.; Heiselberg, P. 2011. Life cycle cost analysis of a multi-storey residential Net Zero Energy Building in Denmark, Energy 36: 5600-
[12] Thiers, S.; Peuportier, B. 2012. Energy and environmental assessment of two high energy performance residential buildings, Building and
Environment 51: 276–284.
[13] Kapsalaki, M.; Leal, V. 2011. Recent progress on net zero energy buildings, Advances in Building Energy Research 5: 123–156.
[14] Ferrantea, A.; Cascella, M. T. 2011. Zero energy balance and zero on-site CO
emission housing development in the Mediterranean climate, Energy
and Buildings 43(8): 2002–2011.
[15] Peuhkuri, R.; Tschui, A.; Pedersen. S. 2010. Deliverable D3 Principles of low-energy houses applicable in the participating countries and their
applicability throughout the EU. p 30.
... A nZEB is defined as a building that has a high energy performance and energy requirement should be covered by renewable energy sources (Kamenders, Rusenieks, Vanaga, Rochas, & Blumberga, 2014 (Dall'O, Bruni, & Sarto, 2013). Public organisations do not give numbers for the exact level of 'nearly zero energy' is. ...
Although the Passivhaus design is rapidly spreading worldwide, limited studies have examined its actual performance during operation. This study used Australia's first student accommodation built to the Passivhaus standard as a case study to assess the gaps between design prediction and in situ performance. Passivhaus criteria, supplemented with the adaptive thermal comfort approach, were applied to evaluate the discrepancies between design predictions and measurements. This year-long study discovered significant gaps in three indicators, including primary energy renewable, overheating frequency, and space heating energy demand. The simulation was over-optimistic in the first two indicators but conservative in the last. The discrepancies were mainly caused by the default assumptions and inherent restrictions of the simulation platform. Improvements can be achieved by incorporating more advanced datasets for the estimation of appliance energy use, improving the feedback process from measurements to the simulation tool and developing a more integrated simulation package. The results of this study contribute toward a deeper understanding of the magnitude, causes, and solutions of performance gaps between design and operation stages for large Passivhaus projects.
The paper starts from the results of one of the six case-studies of the SubTask B in the International Energy Agency joint Solar Heating and Cooling Task40 and Energy Conservation in Buildings and Community Systems Annex 52, whose purpose is to document state of the art and needs for current thermo-physical simulation tools in application to Net Zero Energy Buildings.The authors extend the Net Zero Energy Buildings (Net ZEB) methodological framework, introducing the life-cycle perspective in the energy balance and thus including the embodied energy of building and its components. The case study is an Italian building, tailored to be a Net ZEB, in which the magnitude of the deficit from the net zero energy target is assessed according to a life-cycle approach. The annual final energy balance, assessed with regard to electricity, shows a deficit which makes the case study a nearly Net ZEB, when the encountered energy flows are measured at the final level. Shifting from final to primary energy balance the case-study moves to a non-Net ZEB condition, because of the large difference between the conversion factors of photovoltaics generated electricity and imported electricity. The adoption of a life cycle perspective and the addition of embodied energy to the balance causes an even largest shift from the nearly ZEB target: the primary energy demand is nearly doubled in comparison to the primary energy case.
The concept of a Net Zero Energy Building (Net ZEB) encompasses two options of supplying renewable energy, which can offset energy use of a building, in particular on-site or off-site renewable energy supply. Currently, the on-site options are much more popular than the off-site; however, taking into consideration the limited area of roof and/or façade, primarily in the dense city areas, the Danish weather conditions, the growing interest and number of wind turbine co-ops, the off-site renewable energy supply options could become a meaningful solution for reaching ‘zero’ energy goal in the Danish context. Therefore, this paper deploys the life cycle cost analysis and takes the private economy perspective to investigate the life cycle cost of different renewable energy supply options, and to identify the cost-optimal combination between energy efficiency and renewable energy generation. The analysis includes five technologies, i.e., two on-site options: (1) photovoltaic, (2) micro combined heat and power, and three off-site options: (1) off-site windmill, (2) share of a windmill farm and (3) purchase of green energy from the 100% renewable utility grid. The results indicate that in case of the on-site renewable supply options, the energy efficiency should be the first priority in order to design a cost-optimal Net ZEB. However, the results are opposite for the off-site renewable supply options, and thus it is more cost-effective to invest in renewable energy technologies than in energy efficiency.
This work developed a methodology and an associated calculation platform in order to identify the economic efficient design solutions for residential Net Zero Energy Building (NZEB) design considering the influence of the local climate, the endogenous energy resources and the local economic conditions. One case study of a detached house for 3 climates was analyzed with the tool developed in order to gain insights on the economic space of NZEB solutions and the influence of the climatic context. A methodology for assisting the choice of economically efficient NZEB solutions from the early design stage is now available. Its use in practice may be of great relevance as the results showed that the differences between an economically efficient and economically inefficient NZEB can be over three times both in terms of initial and life cycle cost.
