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Nearly Zero Energy Building (nZEB) in Latvia

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th
International Conference “ENVIRONMENTAL ENGINEERING”
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Corresponding author: Agris Kamenders. E-mail address: agris.kamenders@rtu.lv
http://dx.doi.org/10.3846/enviro.2014.263
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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
Abstract
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
2
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].
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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.
0
20
40
60
80
100
120
140
160
180
1 2 3 4 5 6 7 8 9 10 11 12
month
kWh/ (m²*month)
-10
-5
0
5
10
15
20
North
East
South
West
Global
Ambient
Temp
°C
Fig. 1. Climate date
Intensity of the annual available solar irradiation is between 900 and 1000 kWh/m
2
, which is comparable with other north
European cities, like Stockholm (<1000 kWh/m
2
), Oslo (<900 kWh/m
2
) 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.
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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
2
K) 0.194 0.05
Walls U value, W/(m
2
K) 0.291 0.06
Ground floor U value, W/(m
2
K) 0.242 0.1
Windows U value, W/(m
2
K) 1.745 0.8
Ventilation Natural ventilation 0.3 h
–1
0.3 h
–1
Effective Heat Recovery Efficiency
85%
Infiltration n
50
, h
–1
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
2
a) and for building
redesigned according passive house concept 33 kWh/(m
2
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
2
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.
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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
50
= 0.43 h
–1
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
50
= 0.81 h
–1
. The
results are summarized in Figure 4
y = 7.3908x + 109.12
R
2
= 0.9902
0
100
200
300
400
500
600
700
800
0 10 20 30 40 50 60 70 80
Pa
m
3
/h
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).
'
1
50
499
0.81, ,
619
N
V
V
= = = (1)
where,
V
N
– building volume;
V’ – fan output (m
3
/h).
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
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Conference Environmental Engineering. Selected Papers, Article number: enviro.2014.263
a) Temperature logger b) CO
2
and relative humidity logger
Fig. 5. Temperature and CO
2
measurements
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.
-10
-5
0
5
10
15
20
0
200
400
600
800
1000
1200
1400
1600
1 2 3 4 5 6 7 8 9 10 11 12
oC
kWh/month
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
2
a. In Figure 7, calculation results of
the model are compared with measured data and data from the dynamic model.
0
5
10
15
20
25
30
35
40
Measured Calcul ation TRNSYS
kWh /m
2
a
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
2
) in Latvia whose energy consumption
6 A. Kamenders et al. / The 9
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Conference Environmental Engineering. Selected Papers, Article number: enviro.2014.263
for heating does not exceed 35 kWh/(m
2
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
2
. 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
2
) in case of small single
family houses with reasonable effort and costs, based on an internal heat gains 2,1 W/m
2
. 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
2
×K);
windows <0.65 W/(m
2
×K);
mechanical ventilation with heat recovery >85%;
building air tightness n
50
<0.4 h
–1
;
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.
References
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... 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. ...
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