Green Roofs a Scandinavian perspective Bent C. Braskerud

Green Roofs a Scandinavian perspective Bent C. Braskerud Green Roofs - Part of Scotland s sustainable future 2011 Mars 31 og Framtidens byers workshop om Grønne tak 29. november 2011

Green roof examples in Norway, Sweden and Denmark Historic view Modern green roofs Peat grass contra sedum Green roof and stormwater Green roofs as a BMP in a stormwater strategy BMPs and the local community

The way the Vikings made houses Peat and grass on timber and birch bark Photo: Dylan Kereluk Illustration of Arkikon

From old Norwegian farms to cottages in the mountains

Modern use of peat for green roofing Nittedal torvindustri sells peat for 150 000 m 2 roofs/yr

Modern green roofs Sweden Keeps more than 50 % of the annual precipitation Germany 8 mill. m2/yr 0.1 m 2 /German Sedum-species often used

Peat roofs contra sedum roofs Jan.O.Busklein@sintef.no 7

Peat roofs contra sedum roofs Artificial precipitation: 52 mm in one hour Runoff from roof (mm) Runoff from roof Peat Peat Black roof Wmax = maximum watercontnet compared to dry matter Sedum: 302 % Peat: 978 % Jan.O.Busklein@sintef.no Hours from start 8

Grønne tak Peat roofs contra sedum roofs Artificial precipitation: 52 mm in one hour, then drainage Runoff from roof (mm/2 min.) Black roof Peat Peat Wmax = maximum watercontnet compared to dry matter Sedum: 302 % Peat: 978 % Jan.O.Busklein@sintef.no Hours from start 9

Modern use of peat for green roofing Peat has a very large water holding capacity Suitable for roof gardening It oxidizes to CO 2 and H 2 O Peat recourses is only slowly renewable Grass needs irrigation if the summer is dry Is the total positive effect of peat > than the negative?

Modern green roofs Sweden Keeps more than 50 % of the annual precipitation Germany What about cold climate? Sedum-species often used

Tools for a rough climate 30 Mars 2011 Green roof www.sawa-project.eu

Established summer 2009 Green roof experiment Hvor mye vann holder et norsk grønt tak tilbake? 8 m 2 8 m 2

Green roof system 2-3 cm Vegtech system

Sampling system

July 2009 was 2 x wet as usual 200 200 mm Precipitation Nedbør og avrenning and runoff (mm) 180 160 140 120 100 80 60 Precipitation Reference Green roof Nedbør Avr. vanlig tak Avr. grønt tak 179 mm 25 % 134 mm 40 20 0 1.7. 6.7. 11.7. 16.7. 21.7. 26.7. 31.7.

Extreme precipitation on a dry sedum roof July 3rd 2009 Precipitation and runoff (mm) 8 7 6 5 4 3 29 mm in 30 min 187 l/s/ha 138 l/s/ha - First rain absorbed (9 mm) - Runoff peak delayed a little - Runoff intensity lowered (26 %) - Runoff distributed over a longer time (Difference over 2 hours 6 mm; 22%). Precipitatiton Runoff reference Runoff green roof 2 1 0 18:00 18:05 18:10 18:15 18:20 18:25 18:30 18:35 18:40 18:45 163 l/s/ha 18:50 18:55 19:00 19:05 19:10 19:15 19:20 19:25 19:30 19:35 19:40 19:45 19:50 19:55 20:00 5 minute intervals

30th July 09 Precipitation and runoff (mm) Nedbør og avrenning (mm) 2,50 2,00 1,50 1,00 Runoff from a wet green roof 14 mm in 2 hours 68 l/s/ha 35 l/s/ha - First rain absorbed (2,5 mm ) - Runoff peak delayed a little - Runoff intensity lowered (51 and 36 %) - Runoff distributed over a longer time (Difference over 3 hours 1,3 mm; 11%) Precipitation Nedbør Avr. Reference vanlig tak Avr. Green grønt roof tak 0,50 19 l/s/ha 0,00 18:30 18:40 18:50 19:00 19:10 19:20 19:30 19:40 19:50 20:00 20:10 20:20 20:30 5 minute intervals 20:40 20:50 21:00 21:10 21:20 21:30 21:40 21:50

k r a m n e D, n e g a h n e p o C s f o o R n New houses with roof angle e e r Green Roofs in Copenhagen G less then 30 degrees will have a green roof Dorthe Røhmø City of Copenhagen

Green Roofs drivers: Climate adaptation and greener city Dorthe Røhmø City of Copenhagen

All new flat roofs must be green in new local plans Digit 8 by BIG Dorthe Røhmø City of Copenhagen

Sweden - Malmö

Augustenborgs Botanical Roof Garden Plenty of sedum, but also other types of green roofs

Runoff experiments on 3 cm sedum Results -Annual precipitation 705 mm, retention (47 %) -When field capacity is reached, then runoff ~ precipitation -9 mm storage capacity Lars.Bengtsson@TVRL.LTH.se Lund University, Sweden

Water storage increases with the precipitation intensity 12 0.4 11 10 storage 0.3 mm storage 9 8 7 Precipitation 0.2 mm/min 6 5 Runoff 0.1 4 Lars.Bengtsson@TVRL.LTH.se Lund University, Sweden 9 11 13 15 17 19 hour 0

Priority one: Green roofs need to look beautiful! 17. July 2011 Drought? Roof 1 Roof 3

Frost damage? 25.08.10 8.06.11 11.07.11 New start

Vanning etter behov

Sustainable Urban Drainage Systems SUDS Drainage pipes Paved surfaces Gray solutions Piped solutions Green solutions Local infiltration Detention basins Green roofs Green roofs Root zone retention Artificial ponds Wetlands Reopen streams Surface runoff Rain gardens

Testing av regnbeds kapasitet Hvis regnbed er 7 % av takareal og 50 års nedbør i Oslo. Testet 30 min og 10 min regn Regnbed på leire i Oslo

Foreløpige resultater Max inn: 184 l/min (307 l/s ha) Max ut: 29 l/min (48 l/s ha) Dempet vf-topp med: 84 % Master UMB 2012 Kjetil Kihlgren og Vegar Saksæther

Stormwater BMPs in Malmö Södra systemet Houses from the 50s -Defekt stormwater system -Social problems Ekostaden Augustenborg Kanaler och dammar Kanaler og dammer ISS Landscaping

Results: - No stormwater related water damage - Biodiversity increased 50 % - Turnover sales decreased from 50 % to 20 % - Number of voters from 54 % in 1998 to 79 % in 2002