Prof. Dr. Manfred Köhler, Version February:2005-02-20 Origin of these researches by www.gruendach-mv.de

Green roof research topics

Long time studies on plant species compositions
Climate modification by green roofs
Storm water retention
Energy performance of Green roof systems
Life cycle costs of Green roof construction
Maintenance of Green roof systems
Green roofs and photovoltaics

In the following offers an general overview of the topics of the survey on green roof systems, done by the Green Roof Centre of the University of Applied Sciences Neubrandenburg. It is the overall programme. Additional works will be done in dependence of more collaborators. Future extended works requires a more international network systems. Research Results are the core factor to convince citizens about the benefits of the green roof technology.

Long time studies on plant species compositions

e.g. Paul-Lincke Ufer 2003	e.g. Ufa-fabrik, 2003

Long time studies on biodiversity and plant species development on green roofs.

- Since 1984 (Berlin – Kreuzberg: 10 different inclination and expositions, constructed in 1984),
- Since 1992 (Berlin – Ufa-fabric: 6 different roofs, constructed between 1984 and 1996),
- Since 1998 (Neubrandenburg: Variables: 6 growing media, 4 exposition, three types of implementing green roof plant species: seed, sprouces, pre produced vegetation mats; two depth of growing medium).

Additional studies on tropical green roof vegetation are done in Rio de Janeiro.

Publications: see separate list.

Climate modification by green roofs

Climate research instruments, installed in 1999 on one of the Buildings of the University of Applied Sciences in Neubrandenburg	As an example of data aquisation on the green roofs in Neubrandenburg. Two days of extreme cold winter temperatures in February 2005. What happens inside the two different growing media an inside the gravel layer. And the three infrared temperatures of this.

The most famous effect of green roof benefits are the modification of the urban surface temperatures.
Variables like: type of growing medium, water inside the growing medium, type of vegetation and some others has significant influence on this performance.

On the Portland conference (Second annual North America Green roof Conference, 2004) some facts of this data set of 4 Years are presented. This data set was analysed with the programme of SPSS in steps of 5 degree.

Remarkable are the temperature modification on extreme cold days but also on extreme hot days. On all data together, a green roof will be warmer in Central Europe. But during extreme temperatures green roof equalized the big differences. As an example the last figure, coming from a data set in February 2005 explains the differencies (the data set is taken at the measurements on the following picture). The temperature inside the gravel layer is nearly the same like the surface temperature. Inside both growing media the temperature don not go under 0 Degree of Celsius!


Additional surface temperature measurements with infrared Camera systems

Equipment: Infrarotcamera der Firma Jenoptik, Varioscan HighResolution, 3221 ST

	Summer infrared measurents on the research green roof at about 9.00 o’clock: Three lines: L01: Line on a well growing area, L02: a dark growing media; L03: The concrete path in the morning shad.

Additional to the fixed measurement equipment, Infrared cameras offers the opportunity for surveys of buildings surfaces in a larger scale.

Like this example surfaces under extreme climate situations can be observed. Small differences in the pattern of greened and non greened areas on the same roof becomes visible.

In the same manor, green façade are observed, see the German “Dach + Gruen” 2005, 1. It will be also an objective on the 3 EFB Congress in Ditzingen in March 2005.

Storm water retention

Small scale weighing lysimeter on the research green roof in Neubrandenburg.	Tipping counter equipment installed in the drain pipe systems under the different green roof variables.

If somebody talk about the green roof benefits, the storm water retention is one of the most famous arguments. But on the other hand it is also one of the difficult arguments.
Own researches in Berlin in the 80th explained the annual retention by weekly measurement.

Source: Koehler (1993) see publication list.

The ongoing discussion differs between separate events and some steering facts, like how much water is just inside the growing medium if the rain comes. So it is necessary to make on line measurements. Above some of the research equipment can be seen to have an online data set. From different small scale lysimeter, with a special measurement of the run off and bigger systems (right hand side) to calculate the eluat – run off from real green roof areas. Now each second the data set was stored.

Some results are given at the IGRA Congress 2004.

Some more, like the information about the real water needs of a green roof system will given on upcoming conference.

Precipitation, run off measurements and at the same time the measurement of the change in water content of the growing medium. This is the model of storm water survey in Neubrandenburg

Energy performance of Green roof systems

Model cube to test green roof energy performances.	Climate chamber inside of the lab of Civil engineering.

The urban heat island effect is caused by energetic processes. Like sun radiation and evapotranspiration (see calculation in: Koehler u. Schmidt, Greenroof Yearbook 2002). These measurements are done in Berlin on the green roofs of the Ufa-fabric and also in Neubrandenburg. All these measurements allows conclusions of the cover of buildings.

Additional since 2004 in cooperation with the lab of Civil engineering a survey about the energetic performance are started to simulate hot and cold days and do scientific repetitions.
These model measurements completes the methods in energetic performances.

First results about green roof evapo- transpiration, see IGRA – Proceedings 2004.


Life cycle costs of Green roof construction

Roof garden of Burle Marx, from the 40th in Rio de Janeiro	Green roof living situations in Rio de Janeiro.

A calculation about the green roof benefits and the costs are done by Ulrich Porsche. He compared information from Germany, USA and Brazil.
One surprising result: Roof gardens has a higher benefit for the house owner than buildings without green roofs or only with extensive green roofs.

Results published in Rio03 proceedings. See List of publications.

Maintenance of extensive green roof systems

Sloped green roof area, it is important to observe this carefully (August 2003)	Harvesting of shrups an spontaneous trees in May 2004

Extensive green roofs requires only little maintenance, see FLL Guidelines. But periodical revision are necessary. To quantify this is necessary in accordance to various factors.

The pictures explains two activities:

- Left hand: a sloped green roof is annual monitored about changes.
- Right hand: Students are calculation the annual biomass development of spontaneous woody plant species on the research green roof.


Green roofs and photovoltaics

From Left to right: Ulrich Porsche D, Karsten Jarmer Thai, Manfred Koehler most time in Germany, Melissa Keeley (USA), Steven Peck (most time in Canada),	The plant species grows better (taler) in the shelter of the PV-panels.

On the green roof of the Ufa fabric in Berlin, one of the extensive pv-Power plants are installed. The interaction between green roof and PV are investigated in Cooperation with the Ufafabric and the producer of these systems. Cooling of PV means a better energy efficiency but the shade of the growing plant species could be decrease the results of the energetic production. So only a long time survey can give a clear answer.

First results are published in Proceedings: rio02, ed. by Stefan Krauter. (this publication can be download from the list of pulications).