GUIDE TO DAYLIGHTING

AND EN 17037
CONTENTS

Executive summary 03

Introduction 04

EN 17037 - what is it and why does it matter? 05

The impact of daylight on building performance and occupant comfort 08

Using VELUX Modular Skylight solutions to meet the standard 13

Conclusion 16

Glossary of terms 17

2 VELUX commercial.velux.co.uk
EXECUTIVE SUMMARY

A new European Standard for daylighting in buildings is

helping change the focus of building design, and the role
of glazing in those designs, to improve occupant comfort
and overall energy efficiency. The need to provide glazed
openings and well distributed daylight to interior spaces,
while reducing artificial lighting use, must be considered
with the balance between heat loss and solar gains.

EN 17037 covers four areas of daylighting: daylight

provision, assessment of the view out of windows,
access to sunlight, and the prevention of glare.
Although written for new buildings, its provisions can
also be applied to works to existing buildings.

Used in combination with facade (vertical) glazing, roof

glazing offers greater access to unobstructed sky and
sunlight, and brings daylight deeper into a building.
Modular skylights provide a flexible design solution to
achieve good daylighting while also contributing to the
building’s energy balance and ventilation strategy.

3 VELUX commercial.velux.co.uk
INTRODUCTION

‘Daylighting’ is the name given to the controlled use of whether the building could have been designed to
natural light in and around buildings. It is the deliberate avoid it?
positioning of glazed elements, including windows, roof
The good news is, something can be done about it -
glazing and skylights, within the building design to
and there is now an agreed approach for measuring
provide the best quality of daylight, as well as quantity.
our efforts. The end of 2018 saw the publication of the
We all understand the importance of light in terms of first coordinated European Standard, EN 17037, to help
being able to see, and being able to use buildings and building designers achieve appropriate levels of daylight in
spaces for what they are intended. We also understand any type of building.
that artificial light - however well designed it is - is less
This white paper introduces EN 17037, gives an
able to meet these needs than natural daylight. When
overview of its content and the four different aspects
we allow natural light to enter our buildings, we are also
of daylighting design it covers, and looks at how
maintaining a view out and a connection with our wider
VELUX Modular Skylights can be used to help achieve its
environment - something that artificial light cannot do.
recommendations.
Light impacts our mood as well; a concept that is not
Beyond the provision of daylight for people to be
easy to measure through mathematics and physics. The
comfortable and able to undertake tasks, there is also
proliferation of technology, and the amount of time we
the balance between energy use and daylight provision
spend staring at screens, is beginning to raise awareness
to think about. Also explored in this document is how
of the types of light we expose ourselves to and the ef-
increased heat loss and energy use through glazed
fect it has on sleep and the body’s natural rhythms.
elements can be offset by solar gains, and less reliance
We need that same increased awareness when it on artificial lighting when daylight is well distributed
comes to buildings. We need to control the light entering throughout the space
windows - through appropriate shading and orientation -
so we don’t create spaces that are too bright.

We know we crave a connection with the outside; we

know we want well-lit spaces. If, at face value, we have
those things then we rarely pay attention to exactly how
they’ve been achieved. If we find ourselves in a room
with south-facing glazing, and the room is overheating or
we are exposed to glare from windows, do we question

4 VELUX commercial.velux.co.uk
 EN 17037 - WHAT IS IT It is an oft-quoted statistic that the average person
spends around 90% of their time indoors - around 22
AND WHY DOES IT hours of the 24 hour day. Even leaving aside questions
of indoor air quality (IAQ) and whether our buildings are
MATTER? sufficiently ventilated, most of us would benefit from
spending more time outdoors generally.

We can all pinpoint reasons why decreasing that average

is easier said than done, of course. Work and family
pressures, the weather, and the level of access we
enjoy to high quality outdoor spaces - any or all of these
can mean we unintentionally spend more time inside
buildings than outside them.

Designing buildings to provide healthy, comfortable

living and working spaces is more critical than ever. The
provision of daylight is one such area where design can
be improved. Offering building users improved comfort
through the benefits of daylight, and a connection to
outside, required a dedicated code of practice.

