The cow house for the housing of 120 cows has a length of 73 m and a width of 17,5 m. The height of the side walls are 2,5 m and the height of the ridge is 7,25 m. The milking cows have a production of 25,5 kg milk per day and an average bodyweight of 600 kg.

Two types of building construction for the housing of cows have been tested:

TA:          Construction with nil thermal insulation with a heat resistance of the outer walls

of 0,3 m2k/W and of the roof of 0,07 m2K/W

TC:          Construction with heavy thermal insulation with a heat resistance of the outer walls of 2,2 m2K/W and of the roof of 2 m2K/W

Heat resistance wall construction:

Nil insulation: wallboard panels uninsulated  – 0,3 m2K/W

Heavy insulated: Sandwich panels with 0,07 m polystyrene foam  – 2,2 m2K/W

Heat resistance heavy insulated roof construction:

Nil insulation: Fibre cement sheets without insulation – 0,07 m2K/W

Heavy insulated: Fibre cement sheets with 0,07 m polystyrene foam – 2,0 m2K/W

The ventilation in the cow houses has been created by natural ventilation with stack effect. Stack effect is based on the different of height of the air inlet and the air outlet. The cow houses are provided with an open ridge and closable sidewall openings. Two rates of natural ventilation has been calculated:

Rate 1: Low ventilation with air inlet openings in the side walls of 0,01 m and of 0,02 m in the open ridge.

Rate 2: High natural ventilation with air inlet openings in the side walls of 0,8 m and of 0,8 m in the open ridge.

In table 1 the calculated combinations of building constructions and rates of ventilation are shown.

Table 1 Combinations of building constructions and ventilation rates.

The results of the calculations are given in the tables 2, 3, 4, and 5 at the outside temperatures –28, -20, -10, 0 and +10 °C.

2.    Results

Inside Temperature (°C) – Air temperature inside of the cow house

Relative Humidity (%)  – Relative humidity of the air inside the cow house

CO2 concentration (%) – Concentration of carbon dioxide in the air inside the cow house

Air changes (/h) – Air changes per hour of the air inside the cow house

Roof condition – Condition of the roof inside the cow house: Dry; Condensation or Ice

Table 2: Results of inside climate conditions at different outside temperatures of an uninsulated cow house with low ventilation (TA1).

Table 3: Results of inside climate conditions at different outside temperatures of an uninsulated cow house with high ventilation (TA2).

*) outside the model limits

Table 4: Results of inside climate conditions at different outside temperatures of an insulated cow house with low ventilation (TC1).

Table 5: Results of inside climate conditions at different outside temperatures of an insulated cow house with high ventilation (TC2).

*) outside the model limits

In the figures 1 and 2 the results of the calculations are given at the outside temperatures of –28, -20, 10, 0, and +10 °C. Figure 1 shows the inside temperatures of the different building constructions with the various ventilation rates. Figure 2 shows the relative humidity of the both building constructions with the different ventilations rates.

Figure 1: Inside air temperature at different outside temperatures of two building constructions with the different ventilation rates.

Figure 1 shows there is no difference in inside temperature as well in the uninsulated as in the heavy insulated cow houses wit h a high ventilation rate. In average there is a difference of 7 degrees in inside temperature between the uninsulated cow house and the heavy insulated cow house both with a minimum of ventilation.

Figure 2: Relative humidity of inside air at different outside temperatures of two building constructions with different ventilation rates.

Figure 2 shows in the uninsulated cow house with low ventilation a relative humidity of 100 % at the outside temperatures form -28 up to +10 degrees C. There is almost no difference  in relative humidity  between the uninsulated cow house and the insulated cow house both with high natural ventilation , The heavy insulated building with low ventilation rate gives the lowest relative humidity in the range from –10 °C up to  0 °C. Only at the lowest outside temperature in the heavy insulated cow house with low ventilation there is condensation and ice underneath of the insulated roof construction.

1.1.1     Conclusions

For the housing of milking cows in an area with extreme low outside temperatures a building construction with heavy insulation and a low ventilation rate gives the best performance. The inside temperatures will increase and the chance for freezing surfaces, such as walls, roofs or floors, will be the less.

December 2005

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