NZ Government Announcements
Proposals – set to begin in 2024:
Offices must be upfront about how energy efficient they are – or aren’t – under new green building rules announced by the Government. Avoiding construction materials headed to landfill, large building projects must also create a waste minimisation plan.
The rules will apply to commercial, public, industrial and residential apartment buildings larger than a yet-to-be-determined size, according to the Ministry of Business, Innovation and Employment.
Stand-alone homes won’t need an energy rating – though a ministry spokesperson said the Government “may consider” introducing a similar requirement at a later date.
NZ’s Green Building Council (Chief executive Andrew Eagles), which administers energy efficiency assessments for commercial properties
Nearly 100 buildings are currently rated under the New Zealand version of NABERS. In total, 390 premises have been assessed since the system were licenced by the Energy Efficiency and Conservation Authority.
Individual home builders won’t be required to submit a waste plan to council, the ministry said. But the rules are set to apply to subdivisions and developments as well as commercial building projects.
Energy Modelling
Energy modelling software such as the Passive House Planning Package (PHPP) uses set points for internal conditions (between 20 and 25 degrees) and then calculates the energy required to maintain this healthy and comfortable condition for the whole year. The new Energy and Carbon Calculator for Homes (ECCHO) created for Homestar v5 uses PHPP as the base calculation method. The maximum allowable heating demand for Passive House is 15 kWh/m2/yr, which also happens to be the end cap for New Zealand’s proposed Building for Climate Change framework, and the threshold for achieving maximum points in the new HC1: Winter Comfort credit of Homestar v5.
Where there is good solar access and exposed concrete floors to provide thermal mass, north-facing windows should be approximately 10-15% of total floor area. With timber floors, north-facing windows should be closer to 10% of floor area. Where solar access is poor, the north-facing windows should be less than 8% of floor area.
Glazing that is east, west or south-facing should be smaller and designed mainly to meet daylight and view requirements. This glazing is usually a net heat loser in winter, depending on climate and heating.
East-facing windows should be reasonably small – less than 5% of the home’s total floor area.
South and west-facing windows should ideally be less than 3% of floor area and be designed for daylight, views and cooling cross-flow breezes in summer.
Dynamic 3D Sun-path visualizer: drajmarsh.bitbucket.io/sunpath3d.html
Plan roof openings and north facing windows to fit the winter sun and shade summer sun. 40o and 20o
Thermal mass in direct sunlight should be 3x the window area.
The expected modelling time (in hours) for a house of low complexity is provided to allow comparison.
AccuRate was developed by CSIRO (Australia’s national science agency). AccurateNZ is the New Zealand version of the software. Batch processing, where multiple variables are looked at simultaneously, is possible using a free companion program called AccuBatch. AccuRateNZ is fairly user-friendly and only needs a modest one-off license to operate. However, the NZ version has not been updated for several years. It is a very robust calculation engine. [3.5 hours].
SUNREL software was developed by NREL (a national laboratory of the US Department of Energy). It is quite flexible in the passive technologies it can model and includes algorithms for Trombe walls and programmable window shading. It is free to use but requires skill to use as the user interface is primitive. It is a very robust engine. [4 hours]
IES-VE for architects is produced by Integrated Environmental Solutions, a Scottish-based company that specializes in software programmes for designers and engineers. It has an easy-to-use interface but requires some learning. It is interoperable with many graphics-based interfaces, such as Sketchup, Revit and VectorWorks. It is comparatively costly. There are several packages to suit varied users. It is a robust engine. [3 hours]
SEFAIRA is a London-based company that specializes in software programmes for building designers. It was one of the first simulation companies to make use of cloud computing, rather than having a stand-alone program that users access. It is a very robust engine, the interface is very easy to use and there are useful and comprehensive results built in. It is highly interoperable with design packages. Sefaira is especially good for comparing options and optimization. It is comparatively costly. [2.5 hours]
BRANZ ALF Can demonstrate compliance with Building Code clause H1.3.2E (“Buildings must be constructed to ensure that their building performance index does not exceed 1.55.”)
However, from 3 November 2022, an ALF calculation alone will not be enough to show that a house complies with all the requirements of Building Code clause H1.
HeatCAD 2022 is a drawing-based software for fast and accurate calculation of residential heating and cooling loads.
Estimating home heat loss, including R values of materials, infiltration loses, and the thermal performance of real walls.Simulation software to estimate the thermal performance of a passive solar or conventional home.
builditsolar.com/References/Calculators/HeatLossOld/HeatLoss
Daylight Factor
In architecture, a daylight factor (DF) is the ratio of the light level inside a structure to the light level outside the structure. It is defined as:
DF = (Ei / Eo) x 100%
where, Ei = illuminance due to daylight at a point on the indoors working plane, Eo = simultaneous outdoor illuminance on a horizontal plane from an unobstructed hemisphere of overcast sky.
To calculate Ei, requires knowing the amount of outside light received inside of a building. Light can reach a room via through a glazed window, rooflight, or other aperture via three paths:
- Direct light from a patch of sky visible at the point considered, known as the sky component (SC),
- Light reflected from an exterior surface and then reaching the point considered, known as the externally reflected component (ERC),
- Light entering through the window but reaching the point only after reflection from an internal surface, known as the internally reflected component (IRC).
The sum of the three components gives the illuminance level (typically measured in lux) at the point considered:
Illuminance = SC + ERC + IRC
The daylight factor can be improved by increasing SC (for example placing a window so it “sees” more of the sky rather than adjacent buildings), increasing ERC (for example by painting surrounding buildings white), increasing IRC (for example by using light colours for room surfaces). In most rooms, the ceiling and floor are a fixed colour, and much of the walls are covered by furnishings. This gives less flexibility in changing the daylight factor by using different wall colours than might be expected[2] meaning changing SC is often the key to good daylight design.
A study of daylight factors within a single storey building resulting from different perimeter glazing and rooflight designs and glass types. Undertaken using the IES Radiance software Module.
Architects and engineers use daylight factors in architecture and building design to assess the internal natural lighting levels as perceived on working planes or surfaces. They use this information to determine if light is sufficient for occupants to carry out normal activities. The design day for daylight factor calculations is based on the standard CIE overcast Sky for 21 September at 12:00pm, and where the Ground Ambient light level is 11921 Lux. CIE being the Commission Internationale de l´Eclairage, or International Commission on Illumination.
Calculating daylight factors requires complex repetition of calculations and thus is generally undertaken using a complex software product such as Radiance. This is a suite of tools for performing lighting simulation, which includes a renderer as well as many other tools for measuring simulated light levels. It uses ray tracing to perform all lighting calculations. One failing in many of these calculations is that they are often completed without wall hangings or furniture against the walls. This can lead to higher predictions of the daylight factor than is correct.
To assess the effect of a poor or good daylight factor, one might compare the results for a given calculation against published design guidance. In the UK this is likely to be CIBSE Lighting Guide 10 (LG10-1999), which broadly bands average daylight factors into the following categories:[4]
- Under 2 – Not adequately lit – artificial lighting is required all of the time
- Over 5 – Well lit – artificial lighting generally not required, except at dawn and dusk – but glare and solar gain may cause problems