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 ; and a temperature sensor spaced from the incident light sensor 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 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 , 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 ; and a temperature sensor spaced from the incident light sensor 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 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 , and the second sensor assembly includes at least the temperature sensor . an incident light sensor ; and a temperature sensor spaced from the incident light sensor 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 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 , 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 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 , and the second sensor assembly includes at least the temperature sensor . <EOS>