Natural Light vs. Zoning Code: A Guide to Window Placement in Philadelphia Homes
When starting a home renovation, most people focus on things like square footage, layouts, circulation, finishes, etc. One crucial design factor that can oftentimes be overlooked in the initial stages of design is natural daylight.
Placing windows in Philadelphia homes is not always as easy as it may sound. The city has specific zoning and building code rules around where and how you can place windows, especially when placing them on rear walls, side walls, and additions. These rules go beyond light. Their priority is to protect privacy, fire safety, and sometimes even property lines.
Why Daylight Is Important In A Philly Home
The majority of homes in Philadelphia are row homes, twin houses, and townhouses, which all share the same problem of limiting how much natural light can enter from the sides. This puts pressure on the front and rear windows of the home to do all the work. Homeowners will often ask: “Can I add a window to the side of my house?” Maybe - but not always.
Aside from wanting natural light for aesthetic purposes, Philadelphia building code also requires all habitable rooms such as bedrooms, living rooms and kitchens to have access to natural light. This is not just a suggestion; building code specifies that a minimum percentage of a room's floor area must be met with windows to qualify as a livable space. “Every habitable space shall have at least one window of approved size facing directly to the outdoors or to a court. The minimum total glazed area for every habitable space shall be eight percent (8%) of the floor area of such room.” To find more information about this specific code visit “The Philadelphia Code” chapter 4, section PM-401.
How Zoning/Building Code Limits Window Placement Options
If your home side wall is less than 3 feet from the property line, you may be restricted from placing windows on that wall for the following reasons:
You might be breaching the privacy of a neighbouring property.
Windows near lot lines can be a fire hazard.
Risk of light trespass.
Fire Separation Distance
The International Building Code limits unprotected openings in walls that are near a property line. The distance to the property line is what will dictate whether you can add a window or not.
Less than 3 ft from the lot line = no unprotected windows allowed
Between 3-5ft = limited window area
Over 5 ft = flexibility for adding windows
Zoning Overlay Districts
Some neighbourhoods in Philadelphia, especially in the historical districts, have special zoning overlays that impact the appearance of homes.
Homeowners are required to match existing window sizes and or styles. Sometimes they are prohibited from adding new ones without review.
Solutions
Skylight + Roof Windows
Clerestory Windows
Glass Blocks
Reorienting the room layout to prioritize light
Double-height spaces which are open to the ceiling
Light wells
Daylight plays a major role in how an interior space feels. This then directly impacts the quality of life of the householder. In Philly, it's not always as simple as “let's just add more windows.” With the correct strategy and an understanding of how Philadelphia zoning and code work, you can get the light you need. Jane draws plans can help evaluate your lot and property lines, talk through your design goals and create code-compliant drawings that will maximise the daylight potential of your home.
