Civil Engineering Reference
In-Depth Information
of a new door frame can be expensive, especially if its dimensions are not to the
current standard. This assumes that the door was originally fixed for simple dis-
mantling, preferably with screws.
Defective doors of solid timber can usually be energy recycled or composted,
but laminated products have to be deposited at special tips, or energy recycled
in incinerators that filter the fumes.
Plastic and aluminium windows and doors
Window frames of plastic and aluminium usually consist of profiles filled with
foamed insulation of polyurethane or polystyrene. Some products use both alu-
minium and timber, where timber is the insulating material. Lower quality tim-
ber can be used, as the outer layer of aluminium protects it from the elements.
Plastic windows are usually made of hard polyvinyl chloride (PVC) stabilized
by cadmium, lead and tin compounds and added colour pigments. All these
products have very limited reserves, and pollution during processing is consid-
erable.
The manufacture of an aluminium window uses 30-100 times more primary
energy input than a timber window; a PVC window uses about six times as
much (Phil, 1990). The annual cost, taking into account the investment and main-
tenance, favours timber windows with an estimated life span of 30 years. There
have been some problems with aluminium and plastic windows because con-
densation can easily occur within the frame, due to a profusion of cold-bridges.
In a building the products are not a particular problem. The hard PVC has no
softeners that could emit unpleasant gases.
Both PVC and aluminium windows can be re-used if they are initially installed
for easy dismantling. Pure aluminium windows can be recycled. This is unlikely
for the other products, as they have sealed, complex combinations of different
materials. Waste has to be deposited at special tips if products can contain cad-
mium, lead and tin.
Stairs
Stairs are, in a way, part of the floor. The main materials used are timber, stone,
brick, concrete and cast iron. The steps have structural properties, at the same
time must provide a comfortable underlay for the foot. Common finishes include
linoleum and ceramic tiles.
Wooden stairs
Stairs of non-impregnated timber are used mainly indoors, but they can also be
placed outdoors if they are under shelter. Pine, oak, ash, beech and elm are hard-
wearing materials and can often be used without treatment. The timber should
