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Case History: Prefabricated Houses
Prefabricated houses, as opposed to houses built conventionally from the ground up,
have a history that goes back at least 175 years, when some of the first were shipped
out to Australia and South Africa from England.
One of the largest programmes of prefabricated house building
was in the United Kingdom, following the destruction of World War II.
Over 150,000 were constructed in various designs, typically 2-bedroom units
with around 60 square metres of floor space.
They came pre-decorated, with a fitted kitchen and bathroom connected to a service unit.
They were made to a much higher specification than the houses they replaced.
They cost in the region of £1200 to build, which was more
than a conventional brick-built house at that time.
They were expected to last only for 10-15 years,
although some are still occupied today, seventy years later.
Today, similar construction techniques are widely used for temporary buildings
such as site offices.
And for “mobile homes”.
For permanent housing, people look to prefabricated construction either for
or style and quality - for example in the German Huff Haus
or for low cost. A pre-fabricated house might cost €40,000 excluding the land;
a similar, conventionally built house might cost €60,000.
The SML house, “SML” standing for “Small, Medium, Large”, is a demonstration project
by the Universidad Cardenal Herrera in Valencia; 0:01:50.100,0:01:55.000 this adds a third factor - flexibility.
The idea is that the building can change in size to match the changing needs of the occupants.
The configuration we are about to see is a “Medium” design - a 74 square metre house
with kitchen, bathroom, living/dining area, home office and bedroom, together with
a service module and an enclosed patio area.
The SML House could be made larger by adding more modules,
or smaller by removing modules.
Construction
The six modules were prefabricated at a size that makes them suitable for road transport.
A metal base has been pre-assembled. This allows for any variations
in level on the site and also creates a service area underneath the modules.
One of the main advantages of the house, starting from its concept,
is that it’s designed so it can be located anywhere that is irregular,
the ground does not have to be uniform.
You see, the foundation is formed with a large number of screw jacks
so we can adapt to unevenness in the ground.
The loading on the screw jacks is very light
so there is not much tension.
The house is built in modules so we can transport it on a modified truck
We can erect these modules in larger or smaller combinations
depending on the requirements of the project.
Once the modules are installed, which takes a very short time
usually between 1 hour and 1 hour 15 minutes per module
the module is completely sealed,
meaning we can work in bad weather.
But the big advantage is that we can adapt to a ny terrain, however irregular.
Another advantage is orientation - we can align the house as we want it
so it can make best use of solar power
and the house can be self-sufficient and not need any mains electrical supply.
So now, the way the house is oriented, it’s self-sufficient and fully functional.
A key objective was to demonstrate that the house could generate enough
electrical power to be self sufficient,
so there are photo-voltaic panels on the roof of each module.
And also on walls that face towards the sun.
By following a number of Passivhaus principles, including orientation,
thermal mass, solar protection and gain, as well as domotics
to minimise power consumption and to schedule peak electrical loads
to coincide with peak output, the SML house is a net producer of energy.
The enclosed courtyard patio acts a passive energy-saving system by reducing the effect
of solar radiation on that side of the house, as well as providing privacy.
It is a flexible structure that can be extended to fit the number and
layout of the modules that form the SML House.
As regards materials, these were selected on the basis of sustainability as well as
functionality and appearance. The SML system is mostly wood.
As well as being fully recyclable, this greatly reduces the weight of the building.
Prefabrication and predecoration of the modules reduces the amount of waste created in
the construction. It also allows extensive use of unskilled labour - in this case students.
The service module comes ready plumbed and wired.
Pipework and service units are quickly installed and connected.
In summary, comparing the SML System with a conventional house,
the amount of solid waste from the construction is reduced by 75%.
The total time for construction, including prefabrication of the modules
is reduced by 60%.
The transport and water requirements are reduced by two thirds,
when compared with conventional construction.
And the lightweight construction uses 40% less material.
This project is in cooperation with research departments in industry and the outreach
is not just academic and industrial but to society, so that people
can understand how these houses behave.
So how do these houses behave?
It’s about their ability to respect the environment
At the moment construction is not sustainable in environmental terms
so people who will be working in construction and the professions in future
will have to be aware of the need to use materials efficiently,
to use sustainable materials and to incorporate renewable technologies.