Key Points
- The continental United States is divided into 7 climate zones. Alaska and Hawaii each have their own climate zones not found anywhere else in the continental states.
- Air conditioner efficiency standards are broken into three regions: the North, the Southeast, and the Southwest.
- Furnace efficiency standards do not vary by region.
Some Americans barely experience a hot day. Others never see snow. Those who are particularly unlucky know exactly what high humidity feels like in summer and the sound of ice cracking in winter. Life can be very different depending on the climate zone you live in. Different climes require different clothes, habits, and construction habits. So when it comes to investing in a system for home air comfort, don't disregard your climate zone.
Climate Zone Features
Take a look at the IECC’s updated climate map below for a more visual explanation. The IECC divides the United States first into three categories based on moisture: Marine, Dry, and Moist. From there, each state is examined county by county for average temperature expectations. By combining average moisture levels with average expected temperatures, builders can better predict the special considerations that will be needed for construction projects, from materials needed to expected wear and tear. It’s important to consider the IECC climate zones for your HVAC needs, too. HVAC needs are often described in terms of the number of heating degree days a region demands, set at a baseline of 65 degrees. Broadly speaking, the United States is divided into eight climate regions: Hot-Humid, Mixed-Humid, Hot-Dry, Mixed-Dry, Cold, Very-Cold, Subarctic, and Marine.
Hot-Humid
Folks in the Hot-Humid Climate Zone get to enjoy at least 20 inches of rain each year, and all the wonderful humidity that comes with it. They get long summer days with plenty of heat, averaging at least 6 months of weather sustaining a minimum of 67 degrees Fahrenheit (19.5 degrees Celsius). Cold weather rarely reaches counties in this region. With that in mind, the perfect HVAC system for homes in climate zone 1 is a heat pump. When chilly (but not cold) nights come around, a heat pump will be more than enough to keep you warm, and it will keep you cool during the hot daytime.
Mixed-Humid
People who live in the Mixed-Humid Climate Zone might be used to the catchphrase, “Don’t like the weather? Wait five minutes.” Mixed-Humid Climate Zone 2 gets 20 or more inches of rain per year and solid summer temperatures averaging above 65 degrees Fahrenheit (19.5 degrees Celsius), but they also get winter temperatures with an average below 45 degrees Fahrenheit (7 degrees Celsius). Altogether, this region averages 5400 heating degree days or less per year. Weather throughout the year varies as greatly as the temperature, so your home HVAC needs to be just as versatile. A new, high-performance heat pump will accomplish all the indoor temperature control you need. Plenty of people in this climate zone have furnaces for emergency heating, but most won’t need them. If you’re concerned about the occasional winter day that drops closer to freezing, get a MrCool HyperHeat Central Ducted Heat Pump. This ultra-efficient heat pump maintains performance even when the temperature drops to -5 degrees Fahrenheit (-20 degrees Celsius).
Hot-Dry
The Hot-Dry Climate is a desert. Literally. They get minimal precipitation—less than 20 inches per year—and a lot of heat. Counties in this region rarely drop below 45 degrees Fahrenheit (7 degrees Celsius), no matter the time of year. The only time there was ice here was during the last Ice Age. What kind of HVAC system should you get if you live in climate zone 3? A heat pump is more than enough to cover the coldest night, which might still feel a bit warm. We recommend running a humidifier for the more arid stretches, too.
Mixed-Dry
Climate Zone Mixed-Dry is a bit of a mixed bag. They get less than 20 inches of annual precipitation. Summer temperatures average over 65 degrees Fahrenheit (19.5 degrees Celsius), and winter temperatures often drop below 45 degrees Fahrenheit (7 degrees Celsius). So, they don't have to worry about high summer humidity or tons of snow. Like Mixed-Humid regions, Mixed-Dry regions average less than 5400 heating degree days. The best HVAC for mixed-dry climates is, once again, a heat pump, but we recommend adding an auxiliary heat kit to it. Like Hot-Dry zones, a whole-home humidifier might not be a bad idea either. You shouldn't need a furnace unless you're right on the boundary of a cooler climate zone.
Cold
The Cold Climate Zone stretches across the US North (and a lot of the West). Summers get warm, but on average, they don’t get too warm. They also have long, snowy, cold winters with lots of below-zero days, wind chill, and polar vortices. This region averages between 5400 and 9000 heating degree days. HVAC in cold regions needs a little less emphasis on air conditioning and a bit more on heating. An air conditioner is plenty for the summer, but you’ll want a gas furnace for winter.