5 VELUX commercial.velux.co.uk
What is EN 17037? What aspects of daylight design does the
standard cover?
Published at the end of 2018, after a decade or so of
discussion and writing, EN 17037 is the first Europe-wide To achieve its multiple aims in respect of daylighting and
standard to deal exclusively with the design for, and occupant comfort, EN 17037 covers four different areas.
provision of, daylight in buildings. Some designers may have familiarity with designing to
provide daylight, but the other three aspects of design
It replaces a patchwork of standards across different significantly extend the scope of the standard compared
European countries, or provides one where no standard to existing best practise:
previously existed.
■ Daylight provision.
The UK had BS 8206-2:2008, the code of practice for
Daylight provision, or illuminance levels, allow users to
daylighting, giving recommendations for daylight design
carry out tasks and play a part in determining the likelihood
in buildings - including electric lighting design when used
of artificial lighting being switched on. Assessment can
in conjunction with daylight. By contrast, EN 17037
be via either climate-based modelling or daylight factor
deals exclusively with daylight. It includes methods of
calculations.
calculation for design parameters that do not feature in
BS 8206-2. ■ Assessment of the view out of windows.

Some existing European Standards include daylight Building users should have a large, clear view of the
as a factor - for example, EN 12464-1 and EN 15193. outside. EN 17037 considers the width and outside
However, both of these also look at it in the context distance of the view, as well as landscape ‘layers’ (sky,
of electric lighting provision, and so EN 17037 is truly landscape and ground). The view should be perceived
unique in focusing on the quantity and quality of daylight to be clear, undistorted and neutrally coloured. Width
of view can be established via a detailed or simplified
for building users.
approach. Outside distance and number of layers are
The exact date of adoption for EN 17037 depends on each measured by a single approach.
when it is incorporated into national standard frameworks.
■ Access to sunlight.
Standards bodies in each country must produce a national
annex (NA), detailing local information that helps with Calculating access - or exposure - to sunlight is a comfort
applying the recommendations of the standard in the and health factor for users of dwellings, nurseries and
specific country. hospital wards. Daily sunlight exposure can be established
through detailed calculation or table values.
In the UK, the full BS EN 17037 is expected to become
effective by the end of 2019, and any conflicting national ■ Prevention of glare.
standard has to be withdrawn by mid-2019 - this is As its name suggests, prevention of glare is concerned
expected to include those parts of BS 8206-2 that with removing the probability of glare for building users,
conflict with EN 17037. especially those who do not choose where they sit. It
uses a detailed calculation of daylight glare probability
(DGP), or a standard table of values for sun-screening
materials.

6 VELUX commercial.velux.co.uk
What performance levels does the standard set? This means the standard is not confined to new buildings.
Proposals for renovating and/or converting an existing
To provide flexibility at the same time as making the
building can benefit from the intentions of EN 17037. Its
standard useable and understandable, EN 17037 sets a
tools provide a good means to assess existing openings
minimum level of performance that must be achieved for
in terms of the four aspects of daylighting, and inform
each of these four areas. On top of that, there are two
changes to the building fabric to make it better suited to
further performance levels: medium and high.
the proposed use.
Users of the standard are free to select the performance
Section 5.3 of EN 17037 describes assessment of exposure
level that best relates to the building design and proposed
to sunlight, and is the only part of the standard to of-
building use. A simplified and detailed method is available
fer some building-specific guidance. It says that at least
with which to assess each design area.
one habitable space in dwellings, hospital patient rooms
For example, the minimum illuminance of 300 lux is and nursery playrooms, should be provided with the mini-
based on a number of studies. It is considered as suitable mum performance level for sunlight exposure.
illumination for prolonged office work, and the level at
While access to sunlight is generally desirable, over-exposure
which the probability of switching on electric lighting is
can be detrimental to health and wellbeing. This
low. Typical design levels for artificial lighting also use a
unique example of building-specific guidance within
300 lux threshold.
EN 17037 is an acknowledgement that, in certain
How are local conditions accounted for? situations, building users need a ‘calmer’ space that
does not achieve the levels of sunlight set as medium or
As a standard covering all of Europe, the potential
high performance.
differences between one site and another are considerable.
Daylight hours and angle of the sun vary for two sites
within the same country, never mind at extreme points
of the continent, so calculation results for any of the four
aspects of daylighting will be unique on every project.

