Windows and glass doors (which are "windows" you can walk through) create a strong inside/outside relationship for the person inhabiting the room. And having fresh air and natural daylight blurs the sense that one is "trapped" in a closed room, creates a feeling of freedom, possibilities and a sense of health and belonging.
The placement, style and size of windows all have a huge impact on people's contentment inside their home, and can affect how they feel about themselves and their home as they retreat from the pressures of the outside world. The art of good fenestration requires understanding proportion, aesthetics, ventilation, interior design and visual appeal.
Architects tend to think of windows from a bigger-picture perspective in terms of function and appearance, while interior designers are taught to think of windows and glass doors as they relate to furniture placement and function within each room. Homeowners think of windows and glass doors in terms of physical access to the outside spaces and personal comfort. All of those needs can be successfully addressed if the fenestration is designed well to fit the needs of the homeowner.
Regarding proportion, a window that is too small or too high becomes obvious even to the untrained eye. Have you ever walked into a bedroom and felt like you were in a prison due to the height of the window? A window or glass door that is too large can quickly make a room feel unwelcoming due to lack of temperature control, glare or because the function of the room has been reduced, as there has been no consideration of where to successfully place a much-needed desk or couch.
Concerning aesthetics, the material the windows are composed of, including the color and the number of mullions (or "grids"), has huge visual impact. They help define the tone and style of the home. How much actual glass is in a window is largely controlled by what the window frame is made of. For example, a metal window will have more glass per square foot than one made of wood, as metal is structurally stronger. If you own a home with fantastic views, more glass and fewer mullions may optimize the emotional appeal of the view and the real estate value at the same time. An uninterrupted view of Windy Hill is pretty compelling!
If the window view is not great and privacy is a real concern, having white or obscure glass may solve the need for natural light without exposing oneself unwittingly. There are some beautiful obscure glass choices and some real ugly ones — beware! Try to design the size and placement of your windows and glass doors in such a way that you can maximize your indoor/outdoor living. If you pay for beautiful windows and just leave the curtains closed all the time, why bother having a window there?
An essential part of providing natural light and fresh air for homes can include skylights. Enclosed hallways, bathrooms with no exterior walls and large rooms with dark areas benefit greatly when properly sized skylights are designed into the home. As people tend to spend more time in the areas of their home that have more natural light, a skylight can be a big lifestyle improvement. A good way to spread the light of a skylight without acquiring too much heat gain is to "splay" the well: The skylight might measure 2-feet by 2-feet on the roof, but the interior ceiling opening can be larger, for example 4-feet by 4-feet. Splayed wells, with a lens cover, also provide an opportunity to install artificial lighting for increased lighting at nighttime.
Thoughtful consideration should be directed to your options regarding windows. For example, cross ventilation seems to have become a lost art in window design. I rarely see people bring this issue up without being prompted to think about it.
And remember, windows are not just good for your health and happiness. They'll nourish your soul.