Cronk-y-Berry Primary School on the Isle of Man is of relatively modern construction, having been built within the last 15 years. As is to be expected, the insulation levels of the building are relatively good. However, the annual heat energy usage divided by the floor area of the school is 188kW per m2. This far exceeds the CIBSE benchmark for schools of 160kW. The school is heated by gas boilers feeding both a radiator system and air handling units.
Stroma carried out an air leakage test, revealing that the building had an air permeability rate of 31m3/(hr.m2) @ 50Pa. For schools built under current Building Regulations, the maximum allowable air permeability rate is 10m3(hr.m2) @ 50Pa.
A survey was carried out to explore the potential of improving the school’s air-tightness. It was predicted that a result of between 12-14 m3/(hr.m2) @ 50Pa could be achieved through remedial air-sealing.
In order to predict the impact of the improved air tightness on the building’s demand for heat energy a DSM of the school was produced. The annual heating demand was simulated based on typical occupancy patterns, local ambient temperature and solar gain levels at an air tightness of 31 units. A comparative percentage improvement in heating load could then be calculated for the upper (14) and lower (12) improved air permeability rate. This percentage improvement was then overlaid onto the existing energy bills to calculate the estimated cost/carbon improvement. Based on this data, the Department of Education decided to implement the remedial work.
Remedial air-sealing work was carried out on the building and a re-test undertaken. The schools new air permeability rate was 13.2 m3/(hr.m2) @ 50Pa. The DSM model was then used to estimate the heat energy saving associated with this improved air tightness.