The standard provides common methods of calculation for

evaluating daylight. Those calculations, however, take
into account national and local conditions through
climate-based modelling so solutions are appropriate and
specific to each project.

What building types does EN 17037 apply to?

The standard has been written so that it can be applied

to any building. The areas of design covered, and the
flexibility for designers to choose what performance
level is achieved, means internal spaces can be designed
to suit intended activities.

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 THE IMPACT OF Daylighting can be a daunting concept to think about
when designing a building, but it doesn’t need to be.
DAYLIGHT ON BUILDING While it is undoubtedly a complex subject - especially
when accounting for four different areas of daylight
PERFORMANCE AND design, as covered in EN 17037 - seeking advice at an

OCCUPANT COMFORT early stage and getting the benefit of daylight modelling
calculations will smooth the process considerably.

As is always the case with a construction project,

getting something like daylighting right at the start
improves certainty. Glazing products - among the rest
of the building fabric and services specification - can
be specified to the right dimensions and performance
level, and priced accordingly. It makes it more likely that
the finished building will deliver what is promised at
design stage, in terms of both building performance
and occupant comfort.

The alternative is to avoid the cost of calculations and

modelling exercises, because it seems like a saving. But if
late changes have to be made to a design because something
was not given proper consideration at the outset, the
knock-on effects can prove even more expensive.

If the glazing provision is made incorrectly, the potential

impacts include delays on site or the redoing of
already-completed construction work. Changes to the
product specification, such as finding that blinds should
have been specified and pre-mounted in the factory, can
incur further delays or mean the contractor being called
back at a later date to carry out retrofitting.

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Daylight design for building performance

Good building design requires a holistic approach, otherwise PHPP assessments.

it is impossible to fulfil all of the functional criteria of a
Using daylight to its full potential can reduce, or even
building. Compromises must be made so as to ensure
eliminate, the electricity demand for artificial light-
all functions - comfort, structural stability, weather
ing during the day. To reach this conclusion, VELUX
protection, energy efficiency, security and safety, privacy
investigated the effect of daylight on energy use in
etc. - can be met together and to a reasonable standard.
a building.
It’s a question of balance. In terms of glazing and
A scenario was modelled where a house had no
energy efficiency, that balance means complementing windows and light levels had to be achieved with electric
thermally efficient, airtight building fabric with the right lighting only. Using electric lighting influences heating
area of glazed openings. The result is reduced electric and cooling demand, so the energy use for lighting, cooling
lighting use, thanks to the availability of natural light, and heating was evaluated together.
and avoiding excessive solar gains - as well as giving
occupants a connection to the outside. The results showed that relying on electric lighting to
provide lux levels equivalent to daylight resulted in an
This holistic approach is supported by whole-building energy demand some five times greater than an
assessment methods like the Standard Assessment equivalent house with well-designed glazing and no
Procedure (SAP), the Simplified Building Energy Model electric lighting.
(SBEM), and the Passivhaus Planning Package (PHPP).
All take into account glazing area and orientation as part Studies of office buildings have demonstrated similarly
of predicting the energy use of buildings. positive results. While they are more complex in terms of
having unique occupancies, internal layouts and lighting
The first two, SAP and SBEM, form the basis for calculations controls (manual and automatic), and therefore less
in national building regulations. They are intended to be suited to a ‘definitive’ assessment, energy savings of 20
a reasonable approximation of building performance; to 60% have been evidenced.
a means of establishing compliance and comparing
When it comes to well-designed glazing, roof windows
predicted energy efficiency and running costs of buildings.
and skylights deliver more daylight than facade (vertical)
PHPP is the foundation for the Passivhaus standard windows - at least twice as much, in fact, for windows
(which, contrary to the sound of the name, can be used of the same size. In real terms, that means roof windows
to assess all types of buildings; a number of schools have can help achieve required illuminance levels with a
been built to the Passivhaus standard with good results). smaller total area of glazing - and with a better
Thanks to its increased accuracy compared to SAP and distribution of light in the room as well.
SBEM, PHPP also underpins a number of other voluntary
Using daylight modelling to help refine the client’s
building performance standards.
brief means the balance of facade windows and roof
Since maximising solar gains in winter, while avoiding windows can be part of initial design concepts, ad-
summer overheating, is a key tenet of Passivhaus dressing any overheating concerns and keeping electric
methodology, it should come as no surprise that the lighting demand to a minimum. When whole-build-
thermal performance of glazed openings, their size ing performance is eventually addressed, these
and orientation, and any shading, are key metrics in benefits will contribute to a positive outcome.

