1. Home
2. Categories
3. Windows And Doors
4. How To Choose Replacement Windows (and Your Installer): A Complete 2026 Buyer’s Guide

Updated for 2026 • Based on manufacturer specifications, industry standards, and St. Louis dealer experience

Choosing replacement windows isn’t a single decision — it’s six decisions, and most homeowners learn about them out of order. The brand decision often gets made first (because that’s what shoppers see in ads), when material category should come first. The installer decision often gets made last (or not at all, just delegated to whoever the dealer assigns), when installer quality determines at least half the long-term outcome. By the time most homeowners realize the decisions they should have made, they’ve already signed a contract.

This guide walks through the six decisions in the order that actually matters, plus the questions to ask before signing and the warning signs that should make you walk away. We’re an exclusive Marvin dealer in St. Louis, but the framework is brand-neutral. If after reading this you decide a different brand or product fits your project better, this guide will still have served its purpose.

The short answerMake six decisions in order: (1) material category — vinyl, fiberglass, clad wood, aluminum; (2) brand and product line within that category; (3) insert vs full-frame installation type; (4) glass package and energy ratings; (5) the dealer; (6) the installer. The first four are the product. The last two often matter more. Get itemized quotes from 2–3 established dealers with verifiable references; avoid in-home sales models that pressure same-day decisions; verify whether installation is by the dealer’s trained team or subcontracted; confirm warranty terms are transferable; and walk away from any dealer who pressures you, refuses to itemize, or won’t tell you who’s doing the actual installation work.

Forshaw is an exclusive Marvin dealer in St. Louis since 1871Free consultations, transparent itemized quotes, no in-home sales pressure. We’ll walk through every decision in this guide with you.Call (314) 993-5570

The six-decision framework

These are the decisions, in the order they should be made:

1.  Material category. Vinyl, fiberglass, aluminum-clad wood, solid wood, or aluminum. Each has different cost, lifespan, and aesthetic implications. This sets the price floor and ceiling for your project.

2.  Brand and product line. Within the material category, which brand and which specific line. The differences between premium and mid-tier products within a single brand can be larger than the differences between brands.

3.  Insert vs. full-frame installation. Whether the new window goes into the existing frame (insert) or the entire frame is removed and replaced (full-frame). Depends on existing frame condition; affects cost meaningfully.

4.  Glass package and energy ratings. Dual or triple pane; Low-E coating type; gas fill; tempered glass where required. This is where energy performance actually comes from — not from the frame material.

5.  The dealer. Who you’re buying from. Established local dealers, manufacturer-authorized dealers, and in-home consultation models offer very different experiences and accountability.

6.  The installer. Who’s actually doing the installation work. This is the decision most homeowners underestimate — installation quality affects long-term outcomes as much as product quality.

The first four decisions are the product. The last two are who’s selling and installing it. Most window content focuses on 1–4. We’ll spend equal time on 5–6 because that’s where shoppers most often get burned.

Decision 1: Material category

Start here because it sets your price range and rules out brands. The five mainstream residential categories:

Material	Typical cost/window	Typical lifespan	Maintenance	Best for
Vinyl	$300–$950	20–40 premium; 8–15 cheap	Very low	Budget projects, rentals, shorter holds
Fiberglass	$400–$1,600	30–50+ years	Very low	Long-term ownership, extreme climates
Clad wood	$800–$2,500+	25–40+ years	Low (interior wood: occasional)	Premium homes, design priority, historic districts
Solid wood	$1,000–$3,000+	15–30 standard; 50+ maintained	High (regular painting/sealing)	Historic restoration, willing-to-maintain owners
Aluminum	$400–$1,200	15–30 standard; 25–45 thermally broken	Very low	Modern architecture, large openings

For most St. Louis residential projects, the choice narrows to fiberglass, clad wood, or premium vinyl. For deeper analysis of the trade-offs, see our material education guides linked below.

Decision 2: Brand and product line

Within your material category, the next decision is brand. Marvin, Pella, and Andersen dominate the premium tiers; many other brands (Simonton, Okna, Soft-Lite, Sunrise, Loewen, Kolbe, Sierra Pacific) serve specific segments. The biggest mistake shoppers make at this stage: assuming all products from a brand are equivalent. They’re not.

