Choosing the Best Windows for Hot or Cold Climates

If you live in a cold, snowy area you’d like to keep your home cozier. If you live in a hot climate, you want to keep your home cooler. Your windows can help make your home more comfortable. Here’s how to pick the best windows for your climate.

Best Windows for Your Climate

Knowing the glass glazing options and ratings to follow can help you make an informed decision on windows. Plus, Marvin Replacement’s Ultrex® fiberglass has better insulation than aluminum. That means it can help keep heat and cold out of the home.

Marvin Replacement’s Ultrex fiberglass windows, when paired with the ideal glass coating for your climate, may improve your home’s energy efficiency.* A Marvin Replacement design consultant can review your specific climate needs to find the right window and glass option for your home.

How Windows Get Rated for Performance in Different Climates

Windows get measured by performance window labels from the National Fenestration Rating Council. A window label includes: U-factor, SHGC, Visible Transmittance, and optional Air Leakage ratings. All which can help you find the best windows for your climate.

Window U-factor

U-factor measures how well a window keeps heat in your home and range from 0.10-2.00. A higher number allows more heat to escape.

Window Solar Heat Gain Coefficient (SHGC)

The SHGC measures how much heat from the sun enters a room. In a warmer climate, you’ll want a window with a lower SHGC number. Lower SHGC numbers reduce cooling costs. Higher SHGC numbers can reduce heating costs. SHGC numbers range from 0.00-1.00.

Window Visible Transmittance

Visible transmittance (VT) measures how much natural light enters your home. VT can help homeowners change their indoor lighting use by relying more on natural light. VT numbers range from 0.00-1.00.

Window Air Leakage

Air leakage ratings measure how much air will enter a room through a window. Air leakage rates of ≤ 0.3 mean fewer drafts.

Best Windows for Northern Zone Climates

Specific types of windows suit Northern zone climates, like the Pacific Northwest better than others because of the cool, damp climate. Ultrex resists warping and weathering in any climate. That's important if you live in a rainy climate like Seattle or Portland, Oregon. Other cities in the Northern zone, like Chicago and Detroit, has extremely cold, snowy winters. This means harnessing the sun to keep your home warm by keeping more of its heat inside. The cold and wet Northeast falls into the Northern climate zone in the ENERGY STAR® Climate Zone Map. The zone includes cities like Boston and New York state. It’s best to check with local building officials to learn if your location must follow specific state codes. You can also use the climate zone finder to get the best information about your climate zone.

U-factor and SHGC recommendations

The Northern region of the ENERGY STAR® Climate Zone Map suggests windows with:

• A U-factor equal to or less than 0.22 and SHGC equal or greater than 0.17 or

• A U-factor equal to 0.23 and SHGC of 0.35 or more or

• A U-factor of 0.24 and SHGC of 0.35 or more or

• A U-factor of 0.25 and SHGC of 0.40 or more or

• A U-factor of 0.26 and SHGC of 0.40 or more 

Windows with U-factors of 0.30 and less will keep more heat in. Windows with a higher SHGC number can help reduce heating costs, according to the Department of Energy.

Best Windows for North-Central Climate Zone

The North-Central climate zone includes portions of New Jersey and Philadelphia.

U-factor and SHGC recommendations

ENERGY STAR certification criteria for the North-Central climate zone suggests windows with:

• A U-factor equal or less than 0.25 and SHGC of 0.40 or less

Best Windows for South-Central Climate Zone

Places like Charlotte, North Carolina and Raleigh, North Carolina land in the South-Central climate zone where the ENERGY STAR certification criteria is:

• A U-factor of equal or less than 0.28 and SHGC of 0.23 or less

Best Windows for Southern Climate Zone

The Southern climate region includes Austin and Dallas. It faces higher temperatures and more direct sunlight. The low expansion rate of Ultrex fiberglass, paired with our energy efficient glass options makes it great for Southern homeowners. Plus, Ultrex fiberglass will not melt or lose its shape, even when exposed to temperatures of up to 285° F. Vinyl can start to soften and melt at 163° F.

U-factor and SHGC recommendations

• U-factors of 0.32 or less

• SHGC numbers of 0.23 or less

Window Glass Coatings

Thin coatings of special low emissivity (Low E) metallic material get applied to glass panes to boost energy efficiency and block out UV rays. Low E has a number following the “E” to shows the number of coatings.

Marvin Replacement’s types of window glass include: Low E1, Low E2, Low E3, and Low E3/ERS coatings

• Our Low E3 and our Low E3/ERS glazing work well in hot and sunny climates because they will block solar heat. A Low E3 window will block up to 95% of UV rays.

• Low E1 glass glazing works best in colder climates. It allows more heat in to warm a room while blocking heat loss.

• Low E2 works well in moderate climates because it can help keep heat in winter and reject heat in the summer. It blocks 84% of the sun’s UV rays to reduce color fading.

How Can I Improve My Energy Performance?

If your windows are old, the best way to improve energy performance is replacement windows. Old windows lose energy efficiency as caulk deteriorates or weatherstripping starts to fade. Additionally, replacing old single-pane windows with double-pane windows can boost energy efficiency.¹

1 Savings reflect installing ENERGY STAR certified products compared to non-certified when replacing single pane windows based on the average savings among homes in modeled cities. Actual savings will vary by product type, location, method of installation, individual home characteristics, local climate and conditions, utility rates, and other factors.

*Map via ENERGY STAR