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Daylight design for occupant health and comfort category HEA01 includes a credit for visual comfort,
and requires that 80% of the occupied space meets a
Many aspects of human health, including the length and
minimum daylight factor of 2% - or, for excellent level, 3%.
quality of our sleep, are linked to the light signals we
receive during the day. We perceive spaces with a high Light transmittance is a key measure for glazing, but
level of daylight to be ‘better’; they enhance our mood how that light is distributed is a key measure of comfort.
and morale, and reduce fatigue. A space is better illuminated by diffused light, whereas
occupants are more likely to experience discomfort from
Morning light dictates our alertness levels, and a high
direct light, which causes glare.
level of daylight through to early evening maintains
that alertness and gives the body the signals it needs to
regulate circadian rhythms. Into the evening, decreasing
the level of light to which we’re exposed readies the body
for night-time darkness and sleep.

Work environments with good daylighting have been

shown to improve job satisfaction, and it promotes
more effective learning in classrooms and education
environments. In hospitals, daylight exposure and a
view of green space have been linked to improved
postoperative results.

There is no measurable, universal target for what is

the ‘right’ or ‘necessary’ light dose - but what is clear is
that people need a greater level of interior light than is
prescribed in standards for electric lighting. Daylight is
dynamic; it varies in intensity, colour and direction, and is
therefore more stimulating than artificial lighting.

In terms of a view to the outside - one of the four measures

covered by EN 17037 - a number of generalisations
can be made: a natural view can impact positively on a
building user’s wellbeing, and is preferred to a view of a
man-made environment; a wide, distant view is superior
to a narrow, near view; and a diverse, dynamic view is
more interesting than a monotonous view.

The positive impact of daylight on building occupants

and their wellbeing is recognised by assessment
methodologies like the WELL Standard and BREEAM.
In BREEAM, for example, the health and wellbeing

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Thermal performance of roof glazing

A building’s carbon dioxide emissions and energy use are As well as controlling the amount of short wave radiation
heavily influenced by the balance of heat loss against allowed into the building, glazing can be treated to
solar gains. It is helpful to understand some of the ways reduce the loss of long wave radiation back out of the
in which glazing can be treated to achieve different levels building. Glazing with a low emissivity (low-e) coating
of performance, and how that performance is measured, reflects long wave radiation, keeping it - and its heat -
in order to understand the impact on daylighting. inside the building.

The relationship between light transmittance, or how Like the building fabric in which it is installed, the measure
much light is allowed into the building, and reflectivity is of heat loss from warm to cold through glazing is the
the perfect illustration. thermal transmittance, or U-value.

Specifying a particular level of reflectivity influences the For both g values and U-values, performance can be
level of light transmittance achieved. For example, where quoted for the whole glazing unit, or just the centre
privacy is a concern or a requirement, a high level of pane. As the names suggest, whole-unit values take into
reflectivity might be specified for an almost mirror finish. account both the glazing and the frame, while centre
There is a corresponding reduction in light transmittance, pane values refer to the glass only.
but also an increase in solar control thanks to less solar
Centre pane values appear lower, because the effect of
radiation entering the building.
the frame is not accounted for. It’s important to make
Low reflectivity, by contrast, is designed to make the sure that like-for-like comparisons are made between
glazing almost invisible to the naked eye. While privacy different products - and that representative values are
is greatly reduced, the interior space benefits from a used in whole-building assessments.
greater level of daylight.

The measure of solar energy entering a building through

the glazing is the total solar energy transmittance, or g
value. It is the ratio between the solar gain transmitted
through the glazing and the incident solar gain on the
glazing, expressed as a value from 0 to 1. Accessories,
such as automatic or user-controlled shading, can
work in combination with the glazing to give a
dynamic g value, which can therefore be changed in
response to internal or external conditions.

