The Ministry of Education manages a huge property portfolio (>15,000 buildings, 2100 sites, >$31 billion replacement value). There are a lot of problem buildings, including some that are only a few years old. It has released a new design guide for school buildings, requiring a higher standard in some key respects than the current Building Code.
Image: BRANZ (Build, 183)
Why doesn’t the whole industry follow this advice? The changes are mostly focused on reducing problems with weathertightness and internal condensation: for instance, warm roofs are required if there are steel roof elements). Plus there’s a couple of rational ideas like using cladding that should last the life of the building (50 years) with only normal maintenance.
Can’t we do what they are teaching us at school?
More information here from MoE on weathertightness requirements. Its summary of other key changes:
- “Threshold channels can be used between adjacent exterior doorways when suitably protected.
- Cladding systems are required to have a serviceable life, for the life of the building.
- Cladding systems are not permitted to rely on sealant at their junctions and mechanical flashings must be provided.
- Rigid air barrier board is mandatory for external framed cavity walls.
- Concrete external walls require design or review by façade engineer to address condensation and thermal bridging issues.
- Warm roof form of construction is required for all new buildings with steel roof structures to help eliminate cold and aggravated thermal bridging.
- Roof rainwater collection points are to be positioned at least 600mm from the external face of the building.
- Internal gutters and roof level parapets are not permitted.” [emphasis added]
Sustainable Engineering always specifies an internal air vapour control layer (AVCL) for 140mm framed walls with an external RAB. This generally then requires a service cavity. The High Performance Construction Details Handbook (forthcoming) will have more details.