Premium vs. mid-tier within the same brand

Most premium manufacturers offer multiple product lines at different price tiers. Marvin offers Ultimate (flagship), Modern (contemporary), Elevate (mid-tier), and Essential (entry). Pella offers Reserve (flagship), Architect Series, Lifestyle (mid-tier), 250 Series, Impervia (fiberglass), and Hurricane Shield Series. Andersen offers A-Series (flagship), 400 Series, 200 Series, 100 Series, and E-Series.

The differences within a brand can be larger than the differences between brands at the same tier. A Marvin Essential is a fiberglass window. A Marvin Ultimate is a flagship aluminum-clad wood window. They share a brand name but they’re very different products at different price points.

When you receive a quote, the line item should specify both brand and product line. “Marvin double-hung” isn’t specific enough. “Marvin Ultimate Double Hung G2 in extruded aluminum-clad pine” is.

Brand reputation and dealer network matter

A brand’s warranty is only as good as the dealer network that services it. Marvin’s warranty is fully transferable. Pella’s limited lifetime warranty is original-owner only — not transferable at sale. Andersen 100 Series and Renewal Acclaim windows carry transferable 20-year frame warranties. These differences matter at the 15–20 year mark when you’re either still in the home or selling it.

Consider also where the dealer network is for your area. If you’re considering a brand that has only one local dealer, you have less negotiating leverage and limited service options if issues arise. If you’re considering a brand with multiple established local dealers, you can get competing quotes and have more options if you need warranty service later.

Decision 3: Insert vs. full-frame installation

This decision often gets glossed over by dealers who default to one approach. It’s a meaningful decision that affects both cost and long-term outcome.

Insert (pocket) replacement

The existing frame stays in place; the new window is installed within the existing opening. Faster, less expensive, less disruptive. Appropriate when the existing frame is in good structural condition and you’re primarily replacing the operating sash and glass. Renewal by Andersen and Infinity by Marvin are insert-focused replacement products.

Full-frame replacement

The entire window frame is removed; a new complete window unit is installed. More expensive, more disruptive, more thorough. Appropriate when the existing frame is damaged, rotted, or settled out of square — or when you want to change window sizes or styles. Resets the entire window system rather than patching part of it.

How to tell which is right

The straight answer: a quality consultation includes evaluating your existing frame condition and recommending the approach that fits your project. Walk away from any dealer who quotes a single approach without examining your frames first. Specifically:

• If the existing frame is sound (no rot, no warping, square and plumb), insert replacement is usually adequate and saves money
• If the existing frame has rot, water damage, settling, or has been altered by previous poor work, full-frame is typically required for long-term performance
• For homes 50+ years old in St. Louis (Soulard, Lafayette Square, Compton Heights, much of Webster Groves and Kirkwood), full-frame is more often the right answer because of frame condition
• For newer construction (post-2000) where frames are still in good shape, insert replacement often makes sense

At Forshaw, we sell roughly even numbers of insert and full-frame replacements. The right approach depends on your project, not on a default preference. See our insert vs full-frame guide for deeper analysis.

Decision 4: Glass package and energy ratings

The glass package matters more than most shoppers realize. The frame material gets most of the marketing attention, but the glass is where 70–80% of the energy performance actually comes from. Three components to specify:

Number of panes

• Dual-pane: Standard for most residential replacement in St. Louis climate. Two glass panes with an air or gas-filled space between them.
• Triple-pane: Three glass panes with two gas-filled spaces. Better thermal performance and sound dampening. Worth the upgrade in extreme climates or for noise-sensitive locations. Adds roughly 10–20% to the per-window cost.