Several smaller roof glazing units not only allow a better

distribution of light throughout the day, but they also don’t
need the application of solar control that larger expanses
of glazing require.

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Ventilation

Glazing units, including roof glazing, make an important Ventilation requirements in national building regulations
contribution to ventilation in buildings. Even when the are widely regarded as not having kept pace with the
majority of the fresh air requirement is supplied by thermal performance and energy efficiency requirements.
controlled, mechanical systems, having the option to Undertaking more detailed assessment and modelling
open windows is important for building occupants to is therefore critical to achieving successful real-world
have some say in their own sense of comfort. building performance, especially in complex buildings for
the commercial, education and healthcare sectors.
Ventilation is closely linked to thermal comfort, and
the provision of fresh air is closely linked to feeling a Mechanical ventilation, with filters to keep external
connection to the outside. Taking into consideration pollutants out of the building, is increasingly seen as the
everything we have covered in this document so far, the preferred solution. It provides a predictable, consistent
connection of ventilation to the daylighting and energy and controlled supply of fresh air. Natural ventilation is
efficiency roles performed by roof glazing and skylight driven by external air pressure and air movement, and
solutions cannot be underestimated. therefore cannot be entirely depended upon on the
occasions it is most needed.
Like much of what we have discussed to this point,
ventilation is a compromise, balancing energy consumption, Natural ventilation does have advocates, but is arguably
health and costs. Excessive ventilation increases energy best employed as a supplement to a mechanical
use, as heated warm air is lost and replaced by cold air system, to take advantage of the days when it is
that has to be heated again. most effective.

Insufficient ventilation, while retaining heat within

airtight building fabric, causes poor indoor air quality
and potential health problems. Living and working in
damp, humid environments is the most likely trigger for
illnesses such as coughs, allergies and asthma.

Ventilation removes stale indoor air - odour, pollutants and

moisture - from the building and provides fresh air for
the occupants to breathe. Fresh air is linked to increased
alertness and wellbeing, evidenced by studies in both
schools and office buildings.

It’s critical to make sure that a ventilation strategy

appropriate to the building fabric airtightness is
implemented - or the correct rate of ventilation for the
building use simply won’t be attained. It is this need to
design for airtightness and ventilation with equal care
that has led to the phrase, ‘Build it tight, ventilate it right’.

12 VELUX commercial.velux.co.uk
 USING VELUX Benefits of modular skylights

VELUX Modular Skylights are fully prefabricated offsite,

MODULAR SKYLIGHT complete with customised flashings and integrated
SOLUTIONS TO HELP insulation. Being factory-made, to tight tolerances, they
offer consistent, repeatable and dependable performance.
MEET THE STANDARD Skylight modules are designed to work as a single
system from the moment they are made, and can be
What are the solutions we can implement to help linked together in combinations to suit the building
achieve the standards of daylighting, thermal comfort and shape and roof design. Where required, any optional
ventilation discussed up to this point? accessories - such as blinds, ventilating modules and
We have described the benefits that roof glazing actuators - are installed in the factory too, so the units are
offers in comparison to vertical facade glazing, but delivered to site ready to be fitted with a minimum of fuss.
larger commercial projects require more than a series of It isn’t just the quality and performance that are con-
well-placed individual rooflights. That is where modular sistent either - the appearance of the skylight modules is
skylights come in. too. Ventilating skylights look the same as fixed skylights,
achieving a consistent aesthetic regardless of the mix of
units needed to achieve the ventilation specification.

There is no limit to the number of skylights that can be

installed next to each other in a row or run - the only
constraint is the building structure itself, and the effect
of any movement or expansion joints. Modules of
different widths are easily accommodated, though
the length must be consistent in a run. Meanwhile,
trapezoidal modules offer options at the roof edges
depending on the shape of the building.

Getting the best from modular skylights means, ideally,

factoring them into the design at an early stage. Setting
out the support structure to fit with known module sizes
makes life a lot easier further down the line, compared
to fitting a combination of modules into a random size.

