Daylight Modelling for ESD Report

Local councils also mandate developers to address sufficient levels of daylighting in their ESD reports. Daylight scores for ESD reports are generated through BESS tool. Also, most governing councils in Victoria mandate minimum daylighting levels for the developments that are applied for building permit. Daylight modelling is by far the most promising way to comply with the council’s minimum requirements and to achieve BESS scores in the Indoor Environment Quality (IEQ) section. It is realistic, easy to follow, compare and optimize.
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At Energy Compliance, we offer all avenues to demonstrate your building compliance under any conditions.

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Quotations: Same business day of inquiry.
Daylight modelling reports: 3-6 business days (depends on the complexity and the initial degree of compliance).

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Do I Need Daylight Modelling?

NCC

National Construction Code (NCC) sets the minimum requirements for natural lighting in NCC Vol 1.0 Part F4. This mandatory minimum requirement is as follows:

” Sufficient openings must be provided and distributed in a building, appropriate to the function or use of that part of the building so that natural light, when available, provides an average daylight factor of not less than 2% “.

Above minimum requirement only applies to some building classes (click here for more information on building classes):

  • Class 2 and Class 4:    all habitable rooms.
  • Class 3:                          to all bedrooms and dormitories.
  • Class 9a and 9c:          to all rooms used for sleeping purposes.
  • Class 9b:                       to all general purpose classrooms and playrooms.

Council

Governing councils of Victoria pick up the mandatory minimum requirement of NCC for natural light and build on top of that. This means there is also some mandatory requirement for daylighting provisions from the governing council. Building permit applicants will have to meet these requirements as well.

As an example, City of Darebin mandates building permit applicants to provide evidence of sufficient daylighting through modelling:

” Provide adequate daylight for all spaces. If areas appear to have limited daylight demonstrate a mean daylight factor of at least 2% through modelling “.

Hence, the council’s minimum will have to be met as well as NCC provisions.

Daylight modelling

BESS

Built Environment Sustainability Scorecard (BESS) is a scorecard to assess and prove that a building complies with Environmentally Sustainable Design (ESD) requirements of a local council. Many Victorian councils demand Best Practice that is defined as an overall score of 50% or higher. Daylighting contributes most of the score for IEQ in the BESS tool. Also, IEQ contributes the most overall BESS score after Energy (16.5% of total score). There is also a mandatory requirement in the BESS tool for IEQ:

” In addition to the overall scoring, the proposed building must achieve a mandatory pass score of 50% (of the total 100% score of its category) for Indoor Environment Quality (IEQ) “.

BESS scoring system for daylighting is discussed further on this page for both residential and commercial buildings.

Daylight modelling

BESS Score System for Daylight Access:

Daylight Access points are obtained by four means:

1- Deemed to Satisfy provisions in BESS: using this method, there is no partial compliance.

2- BESS in-built calculator: using this method, some degree of accuracy is lost especially in cases where neighbouring properties are too close to allow for vertical sky angle to be calculated. It also works only for rooms having only a single aspect (i.e one external window to the room) as rooms with more than one aspect are deemed to have adequate daylight.

3- Hand calculation: using this method, evidence of accuracy, valid formulas and assumptions must be provided.

4- Daylight modelling: using this method, daylight levels are assessed with the utmost accuracy. This method also allows for optimisation, comparison and flexibility of solutions.

Obtaining scores for Daylight Access in BESS tool is further explained below:

Residential Buildings

Commercial Buildings

Living areas – Points are awarded where at least 80% of the total number of living areas achieve a daylight factor greater than 1% to 90% of the floor area of each living area, including kitchens. Additional points are awarded where 100% of dwellings comply. BESS in-built tool or daylight modelling software are used to show this compliance.

Bedrooms – Points are awarded where at least 80% of the total number of bedrooms achieve a daylight factor greater than 0.5% to 90% of the floor area in each room. Additional points are awarded where 100% of dwellings comply. Points are also awarded where at least 90% of bedrooms have an external window.

Winter daylight – Points are awarded where at least 70% of dwellings receive at least 3 hours of direct sunlight in all living areas between 9 am and 3 pm in mid-winter. This compliance can only be demonstrated with daylight modelling using accredited software.

All non-residential spaces – Points are awarded where it is demonstrated by daylight modelling software that over 33% of the nominated area achieves a daylight factor of at least 2%. Additional points are awarded where it is shown that over 60% or over 90% of the floor area achieves 2% daylight factor. Maximum points are awarded where 100% of regular use areas (by floor area) achieves the target daylight factor.

This compliance can only be demonstrated with hand calculation or daylight modelling using an accredited software.

What is Average Daylight Factor (ADF)?

As mentioned above, all roads to compliance using daylight modelling reach a single word: Daylight Factor. But what is Daylight Factor?

NCC describes the Average Daylight Factor (ADF) as “the ratio of the illumination level within a room provided by daylight to the level of daylight outside the building during overcast conditions” (NCC 2019 Vol 1.0 Schedule 3 Definitions).