Low-E coating

Low-emissivity coatings are microscopically thin metallic layers applied to glass surfaces that reflect heat back where it came from. Multiple Low-E configurations exist for different climates and orientations:

• Soft-coat Low-E: Higher performance, applied in vacuum chamber, more delicate, requires sealed IGU
• Hard-coat Low-E: Slightly lower performance, more durable, can be used in single-pane storm window applications
• Climate-specific tunings: For St. Louis (Climate Zone 4, mixed-humid), the recommended SHGC (solar heat gain coefficient) is typically 0.25–0.40 — you want some solar gain in winter but not too much in summer

Gas fill

• Argon: Standard premium gas fill, denser than air, modestly better thermal performance
• Krypton: Premium gas fill, denser than argon, used in triple-pane and high-performance windows. More expensive, marginal performance improvement over argon

NFRC ratings to compare

The National Fenestration Rating Council (NFRC) requires standardized labels on residential windows showing performance ratings. The four numbers to check:

• U-Factor: Heat transfer rate. LOWER is better. Range 0.15–0.40 for residential windows. Look for 0.30 or lower in St. Louis.
• Solar Heat Gain Coefficient (SHGC): How much solar heat passes through the glass. LOWER is better in cooling-dominant climates. 0.25–0.40 is appropriate for St. Louis.
• Visible Transmittance (VT): How much visible light passes through. HIGHER means brighter rooms. 0.40–0.60 is typical.
• Air Leakage (AL): How much air passes through frame and sash. LOWER is better. Quality windows are 0.30 or lower.

When comparing quotes, the NFRC numbers should be specified for each line item. If a quote says “energy efficient glass” without NFRC ratings, that’s not a specification — it’s marketing.

Decision 5: Choosing the dealer

The dealer is who you’re buying from, who handles your warranty service, and who you’ll call if anything goes wrong over the next 20–30 years. This decision matters at least as much as the brand.

Types of dealers

• Established local dealers: Family-owned or independent businesses, often multi-generational, with permanent showrooms and local accountability. Best for long-term service relationships.
• Manufacturer-authorized retailers: Dealers explicitly approved by the manufacturer to sell their products. Sometimes overlap with the previous category. Manufacturer training and warranty support are typically stronger.
• Big-box stores: Home Depot, Lowe’s, and similar offer windows through partnerships with installers. Installation accountability sits between the retailer and the installer, which can complicate service.
• In-home consultation models: Renewal by Andersen, Champion, and similar use the in-home sales model where representatives come to your home for 2–3 hour consultations. Heavy on relationship-building and same-day discount pressure. Pricing is typically substantially higher than retail equivalents.
• Online-only retailers: Some windows are now sold online with separately-arranged installation. Lowest cost typically; highest coordination burden on the homeowner.

What to verify about any dealer

• Years in business: Established local presence (10+ years) suggests they’ll be around for warranty service. Be cautious of brand-new businesses or businesses that have rebranded recently.
• Physical location: A real showroom you can visit means a real business with assets to lose if they mistreat customers. Pure online or no-showroom businesses have less accountability.
• Manufacturer authorization: Verify the dealer is authorized to sell the brand they’re quoting. Most manufacturers list authorized dealers on their websites.
• References and reviews: Check Google reviews, BBB ratings, and ask for references on similar projects. Read negative reviews carefully — what kinds of complaints come up, and how does the business respond?
• Licensing and insurance: Verify the dealer carries general liability and workers’ compensation insurance. Ask for proof. Most reputable dealers will provide this without hesitation.
• Warranty handling: Ask how warranty claims work. Who do you call — the dealer or the manufacturer? Who handles labor on warranty service?

Decision 6: Choosing the installer (the decision most homeowners underestimate)

Installation quality affects long-term window performance as much as product quality. Per industry sources, a premium window installed poorly can fail within 5–7 years; a properly installed budget window often reaches its full expected lifespan. Yet most homeowners spend hours researching brands and minutes thinking about who’s actually doing the work.

Models for installation accountability

• Dealer’s own trained installation team: Best accountability. The dealer is responsible for both product and installation, so they own the entire outcome. Most established Marvin and Pella dealers operate this way.
• Authorized subcontracted crews: The dealer subcontracts installation to vetted, manufacturer-trained crews. Quality varies; verify how the dealer monitors and stands behind subcontracted work.
• Unauthorized subcontractors: The dealer subs to whoever’s available at the lowest cost. This is where installation horror stories come from. If the dealer can’t or won’t tell you who’s installing, this is the model you’re likely getting.
• You arrange installation separately: Common with big-box retail and online purchases. You take on the coordination burden and have to manage the relationship between product and labor independently.

