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Main findings: the effect of insulation thickness on ADF was studied

The regulated circadian system controls the body’s sleep and wakefulness cycle and core temperature through an external circadian cycle.

Symptoms of seasonal affective disorder (SAD) decrease, including depression, low energy, fatigue, increased appetite and weight gain.

Maintaining a healthy level of vitamin D is positively associated with healthy bones.

The number of bacteria and viruses associated with common respiratory infections in winter decreased.

For people who spend a lot of time indoors, it can have a positive effect on their mood.

Establish standards

Many top building performance standards now recognize the health and benefits of efficient lighting. Light is one of the eight key concepts in the increasingly popular WELL building standard, which is marked by Light rights, lighting Windows, solar glare control and day and night lighting design.

Good lighting also leads to two credits awarded directly in the Hea 01 part of the latest BREEAM assessment. The standard recognizes that effective lighting can also reduce the “energy need to light up a home”, since electric lights can last longer and help reduce energy costs.


The front of Kingswood Academy makes full use of natural light and multi-layer glass

Design challenges

Seasonal fluctuations are just one of many factors that affect natural light levels in buildings. These changes are a major challenge for lighting system designers. If too much light enters a building, it can lead to problems including overheating. With too little light, space can become dark and unwelcome. To determine the ideal middle ground, designers use various methods. The most common of these is the average daylight factor (ADF).

In short, the daylight factor is the comparison between the light level inside the building and the light level outside the building.

ADF calculates the amount of light that actually reaches the occupant throughout the building.

To do this, draw a horizontal surface (working plane) at the height at which the work is normally performed. The ADF then looks at the amount of sunlight reaching each area of the plane and compares it with its total area. The external daylight levels used in the ADF are based on the standard cloudy day. The final ADF is then expressed as a percentage. This means that the average amount of light (illumination) on the working plane is compared to the outside.

For example, 1% ADF means that the average internal light level is one percent of the outdoor light level.


According to Arup and the green building council of technical papers home health: the sun and the sun, the CIBSE LG10 (building lighting), ADF designer’s goal is to make the room look full of sunlight, this is the “general rules” the consensus of 2%. The environment. Lighting: designer’s guide) and BS 8206-2:20 08 (architectural lighting). Lighting practice specification.

BS 8206-2:2008 stresses that it is a good practice to ensure that rooms in the building are mainly lit by daylight, and to achieve this goal, ADF should be at least 2 per cent. Five percent of ADF rooms are considered daytime.

The lack of natural light within a building may increase its energy needs and cause health problems for its occupants. The code of conduct also sets a minimum ADF for each room, as shown in the table above.

Part of the BREEAM building standard is visual comfort, which is divided into four parts, each with available credit line:

Glare control with a credit limit;

Lighting, according to the type of building, can provide up to two credits;

Check. One credit is available, except for the medical care building in the residential area. Two credits are available.

Internal and external lighting, there is a credit line. The first credit for daylighting is to maintain good lighting in existing homes for renovation or renovation, and to achieve the minimum lighting requirements in the extension of the home. The second credit is for minimum lighting requirements throughout the house.

Need to seriously consider adequate lighting levels through the window or other openings, at the same time does not affect the approval document of England and wales L1A and L1B, L2A and L2B as well as domestic and non domestic technical manuals listed in section 6 hot U value requirements Scottish energy building codes, including structure analysis.

In order to achieve or exceed the minimum U value recommended in the above documents, a certain amount of insulation is required to meet the building codes. However, the more Windows and openings in a building, the thicker the insulation, to minimize heat loss and heat loss. this

Consultancy Peutz BV study compared the wall accumulation average daylight factor and the insulation of the two different types: phenolic insulation (lambda value of 0.020 W/mK) and mineral fibre (lambda value of 0.035 W/mK), thickness of implementation on four different elevation layout of three different U value (0.11 W/m squared K, 0.11 W/m squared squared K and 0.21 W/m K).

The highest ADF comes from the facade layout. Both insulation types have a wide span window.

Compared with all the mineral fiber insulation materials in the facade layout, the percentage of ADF improvement in the phenolic insulation exterior wall facade accumulation was between 10.6% and 63.2%.

All the results including phenolic insulation materials exceeded the minimum lighting standard of BS 8206-2:2008 bedroom and living room.

Compared with mineral fiber insulation materials, using phenolic insulation of exterior wall facade of the building ADF maximum percentage improvement from elevation layout has four Windows, depends on U value, in the range between 18.1% and 63.2%.

The results show that compared with mineral fiber insulation materials, phenolic insulation materials can provide ultra-thin solutions and meet or exceed the minimum daylight lighting requirements specified in BS 8206-2:2008. If there is not enough daylight available, you can change the design (provide additional Windows, roof lights or bulbs, or change the layout of the room) to comply with the guidelines.

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