Types of Window Construction, part 2
The function of windows is not as simple as creating a weatherproof view, they also:
- Allow natural light in
- Often allow ventilation
- Have an aesthetic value
- Allow the inhabitant to see outside the building without leaving it, (security)
- Keep cold and sound transference to a minimum while catering for all of the above
The amount of natural light entering a room will be dependent on the windows, size and shape, how it is made, i.e. the number and size of mullions and transoms, it's position in the room and the effects of internal and external reflection.
Ventilation All habitable rooms must have a form of ventilation either mechanical (using ducts and fans) or natural, this is usually by opening windows. Opening windows for ventilation are the most common and economical forms of ventilation.
Building regulations vary from country to country however a good rule of thumb to use is that the windows for the room must have an opening area of at least 10% of the floor area.
This will need to be checked with your local building regulations. Kitchens, bathrooms, wc's and laundries are different again because of odour, moisture and airborne bacteria.
They are often required to have a form of mechanical ventilation in lieu of or as well as opening windows. (As with all building projects you must check with your local authority and building regulators before you embark on a job that requires construction rather than decoration. It would pay to employ the services of an architect, draftsperson or engineer to establish the legal parameters).
Heat, Cold and Sound Because of its very nature,
a pane of glass is usually quite thin and transparent,
especially in comparison to the wall in which it
sits. The wall has been designed to stop or reduce
the transference of heat, cold and noise and so
should a window while still achieving all of its
other functions. Unfortunately glass is a poor thermal
insulator unless working in conjunction with an
air gap. Various methods are used to stop or reduce
the sound and thermal transference as much as practical.
Double-glazing is the most common method of this.
There are various glasses that have beneficial properties
such as Hush glass, and solar control glasses that
control these factors to a degree. A sealed gap
between two sheets of glass forms a system of double-glazing.
A space of 20 millimetres is enough to improve thermal insulation however a
gap of 150 to 200 millimetres is needed to reduce sound. Typical double-glazing
with 20mm gap does give some sound reduction.
Ensuring that there is a good seal between the
opening part of the window (the sash or casement)
and the frame will reduce heat loss and improve
sound insulation. Metal or plastic rubberised sealing
strips around the rebates of the frame and opening
sash will aid in achieving this.
Glass companies
are constantly improving glass technology and are
experts in this field. They are usually more than
happy to go over the options available as well as
offer brochures and sometimes samples, so if you
are recommending or wanting to use double-glazing,
contact them.
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