Stefko, J., 1998, Technical university Zvolen, SK

Background

There is a new Standard of Thermal Protection since 1995 in Germany that supposes normative U-values of the opaque and transparent structures - walls, roofs, windows and floors and requires maximal energy consumption of the family houses.

Introduction

Account of the energy consumption includes the energy losses from convection and infiltration and the energy gains from the solar radiation and from the casual gains by the form:
 
                                    Q = 0,9 . (Qt + Qv) - (Qs + Qi)    [ kWh/year ]

For determination of the energy losses and gains there are several forms that reach a realistic energy consumption of the building so we can proclaim this standard method as a Simple Simulation Method for the predicting the energy consumption of family houses. The values of energy consumption should be compared with more realistic simulation by ESP-r (see case study 2. - under construction)

Project

All the new project of the family houses built in Germany are required to support by evidence the maximal energy consumption. 90 - 95 % of production of a prefabricated wooden houses made by  BUCINA trade (SK) are placed in German market. Technical University Zvolen - Department of Wooden Structures collaborates with BUCINA on the project of wooden family houses. The accounts of the energy consumption of about 50 houses should represent the database which enable the analysis of influences: thermal proprieties, orientation, geometry, portion of transparent structures ... etc.

Task 1: Analyses of the opaque structures on a reference house 1

There were simulated various U-values of walls and windows  on the object of family house "Katarina" (fig. 1)
and the impact to the energy consumption
 

Fig.1: Reference house No.1 "Katarina"

Tab. 1: Energy Consumption of reference house No.1 "Katarina"

The analysis was made on the object of double house "ANSA" (fig.2).

Fig. 2: Reference double house "ANSA"

 Tab. 2: Energy Consumption of reference house No. 2-3 "ANSA"

Model No.	Orientation	U-value of windows [W/m.K]	solar gains [kW.h/year]	Energy Consumption  Total [kWh/year]	Energy Consumption  Total/m3  [kWh/year]
2.1	north section	1.5	1573.9	8241.9	19.7
2.2	south section	1.5	2322.9	7492.9	17.9
3.1	north section	2.0	1550.0	9140.8	21.8
3.2	south section	2.0	2287.7	8403.1	20.0

 
Task 3: Influence of position in serial layout

Position in the serial layout (middle section, end section and disconnected end section) was analysed on the reference model No. 4. (fig. 3)
 
Fig. 3: Reference model of serial building

Tab. 3: Energy Consumption of reference serial house No. 4
 

Model No.	Section	U-value of windows  [W/m.K]	Energy Consumption  Total [kWh/year]	Energy Consumption  Total/m3 [kWh/year]
4.1	end match	1.3	8336.6	17.66
4.2	end disconnected	1.3	9403.2	19.84
4.3	middle match	1.3	6508.9	14.23
4.4	middle disconnect.	1.3	7387.9	16.14

 

Task 4: Influence of solar gains

There were simulated the influence of dominant facade orientation (with the majority of transparent areas) and the thermal proprieties of transparent structures on the reference model No. 5 (Fig. 4)

 
Fig. 4: Reference model No. 5 (the dominant facade below)

Tab. 4: Energy Consumption of reference  house No. 5-6
 

Model No.	Orientation of dominant facade	U-value of windows  [W/m.K]	total energy consumption [kW.h/year]	solar gains [kW.h/year]
5.1	east	1.5	13270	3736
5.2	south	1.5	12957	4272
5.3	north	1.5	14202	3027
6.1	east	2.3	15592	4246
6.2	south	2.3	14982	4855
6.3	north	2.3	16398	3493

Discussion

The analysis of energy consumption indicates the influence of  thermal proprieties, orientation and position of family houses. The accounts of energy consumption enable the wooden family houses to be proclaimed as "low energy houses". But in the other hand there is the necessity to investigate the indoor environment quality.  This should be realized only by more realistic simulation methods (for instance using ESP-r).