How to Read Window Energy Ratings in Albuquerque
Four numbers decide whether a window works in New Mexico sun. Here is what each one measures and which zone thresholds apply here.
What do the numbers on a window label mean?
Every replacement window sold in Albuquerque carries a rating label with four numbers on it. Here is what each one measures, and which of them decide whether the window actually works in New Mexico sun.
The ratings come from the National Fenestration Rating Council, an independent body that tests and reports whole-window performance to one method, so a number from one manufacturer means the same thing as a number from another. That is the entire point of the label, and it is the only honest way to compare two bids that both say energy efficient on the cover page.
- U-factor is how fast heat moves through the whole window. Lower insulates better. This is the winter number.
- SHGC, the solar heat gain coefficient, is how much of the sun's heat gets through. Lower blocks more. This is the summer number.
- Visible transmittance is how much daylight gets through, on a scale where higher is brighter.
- Air leakage is how much air passes through the assembly. Lower is tighter.
Why is U-factor the winter number?
U-factor measures conducted heat: warmth leaving a heated room through the glass, the frame, the spacer and the sash on a cold night. Albuquerque sits at roughly 5,300 feet, and a clear night in January drops hard after sunset even when the afternoon was pleasant. A low U-factor is what keeps that drop from landing in the room.
One thing worth knowing: the rating covers the whole window, not the glass alone. A very good glass package inside a poorly insulating frame reports a mediocre whole-window U-factor, which is exactly the sort of thing a glass-only sales sheet can hide. If a bid gives you a centre-of-glass number, ask for the whole-window number.
Why does SHGC matter more here than in most of the country?
Because the sun is doing most of the work. SHGC is the fraction of solar heat that makes it through the window, so a rating of 0.30 means roughly thirty percent of the sun's heat lands inside. On a west-facing wall in June that difference is the whole argument. On a south-facing wall in December, some solar gain is a feature rather than a fault, which is why the correct SHGC is rarely the same on every elevation of the house.
Fading works the same way. If sun damage to floors and furniture is your concern, the label is where that conversation starts, and the Albuquerque sun, heat and fading guide covers what the coatings can and cannot do about it.
What ENERGY STAR climate zone is Albuquerque in?
North-Central. ENERGY STAR splits the country into four window climate zones and assigns them by ZIP code and county, and its own ZIP-code climate zone assignments put every Albuquerque ZIP in Bernalillo County into the North-Central zone. That matters, because southern New Mexico sits in the South-Central zone under different thresholds, and a product sheet written for the southern half of the state is not written for the Sandias.
What are the thresholds for this zone?
Under the Version 7.0 specification, a window in the North-Central zone has to reach a U-factor of 0.25 or lower together with an SHGC of 0.40 or lower to earn the ENERGY STAR label. Those are program thresholds rather than a building code minimum, and they give you a straight yes or no test to hold any product against.
Notice the shape of that pair. The U-factor requirement here is tighter than the South-Central zone's 0.28, and the SHGC allowance is looser than its 0.23. In plain terms, at this altitude the program cares more about holding heat in on a cold night and leaves room to keep some winter sun. That is a real design trade-off, not a marketing distinction, and it is why a window specified for a hot southern climate can leave an Albuquerque room cold in February.
Does a lower SHGC always help in Albuquerque?
No. Very low solar gain is the right answer on west and southwest glass that takes the afternoon in summer. On a south-facing living room it can cost you the free winter heat that made the room pleasant in the first place. The useful approach is to choose by elevation and by what each room is used for, rather than buying one specification for the whole house because it looked best on paper.
How much do the ratings change what a house costs to run?
Windows are a small part of a wall and a large part of the energy story. The ENERGY STAR windows factsheet puts it plainly: windows are about eight percent of the surface area of a home but account for almost half of the heat lost or gained. The same factsheet estimates an average saving of about thirteen percent a year on energy costs when poor performing windows are replaced with models that earn the ENERGY STAR label, a national average that moves with climate rather than a figure for your house.
