Window U-Factor and SHGC Explained — The Numbers on Your Quote
Two quotes, two brochures, and a sticker on a sample window full of decimals.
Reply within one business day. Or call / text 763-204-2099.
Window U-factor and SHGC, explained: U-factor is how fast heat leaves through the whole window, and lower is warmer. SHGC is how much sun heat comes in, and in Minnesota a moderate or higher number helps in winter. JMB Builders writes both numbers for each opening on the quote and checks them against the NFRC label on install day. Priced per opening; photos get a reply within one business day, or book a free in-home estimate.
- U-factor: heat out, lower is warmer
- SHGC: sun heat in, wall by wall
- Numbers listed per opening on the quote
Every certified window ships with an NFRC label on the glass. It rates the whole unit, frame and spacer included, for that exact size class, style and glass package. Two of its numbers do most of the work in Minnesota. U-factor is the rate of heat loss; lower is better, and it is what you feel standing next to the glass in January. SHGC, the solar heat gain coefficient, is the share of the sun's heat that gets through, on a scale from 0 to 1.
As of our October 2026 check, ENERGY STAR Version 7.0 sets the Northern zone, which covers Minnesota, at a window U-factor of 0.22 or lower, with an SHGC of at least 0.17. It also allows a slightly higher U-factor when the SHGC is higher, on the reasoning that winter sun is free heat. Those numbers come from ENERGY STAR and window-maker summaries; confirm the current table on energystar.gov before an order depends on it.
The label is only useful if it matches what goes in the wall. The same model can carry different numbers with different glass, and a casement and a double-hung in the same line rate differently. So the quote names the glass package per opening, and on install day we check the label on each unit against the order before the old window comes out. Then the label is yours to keep.
Get a written quote for this job
Three photos and a sentence is enough: a reply within one business day, or ask for a free in-home estimate. Or text the photos to 763-204-2099.
What you supply
- Any quotes or brochures you are comparing, so we read the same numbers
- Which walls get strong afternoon sun and which stay shaded
- Any utility rebate form you plan to file, so the order matches what it asks for
- Photos of each window inside and outside
What JMB supplies
- One in-person measure of every opening before ordering
- A line-item quote with style, glass package, U-factor and SHGC per opening
- Different glass on a hot west wall when it makes sense, in the same frame and color
- Windows ordered through ABC Supply on one order
- Label checked against the order on each unit before install
- Sill pan, low-expansion foam and sealed joints, so the wall performs close to the label
- NFRC labels saved and photos of the finished windows in your job folder
How it is priced: per opening
Quoted in writing from your photos, with a reply within one business day. What moves the number:
- Glass package: dual pane, dual pane with a room-side coating, or triple pane
- Mixed glass by wall vs. one package for the whole house
- Frame material and line
- Insert vs. full-frame replacement
- Window size and style
- Rot repair at sills or framing, quoted first
If you are comparing quotes, send them along with your photos. We list U-factor and SHGC per opening so the comparison is number to number.
How long it takes
The numbers are settled at the measure and on the quote. Install runs a few windows a day; lead time depends on the brand and is written on the quote.
How your project works
- 1
Send photos, get a written quote
Send three photos of the space and a sentence about what you want. You get a clear, itemized reply within one business day. Prefer a look in person? A free in-home estimate is always an option.
- 2
Pick materials, or bring your own
We help you choose profiles and materials that fit the house and the budget, or match your existing millwork exactly — or you buy the door or trim yourself and we install it. Everything is confirmed before the crew is scheduled.
- 3
Clean, precise installation
The crew shows up on time, protects floors and furniture, and installs with tight joints and consistent reveals. Photos of the finished work go in your job folder.
- 4
Walkthrough and invoice
We walk the finished work with you. If anything is not right, we fix it before we call the job done. Then one invoice, paid by check or direct deposit — no card fees, no payment links.
Situations and options
One package, whole house
Every opening gets the same glass and the same label numbers. Simplest to order and compare, and the right call when no wall has a sun or cold problem.
Lower SHGC on the hot west wall
A sun-control coating on the west or large south glass that overheats in summer, with the standard package elsewhere. Same frame and color, so it looks the same from outside.
Lowest U-factor on the cold sides
Triple pane or the best dual-pane coating on north walls and bedrooms where frost forms, standard glass elsewhere. The upgrade goes where the glass surface is coldest.
Window U-Factor and SHGC Explained — The Numbers on Your Quote: questions, answered
What does U-factor mean on a window?
U-factor is how fast heat passes through the whole window, frame and spacer included. Lower is better: a lower number means less heat lost and warmer glass on the room side in winter. In a heating climate like Minnesota, it is the number that matters most on the label.
What U-factor do I need in Minnesota?
As of our October 2026 check, ENERGY STAR Version 7.0 sets the Northern zone at a U-factor of 0.22 or lower for windows, with a trade-off that allows slightly higher when the SHGC is higher. The code minimum is looser than that. Confirm the current numbers on energystar.gov, and ask your utility what any rebate requires.
Is a high or low SHGC better in Minnesota?
For most walls, moderate or higher is fine, because winter sun through the glass is free heat. ENERGY STAR's Northern zone even sets a minimum SHGC rather than a maximum. A west wall that overheats in summer is the exception, where a lower SHGC coating on just those openings makes sense.
How do I read the NFRC label on a new window?
Find the U-factor and the solar heat gain coefficient first; those two drive comfort and heating. Visible transmittance tells you how much daylight gets through, and air leakage and condensation resistance appear when the maker rates them. The label applies to that product and glass package, so check that it matches the window on your quote.
Why do two windows from the same brand have different U-factors?
The label rates the whole unit, so the style, frame and glass package all change the number. A casement and a double-hung in the same line rate differently, and the same window with a different coating or triple pane carries a different label. That is why the quote should list the glass package for each opening.
Does installation change a window's U-factor?
The label number belongs to the unit and does not change. But the gap between the frame and the wall is not rated, and that is where air leaks. A sill pan, low-expansion foam and sealed interior and exterior joints keep the installed window close to what the label promises.
Recent JMB work, from our job log
59 installs recorded across 30 Twin Cities communities since Dec 2025. Window and door installs for homeowners and the builders we work with. Counts come straight from our job log; no customer names.
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Read morePage reviewed October 9, 2026 · JMB Builders LLC, MN license BC809005 · All windows pages
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