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 major impact:

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 off.
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 harvesting systems.
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.

Roofing Membranes

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

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 roof structures.
Phosphor bronze - securing bolts and anchor plates for masonry fixings for heavy wall cladding.

More on Copper in Construction. http://www.copperinfo.com/cproducts/building.html

Slate

Slate roofs are extremely durable, lasting over a 100 years. Most damage to slate roofs occurs during repair work, largely due to poor workmanship.

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 tiles.

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

Lead is a leading sustainable, green building material:

It is the most recycled and recovered building material in use today
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.

Flat Roofs

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.

Low Toxicity

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

Project Blog

Keep up with the latest progress in our feature home renovations project....more