Vesa Isakov: Green roofs in building supervision

1. GreenRoofsinBuildingSupervision-
Viherkatotrakennusvalvonnannäkökulmasta
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2. Whoweare
• The Building Control Dept. of H:ki app. 115 employees of which city
officers …, divides to 3 sections; permitting (KO), controlling (RO) &
support (YO; ict, archives, juridical, cost controlling…).
• Guided by a city member; the Construction Committee
• Runs on its own collecting permitting charges, and to lesser degree
survey charges, etc.
• ”Ei kai rakvv:lla noin lähtökohtaisesti ole nimenomaan
kaupunkikuvallisessa katsannossa mitään erityisempää viherkattoja
vastaan? Pikemminkin kai päinvastoin – haluamme niitä suosia.”
translates roughly to ”Initially the B.C. does not have anything
against green roofs? Rather - we would like to make them possible.”
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3. AndWhatWeDo
• The Building Control Dept. writes permits following the detailed
plan(s), if the owner wants something else not complying with the
detailed plan; exemptions -> consultation with the city planners (City
Planning Committee) and permitting officers, or denial of the idea.
• Or, in the worst case, administrative enforcement measures if the
given b-permit not followed by the owner (Construction Committee to
enforce, even fines may apply!)
• Professional skills evaluation
• Site surveying, and so on.
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4. Initiative
• Green Roof – >key role played by the detailed plan(s)/, otherwise
it’s more or less the owner <-> permitting officer interaction.
• Owners’ rarely, if ever, propose green roofs - > willingness,
awareness?
• Helsinki City Strategy on urban runoff management; In-situ
management of rain water. Desirable situation where far less rw to
municipality’s rw network -> effects rather on geotech & landscape
plans (buffer ponds, tanks, infiltration areas, porous asphalts &
paving, overflow systems…) green roofs less so
• We are at the verge of the climate change;
– Rise of the Baltic Sea? - > sewer systems to work “backwards”
no further strain to pipes from roofs, pls…
– Precipitation rises? -> Capacity of the present RW system?
– Infill development? - >We tend to cover sites /plots all over by
sheet metal, bitumen felt …
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5. • Finland is still one of the driest areas in Europe, good…
• However, no drought ahead…
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PROS & CONS

6. • For some decades we have been taught that unintentional water in
or on the building is no good, any excess water should be led asap
far & further away.
• Traditions of green roofs vanished long ago, no one has references.
Wooden tar impregnated shingle /shake roofs ok, but…
• Building Control Dept.s are probably not the 1st to push forward or
to propose green roofs, if not assisted by detailed plans, or the
owners!
• After all, g.r. is pretty new to us.
• Long term behaviour ref.?
• Maintenance, quite a few other
things to do as well?
•New houses are complex
• E-number
• HEPAC:
• ducts, compressors
• pumps, heat recovery…
• Solar cells, batteries, inverters..?8/26/2016 6

7. • One further dead load, its magnitude somewhat the present snow
load 2,5* x*y kN/m2 (Snow + GR, Snow or GR, Snow 50% + GR
100%...) dependent, independent, …
• At the moment we’re not going to decrease snow loads, despite the
climate change. Not in the foreseeable future.
• EN 1991-… (Finnish translation & annexes)? Multilayered subtrata
immersed totally/partially/to max. Immersion? -> xxx kN/m2
Designer’s choice as always, but based on what? -> 3rd party
inspection on str.design?
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8. • U-value improves, yes, but if the present ref.value used, not
significantly.
• Albedo, cooler on the terraces, may be indoors as well, energy
savings in cooling?
• The B.C.’s present guidance on moisture controlling and handling
during (and after) construction phases? Contradiction?
• Flora & Fauna, green roofs are generally considered nice &
comfortable, people like it. They are different from the mainstream!!!
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9. • Who weeds birch & willow shoots & their roots, maintenance again.
• Cuts peak flow rate during heavy rainfalls, for how long? total
annual, to what extend (ref. Augustenborg up to 50%)? Can it be used in flow
calculations? Dimensioning of municipalitys’ run off networks? For
how long the buffer lasts? Formulae & expertise behind these?
• And if the most undesirable happens, a leaking roof, what then?
• Yes, we know that (foreign) investors are interested in LEED,
BREEAM etc. , for some reason, when it comes to green roofs, their
ranking system does not give enough points?
• But again, fire properties are a big question mark (A1…D, s1, d1,
…. Fire walls. Classifications, etc?) fire dept.s’ opinion? And not
forgetting interesting letter combinations like ETA, CE, i.e. legislation
on building products
• All that said; the B.C. is a bit conservative as always, but tries to be
somewhat neutral, even positive.
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Vesa Isakov, Building Control Dept.