Buildings
Windows Are Sized By The Energy Model Before The View
Glazing area is set by heat loss, overheating and daylight calculations run during design, which means the window a resident gets was decided by a spreadsheet, not a viewpoint.
The proportion of glass on a modern facade looks like an aesthetic decision. In practice it is usually the output of calculations run long before anyone considered the view.
Glass performs worse than wall
Even good glazing loses heat faster than an insulated wall of the same area, so increasing the glazed proportion raises the energy needed to keep a room comfortable in winter.
Compliance calculations compare the whole building against a notional target, and the simplest lever available to a design team is the ratio of glass to solid wall.
When a scheme fails its target, glazing shrinks. The change is made in the model and appears on the facade weeks later.
Overheating pulls in the same direction
Large windows admit solar gain, which is welcome in winter and a problem in summer, particularly in well-insulated flats that struggle to shed heat once it is inside.
Assessments of summer comfort have become a standard part of approval, and a room that fails one is usually corrected by reducing glass, adding shading or improving ventilation.
Shading is often the first casualty of cost cutting, so the reduction lands on the window instead, and the room ends up darker rather than better protected.
Daylight sets a floor under the shrinking
Working against both effects is the requirement that habitable rooms receive adequate daylight, assessed against the room's depth and the obstruction outside the window.
A deep room needs a larger window to reach the same level of daylight at the back, so plan shape and glazing area cannot be decided independently.
The final window size is the point where daylight, heat loss and overheating are simultaneously satisfied, which is rarely the size that would have framed the view best.
Opening area is a separate calculation
How much of a window opens is governed by ventilation requirements, restrictors for safety, and in noisy or polluted locations by whether opening it is realistic at all.
Where opening windows cannot be relied upon, mechanical ventilation takes over, which adds equipment and running cost but removes the constraint on the facade.
Residents often read a small opening as a cost saving when it is a safety restriction, and a fixed pane as meanness when the room is ventilated another way.
Orientation should change the answer and often does not
A window facing the midday sun and one facing away from it have entirely different requirements, and treating them identically guarantees that one of them is wrong.
Repeating a single facade around all four sides is cheaper to procure and simpler to build, and the penalty is paid by whichever flats face the sun.
The buildings that get this right vary glazing and shading by orientation, and their facades look less uniform as a direct result.
Questions readers ask
Can old car parks become housing?
Some can, mostly those with flat decks, external ramps and generous clear heights. Continuously sloping decks are rarely worth converting, and demolition often prices out as the cheaper route.
Why are car parks placed at the base of buildings?
Because building below ground is expensive and building above is structurally awkward. The base is the cheapest place to put them, and it is also the part of the building the street uses.
