Most of the energy loss in a home is through the roof. The choice
of roofing material can therefore have a significant effect on the
solar gains of a building. Even simple design choices can have a
- Light coloured roof finishes reflect radiant heat - dark colours
absorb radiant heat.
- Heavy weight roofing materials such as concrete even out heat
absorption and dispersion to the interior.
- Roof pitch can determine how much roofing area is exposed to
sunlight during the day and also the water collection and run
- Heavy roof tiles can account for 25% of a building’s mass
above ground. This weight requires additional structure, with
additional environmental and economic cost.
- The durability and matainence requirements of a roofing material
can add to environmental impact, not only in regular care, but
in recyclability upon demolition. For instance, metal profiled
roofing can be recycled but zinc requires less or no surface finish
and lasts a lot longer.
Non-Environmentally Friendly Roofing Materials
Certain roofing materials have proven to have a negative impact
on the environment. This includes:
- Fibrous cement sheet contains both sustainably managed cellulose
fibres, and also cement, a known significant contributor to man-made
greenhouse gas emissions.
- Copper and galvanised steel increase the levels of zinc and
copper pollution in waterways with rainfall runoff.
- Roofs with flaking toxic paintwork may also contaminate rainwater
- Some roofing membranes contain chemicals harmful to human health,
in particular, the hot application of bitumen and mastic. In addition,
any man-made chemical sprays should be treated with care.
Flat roofs are often problematic, largely due to the failure or
poor installation of the underlying membrane. To reduce the time
when membranes need to be replaced, requires some care and protection.
To extend the life of your roof membrane:
- Protect the membrane from UV damage and traffic by surface coverings
such as insulation slabs, concrete slabs, gravel, etc. will extend
its life and help prevent seepage.
- Use light coloured membrane and light coloured gravel to reduce
the solar gains on the roof.
- Look for low toxicity membranes, such as those manufactured
from ethethyne propylene rubber.
- Employ an upside down roof construction, where the insulation
is laid in panels over the membrane. This both increases the life
of the membrane and reduces solar loads. In addition, concrete
roofs constructed in this manner keep the thermal mass within
the insulated envelope.
- Consider a Green Roof - to increase
insulation levels, absorb stormwater and provide for local biodiversity.
Green roofs do need additional structure and care, which can increase
the cost. More on Green Roofs
- To allow for recycling - choose a membrane that does not fully
adhere to the substrate.
Copper is also an important structural component in many buildings.
Apart from hot water piping, gas tubing, heating and air conditioning
systems, spouting and decorative elements, copper is used for roofing.
Copper is an ideal green building product as it is generally always
recycled, with high demand for copper scrap material. Copper derivatives
used in building also include:
- Aluminum bronzes - support the entire weight of reinforced concrete
- Phosphor bronze - securing bolts and anchor plates for masonry
fixings for heavy wall cladding.
More on Copper in Construction.
Slate roofs are extremely durable, lasting over a 100 years. Most
damage to slate roofs occurs during repair work, largely due to
The durability of roofing slate depends upon the type, thickness,
method of attachment, slope, and other factors.
Typical repairs include: fixing leaks, replacing broken or lifted
The condition of slate tiles is determined by its surface texture.
If thye surface of the slate is smooth, the tile still has some
life yet, if the surface is crumbly and flaky, the slates need replacing.
Lead is a leading sustainable, green building material:
- It is the most recycled and recovered building material in use
- It lasts longer - Its fail rate is negligible
- It is resistance to atmospheric corrosion
- It ages more aesthetically than synthetic alternatives
It is more environmentally friendly than alternatives
- Its reclamation is energy efficient.
Lead may at first appear more expensive than other roofing materials,
but in the longer term, and in ecological terms, it provides the
best value - and it looks great!
Recent developments in lead products include 'The Lead Sheet Panel
System' designed by architects Michael Hopkins & Partners. Lead
panels are fully pre-formed on or off site - making it possible
to install up to a hundred panels a day. The integrated design also
ensures a uniformity of finish.
Lead is an ideal solution for flat roofs,notorious for their water
penetration problems. Lead is used as a roofing membrane, surmounted
with lightweight roofing panels with a cement-like upper surface
and water resistant extruded polystyrene backing. This provide a
high thermal insulation value and an expected roof life 4 times
that of existing flat roof systems
Rolled Lead Sheets
Lead sheets can now be rolled using computer control to give extremely
consistent thickness – as little as 5% variance. When Lead
Sheet is fitted to a roof, this minimal variance provides for more
accurate prediction on thermal movement, helping to ensure the correct
fixing method is used.
Lead remains stable and has a very high resistance to atmospheric
corrosion. The Lead Sheet forms a surface film of protective oxides
[ patina] that is adhesive and highly insoluble. Any low levels
of corrosion products exposed on the roof surface are very small
and become highly diluted with rainwater.
Lead naturally binds to the soil, hence, even the minute discharge
levels with extremely limited bio-availability within the eco-system.
In extremely rare cases, Lead corrodes on the underside in old buildings.
Studies maintain that this is due to weather variations during installation
and subsequent changes to the interior of the building. If no unusual
decay is encountered during repair, all is well. Changes in roof
construction mean that Lead used in building today is not subject
to this problem.
For more information: http://www.leadsheetassociation.org.uk/
Next: Green Roofs
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