Costs,
Pros and Cons of Green Roofs
Green roofs (roof top gardens) have some important advantages over
traditional roofing. But they involve higher costs, higher
maintenance and some potential problems that should be taken
into account.
 Left:
Green Roof in Atlanta, on the GA City Hall.
Image Source: EPA
Pros of green
roofs
Green roofs are an environmental solution. They reduce urban
«heat islands» (higher urban temperatures caused by traditional dark colored roofs
and pavements and
the materials used in them) and they can be an important solution to reduce
city pollution.
From the homeowner’s perspective, green roofs are a way for
reducing the use of air-conditioning (they provide excellent insulation
and cooler indoor temperatures).
Other (environmental) advantages:
- green roofs are an excellent sound insulator.
- the vegetation element of green roofs may be a good habitat
for birds and other small animal life;
- they assimilate large amounts of rain, reducing the needs of
sewage systems and mitigating storm water runoff (rooftop
gardens have an
important role in storm water management, since they act as
sponges during rainstorms).
- green roofs vegetation absorbs negative air toxins, purifying
urban air.
- extended life of the roof base.
Costs of green roofs
Green roofs involve higher costs than traditional roofing. $8
per square foot is a minimum (includes materials, work costs and
installation). Values around $12 to $24 per square foot are
common. These values may amount to 5 to 10 times the cost of
most traditional built-up roofs (and also much more than roofing
based on new cooling materials: see
Roof coatings and membranes and
Roof clay and cement tiles).
These much higher up-front costs may me at least in part offset
through air conditioning energy savings, but the return of the
investment may be too long or you may never achieve it.
Cons of green roofs
Besides their higher costs, green roofs pose other possible
drawbacks:
-
higher maintenance costs;
- restrictions involving climate and weather conditions (un
example: rooftop gardens are inappropriate in very windy places; plants are
fragile and can be blown away).
- complex drainage systems;
- eventually, stronger roof beams in order to support the weight of
the
several layers of the
green roof, namely
the soil layer;
- more costly repairs and fixings (finding and repairing eventual leaks is more
expensive and difficult).
See also:
Installing a green roof
Roof basics
Roof membranes and coatings
Metal and ceramic roof
materials
Roofing and environment
Roofs and climates
Attic insulation
Roof and ceiling
insulation
Reflective
insulation
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