Pitched roofing materials compared

Key issues

• Embodied energy - there's a wide scale of embodied energy from wood shingles at the low end of the range to aluminium at the high. The main energy components are those derived from manufacture and transport. As with other materials, sourcing a product in the UK (and close to site if possible) can dramatically reduce its embodied energy.

• Material efficiency - Selecting a material can be made more complicated once its efficiency is considered. For example in some circumstances it can be argued that a strong, lightweight material used over a large span can have a lower environmental impact than a heavier, more sustainable material once the degree of structural support is introduced into the equation.

• Durability - The longer lasting roofing material has a lower environmental impact.

Types of roofing materials:

Timber shingles and shakes
	As a sustainable roofing material, the timber shingle ( in cedar or oak) can only be matched in its low environmental impact by thatch. If sourced in the UK it has the lowest embodied energy of all roof coverings. Western Red Cedar is commonly imported from the USA where transport adds considerably to the embodied energy figure. Care should also be taken in specifying FSC sources as a number of imported timbers are unsustainably harvested. Shingles have relatively smooth faces and backs, while shakes have a highly textured, natural grain face and either a sawn or split back.
	Reusable and recyclable
	Very low embodied energy if sourced in the UK
	Renewable resource but be sure to use FSC sources
	Can be re-used though there are no facilities for recycling
	No pollution
	Production can make use of otherwise unusable logs and parts of logs
	Biodegradable
	Lightweight compared with clay and concrete
	Offers some thermal insulation K=0.1067W/m ²
	Maintenance issues
	Concerns over fire
	Care should be taken with acid run-off from cedar.
	30 - 50 years life expectancy

Natural slate
	If sourced in the UK, natural slate has a very low embodied energy. Imported slate often comes with quality issues along with added embodied energy from transportation. Slate is very durable and can be reused with relative ease.
	Reusable and recyclable
	Low embodied energy if sourced in the UK (130 - 160 MJ/m²)
	High embodied energy if imported
	Low toxicity
	Highly durable
	UK reserves relatively low
	High level of waste (around 90%) generated during production
	75 - 100 years

Rubber tiles / slates
	Reusable and recyclable
	Recycled content
	Low embodied energy
	Low toxicity
	Short track record of use
	Unknown

Clay tiles
	Reusable
	Large reserves
	Low toxicity
	Durable
	High embodied energy (230 - 470 MJ/m²)
	50 - 70 years

Concrete tiles
	Reusable
	Low embodied energy (40 - 90 MJ/m²)
	Large reserves
	Greenhouse gases
	Heavy, require appropriate structure
	50 - 60 years

Fibre-cement tiles / slates
	Reuseable
	Low embodied energy
	Highly durable
	High toxicity
	Greenhouse gases
	20 - 30 years

Coated steel
	Recyclable
	High material efficiency (7.1 Kg/m²)
	High toxicity
	Greenhouse gases
	Some coatings include PVC
	30 years

Alluminium
	Recyclable
	May have recycled content
	High material efficiency (<10 Kg/m²)
	Durable
	Very high embodied energy (virgin Al: 900 MJ/m²)
	Greenhouse gases
	Powder-coated Aluminium is not recyclable
	100+ years

Lead sheet
	Recyclable
	May contain recycled metal
	High material efficiency
	Durable
	High embodied energy
	Limited resources
	Greenhouse gases
	Toxic in use
	100+ years

Copper sheet
	Recyclable
	May contain recycled metal
	High material efficiency
	Durable
	Limited resources
	Greenhouse gases
	Toxic biproducts
	Copper corrosion contaminates rainwater
	100+ years

We would specify:

First choice:• Reclaimed slates/tiles • FSC sourced wood shingles • Reconstituted slates
• UK sourced natural slates • Rubber tiles
Second choice: • Clay tiles • Concrete tiles • Fibre cement tiles

Tile and slate products:

L521 Roof tiles and slates

Further information

• Durability - Pitched roof coverings