What to verify about installers

• Who specifically is installing your project: Ask for the lead installer’s name and experience level. The answer “whoever we have available that day” is a warning sign.
• Manufacturer training certification: Marvin offers installer certification programs. So do Pella and Andersen. Certified installers are trained to manufacturer specifications and often required to maintain warranty coverage.
• Years of experience: Window installation is a skilled trade. Crews with 5+ years of experience produce meaningfully different results than first-year apprentices.
• References on similar projects: Ask to talk to homeowners whose windows the installer recently completed. Ask specifically about flashing, air sealing, trim work, cleanup, and timeline adherence.
• Workmanship warranty: Manufacturer warranties typically cover product defects but not installation defects. Ask about the dealer’s separate workmanship warranty — length, coverage, and how claims work.
• Insurance coverage: Verify the installer carries workers’ comp and general liability. Without these, if an installer gets hurt on your property or damages your home, the financial exposure can fall on you.

Warning signs that should make you walk away

Red flags in dealers and installersThese warning signs should make you walk away from the quote regardless of how good the price looks:

• Same-day-only discounts. Legitimate pricing is consistent. If a price expires when the salesperson leaves your home, the original price was inflated. This is the single most common pressure tactic in in-home sales models.
• Refusal to itemize the quote. A lump-sum quote without product line, glass package, installation type, and labor breakdown is a sales tactic. Quality dealers itemize because they have nothing to hide.
• Pressure to sign on the spot. Replacement windows are a 20–30 year decision. Any dealer who needs you to decide same-day knows the quote won’t hold up to comparison.
• Refusal to identify the installer. If you can’t find out who’s installing your windows before signing, you can’t evaluate installation quality. This is non-negotiable.
• Excessive disparagement of competitors. Any dealer who spends their consultation trashing other brands instead of explaining their product’s strengths is selling on fear rather than value. Particularly suspect: blanket claims that all competitors are dishonest, that vinyl windows only last 6 years, or that anything other than the dealer’s preferred installation type is a scam.
• Demands for large upfront payment. Standard payment schedules are roughly 30–50% deposit at order, balance due at completion. Demands for 100% upfront or 80%+ deposit are warning signs. Reputable dealers don’t need your full payment before the work is done.
• No physical showroom or address. A dealer without a real location is a dealer without skin in the game. They can dissolve and reincorporate under a new name if customer complaints accumulate.
• Reluctance to provide insurance certificates. Workers’ compensation and general liability are basic business protections. Any dealer reluctant to provide proof is likely not carrying adequate coverage — which means exposure shifts to you.
• Refusal to put verbal promises in writing. If the salesperson promises something verbally during the consultation — a specific timeline, a specific feature, a specific warranty term — it should appear in writing in the contract. “Don’t worry about that, we’ll handle it” is not a contract term.
• Reviews show consistent negative patterns. One bad review on a dealer with 200 positive reviews is normal. Twenty bad reviews on a dealer with 50 reviews showing the same complaint pattern (poor installation, slow warranty service, unresponsive after-sale) is a pattern worth taking seriously.

20 questions to ask before signing

These are the questions every shopper should ask before committing to a window replacement contract. If a dealer can’t or won’t answer these clearly, the answer itself tells you something.

About the product

1.  What’s the specific brand and product line on this quote?

2.  What’s the cladding type (if applicable)? Extruded or roll-formed?

3.  What AAMA finish standard does the exterior coating meet (2603, 2604, or 2605)?

4.  What’s the NFRC rating on the glass (U-factor, SHGC, VT, AL)?

5.  What’s the glass package — dual or triple pane, gas fill, Low-E type?

6.  Is this insert or full-frame installation, and why is that the right approach for my specific frames?

About the warranty

7.  What’s the warranty length on the frame, glass seal, hardware, and finish?

8.  Is the warranty transferable to a future homeowner if I sell?

9.  Who handles warranty claims — the dealer or the manufacturer?

10.  Is labor covered under warranty? For how long?

About the installation

11.  Who specifically is installing my windows — your trained team, certified subcontractors, or unaffiliated installers?

