1. FACULTY OF HEALTH AND MEDICAL SCIENCES
UNIVERSITY OF COPENHAGEN
Window Glass Quality and Depression Carlo Volf1, Ida Hageman1, Klaus Martiny1, Paul Michael Petersen2 1 Mental Health Centre, Department O, Copenhagen Denmark, 2 DTU Photonics, Copenhagen Denmark
Background
Since the invention of the insulating glass units (IGUs) in the 1970s, a lot of innovative effort and talent has been put into optimizing the performance of window glass as climate screens. Unfortunately these efforts have served only one purpose; energy. Optimizing the ability of the window glass to reduce heat gain and heat loss, respectively. This energy optimizing of the window glass has made it possible to build large glass buildings, which was utopia only a few decades ago, now they are a reality all over the world. Unavoidably, this development in the glass has also meant that the quality of the light has been reduced over the past decades. New high performance, low-energy windows only transmit visible light and efficiently block out IR and UV, and reduce the light transmittance (Lt) from 0,81 to 0,4. A development which seems to continue in the build environment in the near future, and seems to be the most rational choice, if we do not consider other parameters, such as health.
Challenge
Depressive patients at psychiatric inpatients wards often find it difficult keeping a stable rhythm. Recent discoveries about the missing piece in the lighting puzzle, the non-visual ipRGC in the retina, have put emphasis on light and its beneficial effects as an efficient zeitgeber, able to entrain the sleep-wake cycle. Light is an acknowledged anti-depressant agent and alerting agent. Artificial lighting, such as LED-lighting, rich in the blue, short-waved spectral area can play an important role in effective chronotherapy by inducing a regular sleep-wake cycle, but natural daylight is far more optimal regarding both spectral composition and the timing of intensity in relation to the sleep-wake cycle. As patients spend a lot of time in the indoor environment, the quality of the window glass at the ward may play a very important role for their circadian rhythm, sleep and wakefulness.
Methods
The ipRGC melanopsin receptors in the retina, regulate, among other things, the sleep-wake and melatonin rhythms, and are most sensitive to light in blue region of the spectral area, appr. 460 – 480 nm. In this study we measured spectral irradiance and light transmittance of five different glass types typically used in windows today (using two different meters). The transmittance of the glass types was measured in a dark room, with each glass type mounted, one by one, providing a closed envelope to the daylight outside, filtering the natural light into the room. The spectral composition of the transmitted light subsequently was measured using UPRTek units and test glass compared to each other.
Results
The study showed that the glass types had a major filtering effect on the short-waved light, thus theoretically reducing the entraining effect of light on the sleep-wake cycle. Clear, low-iron glass had the lowest filtering effect of the tested glass types.
Furthermore, there was a large difference in the transmission of UVA and UVB light. The UVB is especially absorbed and reflected in most common glass-types. Only low-iron glass transmits UVB light, however this glass-type is very seldom used in new architecture. This may be an explanation on the often very low D3-Vitamine levels seen in the patients, spending much time in the indoor environment due to their mental condition.
Conclusion
The differential ability of glass to transmit light may effect the human sleep-wake cycle and the level of D3-vitamine. Lower transmittance thus effects health-parameters negatively. Glass seems to play a very important and overlooked role when it comes to planning a healthy indoor environment at psychiatric wards. By reducing the short-waved light and the UVB light stimulating the circadian rhythm and the transformation to active D3-vitamine in the blood, respectively. From the results, we suggest that an Unhealthiness Factor (1) of glass is introduced, or at least discussed at hospitals and at psychiatric wards. The exact effect of different window glass types remains to be studied on humans, relating the glass quality to levels of depression and D3-vitamine in the blood. We therefore suggest further controlled studies at psychiatric in-patients wards.
1. “Light, Architecture and Health – a Method”, Ph.D.-dissertation, Volf C. 2013
Fig. II. Five glasstypes and their different transmission of shortwaved light – their Unhealthiness Factor (UH):
1 = Low-iron glass
2 – 5 = Solarprotective glasstypes
NB. Light transmission is measured as the irradiance of the daylight transmitted through the different glasstypes in the sensitive area of iRGCs 460 – 480 nm (468 nm) (top). Subsequently, light transmission is measured as the transmittance (0-1) in the full spectrum (bottom)
Irradiance (μW/cm2/nm)
5-CL Extreme
4-Cool Lite
2-Climaplus
3-Climaplus One
1-Climaplus PLT
Wavelength (nm)
Transmittance (0,0 – 1,0) 5 4 2 1 3
Wavelength (nm)
1 Climaplus PLT
2 Climaplus
3 Climaplus One
4 Cool Lite
5 Cool Lite Extreme
Fig I. A comparative analytic photograph, using a SLR-camera shooting only one picture. The different types of glass laid out, side by side, on a white background. Clear, low-iron glass (1) and solar protective types of energy glass, ranked from left to right (2-5)
Presented at the 27th annual meeting
Society for Light Treatment and Biological Rhythms
San Diego 2015