Very-Cold
Climate Zone Very-Cold is quite a jump up from the weather we see in Cold regions. Heating degree requirements jump up to anywhere between 9000 and 12,600 days. As per the name, it gets very cold in this region in the winter, and not terribly warm in the summer. You won’t need air conditioning in this region at all. Instead, the best HVAC to invest in for homes in the Very-Cold climate zone is a gas furnace. Some ductless mini-split heat pumps are rated to maintain efficiency when the weather drops as low as -22 Fahrenheit, but a gas furnace is the safer way to go
Subarctic
Very few people in the continental US live in Subarctic climate zones. In the US, this zone mostly applies to citizens in Alaska, although some regions of northern Minnesota and North Dakota fall under this classification. This climate zone is COLD, requiring 12,600 or more heating degree days annually. The best HVAC solution for Subarctic climate areas is a high-efficiency furnace. Moreover, you need to make sure you have a good warranty plan. With weather that gets as dangerously cold as it does in this climate zone, you need to be prepared to resolve heating issues quickly. For absolute emergencies, try adding a fireplace or wood stove to your home.
Marine
The entirety of the West Coast is in a Marine Climate Zone, varied only by the temperature expectations. Warm ocean currents and breezes mean that it usually stays relatively comfortable for most of the year, but this varies depending on the latitude. The US Department of Energy states that for a region to be considered Marine, it must:
- Have an average temperature between 27 degrees Fahrenheit (-3 degrees Celsius) and 65 degrees Fahrenheit (18 degrees Celsius) in the coldest month of the year
- Not exceed 72 degrees Fahrenheit (22 degrees Celsius) on average in the warmest month
- Experience dry weather in the summer, with the wettest season falling in the cold season (October-March in the Northern Hemisphere and April-September in the Southern Hemisphere), wherein the wet season experiences at least three times the amount of precipitation that the driest month of the year experiences.
The weather in these regions, although at times very wet, is moderate enough that dedicated HVAC might be an afterthought. Still, an energy-efficient heat pump will be enough to combat the odd extreme temperature days. For people in regions where the temperature dips a little cooler, a heat strip will be sufficient to keep warm.
Climate Zone Cooling Impact
Cooling energy efficiency is typically measured according to the Seasonal Energy Efficiency Ratio (SEER). The higher the SEER, the more efficient the air conditioner or heat pump is at cooling a home. In northern states, the Midwest, the mountain states, and the Pacific Northwest, the federal minimum is 13 SEER. Which means that if you live in Portland, you can install, at minimum, a 13 SEER air conditioner. The Federal standard is much higher in Florida, Texas, New Mexico, and pretty much anywhere else that really needs air conditioning. The warmer the climate zone you live in, the more you are going to use that air conditioner. Multiply that by every home with an air conditioner, and you can see how requiring high-efficiency systems mitigates a ton of energy waste. By contrast, Portland and places like it never get that hot. Which means that even when they do run their relatively inefficient air conditioners, they're not using nearly as much energy.
Efficiency Regions: North, Southeast, and Southwest
To keep it simple, the Department of Energy has divided the country into three big air conditioner efficiency regions. There is the North, the Southeast, and the Southwest. There aren’t many regulations for the North. Any new heat pump or air conditioner they install can be as low as 13 SEER. The Southeast is more strict. They can only install 14 SEER equipment. The Southwest, where all that desert is located, is even more strict. Their equipment has to be 14 SEER, but it also has to be 11.7 EER or better, depending on size. So, for you Floridians who just found a great deal online for a new 13 SEER air conditioner, don't get too excited. That 13 SEER unit is about as useful to you as a wooden nickel.
The Price of High Efficiency
Let’s talk about dollars. 14 SEER units are more expensive to buy. But the good news is their superior efficiency means they cost less to run. Anyone required to buy a 14 SEER system will run them often, so the increased efficiency pays off over time. Upgrading from 13 SEER to 14 SEER means your air conditioner or heat pump is roughly 7% more efficient. If you spend $100 on air conditioning each month, you would save about $70 per year. Which, over a decade, is a not-small amount of money. Obviously, if you spend even more than that each month, and some people do, the savings can really start to add up. In the long term, you can recoup real dollar value thanks to the extra efficiency. Plus, large groups of people investing in energy efficiency products help us keep energy prices low overall.
How Does Climate Zone Impact Heating?
In 2015, the DOE finalized the standard for gas furnaces at 80% Annual Fuel Utilization Efficiency (AFUE). As with SEER, the higher the AFUE, the better. That rate held until 2023, when the Department of Energy released new efficiency standards for gas furnaces and mobile home furnaces. Due to go live after 2028, these furnaces will require a 95% AFUE.
Master Your Climate Zone With IWAE
Climate and weather play an obvious, unalterable role in our lives. But that doesn't mean we have to be miserable. Invest in the right heating and cooling technology to ensure your home is as comfortable as modern technology will allow. If you have questions about HVAC needs to suit your climate zone, just give the experts at IWAE a call. As always, we're here to help answer your questions and find the best heating and cooling solution.
