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Function of windows

Primary function of windows are to admit light and fresh air into the building.

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Design Features of Windows

1. LIGHT

2. VENTILATION

3. THERMAL INSULATION

4. ACOUSTIC INSULATION

5. SECURITY

6. DURABILITY

7. AESTHETICS

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1. Light Amount of light required

in any room depends on the activities that occur in the room

Minimum requirements for window area of a room is at least 10% of the floor area

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2. Ventiliation Rooms to a house to which ventilation requirements

apply are called “habitable rooms”

Habitable Room is a room with minimum floor area of 6.5m² that is used for living or sleeping.

There are two types of ventilation required for rooms

1. background ventilation _permanent

2. rapid ventilation – opening in window

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Background ventilation: This is ventilation provided by a permanent vent through an external wall.

Rapid ventilation: Provided by window openings

In habitable room the opening space must be at least 5% of floor area

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3. Thermal Insulation Primarily achieved

through the use of double glazing of windows and weather strip between the glazing.

Double panes reduce heat loss through glass

Weather strip prevents draughts

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4. Acoustic Insulation Usually solved by the

thermal insulation measures already taken.

Use of synthetic rubber seals around opens.

Sound insulation will be covered separately later.

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5. Security Depends on locking

mechanisms.

Some are designed to allow air circulation when the house is not occupied.

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6. Durability Windows should require

minimal maintenance

Teak timber window are resistant to rot.

Softwoods need regular maintenance

uPVC are more commonly used but are harmful to the environment.

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7. Aesthetics Fenestration is a term

used to describe the arrangement of windows on the façade (front) of building

Features to consider include pattern of windows, subdivisions of window, proportion of panes, recessing and projection of windows

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Other Features Fire Escape

In newly constructed houses windows must have a minimum opening width and height of 450mm.

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Other Features

Solar heat gain: is a term used to describe the warming of living space caused by sun shining through the window.

This is controlled at design stage: Position and size of windows?

Glare: is a term used to describe visual discomfort caused by excessive brightness.

Use of blinds and non-glossy surfaces with minimise this.

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Timber Casement Windows

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Weatherboard

(drip mould)

Sash top

rail

Side hung

casement

stile

Jamb

Sash

Bottom rail

Head

Vent

light

Transom

Dead

light

Mullion

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Top swung

casement

Side hung

casement

Joints Used Window frames are constructed using mortice and

tennon joints.

The sashes are constructed uing bridle/comb joints.

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A

B

C

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Top rail

Stile

Bridle joint

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Joint A

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Sill

Jamb

B

Joint B Mortise & Tennon

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C

Mullion

Transom

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Joint C Combed Joint

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A

A Head

Transom

Sill

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Head

Bone Sash head Glass

Sash bottom

Transom

Sash Head

Sash sill

Sill Rebate 2 Section A-A D. O' Dowd

Anti-capillary grooves are machined in the outer edges of the sashes to correspond with similar grooves in the frames. These prevent moisture penetration by capillary action.

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Sash bottom

Sash Head

Transom

Anti-capillary grooves

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24 Glazing sprig

Glass

Silicon Panel pin

Bead

Silicon or glazing beads secure the glass.

Putty was used before the arrival of silicon. D. O' Dowd

Opening sashes are usually hinged using two part alloy hinges. This allows the sashes to be easily removed for glass cleaning or for maintance.

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Plan view of window head

Open sash

Silicon

Glass

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Advantages of wooden frame windows:

Made from renewable resource.

Aesthetic.

Easily painted to a variety of colours.

Generally cheaper than other window materials such as aluminium and u-PVC.

Good insulators.

Available in both hardwood and softwood.

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Disadvantages of wooden frame windows:

Regular painting or varnishing is required.

Softwood windows are prone to rotting over a 10-20 year life cycle.

Hardwood windows have a tendancy to warp if the wood in not seasoned correctly.

Difficult to seal wooden window sash openings. This may lead to draughts.

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