A Dublin school said it was forced to close early on Friday due to cold temperatures as a result of keeping windows open for "compulsory ventilation".
Separately, teachers across dozens of other schools complained of “freezing” temperatures as low as 10 degrees as they struggled to meet Covid-19 ventilation standards.
Under health and safety laws, workplaces are required to have a minimum temperature of 16 degrees.
St Kevin's College, an all-boys secondary school in Finglas, Dublin 11, informed parents on Friday that the school was closing at 1.05pm – two classes earlier than scheduled – due to "low temperatures inside and outside the school due to compulsory ventilation".
It is understood the school was missing 10 teachers for Covid reasons and had no caretaker available.
Under public health guidance, schools are required to consider if ventilation in classrooms can be improved “without causing discomfort”.
They are also advised to ensure that, wherever possible, doors and windows are open to increase natural ventilation, “weather permitting”.
Many schools, meanwhile, shared photographs of temperature readings in their classrooms across social media on Friday.
One school teacher said the temperature in their school at the start of the day was 8 degrees and rose to a “balmy” 10 degrees by the time children left at 2.30pm.
Another teacher, showing a temperature reading of 11.2 degrees, said staff and pupils were all wrapped up in coats to protect against cold and wind.
In another school, a teacher showed a reading of 9.9 degrees and added: “This is what we had to work with today. Baltic.”
Another added: “15 degrees at the front of the room, 8 degrees if you’re unfortunate enough to sit near a window despite a radiator underneath the window. Had three thermometers from science lab to verify.”
In a Carlow primary school, a teacher posted a reading of 13.4 degrees, and added: “Can we continue like this? Surely we need to start sending kids home? This isn’t safe!”
The Department of Education said the overarching approach for schools should be to have windows open as fully as possible when classrooms are not in use – such as during break-times or lunch-times and also at the end of each school day – and partially open when classrooms are in use.
“It is worth noting that windows do not need to be open as wide in windy/colder weather in order to achieve the same level of airflow into the classroom. This will assist in managing comfort levels in classrooms during periods of colder weather,” a department spokesman said.
“In colder weather any local chilling effect can be offset by partially opening the windows nearest to and above the radiators.”
Last month the National Public Health Emergency Team warned against “over-ventilating” classrooms to stop the spread of Covid-19 by leaving windows “open all the time”.
Carbon dioxide levels
However, many teachers say windows need to be left open to ensure carbon dioxide levels are within recommended ranges.
A department spokesman added that a dedicated team has been established in the department to support schools that may have concerns about ventilation.
Officers are also available to contact schools where required, walking through the steps the schools should take to deploy good ventilation practices.
Where it is not possible for a school to access the expertise of an engineer or architect, a technical assessment to assist the school can be facilitated through the department.
“Schools that identify inadequate ventilation in a room can utilise their minor-work grant or apply for emergency works grant assistance to address ventilation enhancements on a permanent basis.”