12.  Are the installers manufacturer-trained or certified?

13.  What’s the lead installer’s years of experience?

14.  What’s your separate workmanship warranty, and how long does it last?

15.  Do you carry general liability and workers’ compensation insurance? Can I see the certificates?

About the project

16.  What’s the expected timeline from contract signing to completed installation?

17.  Do you handle permits, or am I responsible for permit pulling?

18.  What’s the payment schedule — deposit at signing, balance at completion?

19.  What does the contract say about delays, weather rescheduling, and damage during installation?

20.  Can I have 48–72 hours to review the contract before signing?

A reputable dealer will answer all 20 of these questions directly and provide written documentation for the answers that should be in writing (warranty terms, insurance, contract language). A dealer that resists any of these is telling you something about how they’ll respond when you have a real issue.

What a good quote looks like

A quality window replacement quote should include all of the following, in writing:

• Specific brand and product line for each window opening (not “Marvin double-hung” — “Marvin Ultimate Double Hung G2”)
• Exterior cladding type and finish standard (extruded or roll-formed; AAMA 2603/2604/2605)
• Wood species for clad-wood and solid wood (Pine, Mahogany, Cherry, etc.)
• Interior finish (unfinished, primed, factory-stained)
• Exterior color (specified by name, with sample shown)
• Glass package details (dual or triple pane; specific Low-E coating; gas fill; tempered where required)
• NFRC ratings for the specified glass package (U-factor, SHGC, VT, AL)
• Installation type (insert or full-frame, with reasoning explained for your specific frames)
• Permit handling (included in price, or pass-through at actual municipal cost)
• Detailed line-item pricing for each window, plus labor, materials, and any extras
• Warranty terms on frame, glass, hardware, finish, and labor — with transferability spelled out
• Expected timeline from contract signing through completed installation
• Payment schedule (deposit percentage, milestone payments, balance at completion)
• Contract terms covering delays, weather rescheduling, damage during installation, and dispute resolution

Why Forshaw for your window project in St. Louis

Forshaw has been a family-owned St. Louis business since 1871. We’re an exclusive Marvin dealer for our window and door division.

• 150+ years of local accountability. We’re going to be here in 20 years when you need warranty service. A real showroom, a real local team, and a multi-generational family business with reputation to protect.
• Free consultations with no pressure. We don’t run the in-home sales model. Visit our showroom or schedule an in-home assessment. Take the quote home. Compare it. Decide on your timeline.
• Transparent, itemized quotes. Every quote includes brand, product line, cladding type, AAMA standard, glass package with NFRC ratings, installation type, permits, warranty terms, and timeline. Nothing hidden in lump-sum totals.
• Trained installation team. Our installers follow Marvin’s installation specifications and are accountable to our local team from consultation through completion. We’ll tell you the lead installer’s name and experience level before you sign.
• Insert and full-frame, both done well. We sell roughly even numbers of each. We’ll evaluate your existing frames and recommend the approach that fits your project — not the approach that’s easiest for us.
• Marvin’s warranty plus our workmanship warranty. Two-warranty structure. Marvin covers product (20 years on glass, finish, etc., transferable to subsequent owners). We cover installation labor separately.
• Bring us competing quotes. We’ll walk through them line by line and tell you what’s comparable and what’s missing. Many shoppers find competing in-home-sales quotes are 30–70% higher than equivalent retail work.

Start with a free consultationWe’ll walk through every decision in this guide with you, evaluate your existing windows, and provide an itemized written quote on the right Marvin product for your project. No pressure, no in-home sales tactics, no same-day discount expirations.Call (314) 993-5570or schedule a free consultation online

Frequently asked questions

How do I choose the right replacement windows for my home?Work through six decisions in order: (1) material category — vinyl, fiberglass, clad wood, solid wood, or aluminum; (2) brand and specific product line within that category; (3) insert vs. full-frame installation; (4) glass package and energy ratings; (5) the dealer; (6) the installer. The first four are the product. The last two often matter more for long-term outcomes. Get itemized quotes from 2–3 established dealers and compare them on equivalent specifications, not just price totals.

