An agricultural or horticultural environment multi-sensor unit, without a separate fan unit for the management of air flow through the multi-sensor unit, the multi-sensor unit including: a plurality of environmental sensors; and a louvred housing in which the plurality of environmental sensors are mounted; wherein the environmental sensors include at least: an incident light sensor (51, 52); and a temperature sensor spaced from the incident light sensor (51, 52) and positioned such that air may flow freely through the louvred housing and over the temperature sensor; wherein airflow through the multi-sensor unit is allowed by the louvred housing to provide accurate sensor measurements without the use of powered fans, characterised by a first sensor assembly mounted near the top of the housing, and a second sensor assembly spaced from the first sensor assembly and mounted lower in the housing, in which the first sensor assembly includes at least the incident light sensor (51, 52) positioned near a top surface of the housing, which is configured to allow light to enter the housing to fall on the incident light sensor (51, 52), and the second sensor assembly includes at least the temperature sensor. a plurality of environmental sensors; and a louvred housing in which the plurality of environmental sensors are mounted; wherein the environmental sensors include at least: an incident light sensor (51, 52); and a temperature sensor spaced from the incident light sensor (51, 52) and positioned such that air may flow freely through the louvred housing and over the temperature sensor; wherein airflow through the multi-sensor unit is allowed by the louvred housing to provide accurate sensor measurements without the use of powered fans, characterised by a first sensor assembly mounted near the top of the housing, and a second sensor assembly spaced from the first sensor assembly and mounted lower in the housing, in which the first sensor assembly includes at least the incident light sensor (51, 52) positioned near a top surface of the housing, which is configured to allow light to enter the housing to fall on the incident light sensor (51, 52), and the second sensor assembly includes at least the temperature sensor. an incident light sensor (51, 52); and a temperature sensor spaced from the incident light sensor (51, 52) and positioned such that air may flow freely through the louvred housing and over the temperature sensor; wherein airflow through the multi-sensor unit is allowed by the louvred housing to provide accurate sensor measurements without the use of powered fans, characterised by a first sensor assembly mounted near the top of the housing, and a second sensor assembly spaced from the first sensor assembly and mounted lower in the housing, in which the first sensor assembly includes at least the incident light sensor (51, 52) positioned near a top surface of the housing, which is configured to allow light to enter the housing to fall on the incident light sensor (51, 52), and the second sensor assembly includes at least the temperature sensor. a first sensor assembly mounted near the top of the housing, and a second sensor assembly spaced from the first sensor assembly and mounted lower in the housing, in which the first sensor assembly includes at least the incident light sensor (51, 52) positioned near a top surface of the housing, which is configured to allow light to enter the housing to fall on the incident light sensor (51, 52), and the second sensor assembly includes at least the temperature sensor.