Summary Report Mid-European Climate

Department of Microenvironmental and Building Services Engineering

Faculty of Civil Engineering, Czech Technical University in Prague

Thermco project

CTUP partner

Mid-European climate

1.Climate

1.1.Climate in the Czech Republic

Czech Republic (CR) has a surface area of 78,866 km and is located in central Europe within the temperateclimate zone of the northern hemisphere. The country’s territory extends along the 50th parallel. CR is traversed by the 15th meridian.

Mt. Snezka (1,602 m above sea level) is the highest point of CR, located in the Krkonose (GiantMountains), and the lowest is the point at which the Labe River leaves the country’s territory (115 mabove sea level).

Figure 1. Europe

The country’s natural environment is characterized by a moderate, humid climate and fouralternating seasons. Its vegetation is determined by the merging of the Hercynian and Carpathianforest areas and the warm Pannonian steppe. The overall character of the landscape reflects thevertical variation in the georelief.

The climate is generally favourable and has a rather maritime character. Despite the small surfacearea of the country, the climate is highly varied. The elongated shape of the territory results in a slightincrease in continentality as one moves east.

In CR, the basic air temperature profile is characterized by a decrease in temperature in linewith elevation, and can be substantially influenced by individual meteorological conditions and by the terrain.

The frontal systems periodically alternate with anticyclones. Frontal systems areassociated with both increased cloud formation and the change of temperature as a result of the exchange of airmasses of different origin, e.g. inflow of tropical or arctic air. Temperature conditions therefore, are mainly theresult of the physical features of incoming air masses and have an irregular course during the day. In contrast,in regions with anticyclones, local properties of the terrain and radiation conditions come into full effect.

Temperature during anticyclonic weather has a simple daily course with the maximum in the afternoon andminimum in the morning. The difference between the maximum and minimum is indirectly proportional to theamount of cloudiness. During inversion situations in winter, when the temperature rises with elevation (instead offalling), there is often cold weather with small temperature amplitudes in lowland areas, while inthe mountains the weather is clear with relatively high temperatures by day and low temperatures at night.

Figure 2. Prague-Ruzyne –Average daily air temperature in 2007 (°C)

Figure 3. Variation of average air temperature for winter half-year (October to March)

Figure 4. Variation of average air temperature for winter half-year (April to September)

Figure 5. Variation of average annual air temperature

Figure 6. Average annual air temperature in summer half-year in CR

Figure 7. Average annual sum of daily air temperature of 10°C and more in CR

Average monthly air temperature calculation:

θ = θS + (H – HS) · C1

where θ is average monthly air temperature, θS average monthly air temperature in the nearest weather station, H altitude, HS altitude of the nearest weather station and C1 coefficient.

Degreedays calculation:

D = DS + (H – HS) · C2

where D is number of degreedays (with 13°C), DS number of degreedays of the nearest weather station and C2 coefficient.

Table 1. C1 and C2 coefficient

Table 2. Mothly air temperature T, normal temperature deviation dT and standard degreedays in autumn 2007

Figure 8. Degreedays and meterological station altitude

2.Methods of heat loss calculation

2.1.National standard CSN 060210

The original Czech standard CSN 060210 specifies heat losses as a sum total of a transmittance heat loss QT and a ventilation heat loss QV reduced by permanent internal profits QG. Formulas for the calculation are based on physical equations of heat sharing.

where U is overall heat transfer coefficient (W/m2.K), A surface area (m2), θ temperature (K), ACH air change per hour (h), Vspace volume (m3), i.L infiltration characteristic, M.B building characteristic (-),px coefficients (-), H heat loss coefficient (W/K), ρ air density (kg/m3) and c specific heat capacity at constant pressure (J/kg.K).

The permeability heat loss has also been modified by p1, p2, p3 coefficients.

In the case of interrupted heating the p1 coefficient raised the loss according to the formula:

In a practical way the coefficient got the value up to 10 %, p2 then represented the rise of performance necessary for heat contentment in the case of interrupted heating in the period of low external temperatures (10 %). However, this coefficient had already been used only exceptionally for sources of solid/fossil fuel.

Finally, p3 considered the impact of glazing site orientation towards cardinal points, when at adverse/severe northern increased the loss by 10 % again and on the contrary at favourable southern orientation decreased by 5 %.

In practice it meant that the impact of additional charges themselves could decrease the calculated value of losses by approximately 4 % in the limit case of significant orientation towards the south and at adverse orientation increased almost by 20 %.

Heat bridges have been neglected at the calculation, as they had not been important before and their impact has been included at the calculation of the construction height, where the height construction has been used.

Ventilation and the problem of window and door infiltration have been solved by taking into a consideration a higher value of the quantity of air stated from the multiplication of the change of air and from the infiltration through gaps.

2.2. European standard CSN EN 12831

The calculation in accordance with CSN EN12831 standard:

Overall heat lossis

(W)

where transmission heat loss is

(W)

Where H heat loss coefficient (W/K) and for example heat loss coefficient to the exterior is

(W/K)

where Ψ is linear thermal transmittance (W/m.K), l element length (m) and e coefficient.

Ventilation heat loss is

(W)

where ventilation heat loss coefficient is

Vi (m3/h) represent air flow rate of heated space.

