Yes — if your building is located in a designated landmark or historic district, window replacement typically requires approval from the Landmarks Preservation Commission.
Approval is required when:

• replacing windows visible from the street
• changing window configuration, materials, or operation
• altering frame profiles or proportions

In some limited cases (rear elevations not visible from public streets), approval may be simplified or not required — but this should always be verified before starting work.

The Landmarks Preservation Commission does not approve materials universally — it evaluates whether the proposed windows match the historic appearance.
Commonly accepted:

• Wood (most preferred for historic façades)
• Steel (for buildings with original steel windows)

Conditionally accepted:

• Aluminum-clad wood
• Aluminum (typically only on rear elevations or non-visible areas)

The key factor is not the material itself, but how closely it replicates original sightlines, profiles, and detailing.

Yes — but with limitations.
Double glazing is widely accepted if:

• it does not significantly alter the window thickness
• sightlines remain historically accurate

Triple glazing is more challenging because:

• it increases frame depth
• it often changes proportions and profiles

In most landmark projects, double glazing is the practical balance between performance and approval.

Slim sightlines are critical for approval.
Typical ranges:

• Wood windows: ~1 ¼″ – 2″ visible profiles
• Steel windows: can achieve even slimmer lines (~1″ or less in some systems)

Steel systems are often used when ultra-thin sightlines are required to match original historic windows.
The goal is always:

• to replicate the original visual depth
• not to introduce bulkier modern frames

Approval timelines vary depending on the scope:

• Staff-level approval (simple replacements):
  ~2–6 weeks
• Full commission review (complex or visible changes):
  ~6–12+ weeks

Factors that affect timing:

• completeness of submission
• accuracy of drawings
• whether revisions are required

Projects with well-prepared documentation are significantly faster.

Typical submission package includes:

• Existing condition photos (interior and exterior)
• Proposed window drawings (elevations and sections)
• Detailed profiles (muntins, frames, sightlines)
• Material and finish specifications
• Window schedules (sizes, types, locations)

For more complex projects:

• mockups or samples
• architect-prepared drawings
• context photos of the building and streetscape

The Landmarks Preservation Commission reviews how closely the proposal matches the historic condition.

It depends on the building — but for many landmark projects, steel is often preferred.
Steel windows:

• ultra-slim sightlines
• closer match to historic industrial and early 20th-century windows
• higher likelihood of approval in certain building types

Aluminum windows:

• more cost-effective
• lower maintenance
• typically used on rear elevations or non-visible faсades

For street-facing landmark façades, steel is often chosen when matching original profiles is critical.