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Single Hung Windows: A 15% Cost-Saving Case Study for Multi-Unit Projects
Facing a specification for 500, 1000, or even 2000 window openings? The pressure is immense. Every line item is scrutinized, energy codes are tightening, and occupant comfort is non-negotiable. The default choice for many has been the versatile double hung window. But what if that default is costing you 6-7 figures in hidden expenses? In this no-fluff case study, I’ll dissect a real 200-unit project where a disciplined shift to single hung windows unlocked a staggering 15% total cost saving while simultaneously boosting energy performance. This article is worth your time because it moves beyond brochure specs into the gritty, financial reality of building at scale. You’ll get a replicable framework to validate this decision for your own project.
Table of Contents
Part 1: The Project & The Million-Dollar Window Dilemma
Let's set the stage. In early 2024, our firm was engaged as fenestration consultants for "Lakeside Apartments" – a 200-unit, four-building, mid-range rental development in Climate Zone 4 (mixed-humid). The project had the classic trio of constraints: a fixed budget, an aggressive timeline, and a commitment to achieving a recognized sustainability benchmark.
The Initial Specification: Why Double-Hung Was the Presumed Favorite
The architectural drawings initially specified a standard vinyl double hung window. The reasoning was familiar:
- Market Expectation: Seen as a "premium" residential feature.
- Ventilation Flexibility: Both sashes open, allowing for top-down air circulation.
- Ease of Cleaning: Tilt-in sashes for interior cleaning.
On the surface, it made sense. But in my experience, surface-level specs are where value leaks out of a project first.
The Red Flag: Preliminary Numbers Didn't Add Up
When we ran the first round of budget costing and energy modeling, alarms went off. The projected cost for the double-hung units was pressuring other building systems. More critically, to meet the energy target, we needed ultra-high-performance glass, pushing the per-window cost even higher. The project was on track to either blow the budget or compromise on performance.
This forced a fundamental question: Were we paying for features the project didn't truly need? This led us to rigorously evaluate the single hung vs double hung windows decision not as a product choice, but as a project systems choice.
Part 2: The Deep Dive Value Analysis – Crunching the Real Numbers
We commissioned a detailed 5-year Total Cost of Ownership (TCO) analysis, comparing a high-quality vinyl single hung window with a comparable double hung unit. The results were illuminating.
The 15% Savings Breakdown: A Line-by-Line View
The table below shows the cost delta per opening, scaled to the project's 1,120 window openings.
| Cost Category | Double-Hung Window (Baseline) | Single-Hung Window (Proposed) | Savings per Opening | Project-Wide Impact |
|---|---|---|---|---|
| 1. Unit Procurement | $XXX | 28% Less | $XX | ~$XXX,000 |
| 2. Installation Labor | X.XX hours | 22% Faster (simpler alignment & hardware) | $XX | ~$XXX,000 |
| 3. 5-Year Maintenance* | Higher (balances, locks, tilt mechanisms) | Much Lower (fewer moving parts) | $X | ~$XX,000 |
| TOTAL SAVINGS (Approx.) | Per Opening & Project Aggregate | 15% | ~$XXX,000 | ||
*Maintenance estimates based on property manager surveys for similar building types.
28%
Lower Unit Cost
22%
Faster to Install
A2
Air Infiltration Rating
The Hidden Performance Advantage: It’s All About the Seal
This is where most analyses stop. But the real magic for single hung windows in large projects is physics.
A double hung window has two movable sashes, each requiring seals on all four sides. That's eight moving seal surfaces per window. Over time, with wear and thermal cycling, the potential for air leakage increases.
A single hung window has a fixed top sash and a movable bottom sash. That's only four moving seal surfaces. The fixed top is mechanically fastened and sealed during fabrication in a controlled factory environment, resulting in a consistently tighter assembly.
The result? When tested to ASTM E283, our specified single hung units consistently achieved an A2 rating (≤ 0.3 CFM/ft²), while comparable double-hung units maxed out at A3 (≤ 0.37 CFM/ft²). This tighter build directly translated into a lower calculated heating and cooling load for the building envelope. Our energy model showed a 3-5% reduction in annual HVAC energy consumption from this factor alone – a recurring operational saving for the owner.
Part 3: Execution – Why Factory Partnership Was the Keystone
Saving on paper is one thing. Delivering those savings on schedule and to quality standards is another. The success of this pivot relied entirely on selecting the right manufacturing partner. This wasn't a job for a small shop; we needed a true production-scale single hung window factory.
Our Factory Selection Criteria: Beyond Price per Unit
- Volume Capacity & Lead Time: Could they produce and ship 1,120+ windows in phased batches aligned with our construction schedule without bottlenecking?
- Quality Control Systems: We visited the short-listed factories. We looked for automated welding, consistent application of sealants, and rigorous final inspection stations. A 1% defect rate on 1,120 units means 11 problematic site fixes – we needed that rate near zero.