2.3.Case studies:

Case 1 Family House

The case is represented by a small one-floor house in the location of external calculated temperature of -12°C. Heat losses are relatively low and the house is relatively well insulated with additional heat insulation. The windows are original.

Table 3. Familly house

In this case the difference between the methods is insignificant and both methods for the design of heated site are possible to use with a relatively high accuracy.

Case 2 Block of flats

The model depicts a ten-floor block of flats.

The case that was examined was a building without heat insulation and heat bridges are not solved or they are not solved correctly. This type of building is represented by a typical building for living from the beginning of the 80‘s (parameters of a wall correspond to a 450mm thick brick wall).

The second case deals with a heat insulated building, where external/peripheral constructions is formed by a 300mm-thick concrete wall and 150mm heat insulation. At the same time the details of insulation of outside corners, attics and connection of windows to heat insulation of housing are properly solved. In this case the coefficient of heat bridges has usually a negative value and a heat loss is reduced.

Table 4. Old block of flats

Table 5. New block of flats

3.Measurement

3.1.Indoor air quality

Indoor air quality parameters –indoor air temperatures, relative humidity, air velocity, CO2 concentration, external air temperature-were measured in tested buildings in Nebrich.Data were measured in period 16th of August to 12nd of October 2008.

IAQ measurement tripod was situated in the room XXX in residential part of the building.

Figure 12. Example of data measurement (18.8-25.8.2008)

Figure 13. Example of data measurement (external temperature 15.8.-12.10.2008)

4.Simulations of building energy consumption

4.1.Building envelope parameters

Building envelope parameters are described in Standard CSN 730540 Thermal protection of buildings – Part 2: Requirements.

Table 6. Heat transfer coefficient required and recommended values

4.2.Building energy demand for heating

Degreeday method calculation

Building energy demand for heating is

whereD is sum of degreedays during heating period, d heating period (days) and ε efficiency coefficient.

5.Results

5.1.Heat loss calculation

From the mentioned results (Case studies) we can come to the conclusion that the new methods of the calculation with their results correspond to present methods of calculations. It is also obvious that the possibility of differentiation between various types of the solution of heat bridges enables more accurate determination of heat parameters of buildings with a low heat loss, where a high accuracy of the calculation is necessary. The differences between the methods are in their accuracy and that is why they are not significant in above mentioned cases.

All the present methods of the heat loss calculation take into a consideration the ventilation loss in accordance with the multiplication of the change of air, as the infiltration at new buildings is low due to the impact of very tight glass gaps. Thanks to that the results do not differ a lot. New calculation methods provide us with similar results as the methods used before their introduction. However, using CSN EN 12831 standard there is a higher risk of a wrong calculation because of using irrelevant coefficients. On the other hand the result is more precise, even though more time consuming. Nevertheless, a number of input data is not known at the beginning of evaluating parameters.

REFERENCES

[1]CSN 060210 Calculation of heat losses in building with central heating: May 1999. Czech version. Standard was cancelled in August 2008.

[2]CSN EN12831 Heating systems in buildings – Method for calculation of the design heat load: 2005, Czech version.

[3]CSN EN832 Thermal performance of buildings – Calculation of energy use for heating-Residential buildings: September 1998. Czech version.

[4]CSN 730540 Thermal protection of buildings – Part 2: Requirements.

[5]TOLASZ, R.: Climate atlas of Czechia. Published by Czech hydrometeorological institute, Prague: 2007. ISBN 978-80-86690-26-1

Poznámky:

Task 2.3 Application of (existing) design guidelines in Mid-European countries. Energy performance and indoor environment, will be analysed on the basis of complex simulation on examples of standard buildings with different energy systems, designed according to existing guidelines. Simulated buildings will be designed using standard, low-energy and passive concepts. Comparisons will be made of the thermal behaviour of light-weight (timber structure) and traditional heavy weight (thermal insulation + ceramic + concrete) buildings with different heating and cooling systems. Design according to EN 12832 will be compared with Czech national standard SN060210. Various passive cooling techniques will be assessed , adapting them to Mid-European climate conditions. Simulation will be supported by measurements of specific parameters, i.e. energy consumption and thermal comfort.

Analysis of Energy performance and indoor environment, based on complex simulation on examples of standard buildings with different energy systems, designed according to existing guidelines. Design according to EN 12832 compared with Czech national standard SN060210.

Content:

6.Climate

6.1.Climate in the Czech Republic

7.Methods of heat loss calculation

7.1.National standard CSN 060210

7.2.European standard CSN EN 12831

8.Systémy vytápění a chlazení

8.1.Systémy vytápění

8.1.1.Vodní

8.1.1.1.Otopná tělesa

8.1.1.2.Zabudované systémy (podlahové vytápění,..)

8.1.2.Teplovzdušné

8.2.Systémy chlazení

8.2.1.Aktivní

8.2.2.Pasivní

8.2.2.1.Stínění

8.2.2.2.Úprava parametrů zasklení

[MK1]

9.Measurement

9.1.Indoor air quality

9.2.Energy consumption

10.Simulations of building energy consumption

10.1.Building envelope parameters

10.2.Building energy demand for heating and cooling[MK2]

1

[MK1]Zpracuje Lenka

[MK2]Vázáno na dokončení modelu esp-r Roman