Average Daylight Factor (ADF) depends on:

  • Area of glazing: the greater the area of the glazings serving a room, the higher the ADF.
  • Orientation of glazing: the more angled the window (e.g. roof lights) the more daylight could be let inside that room. This is simply due to a wider view range of skylight to the sky.
  • Sill height: higher sill heights, especially in rooms with higher depths guarantee higher levels of daylight.
  • Depth of room: deeper rooms (where the distance between windows and distant walls is great), are subjects of lesser ADF.
  • Outside obstacles: outdoor buildings and other features are considered as obstacles to the clear sky view from the windows. Window location, area and sill height can be set to minimize the obscured view.

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  • Reflectivity of fabrics: brighter floors, ceilings and internal walls reflect more light and increase ADF. The typical light reflectance of some materials are:

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  • Visible Light Transmittance (VLT) of glazing: ADF mainly revolves around the visible spectrum of light. Indoor daylight level contribution of a clear window is more than that of the tinted window. Typical light transmittance values of different windows are shown below:

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VLT is the portion of visible light that is transmitted through the window, whereas SHGC is the total solar radiation (including Infrared) that is transmitted through the window. In most cases, SHGC directly correlates with VLT so the higher the SHGC the higher the VLT. However, this is not the case in many modern Low-E technology windows.

What is overcast sky condition?

Evaluation of Average Daylight Factor (ADF) is done assuming an overcast sky condition. The luminance of the standard overcast sky reduces looking from vertical to the horizon (Zenith angle below) but not with horizontal orientation and location. In other words, luminance is consistent across azimuth angles while gradually reducing across the zenith angle. For ease of understanding, an overcast sky condition could be deemed similar to a cloudy sky where it is brighter near the zenith compared to locations near the horizon. Simply put, the orientation of windows doesn’t change ADF for two identical rooms with identical window areas, whereas window angle does.

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How Average Daylight Factor (ADF) is measured?

We can measure ADF in three ways:

  • Experimental: one can calculate ADF using a typical Lux meter by simply measuring outdoor illuminance and divide it by the average illuminance inside a room. Measurement of indoor illuminance levels must be done by averaging out the measured data in various bright and dark locations. The more the measuring locations, the more accurate the average illuminance of the room.

The experimental method is costly and has no use in the pre-construction stage.

  • Theoretical: there are a set of formulas that estimate the ADF inside a room. For instance, NCC Vol 1.0 prescribes using the formula below to calculate ADF from each window:

Where:

Daylight modelling

W = Net area of the light-transmitting area of the window (m2);

A = Total area of the internal wall, floor and ceiling surfaces (m2);

T = Diffuse light transmittance of the window;

θ = Visible sky angle in degrees, measured in a vertical plane normal to and from the centre of the window, and

R = Area-weighted average reflectance of area A.

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We use the theoretical method as an estimate, and this method is not 100% accurate. Also, evaluation of ADF using this method is not possible for complex building geometries with many openings and various and non-uniform outdoor obstacles.

  • Modelling: the best method of ADF evaluation is modelling using certified software. This method is used widely in the design stage of any type of building to accurately address daylight levels.

At Energy Compliance, we undertake daylight modelling for residential and commercial buildings using accredited commercial tools. We aim for accuracy of assessment and superiority of solutions. Contact us for undertaking daylighting compliance and solution.

What is the importance of daylighting in building designs?

We have concealed ourselves in our comfortable homes, separated from natural aspects of the world. Perhaps a little flower pot, or perhaps a little daylight, would give us a sense of time and space and connection to our surrounding environment.

Daylight is an important parameter for the well-being of the occupants in any type of building. Daylighting is associated with improved mood, enhanced morale, less fatigue and reduced eye strain (Robbins, 1986).

The introduction of fair amounts of daylight in buildings has some significant benefits:

  • It promotes wellbeing and maintains our health as it sets our body clock to the level of awareness we need throughout the day, and a sense of connection to our natural world.
  • Well-day lit spaces make people more productive and more alert. Various studies show that work performance is elevated where a fair amount of daylight is introduced to the office buildings.
  • The introduction of natural daylight through glazing is a game-changer in the overall cost of dwellings and commercial buildings. The preference for a clear and deep view generates financial benefits for the builders.
  • With acceptable levels of daylighting, comes the decrease in using artificial lighting and consequently, cooling demand to offset the heat generated by lighting fixtures.

There are also some restrictions to the levels of daylighting in the buildings. A good building design must address acceptable levels of daylight into the rooms while preventing the defects of too much daylighting:

  • Minimum daylighting maintains visual benefits. However, too much daylight may cause glare and reduce the performance efficiency of workers.
  • Too much daylighting in an office environment adds to the reflectance from surfaces and screens. To work properly, workers prefer the use of artificial ambient and task lighting which is costly and adds to the cooling demand.
  • Too much daylighting is directly related to the ratio of the glazing area to the floor area. Glazing is one of the major costs in construction development, therefore, non-optimized daylighting through glazings adds to the overall construction cost.