Before we quote new windows, storefront or curtain wall for a building that needs a better energy grade or a Local Law 97 plan, we walk it and record what is actually there. Here is what we check, how, and what the owner and the energy consultant get from it.
In short: An envelope survey is the first step before any window, storefront or curtain wall upgrade meant to improve a commercial building's energy performance. We walk the building floor by floor and record, for every opening type, what the glass actually is (single, double, low-E or not, gas-filled or not, seal condition), what the frame is and whether it has a thermal break, how the unit operates and seals, and how the perimeter is sealed to the wall. The result is a window schedule with a condition and a measure for each type, which is what an energy consultant needs for the Local Law 87 audit and the Local Law 97 plan, and what we need to price the three routes: glass only, full unit or facade overhaul.
Most requests we get for an energy upgrade start with a grade letter on the door or a Local Law 97 projection from a consultant, and a question: "what will new windows do for us?" Nobody can answer that from the street. Two buildings of the same age on the same block can have single glass in one and a 1990s double-glazed retrofit in the other, and the right route for each is different. So we do not quote first. We survey, and the quote follows from the survey.
The survey also protects the owner from the most common mistake in this work: replacing windows that were not the problem. A building with tight double-glazed windows and a leaking roof, an uninsulated spandrel or a boiler running at 60% efficiency will not move its grade with new glass. We say so when we find it, and the property energy performance page sets out what we will and will not claim.
| Item | How we check it on site | Why it matters |
|---|---|---|
| Glass make-up | Low-E detector and glass thickness gauge through the lite; count of reflections with a flashlight for the number of panes and the coating surface | Single glass loses about three times the heat of a modern low-E insulated unit; whether a low-E coating exists, and on which surface, decides whether glass-only replacement is worth doing |
| Insulated unit condition | Look for fogging, dirt or a tide line between the panes; check the spacer type and the edge seal; date or manufacturer stamp on the spacer | A failed seal means the argon is gone and the unit has lost part of its insulating value, even if the glass looks fine from a distance |
| Frame material and thermal break | Magnet, visual at the sash edge, a feel for cold on the interior face in winter; the profile section where a unit can be opened | An aluminum frame with no thermal break conducts heat straight through; frame can be a quarter of the opening area |
| Operation and weatherstrip | Open and close a sample of each type; check locks, balances, weatherstrip condition, visible gaps at meeting rails | Air leakage through a worn window can cost as much as the glass; it is also what tenants complain about |
| Perimeter seal and flashing | Exterior sealant condition, interior staining, probe at the sill | A unit that leaks at the perimeter is a water problem before it is an energy problem, and it changes the scope |
| Size, count and exposure | Measure each type, count per elevation, note orientation and shading | Gives the glazed area per elevation, which drives both the energy numbers and the price |
We photograph every type from inside and out, and at least one unit per type is opened and measured in detail. On a building with mixed replacements over the decades there can be eight or ten types; each gets its own line in the schedule.
We do not run the building energy model or the Local Law 87 audit ourselves; that is the consultant's work and their license is on it. Our schedule is the input they need for the envelope part, and it saves them a site day they would otherwise bill.
A few patterns repeat across the buildings we have walked in Brooklyn, Manhattan and on Long Island:
Send us the address, the number of floors, roughly how many windows and storefront bays there are, and your energy grade letter or Local Law 97 projection if you have one. For a building of up to about 150 openings the survey is a one-day site visit with two people and the schedule follows within the week. Larger buildings are surveyed by elevation over several days. For how we take the measurements themselves, see how we measure a window opening; for the routes the survey leads to, glass-only vs full replacement.
A site inspection that records, for every window, door, storefront and curtain wall type in a building, what the glass and frame are, what condition they are in and how they seal to the wall, so that energy measures can be chosen and priced for each type.
A low-E detector shows whether a coating is present and on which surface; a flashlight shows the number of panes by the reflections; a glass gauge reads thickness; and the spacer between the panes usually carries a manufacturer stamp.
A building of up to about 150 openings is a one-day visit with two people; the window schedule follows within the week. Larger buildings are done elevation by elevation.
No. Those are prepared by a registered energy auditor or engineer. Our schedule is the envelope input for that work.
No. The survey produces a schedule and a recommended measure per type; often that includes leaving some types as they are.
Either. For co-ops and condos it is usually the board through the managing agent; for commercial buildings the owner or the asset manager. We need access to a sample of units of each type.
Property energy performance Local Law 97 and your windows NYC building energy laws Glass-only vs full replacement Commercial property services
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 November 2026. Credentials
Send the address, floor count and your energy grade or LL97 projection. We will schedule the survey and deliver the window and storefront schedule your consultant needs.
