Three Reynaers window systems, three jobs: the all-round MasterLine 8, the steel-look SlimLine 38 and the proven, security-rated CS 77 — depths, sightlines, U-values, variants, price position and where each belongs, plus the rest of the Reynaers window range.
Short version. MasterLine 8 is the all-round Reynaers window: the widest choice of looks, three insulation levels, big sashes, and the one we fabricate most. SlimLine 38 is the steel-look window: the slimmest sightlines Reynaers makes, for loft, industrial and landmark-replacement work, at a premium. CS 77 is the earlier workhorse: proven, robust, the security and fire-rated specialist, still a good value where the look is plain. Below is what the numbers say and where each one belongs.
Reynaers names its windows by family and depth. MasterLine is the current generation (MasterLine 8 at roughly 77–87 mm deep, MasterLine 10 at about 100 mm), designed for fast fabrication and a modular choice of insulation. SlimLine is the slender family: SlimLine 38 is the steel-look window named for its slim sightlines, SlimLine 68 the slim contemporary outward-opener. ConceptSystem (CS) is the older platform — CS 77, CS 68, CS 86-HI — still sold because it is proven, and because CS 77 carries certifications (bullet and fire resistance, RC3) that the newer lines do not.
All three are thermally broken aluminium: two aluminium shells joined by glass-fibre-reinforced polyamide bars so the outside cold does not reach the inside face. All three take double or triple glazing and open inward as tilt-and-turn, turn-only or bottom-hung, with outward-opening variants. The differences are in sightline, depth, insulation level and what each was designed to look like.
| MasterLine 8 | SlimLine 38 | CS 77 | |
|---|---|---|---|
| Designed as | The all-round current window; fast to fabricate, modular insulation | Steel-look window with the slimmest sightlines; a Crittall-style replacement | Proven multi-purpose system; security, fire and bullet-resistant variants |
| Frame depth | 77 mm (Functional, Block) / 87 mm (Renaissance, Deco); vent 87 mm | 76 mm (Cubic, Ferro) / 99 mm (Classic); vent 72–86 mm | Frame 68 mm, vent 77 mm |
| Sightline, frame + vent (inward) | About 119 mm on the standard section | The slimmest of the three — the steel-window look | About 89 mm minimum; 102–115 mm typical section |
| Insulation levels | Standard, HI, HI+ | Standard and HI; HI+ (deeper) for passive levels | Standard, HI, HI+ |
| Frame U-value, Uf (W/m²K) | 1.9 standard / 1.5 HI / 1.2 HI+ | About 1.9 (HI+ deeper variant lower) | 2.2 standard; 1.7 on a typical HI section; HI+ down to about 1.2 |
| Whole-window Uw, best case | Down to about 0.85 with triple glazing | Below 1.15 standard; HI+ down to about 0.74 | About 1.4 with 36 mm double glazing on the standard level; lower with HI/HI+ and triple |
| Max vent size (guide) | Large sashes without couplers; reinforced profiles for multi-pane frames | Up to about 3 m tall vents in the HI+ version | About 2.8 m tall, 170 kg per vent |
| Design variants | Functional, Block, Deco, Renaissance, Hidden Vent, SoftTone | Classic (inclined), Cubic (square), Ferro (steel profile look), Functional; new crank-out casement for North America | Functional, Renaissance, Softline, Hidden Vent |
| Security / special | RC2 and RC3 options | RC2 + PAS24 certified (HI+) | RC2 and RC3; fire-resistant (EW) and bullet-resistant variants |
| Acoustics (with the right glass) | Up to mid-40s dB Rw | Up to about 45 dB Rw | Up to about 42 dB Rw |
| Price position | The reference point | Highest of the three — slim profiles cost more to make and to glaze | A little below MasterLine 8 on plain configurations |
| Where we use it | Houses, townhouses and small buildings that want slim black tilt-and-turns and big glass | Lofts, industrial conversions, landmark facades that had steel windows, steel-look new builds | Plain commercial and institutional work; where RC3, fire or bullet resistance is specified |
Figures are Reynaers’ published European values (EN standards, 1.23 × 1.48 m reference window) and depend on configuration and glazing; a US NFRC U-factor in BTU/h·ft²·°F is roughly the metric Uw multiplied by 0.176, so a Uw of 1.1 is about 0.19. Ask us for the values for your configuration.
MasterLine 8 is the window Reynaers designed to replace CS 77 as the everyday system, and it shows in two ways. The first is fabrication: a single platform of profiles, gaskets and hardware serves every design variant, so it is faster and cleaner to make, which is why it is the Reynaers window we fabricate most. The second is the modular insulation: the same frame is built to a Standard, HI or HI+ level by changing the thermal-break bars, so a project can buy the insulation it needs rather than the system it can afford. The Functional variant is the flat, modern one; Deco and Renaissance mimic wood joinery for a traditional facade; Hidden Vent makes the opening sashes read as fixed from outside so a facade is a grid of identical glass. The Ocean Parkway house is MasterLine 8 in black, including the custom arched units.
