Terminology

• Upper and lower sash: the two sliding panels; both operate in double-hung, only the lower in single-hung
• Meeting rail (check rail): horizontal rails where the sashes overlap and lock
• Balance: spring, block-and-tackle, or constant-force coil that holds the sash in position
• Weights and pulleys: traditional counterbalance in historic sash windows
• Tilt sash: sash that tilts in for cleaning
• Sash lock: cam lock at the meeting rail; pulls rails together to seal
• Jamb liner: vinyl or metal track in the jamb that guides the sash and carries weatherstrip
• Sliding seal: brush or bulb weatherstrip that the sash slides against
• Simulated divided lites (SDL): bars applied to both faces of the glass with a spacer between panes
• Grilles between the glass (GBG): muntins inside the IGU
• Hung commercial window: heavy aluminum hung units rated CW or AW for schools and historic replacement
• Sash limiter: stop that limits the lower sash opening for fall protection

Standards

Sizes

• Clear opening is less than half the frame area; check egress sizes against the manufacturer's net clear opening tables
• Tall units need heavier balances; balance capacity limits sash size and glass weight
• Historic replacement often requires custom sizes and matched sightlines

Ratings

• NAFS class: R and LC common residential; CW and AW in commercial aluminum hung lines
• Air leakage: higher than casements and awnings because of sliding seals; single-hung leaks less than double-hung
• Design pressure: limited by meeting rail and sash stiffness on large units

Test standards

• AAMA/WDMA/CSA 101/I.S.2/A440 (NAFS-22): including operating force
• ASTM E283, E331, E330
• NFRC 100, 200, and 400
• ASTM F2090: sash limiters and window opening control devices

Materials

• Vinyl: most common residential double-hung
• Fiberglass: stiffer sashes and narrower frames than vinyl
• Wood and clad wood: historic districts and traditional design
• Aluminum, thermally broken: commercial and institutional hung windows
• Glass: low-E IGUs; laminated for sound control on busy streets

Detailing

• Use sash limiters or opening control devices on upper floors with low sills
• Check egress clear opening early; double-hungs often need to be larger than casements for the same egress
• Match historic sightlines, meeting rail heights, and muntin profiles where required
• Provide exterior screens on the half that opens, or full screens
• Flash and integrate with the WRB; replacement inserts need careful sealing to the old frame

Uses

Specific uses

• Traditional houses and multifamily facades
• Historic window replacement in landmark buildings
• Schools and dormitories (commercial hung units with limiters)
• Rooms opening onto walkways, porches, or decks where a projecting sash is a hazard
• Window air conditioner locations in older housing

Pros and cons

Pros

• Traditional appearance suited to historic districts
• Sash does not project into exterior or interior space
• Top-and-bottom ventilation possible in double-hung
• Tilt sashes make cleaning easy from inside

Cons

• Higher air leakage than compression-seal windows
• Only about half the unit opens; larger unit needed for egress
• Balances wear and need adjustment or replacement
• Meeting rail interrupts the view

Manufacturing and cost

Construction

• Frame with jamb liners or tracks; sashes glazed and fitted with balances, locks, and weatherstrip
• Shipped with nailing fins for new construction or as pocket replacement inserts

Main manufacturers and suppliers

• Andersen
• Pella
• Marvin
• JELD-WEN
• Ply Gem
• Graham Architectural Products (commercial hung windows)

Trade associations: Fenestration and Glazing Industry Alliance and Window and Door Manufacturers Association.

Typical costs

• Residential double-hung, installed: $500 to $1,100 per window
• Vinyl double-hung from about $600 to $900 installed; wood and clad units higher

Sources

• Fixr: window installation cost breakdown, https://www.fixr.com/articles/window-installation-cost-a-detailed-breakdown
• Homeyou: window cost, https://www.homeyou.com/windows-cost
• Green Building Advisor: single- vs. double-hung sealing, https://www.greenbuildingadvisor.com/question/single-vs-double-hung-window-ee
• Ecoline Windows: hung windows pros and cons, https://ecolinewindows.ca/hung-windows-pros-and-cons
• FGIA: NAFS-22, https://store.fgiaonline.org/101/I.S.2/A440-22/
• Wikimedia Commons: Modern Double Hung Window 01.jpg, by Stilfehler (CC BY-SA 4.0), https://commons.wikimedia.org/wiki/File:Modern_Double_Hung_Window_01.jpg