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Energy-efficient windows for Des Moines winters

Des Moines averages about 6,178 heating degree days a year and 10.4 nights below 0 degrees (NOAA 1991 to 2020 normals). That is a long heating season, and it is why the number to read on a window sticker is the U-factor.

Updated October 29, 2026 ยท Sources listed at the end

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Frost crystals covering a window pane
Frost forms where warm, humid indoor air meets glass colder than its dew point. Photo: Osman Rana / Unsplash
On this page
  1. Read the NFRC label
  2. The ENERGY STAR numbers for Iowa
  3. Double or triple pane?
  4. Tax credits
  5. Installation matters too

Read the NFRC label

  • ENERGY STAR qualification for windows is based on U-factor and solar heat gain coefficient (SHGC) ratings only, and the NFRC label on every certified window lists both.
  • U-factor measures the rate of heat transfer and tells you how well the window insulates. Lower is better.
  • SHGC measures the fraction of solar energy the window lets through. In a heating climate, a moderate SHGC on south-facing windows lets in some free winter sun.

The ENERGY STAR numbers for Iowa

Under ENERGY STAR Version 7.0, which took effect in October 2023, windows in the Northern climate zone, which includes Iowa, need a U-factor of 0.22 or lower and an SHGC of at least 0.17, with equivalent performance options allowed. Compare the U-factor of the whole window on the NFRC label, not a glass-only number in a brochure.

Average low and high by month, Des Moines (degrees F)

January: average low 13.8 F, average high 30.9 F1431JanFebruary: average low 18 F, average high 35.7 F1836FebMarch: average low 29.6 F, average high 49.2 F3049MarApril: average low 40.6 F, average high 62 F4162AprMay: average low 52.3 F, average high 72.4 F5272MayJune: average low 62.4 F, average high 81.9 F6282JunJuly: average low 66.4 F, average high 85.6 F6686JulAugust: average low 64.2 F, average high 83.6 F6484AugSeptember: average low 55.4 F, average high 76.9 F5577SepOctober: average low 42.9 F, average high 63.4 F4363OctNovember: average low 30.2 F, average high 48.3 F3048NovDecember: average low 19.5 F, average high 35.9 F2036Dec32 F
Each bar runs from the normal low (number below) to the normal high (number above). Darker blue months have lows under 20 F. Source: NOAA NCEI U.S. Climate Normals 1991 to 2020, Des Moines International Airport (USW00014933).

Double or triple pane?

Triple-pane windows insulate better and cost more: $1,000 to $4,000 per window against $450 to $2,000 for double pane (Fixr). They make the most sense on north and west walls and on big picture windows. A good double-pane window with low-e glass and gas fill can still meet the ENERGY STAR Northern criteria.

Tax credits

The federal Energy Efficient Home Improvement Credit (30% of the cost of qualifying windows, up to $600 a year) applied to improvements made through December 31, 2025. Windows installed in 2026 do not qualify. If you see a 2026 ad promising a federal window credit, ask which law it relies on.

Installation matters too

A well-rated window loses its advantage if the gap around the frame is not insulated and sealed. What a careful install looks like.

Questions Des Moines homeowners ask

What is a good U-factor for windows in Iowa?

ENERGY STAR Version 7.0 sets 0.22 or lower for the Northern zone, which includes Iowa, with some equivalent options. Lower is better.

Do new windows pay for themselves?

Rarely on energy savings alone. Homeowners usually replace windows for comfort and looks, or because of drafts and rot. Energy savings come along the way.

Keep reading

Serving West Des Moines, Ankeny, Urbandale, Johnston, Waukee, Clive, Altoona, Grimes, Pleasant Hill, Norwalk and all of Des Moines.

Sources

  1. ENERGY STAR: Independently Tested and Certified Energy Performance (NFRC label)
  2. ENERGY STAR: Key product criteria for residential windows
  3. Door and Window Market: Who Needs ENERGY STAR? (Nov/Dec 2023, Version 7.0 criteria)
  4. IRS: Energy Efficient Home Improvement Credit (last reviewed April 28, 2026)
  5. ENERGY STAR: Federal tax credits for windows and skylights
  6. Fixr: Window Replacement Cost (updated January 21, 2026)
  7. NOAA NCEI: U.S. Climate Normals 1991 to 2020, Des Moines International Airport (USW00014933)