Knowledge.
What makes a window high performance — the testing, the codes and the glass, explained by the people who write the submittals.
R, LC, CW, AW. What a window's class really tells you.
The letters on a test report decide which buildings a window belongs in. Here is how to read them.
Vistaza Engineering · Sep 18, 2026 · 6 min read
STC and OITC are not the same number.
Which one matters next to a rail line, and why the glass decides both.
Vistaza Engineering · Jul 8, 2020 · Updated Sep 18, 2026 · 3 min read
What uPVC is, and how a frame is built.
The material, the parts inside a frame, and what it is good and not good at.
Vistaza Engineering · Dec 29, 2022 · Updated Sep 4, 2026 · 5 min read
uPVC or aluminum. Where each one belongs.
A fair comparison of the two frame materials, and a way to choose opening by opening.
Vistaza Engineering · Nov 12, 2023 · Updated Sep 11, 2026 · 5 min read
Who decides the windows, and how to make sure someone does.
Five parties, five interests, and a way to keep the window decision from being made by accident.
Vistaza Engineering · Mar 1, 2024 · Updated Sep 17, 2026 · 5 min read
Writing the window spec for a mid-rise building.
What the specification and the window schedule must state, and the evidence to ask for with each item.
Vistaza Engineering · Nov 10, 2023 · Updated Sep 18, 2026 · 6 min read
Condensation on windows: the window's part and the building's.
Why water forms on glass, what a better window changes, and what only ventilation can fix.
Vistaza Engineering · Dec 7, 2023 · Updated Sep 17, 2026 · 5 min read
Five window types, and how each one seals.
How fixed, casement, hopper, hung and sliding windows open, seal and clean, and what that does to their ratings.
Vistaza Engineering · Feb 23, 2023 · Updated Sep 17, 2026 · 5 min read
uPVC or wood. A fair comparison.
What each frame does well, what each one asks of the owner, and how to decide on a multi-unit building.
Vistaza Engineering · Nov 13, 2023 · Updated Sep 4, 2026 · 5 min read
Windows with a PTAC below.
What to coordinate when a through-wall unit and its louver share the opening with the window.
Vistaza Engineering · Nov 25, 2023 · Updated Sep 20, 2026 · 5 min read
Nine mistakes developers make when buying windows.
Where window packages go wrong at bid stage, and the questions to put to any supplier, including us.
Vistaza Engineering · Apr 20, 2023 · Updated Sep 1, 2026 · 6 min read
Nailing fins.
What a fin does, where it belongs, and what the installer has to get right.
Vistaza Engineering · Feb 9, 2023 · Updated Sep 20, 2026 · 3 min read
LEED, net zero and the part windows play.
What these programs and goals are, where windows count toward them, and what to ask a window supplier for.
Vistaza Engineering · Nov 23, 2023 · Updated Sep 17, 2026 · 5 min read
The hardware that makes a window work.
Handles, hinges, locking points, keepers and limiters: what each part does, and what to ask for by name.
Vistaza Engineering · May 18, 2023 · Updated Sep 8, 2026 · 5 min read
Exterior trims.
The profile that finishes the joint between the frame and the facade.
Vistaza Engineering · Feb 9, 2023 · Updated Sep 20, 2026 · 4 min read
The five guides.
Long, complete and kept up to date. If you only read one thing before you specify, read the one that matches your problem.
How a window earns its class and grade, what each test proves, and what to ask for before a rating goes into a specification.
9 min read ›What the numbers on an NFRC label mean, which parts of the glass move them, and how they meet the energy code.
9 min read ›
Two ratings describe how much noise a window stops. Here is which one to specify, and what in the glass earns it.
8 min read ›
The ways glass is made visible to birds, how each one looks from the room, and how a threat factor is earned.
9 min read ›Profile, steel, glass, hardware and the bench where they meet — and what each step means once the window is in the wall.
10 min read ›Swipe for more ›
All articles.
What a low sill does to the water rating, and how to specify around it.
What building staff should clean, clear, oil and adjust, and how a glass unit is replaced from inside.
Where to find the NFRC certificate number, and what it means when there isn't one.
Why it is a laminated foil and not paint, what makes color fade, and what to ask for before you specify.
Why water forms on glass, what a better window changes, and what only ventilation can fix.
Two programs architects ask about on every energy-focused job, what each one asks of a window, and which numbers actually govern on a mid-rise building.
The profile that finishes the joint between the frame and the facade.
Air, water and structure on your own configuration, before the order is built.
What the material is under the code, the test we ran, and how a uPVC window gets approved on a non-combustible building.
What each looks like from the room, and how each is rated.
What these programs and goals are, where windows count toward them, and what to ask a window supplier for.
What a fin does, where it belongs, and what the installer has to get right.
What the test measures, why it matters for accessible rooms, and what makes a sash heavy or light in the hand.
What to coordinate when a through-wall unit and its louver share the opening with the window.
What each glass does when it breaks, and where the building code asks for it.
Plain slider, lift-and-slide, tilt-and-slide and the pull-shut slider: how each one moves, seals and meets the floor.
Which one matters next to a rail line, and why the glass decides both.
Fresh air with the window shut: where they go and what they do to the ratings.
What uPVC is made from, how long it lasts, what happens to it afterwards, and the fair criticisms of PVC.
A fair comparison of the two frame materials, and a way to choose opening by opening.
What is really different between a vinyl window and a High Performance uPVC window, and how to tell from the paperwork.
What each frame does well, what each one asks of the owner, and how to decide on a multi-unit building.
What to look at when a corner sample lands on your desk, and what to ask for on paper.
Vistaza supplies and does not install. Here is what arrives on the truck, what the installer owns, and what a general contractor should check.
The six parts of a window that decide its energy numbers, and what to ask about each one.
The material, the parts inside a frame, and what it is good and not good at.
Five parties, five interests, and a way to keep the window decision from being made by accident.
Where window packages go wrong at bid stage, and the questions to put to any supplier, including us.
Handles, hinges, locking points, keepers and limiters: what each part does, and what to ask for by name.
Where opening limiters are required, and how they are built into the sash.
The letters on a test report decide which buildings a window belongs in. Here is how to read them.
How fixed, casement, hopper, hung and sliding windows open, seal and clean, and what that does to their ratings.
How to receive, store, move and protect windows so that none are replaced before anyone moves in.
What the specification and the window schedule must state, and the evidence to ask for with each item.
Two ways to meet the wall, and which wall types each one suits.
The people who write the submittals.
Written by Vistaza Engineering: the people who write the submittals, check the shop drawings and read the test reports. Every article carries a date, and a note when it is updated.
When a code changes, we write it up.
One short email when a code or a standard changes and it touches the windows. Nothing else, and you can stop it with one reply.