SlimLine 38 exists to do one thing: give the sightlines of a hot-rolled steel window with the insulation of a thermally broken aluminium one. The Classic variant has the inclined face of a traditional steel section; Cubic is squared; Ferro copies the projecting bar of an original steel profile so that a replacement in a landmarked loft or a 1920s factory conversion is close to the original from the street. It is the answer where the Landmarks Preservation Commission wants steel sightlines but the owner wants a warm frame, and where a new build wants the industrial look without the condensation that real steel brings. The costs are the price of the slimness: less metal means more careful fabrication and glazing, and the deeper HI+ version is what gets it to passive levels. For North America Reynaers has added an outward-opening crank casement variant that takes an interior insect screen — the arrangement American buyers expect. Where the original was steel and steel is what the approval demands, the alternative is a thermally broken steel window such as Optimum.
ConceptSystem 77 predates MasterLine and is still in the catalogue because it has done everything a window can be asked to do: RC2 and RC3 burglar resistance, EW fire-rated variants, bullet-resistant variants, a Minergie component label, and a long record in schools, offices and public buildings. Its sightlines are a little heavier than MasterLine 8 and its standard-level insulation a little lower, but with HI+ bars it reaches the same territory. It couples with CS 77 doors and CP 130 sliding systems. We specify it where the schedule asks for a security or fire rating MasterLine does not carry, and on plain commercial work where the slight cost advantage matters and nobody will be looking at the profile.
| System | What it is | When it comes up |
|---|---|---|
| MasterLine 10 | The deep version of MasterLine (about 100 mm), Passive House certified, Uf down to about 0.9 and Uw to about 0.78 with triple glazing; vents to 2.8 m and 200 kg; same hardware family as MasterLine 8 | Passive-house and low-energy projects; very large sashes; the Local Law 97 buildings that need the envelope to do the work |
| SlimLine 68 | A slim contemporary system, principally outward opening, with very narrow sightlines and a flat modern face | Modern houses that want a slim outward-opening casement rather than a tilt-and-turn |
| CS 68 | The three-chamber ConceptSystem below CS 77 (frame 59 mm, vent 68 mm); RC2/RC3 and EW 30 fire-rated variants | Budget-conscious commercial work where CS 77 is more than needed |
| CS 86-HI | The high-insulation ConceptSystem; the passive-level window before MasterLine 10 existed | Legacy specifications; superseded by MasterLine 10 for new work |
| ES 50 | Reynaers’ entry-level thermally broken window | Where a European aluminium look is wanted at the lowest Reynaers price; we usually steer to Cortizo or Alutech instead |
| MasterLine 8 SoftTone | MasterLine 8 with a softened, rounded profile face | Renovations where a hard modern edge would look wrong |
Most residential work in Brooklyn, Queens and the suburbs lands on MasterLine 8: it gives the slim black tilt-and-turn that the market wants, in any of the four looks, at the insulation level the drawings call for. SlimLine 38 is the choice where the building had steel windows or wants to look as if it did — lofts, converted factories, the industrial-style new builds in Bushwick and Greenpoint, and landmark facades where the LPC has steel sightlines in mind. CS 77 is specified rather than chosen: when the schedule says RC3, EW30 or bullet resistance, it is the Reynaers window that has the certificate. MasterLine 10 comes in when the energy model needs a passive-level frame. And where the budget does not reach any of them, Cortizo and Alutech give a similar slim European window a step down in price; our Alutech vs Cortizo comparison covers that pair.
MasterLine 8 is the current-generation everyday window: one fabrication platform, slimmer sightlines, three insulation levels (Uf 1.9 / 1.5 / 1.2). CS 77 is the earlier platform, slightly heavier and a little less insulating at the standard level, but with security, fire-rated and bullet-resistant variants MasterLine does not offer.
No. It is a thermally broken aluminium window designed to reproduce the sightlines and, in the Ferro variant, the profile of a steel window, with far better insulation and no condensation. It is used to replace or imitate Crittall-style steel windows.
MasterLine 10 (Passive House certified, Uf to about 0.9). Among the three compared here, MasterLine 8 HI+ and SlimLine 38 HI+ reach the lowest whole-window values, around 0.74–0.85 W/m²K with triple glazing.
SlimLine 38, by design. MasterLine 8 and CS 77 are conventional widths, MasterLine 8 the slimmer of the two.
ES 50 is the entry level; among the three compared, CS 77 in a plain configuration is usually a little below MasterLine 8, and SlimLine 38 is the most expensive. All Reynaers systems sit above Cortizo and Alutech.
Yes. MasterLine profiles are roll-bent to the radius; the Ocean Parkway house has custom MasterLine 8 arches. See our arched windows page.
From a fabricator-installer; Reynaers sells systems to fabricators, not finished windows. Alex GC fabricates and installs MasterLine, SlimLine and CS 77 across NYC, Long Island and New Jersey.
Reynaers Aluminium Systems Alutech vs Cortizo Aluminum vs uPVC vs Wood Tilt-and-Turn Windows Optimum Steel Windows Arched Windows Ocean Parkway House — MasterLine 8 All Comparisons
About this page. Written by Alex GC Inc. d/b/a Alex Glass Construction and reviewed before publication by Aleksandr Chernovolenko, Managing Partner, with our design and estimating lead and a field foreman. Our foremen hold the NYC DOB Site Safety Training supervisor card and our crews the 40-hour worker card; we are certified to fabricate, install and service Alutech and Everest aluminum systems. Facts are drawn from our own projects, manufacturer test data and the applicable codes; where we are giving an opinion, we say so. Last reviewed September 2026. Credentials
Send drawings or photographs and tell us the look and the energy target. We will recommend the system and insulation level, and quote it fabricated and installed.