13 VELUX commercial.velux.co.uk
Thermal and ventilation performance Whole-building assessment methodologies

VELUX modular skylights are available as double or triple There are some twelve different areas in which VELUX
glazed units. The thermal performance of double glazed Modular Skylights can help obtain credits as part of a
units is a good fit for most building designs, but triple BREEAM assessment. And as the role of buildings in
glazed modules are available for projects where the spec- wellbeing is increasingly recognised, accepted and designed
ification requires them. for, assessments under the WELL standard are also likely
to increase - with a corresponding increase in focus on
Modular skylights also contribute to the chosen ven-
daylighting, thermal comfort and ventilation.
tilation strategy - be it a fully natural solution, or a hybrid
solution featuring mechanical and natural ventilation. UK Hydrographic Office (UKHO)
They provide background ventilation, such as via the VE-
LUX ventilation flap, providing a permanent-but-limited VELUX Modular Skylights were used to provide daylight
flow of air to contribute to the overall air change rate. and ventilation to the atrium of the new UK Hydrographic
Office building, which is part of the Ministry of Defence.
They can also be opened to provide purge ventilation,
when the internal climate has become too warm or With office spaces either side of the atrium, the roof
‘stuffy’ and a rapid, usually user-driven, airing is required. design featured multiple rows of modular monopitch
skylights, with trapezoidal units stepping out to suit the
As well as manual controls, modular skylights with curve of the building where appropriate. The skylights
programmable and sensor-driven controls, for both were supported on pre-cambered concrete beams, which
background and purge ventilation, remove the need meant factoring in not just initial settlement but future
for continuous manual adjustment, which can easily get deflection too.
forgotten.
That long-term view was evidenced in the ventilation
Operating modular skylights provision too. More opening rooflights than needed
were installed, ensuring the building has extra
Modular skylights can be supplied in one of two control
ventilation capability in the future should the changing
styles: open, or ‘plug and play’. Open operation allows the
climate make it necessary.
skylights to be incorporated into a Building Management
System, from which they can be operated based on Architects AHR designed baffles below the skylights
temperature, humidity or carbon dioxide levels. Where to help disperse light, eliminate glare and create a
automatic smoke ventilation is provided as part of the ‘wave ripple’ visual effect. The baffles were an integral
building’s fire safety strategy, that can only be provided architectural feature of the building as well as assisting
via a Building Management System. in the distribution of good quality daylight through
the atrium.
‘Plug and play’ modules, like the VELUX INTEGRA®,
feature sensors as part of the module, but the control
units can have additional sensors connected in.

14 VELUX commercial.velux.co.uk Photograph: AHR Architects

15 VELUX commercial.velux.co.uk
 CONCLUSION

Like any code of practice, the contents of EN 17037 the perfect complement to vertical windows in external
constitute recommendations only. The more those walls that might be faced with significant constraints
recommendations are adopted, however, the greater from adjacent buildings or other obstructions.
the weight and authority that the standard will come to
VELUX Commercials expertise in providing modular
carry in design offices and on construction sites - and the
skylights for education, healthcare and office buildings -
more it will come to feature in client briefs.
like UKHO - means we can assist designers and specifiers
Architects and design professionals must rise to the from an early stage on how roof glazing can help achieve
challenge of delivering buildings that respond to the the right performance levels across the four areas of
current climate and achieve genuine occupant comfort. daylighting covered by EN 17037.
Indeed, future versions of building regulations may
For project and technical support, or price estimates for
give them no choice. As a result, awareness of glazing
commercial roof glazing solutions, contact us to discuss
performance and, in particular, its contribution to
your requirements. Brochures and guides are available
daylighting is only going to increase.
from our website, as are CAD and BIM object downloads.
In the short term, EN 17037 is likely to feature mainly in
We also offer a comprehensive, RIBA CPD-accredited
projects aiming for standards like BREEAM and WELL,
learning programme, highlighting the importance of
where meeting its requirements will assist in claiming
daylight in commercial buildings, and the benefits of
extra credits. In time, though, its reach will extend
modular products in creating better environments for
beyond that and feature in more specifications.
learning, working and recovering.
Perhaps unsurprisingly, initial modelling suggests it’s the
upper storeys of taller buildings where the performance Sources and further reading
levels of EN 17037, especially the high and medium For a more in-depth exploration of the topics covered
performance thresholds, are most likely to be met. in this white paper - including a wider discussion of
For new-build developments on open sites, meeting the studies referenced in the section on ‘The impact of
required performance levels might be relatively daylight on building performance and occupant
straightforward; the development of tighter sites could comfort’ - VELUX’s Daylight, Energy and Indoor Climate
need significant changes if good daylighting is to be book is a comprehensive and readable guide, intended
properly embraced. for architects, engineers, students and researchers alike.

