Tips & Tricks

Tips and Tricks: No. 2, Domestic Hot Water Systems

Generally design professionals, in dealing with the NZBC clause H1, address issues relating to building thermal insulation.

Additionally, H1 also addresses issues of ventilation, lighting design and domestic hot water generation.

A pertinent aspect is the restriction imposed on the length of hot water piping between a domestic kitchen sink and the hot water unit.

This stipulation translates to a maximum total pipe length of 7m for a 20mm diameter pipe (the equivalent of 2 litres of water).

Further information on Clause H1 is available here.

When designing for a mechanical ventilation system, engineers follow the requirements of the NZ Building Code which stipulates AS1668 as an acceptable solution. AS1668 dictates the use of supply or extract air ducting or both with stringent requirements on the placement of supply and extract air grilles to achieve compliance often based on extract rates of 3.0 litres/s/m² of car park area.

An alternative solution lies with NZS4303. Whilst the ventilation rate is double at 7.5 litres/s/m², the use of ductwork, supply and extract air grilles is not mandatory. This approach yields a simple solution of a number of plate type extract fans fixed to the car park external walls strategically located to ensure a good “sweep” of the car park floor with fresh air. The absence of ductwork provides for an economic, uncomplicated and simple design with maximum available floor to ceiling heights.