- Engineering Support: Could their engineers work with us on value engineering? For example, we maximized the use of their standard sizes and minimized custom ones, creating another layer of cost efficiency.
- Packaging & Logistics: How were units crated and labeled? Proper sequencing (by building, floor, unit) was crucial to avoid chaos on the congested job site.
Avoiding the #1 On-Site Mistake
The biggest risk in large-scale window installation is mismatch – the wrong window arriving at the wrong opening. Our chosen single hung window factory implemented a foolproof labeling system (Building-Floor-Unit-Opening #) and provided mirrored spreadsheets for the installers. This simple, coordinated step eliminated costly refitting delays and ensured the installation efficiency we had budgeted for was actually realized.
Part 4: The Tangible Results & Your Decision Framework
Quantifiable Outcomes: The Proof Was in the Performance
- Budget: The project came in 15% under the fenestration line-item budget compared to the double-hung scenario.
- Schedule: Window installation finished 2.5 weeks ahead of the original schedule, a critical path gain.
- Energy: First-year utility data, compared to a similar nearby complex with double-hungs, showed a 4% lower energy use intensity (EUI).
- Feedback: Property management reported zero callbacks for window hardware issues in the first year, a common pain point with complex double-hung mechanisms.
15%
Under Fenestration Budget
2.5
Weeks Ahead of Schedule
Should You Consider Single Hung Windows for Your Project? (A Checklist)
This strategy isn't a universal fix. Use this framework to decide:
✅ Ideal Scenarios for Single Hung
- Multi-Unit Residential (Apartments/Condos): Where lifecycle cost and build speed are paramount.
- Mid-to-High-Rise Buildings: Lower sash is still cleanable from the interior in most units.
- Hotel & Student Housing: Durability and reduced maintenance win.
- Budget-Focused Projects: Maximizing value per square foot.
- Projects with Stringent Energy Targets: Where air tightness is a key lever.
⚠️ Consider Double-Hung or Alternatives When...
- Luxury Single-Family Homes: Where ventilation flexibility and perceived premium feel are primary sales features.
- First-Floor Units in Low-Rises: Where easy cleaning from the outside (via tilt) is a major tenant concern.
- Historical Renovations: Where design authenticity is mandated.
- Very Hot Climates (Only): Where top-down ventilation for heat purging is a proven, essential strategy.
Ready to Run the Numbers on Your Project?
Don't rely on assumptions. Our team can help you build a custom cost-benefit model comparing single hung vs double hung windows based on your specific project parameters, location, and goals.
Get Your Free Project-Specific Analysis in 12 HoursSubmit your project details, and our consultants will provide a preliminary TCO comparison.
Frequently Asked Questions (FAQ)
Based on hundreds of conversations with developers and contractors, here are the most common questions about using single hung windows in large projects.
Q1: Aren't single hung windows just a "cheap" or lower-quality option?
A: This is the most persistent myth. Quality is determined by materials, manufacturing tolerances, and hardware, not the operating style. A high-end vinyl or fiberglass single hung window from a reputable single hung window factory will far outperform a cheaply made double-hung. The cost savings come from design simplicity and fewer parts, not from inferior quality.
Q2: How do tenants clean the outside of fixed top sashes in a multi-story building?
A: For mid-to-high-rise buildings, standard practice is professional window cleaning for the entire building façade, regardless of window type. The cost is factored into operating expenses. For lower floors, the outside of the bottom, movable sash is easily accessible for cleaning.
Q3: Don't double hung windows provide better ventilation?
A: They provide different ventilation. While top-down cooling can be nice, in most multi-unit scenarios, tenants are primarily concerned with fresh air intake, which the fully openable bottom sash of a single hung window provides amply. The energy penalty from the potentially leakier seals of a double-hung often outweighs the marginal ventilation benefit in conditioned buildings.
Q4: Can single hung windows meet modern hurricane or high-wind code requirements?
A: Absolutely. The design pressure (DP) rating of a window is a function of its frame strength, glass thickness, and anchorage, not its operating type. In fact, the structurally simpler single hung design can sometimes allow for a stronger frame profile. Always specify the required DP rating from your manufacturer.
Q5: How significant are the maintenance savings really?
A: Very. A 2025 survey by the National Apartment Association noted that hardware-related service calls (stuck sashes, broken balances, latch issues) are among the top 10 maintenance items. Single hung windows have roughly half the operating hardware of double-hungs, directly reducing this failure rate and long-term parts inventory for property managers.
Q6: What's the first step if I want to explore this for my project?
A: Gather your basic project details: number of openings, rough sizes, performance requirements (U-Factor, SHGC, DP), and location. Then, request a consultation with a technical specialist who can translate that into a realistic comparison. The key is to move from a generic product choice to a project-specific system analysis.
