The guidance paper highlights the ventilation requirements within the new Output Specification, along with recommended solutions and data from Breathing Buildings sites such as Linton Village College.
"The new Facilities Output Specification was issued in Summer 2013, and involved a number of key changes from the draft version in Autumn 2012. The main changes are as follows:
- The EFA have removed any uncertainty about what constitutes a cold draught - it is now defined. The new specification states that the fresh air entering a naturally ventilated space needs be mixed sufficiently with the room air so that the mixed air is within 5C of the ambient room temperature by the time it gets to 1.4m from the floor.
- There are some changes to the three design summertime overheating criteria cited in the Autumn 2012 document. In particular, the formula for the second one has changed. Criterion 2 is the sum of the Weighted Exceedance for each degree K above the Tmax (1K, 2K and 3K) and must not exceed 6 on any one day. Previously the equation involved the square of the difference in temperature and the daily maximum was 10.
- Finally, a fourth condition for summertime overheating has been introduced. This is the one which the school will actually be measured on once the building is occupied. It is the Performance in Use criterion and is based on the average temperature difference, over the course of a day, between the interior and exterior when the outside is above 20C. The maximum difference allowed is 5C."
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