[Passive Measures]
New Housing, Integration of fabric / services and human factors, Built form
Passive solar design was first discussed in the beginners guide and, involves using the energy from the sun to try and offset heating costs. Buildings of all kinds - houses, offices, schools etc - can be made to make the most of the sun’s energy. For example, large windows can be put in rooms which receive a lot of sunlight; buildings can be made of materials which are good at holding the sun’s heat; and buildings can be orientated to maximise "solar gain", eg by ensuring that main living spaces are located in a sunny, south-facing part of the building.
Passive Solar
design tries to optimise the amount of energy that can be derived directly from
the sun, by careful planning of buildings to collect the sun’s heat, thus reducing
the need for heating. Similarly careful consideration of building materials
and fabric can help to further reduce the need for space heating, ventilation
and artificial lighting. The form of a building and the materials it is made
from are not easy to change or upgrade, this makes the design of new buildings,
or alterations to old ones, particularly important when considering the effects
of the environment. Careful thought should be given to the effects that the
natural environment can have on a building, designers must try to make best
use of natural light and natural ventilation, the useful energy available from
the sun must also be considered. Equally important is being careful to avoid
unnecessary heat losses or overheating and consideration can be given to reducing
these and saving money and also helping to reduce the effects of climate change.
In a typical
British home, around one-third of the heat produced by a central heating system
is rapidly lost through the roof, ceiling and walls. This does not have to happen:
simple insulation measures can eliminate this loss almost completely. Insulation
and draught stripping can help to keep more heat in your house without the need
to spend more money on fuel. UK homes can cost up to four times as much to heat
as Scandinavian homes. For
more info try; http://www.natenergy.org.uk/ensave1.htm
The
main focus of this section is going to be based around passive solar heating
and how the sun can help reduce heating costs, first a few simple tips illustrate
just how you can save
money in the
home without spending any more. Try using a low heat setting for a longer
period of heating, is cheaper and also more comfortable than short periods of
high temperatures. Don’t put furniture in front of radiators; similarly don’t
hang clothes over them to dry. Close the door behind you, this can help keep
heat in a room. Turn off heating in rooms that are not used very often.
These measures are important as they can help save energy and also money about
the home. We are going to look at how the heat from the sun can be used in the
home and how it can help to reduce energy use.
The
sun’s energy that comes in through windows can be used to heat our homes directly
or stored in the building fabric where it will be ‘released’ later in the day
when it is needed.
The
sun’s energy can help reduce the need for heating and it is important any ‘free’
useful heat is not wasted. Shutting curtains when it gets dark can help prevent
heat loss, make sure to tuck the bottom of the curtains on to the window sill
to stop cold down draughts.
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The
consideration of these early in the design stage can have considerable benefits
throughout the life of a building. The need for daylight within a building can
vary depending on the function of the building and the tasks being undertaken
within it. Whether tasks require specific levels of lighting (illuminance) in
particular locations or whether natural day lighting can be sufficient to satisfy
most requirements. The requirement for specific levels of lighting can directly
influence the need for window design – the amount of glazing within the facades
and the type of glass used in particular locations. The amount of glazing on
a building will also affect the influence of solar gain on the building. It
has been shown that on average 2.64 kWh/m2 falls on the earth every
day. The table illustrates the recommended illuminance for various activities/
interiors.
The amount of glazing on a building can also affect whether or not a building requires the need for;
Solar Shading
Air conditioning due to solar gains
Subsequent plant capacity and space requirements Many of these decisions can be based upon the;
Costs of such measures to implement
The required quality of the internal environment
Energy consumption of the strategy
How easily the system can be operated
Integration of fabric / services and human factors
It is important to realise that the function of a building needs to be carefully considered as a means of modifying the effects of the weather, able to use the weather to its advantage – i.e making use of solar gains whilst at the same time avoiding possible overheating which would lead to the need for air conditioning – cooling plant.
The balance has to be struck between ensuring that the heat from the sun does not over heat whilst allowing enough natural daylight into the building. In this way it is important that services are employed carefully to make best possible contribution for best return. Similarly good fabric design and consideration to materials can limit the need for services. The key to successful design is to avoid to high a dependence on mechanical plant – air conditioning can increase capital and running costs but still is often necessary in many of today’s offices and shops. In such cases where it is unavoidable the principles of integrated design can still help to reduce the size and complexity of the system and hence the capital / running costs. The following table illustrates some of the important factors for consideration.
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Minimising
the need for services and using those necessary as efficient as possible help
to ensure that natural resources such as daylight and cooler outdoor air have
been used to the full. Simple measures can help make the building as efficient
as possible and help reduce running costs
a) Optimise Internal Heat Gains – gains arise from occupants, equipment, lighting and solar radiation. Such gains can offset a significant part of the fabric and ventilation heat losses. In summer such gains actually increase the need for mechanical or natural cooling.
b) Optimise Natural ventilation by ensuring that windows are fully operable and by questioning the need for air conditioning.
c) Optimise Day lighting by ensuring that natural daylight is well distributed through out the buildings to make best use of it. Ensure that lights are switched off when there is sufficient daylight.
d) Thermal Storage – the building itself can be used as a passive thermal store and can improve energy in the same way that electric storage heaters work – see beginners guide.
e) Minimising heat losses – this can be dependant on the shape and size of the building, how well it is constructed and with what materials it is made from.
f) Integrating Human Factors Within a building it is vital to taken into account the requirements of the occupant, as the building is essentially build for them to help shelter from the elements.
It is often the case that building and services that take into account the needs of the occupant during design are generally more widely appreciated providing better levels of comfort, acceptability and generally more efficient. As a user it is far better to be able to turn the temperature of a room up during winter and open a window during hot summer days than to have the working environment controlled from a main system.
The buildings main function is to shelter the occupants from the elements and allow them to perform tasks within this enclosed environment, which would otherwise prove difficult. It is important however to remember that the building does not exclude the external climate condition but rather make good use of the climate to achieve a successful and comfortable environment.
A building
construction typically has four main functions
· During warm weather, it must minimise the heat gains from the sun to avoid overheating – either by shading or thermal mass.
· During cold weather it is important that the building makes best use of available heat whether from the sun or internal heat gains – occupants, equipment. At the same time it must ensure that losses of heat through its walls, roofs windows are reduced as much as possible little.
· It must provide optimum levels of day lighting.
· Whilst also providing optimum levels of natural ventilation.
These four factors can be easily adjusted and considered during early design stages of a building and can have great benefits on future energy consumption. Energy efficiency can be influenced during this design stage in a variety of ways. ·
Shape and size of the building
Building materials and thermal response
Insulation levels and subsequent heat losses or heat conserved
Window design (% of building area)
Ventilation Strategy
Day lighting strategy
Home, Passive Solar, Urban Developments, Household electricity consumption