Roof glazing, and modular skylights particularly, offer The VELUX DEIC book is available online at:
greater access to unobstructed sky and sunlight, and are www.velux.com/deic

16 VELUX commercial.velux.co.uk
GLOSSARY OF TERMS

Access to sunlight Daylight provision Light (artificial) Thermal comfort

Daily sunlight exposure, established through detailed Illuminance levels, allowing users to carry out tasks. Also Light emitted from lamps or LEDs, usually through the The subjective view of building occupants as to whether they
calculation or table values. determines the likelihood of artificial lighting being switched on. application of a current, to provide illumination when daylight feel too hot or too cold.

Daylighting is not sufficient or unavailable.

BREEAM U-value
The controlled use of natural light in and around buildings. Light (natural) Measure of thermal transmittance in W/m2K, the amount of
The Building Research Establishment’s Environmental
Diffused light The part of the electromagnetic spectrum possessing heat energy that passes through one square metre of building
Assessment Method.
wavelengths recognised by the human eye. fabric, for every degree of temperature difference between the
BS 8206-2 A softer light that does not have the glare or intensity of warm and cold sides.
direct light. Light transmittance
‘Lighting of buildings. Code of practice for daylighting’ - British VELUX INTEGRA®
EN 12464-1 The ratio of light that passes through a medium to that
Standard dealing with daylight design prior to the publication
An innovative system that uses VELUX supplied operation
‘Light and lighting. Lighting of work places. Indoor work places’ absorbed by the medium.
of EN 17037. devices to operate venting modules and roller blinds to any
EN 15193 Lux desired position.
Centre pane values
‘Energy performance of buildings. Energy requirements for The unit of illuminance. Ventilation
A g value or U-value given for glazing only, not accounting for
lighting. Specifications’
any frame material. Modular skylights The removal of stale air from a building, which causes poor
EN 17037 indoor air quality, replacing it with fresh air. Removes moisture,
Climate-based modelling Factory-assembled rooflights designed to be linked together
odour and pollutants. Ventilation strategies can be natural,
‘Daylight in Buildings’ - The first harmonised European standard to cover large roof areas, delivered to site with all accessories
A technique developed to assess daylight provision based on mechanical or hybrid (a combination of the two).
dealing with the design for, and provision of, daylight in ready-installed. Usually double glazed, but can be triple glazed
building-specific location and orientation, and 365-day climate buildings, published in 2018. View, assessment of
for a lower (better) U-value.
data. Allows glare to be calculated.
g value National annex (NA) Consideration of the width and outside distance of the view, as
Daylight factors Solar energy transmittance, or the measure of solar energy well as landscape ‘layers’ (sky, landscape and ground). Should
Section of a European Standard detailing local information that be perceived to be clear, undistorted and neutrally coloured.
The traditional method of assessing daylight provision, entering a building through glazing.
helps with applying the recommendations of the standard in
developed some 60 years ago. Assesses the ratio of external Glare the specific country. WELL Building Standard
light to internal light, but based on permanently overcast
Excessive and uncontrolled brightness, especially from Evidence-based system for measuring, certifying and monitor-
Solar gains
conditions, which lacks accuracy and can’t predict glare. ing building features that impact on health and wellbeing.
direct light.
‘Free’ heat energy from the sun which, when planned for in a
Daylight modelling calculations Indoor air quality (IAQ) Whole-unit values
building design and accompanied by efficient building fabric,
The process of undertaking climate-based modelling to assess A measure of how the air inside a building impacts on the can reduce space heating in winter without risking overheating A g value or U-value given for a whole glazing unit, including
daylighting in respect of a particular building design. health and comfort of building users. in summer. the frame.

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