What questions should I ask a window installer?Before signing, verify: who specifically is installing your windows; whether they’re manufacturer-trained or certified; how many years of experience the lead installer has; what separate workmanship warranty exists beyond the manufacturer’s product warranty; and whether they carry general liability and workers’ compensation insurance (ask for certificates). The full 20-question checklist is in the body of this guide.

What’s the most important thing to look for in replacement windows?It’s not a single feature — it’s the alignment between the product, the dealer, and the installer. A premium window installed poorly will fail faster than a budget window installed well. Most homeowners over-focus on brand and under-focus on installation accountability. The single biggest predictor of a successful 20–30 year outcome is choosing a dealer whose installation team you can identify before signing the contract.

How do I compare window quotes fairly?Make sure each quote specifies the same items: exact brand and product line; cladding type if applicable; AAMA finish standard; wood species and finish; glass package with NFRC ratings; installation type; permits; warranty terms; payment schedule; and timeline. Without these specifications, you’re comparing apples to oranges. Reputable dealers itemize because they have nothing to hide. If a quote arrives as a lump sum without breakdown, ask for itemization — the response will tell you something.

What’s the difference between insert and full-frame window replacement?Insert replacement leaves the existing window frame in place and installs the new window within it — faster, less expensive, less disruptive. Appropriate when the existing frame is structurally sound. Full-frame replacement removes the entire existing frame and installs a new complete window unit — more expensive and disruptive but appropriate when the existing frame is damaged, rotted, or settled out of square. A quality dealer evaluates your specific frames and recommends the approach that fits your project.

Should I avoid in-home consultation window companies?Not categorically — but understand what you’re signing up for. The in-home consultation model (Renewal by Andersen, Champion, and similar) is built around 2–3 hour presentations with same-day-discount pressure and pricing that’s typically 30–70% higher than equivalent retail work for the same products. Some homeowners value the bundled experience and single-source accountability. Many find that retail dealers offering the same products without the sales pressure deliver better value. Get a retail quote alongside any in-home quote so you can compare on equivalent terms.

What red flags should I watch for when choosing a window dealer?Same-day-only discounts; refusal to itemize quotes; pressure to sign on the spot; refusal to identify the actual installer; excessive disparagement of competitors; demands for large upfront payment (more than 50% deposit); no physical showroom or business address; reluctance to provide insurance certificates; verbal promises that aren’t put in writing; and review patterns showing consistent customer complaints. Any one of these is a yellow flag; multiple are a reason to walk away regardless of price.

How long should I take to choose replacement windows?Reasonable: 2–6 weeks from initial consultation to signed contract. That’s enough time to get 2–3 itemized quotes, visit showrooms, check references, review contracts, and compare warranty terms. Rushing the decision in days favors the dealer’s timeline, not yours. Dragging it out beyond a few months can cause manufacturer pricing or product availability to change. A 2–6 week window balances thoroughness with practical scheduling.

Does the brand of windows matter as much as the dealer and installer?Less than most shoppers assume. The major brands (Marvin, Pella, Andersen) all produce quality products at their flagship tiers. Within each brand, there’s substantial variation across product lines — the difference between premium and mid-tier within a brand often matters more than the difference between brands at equivalent tiers. The dealer’s installation quality and warranty service capability frequently matter more for the 20-30 year outcome than which brand name is on the window. Quality install + mid-tier product often outperforms premium product + poor install.

What should I expect at a Forshaw window consultation?A Forshaw consultation includes: evaluation of your existing windows (condition, age, performance issues); measurement of each opening; walk-through of Marvin product line options that fit your project; discussion of insert vs. full-frame approach based on your specific frame condition; and a written itemized quote with specific products, glass package, installation type, permits, warranty, and timeline. We don’t pressure same-day decisions and we don’t use time-limited discounts. You take the quote home, compare to others, and decide on your timeline. Free, no obligation.

Previous Next