There is a large amount of literature that deals with windows, covering aspects such as their history, design and production in depth and detail. However, very little has been written and published about how windows should actually be placed and designed in order to achieve the best daylight conditions in a room.
The correlation between the figuration of a building and the daylight conditions has interested people for a long time. In recent times, the focus on windows’ technological development has increased. Combined with increasing demands from customers and entrepreneurs a large quantity of the aesthetic values of a window has been lost. The idea of this thesis arose while the students asked themselves the following question: In what way does the impression of a room change if the window is placed differently but the other conditions of the room remain the same?
1.1 Intended objective
The intended objective of the content is to find at least five factors that have a decisive impact on the daylight in a room’s measurable and immeasurable qualities.
2. Description of current situation
Nowadays when looking at a window as an architectural element, more and more focus is placed on how windows should be created. Window designers must take into account what type of glass the window should consist of to create a proper U-value or what type of glass should be used in areas with high levels of noise.
According to Lars Dahlborg, a lightning designer at Sweco, awareness in the industry of light and its properties is increasing while the knowledge of the subject still is very low, especially in terms of creating an optimal flow of light.
The different methods that have been used to fulfill the goals with this thesis can be separated into three different parts, each described down below.
3.1 Full-scale experiments
To get a realistic impression of each and every window placement and its impact on different lightning parameters a full-scale experiment has been made in a daylight room located at The Royal Institute of Technology in Handen, Stockholm. The daylight room is 7.1 meters deep and 4.2 meters wide, which gives a floor area of 30 m². The room is located at the fifth floor and the short side of the room consists of a window section which is oriented through north.
By photographing the daylight room at different window placements in the full-scale experiment the experience of the room has been able to become documented. The room has been photographed from three different angles, at the middle of each long side and in the middle of the short side wall at the far end of the room. Every angle has been photographed from a standing and seated perspective. To measure the illuminance created by the different window placements an instrument who calculates the specific illuminance in a definite point has been used. In this case the instrument has been used at 12 different points on the floor for each and every experiment to create an average value for the entire room.
During the implementation of the full-scale experiment different parts of the window section has been covered with pieces of cardboard, according to what the different window placement has allowed.
The room's character in each window placement has been described based on the following measurable and immeasurable qualities:
Window glass share - the size of the window glass area in relation to the size of the floor area
Time and date of the experiment
Daylight factor – calculated partly on the basis of the full-scale experiment, partly as an average in Velux Visualizer
Average of the illuminance in the room
Safety – what actions should be taken to the current window type if it should follow BBR's requirements for personal safety in connection with glass?
Light level – how light or dark the room is experienced
Size – does the window type affect the impression of the room size?
View – how is the contact with the external environment at the current window type?
Light distribution - how is the light distributed in the room?
Shadows – how the shadows in the room are perceived in connection with the current window type
3.2 Velux Visualizer
Velux is a company that among many other things offers the program Velux Visualizer, a program that can be downloaded for free at their webpage. This program gives the opportunity to build a model of a room or a building in order to see how different windows and window placements would appear in a certain environment in reality. Velux Visualizer is constructed to show the luminance, illuminance and daylight factor of a specific area in the created model. Concerning illuminance and daylight factor the program is capable of producing an average value of a specific area of the model. In this study a depth of the room corresponding half of the room is relevant.
3.3 Building project
How the light affects the architectonical experience in a room is not always corresponding to what once was planned, especially if not looking at different seasons of the year. The formation of the window recess and the impact on different lightning parameters are something that has not been possible to study in the earlier mentioned full-scale experiment. To widen the knowledge on the subject daylight flow in a room, different building projects have been visited. Following projects have been visited where two out of three were unfurnished:
Sjövikshöjden 5, JM new production, Liljeholmen (unfurnished).
Apartment in Enskede (unfurnished).
Brf Borggården, Bonum, Bromma (furnished).
A variety of background theory has been studied to investigate how window placement affects the daylight conditions of residential interiors. The background theory is presented from different subject areas such as window’s architectural history, view, current Swedish rules for glass in buildings, the Swedish certification system Miljöbyggnad and the program Velux Visualizer. Glare, daylight factor and indicative values for light are also examples of topics that have been studied, and where the background theory has been explained in this thesis.
A room with a good daylight illumination is characterized by acceptable levels of illuminance and low glare levels. The glare impact itself is difficult to measure. Glare arises when there are great contrasts in brightness between an area and its surroundings. The contrasts between the window glass and the wall surface could be mitigated if the window and its surroundings have a bright color scheme.
There are different methods to calculate the daylight factor, but every method is based on calculations from a uniform overcast sky. The daylight factor is stated in percentage and is the ratio between the daylight’s illuminance inside and outside during the same weather conditions. For example, if the illuminance inside is 300 lux and the corresponding value outside is 15 000 lux the value of the daylight factor is 2 %.
The average of the daylight factor could be linked with the need of artificial light by:
DF-value > 5 % - is a relatively high value for the daylight factor. Artificial light is not usually essential during daytime.
5 % > DF-value > 2 % - the daylight in the room is significant, areas of work and desks should have artificial light.
DF-value < 2 % - the need of artificial light in the room is big and will be the major light source in the room.
The daylight’s illuminance from the sky varies widely depending on weather and season. The following values can be used as a guideline for calculations of daylight factors. All the values are very approximate and can only be used for general estimations.
Illuminance values outside during different seasons, clear sky:
Illuminance values outside during different seasons, overcast sky:
The impact of window placement on the daylight conditions of residential interiors have been investigated in this thesis through different methods and solutions. The data collected by each method is presented through pictures, sheets and diagrams together with an associated comment on the result.
The conclusion of the methods is summarized through the measurable, immeasurable and general issues below:
Increase the recommendation: The recommendation in the current situation from the authority Boverket should increase from today’s value of 10 % window glass area in relation to the floor area. Based on the results of this thesis, the recommendation should as a suggestion be raised to a value of 13 % of the floor area.
A large percentage of the window glass area does not guarantee that the illuminance and the daylight factor get high values.
High placed windows causes that the daylight reaches further into the room. The experience of the width of a room can be enhanced through horizontal window placements.
Bright color schemes gives gentle light contrasts and reduces the risk of glare.
Consider the external environment’s impact on a light beam, such as adjoining facades and objects, when it comes to window placement.
Maximize the use of daylight.
The large amount of depending factors makes it difficult to prescribe a general work module that can be used during window projection.
2015. , 45 p.
Bachelor of Science in Engineering - Constructional Engineering and Design