The term Net ZEB, Net Zero Energy Building, indicates a building connected to the energy grids. It is recognized that the sole satisfaction of an annual balance is not sufficient to fully characterize Net ZEBs and the interaction between buildings and energy grids need to be addressed. It is also recognized that different definitions are possible, in accordance with a country's political targets and specific conditions. This paper presents a consistent framework for setting Net ZEB definitions. Evaluation of the criteria in the definition framework and selection of the related options becomes a methodology to set Net ZEB definitions in a systematic way. The balance concept is central in the definition framework and two major types of balance are identified, namely the import/export balance and the load/generation balance. As compromise between the two a simplified monthly net balance is also described. Concerning the temporal energy match, two major characteristics are described to reflect a Net ZEB's ability to match its own load by on-site generation and to work beneficially with respect to the needs of the local grids. Possible indicators are presented and the concept of grid interaction flexibility is introduced as a desirable target in the building energy design.
The «positive energy building» concept combines energy saving and electricity production using renewable resources, aiming a positive primary energy balance on a yearly basis. Compared to other concepts of high energy performance buildings, it is very ambitious on an energy point of view, but more materials and components are used, this is why the environmental relevance of this concept has to be questioned.In order to contribute to answer this question, a life cycle assessment (LCA), including the fabrication of components, construction, operation, maintenance, dismantling and waste treatment, has been used to evaluate the environmental impacts of two high energy performance buildings: a renovated multi-family social housing building and two passive attached houses. Both buildings are located in North of France. For the purpose of this study, renewable energy production has been assumed to achieve nearly positive energy balances.For these buildings, four different heating solutions have been studied: an electric heat pump, a wood pellet condensing boiler, a wood pellet micro-cogeneration unit, and district heating.Modeling and simulation have been performed using the building thermal simulation tool COMFIE, to evaluate the heating load and thermal comfort level, and the LCA tool EQUER to evaluate twelve impact indicators.The results show the level of performance as well as the influence of the choice of the heating system on the environmental impacts considered in this assessment.
Directive 2010/31/EU adopted that by the end of 2020 all new buildings should be nearly Zero-Energy Buildings (nZEB) and Member States should achieve cost-optimal levels by ensuring minimum energy performance requirements for buildings. This paper discusses how low should be the energy required by a nZEB, in the context of housing energy consumption in a Mediterranean climate (Lisbon). For selected houses built after 1990, the calculated primary energy loads for regulated uses – heating, cooling and domestic hot water – are found to be below 90 kWh/(m2 year). Applying the cost-optimal solutions of thermal insulation and glazing type and considering energy efficiency improved systems, this study concludes that housing energy loads are ‘low’ for the indicative range of 70 kWh/(m2 year) for regulated uses or 100–110 kWh/(m2 year) for total uses, taking primary energy indicators (PEI) from EN 15603. Assuming PEI from Passive House Planning Package or those to be assumed in Portugal for 2013, the threshold decreases to 60 kWh/(m2 year) for regulated uses or 90–100 kWh/(m2 year) for total uses. Only the first nZEB condition is explored by this paper. The second condition requires that the nZEB energy load is covered by a ‘significant’ part of renewable energy sources produced on-site or ‘nearby’.
Hong Kong is a typical metropolis in the subtropical South China, where high-rise buildings are all around the city. This generally implies that the density of energy demand is extremely high, even the renewable energy facilities are involved, they can just play as a minor energy provider at the current technology level. It seems only the low energy design for buildings can be made possible, not the zero energy. Nevertheless, one group of the feasible places for implementing the net zero energy (NZE) design is the low-rise residential buildings in Hong Kong. Typically they are three-storey village houses, in which the renewable energy provisions can be installed in the available space, like the flat roof and the external walls. However, the question is still there - can the NZE target be achieved in this type of building even all the possible space is used up for the renewable energy facilities? As such, a dynamic simulation study was carried out to evaluate the year-round energy performances and the related factors. The answer opens a way to both the new and retrofit projects, which would enhance the low carbon roadmap in the subtropical Hong Kong.
The concept of net zero energy building (NZEB) is relatively new, but its deployment in building design construction practice is occurring quickly, with many countries now promising to make it mandatory for new constructions in a few years. It is therefore important to determine the relationship between research and NZEBs, in a context in which the research questions regarding NZEBs may not be obvious. This chapter discusses the recent progress in NZEB research and practice, dividing the analysis into the following sections: definition of the concept of NZEB; policy instruments; demonstration buildings (residential and non-residential); design strategies; and technologies for NZEBs. It shows that the feasibility of NZEBs has been demonstrated widely, in particular in low-rise buildings. The NZEB-specific research effort seems now to be moving towards issues of methods to assist efficient design (as an evolution from effective design) and their efficient monitoring and operation. NZEBs continue to benefit from motivating research in the areas of energy efficiency and on-site renewable energy, which may apply to all buildings, whether an NZEB or not.