The comfort change usually shows up before the bill does. A room with a west window that was unusable from four o'clock onward becomes usable. The cold draft along the floor under an old aluminum frame stops. Those are the outcomes people actually notice, and they track the label numbers closely.
What should you compare when bids come back?
- Whole-window U-factor and SHGC for each product, taken from the rating label rather than from a brochure adjective.
- Whether the numbers were chosen per opening or applied as one figure to the whole house. Different elevations often want different glass.
- Air leakage, which is where frame design and assembly quality show up.
- Whether the same window model appears in every bid, because two bids on two different products are not a comparison at all.
If the bids in front of you differ on installation method rather than on glass, the full-frame installation page explains what changes between an insert and a full-frame job, and repair or replace covers the case where the frame is fine and only the sealed glass unit has failed. Market ranges for the work itself live on the cost guide, and how to choose replacement windows covers the frame and style decisions that sit alongside the glass.
Where do these windows sit against those numbers?
The windows here are made for New Mexico, in New Mexico, with low emissivity windows and SHGC ratings treated as part of the specification rather than a footnote. The honest way to settle it is to look at the openings, see which way each one faces, and put the ratings against them. Call (505) 336-9753 for a free, in-home estimate, or start with window replacement in Albuquerque for how the work itself runs.
Last updated August 5, 2026.
Window energy ratings FAQ
What do the numbers on a window's NFRC label mean?
Four ratings carry most of the weight. U-factor is how fast heat moves through the whole window, SHGC is how much of the sun's heat gets through, visible transmittance is how much daylight comes through, and air leakage is how much air passes the assembly. Lower is better on all of those except visible transmittance.
What ENERGY STAR climate zone is Albuquerque in?
North-Central. ENERGY STAR assigns its four window climate zones by ZIP code and county, and its published assignment file places every Albuquerque ZIP in Bernalillo County in the North-Central zone, not the South-Central zone that covers southern New Mexico.
What U-factor does a window need to earn the ENERGY STAR label here?
Under the Version 7.0 specification, a North-Central zone window needs a U-factor of 0.25 or lower together with an SHGC of 0.40 or lower. Those thresholds come from the ENERGY STAR program itself, and they are stricter on insulation than the South-Central zone to the south.
Does a lower SHGC always help in Albuquerque?
No. A very low solar heat gain coefficient is the right call on west and southwest glass taking the summer afternoon. On south-facing rooms it also blocks the winter sun that used to warm them for free, so the best number often differs by which way the opening faces.
What is visible transmittance, and does it matter?
Visible transmittance is the share of daylight the window lets through, on a scale where higher is brighter. It matters when a coating chosen to block heat also dims a room more than the owner expected. Two windows with the same SHGC can differ noticeably on this one.
How does air leakage get measured on a window?
Air leakage is reported as the volume of air passing through the window per unit of area at a set pressure difference, and lower is tighter. It is the rating that most reflects frame design and assembly quality rather than the glass package alone.
What is the difference between glass ratings and whole-window ratings?
A centre-of-glass number describes the glazing only. The rating label describes the whole assembly, including frame, spacer and sash, which is what you actually live with. Strong glass in a weak frame reports a mediocre whole-window figure, so ask which one a bid is quoting.
What does a low emissivity coating change on the label?
Low emissivity coatings are a nearly invisible metallic layer that reflects infrared heat back where it came from. On the label they pull U-factor and SHGC down together, which is why an uncoated insulated unit and a coated one can look similar and perform nothing alike.
What should you compare when bids come back?
Set whole-window U-factor and SHGC side by side per product, check whether ratings were chosen per elevation or applied to the whole house, look at air leakage, and confirm every bid is priced on the same window model. Two bids on two different products are not a comparison.
How much can better windows change an energy bill?
The ENERGY STAR windows factsheet estimates an average of about thirteen percent a year in energy cost savings when poor performing windows are replaced with models earning the label. That is a national average and shifts with climate, so treat it as a direction rather than a number for your house.
Want the right ratings for your openings?
A free, in-home estimate walks every window and matches the glass to the sun it takes.
(505) 336-9753