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Community and Q&A

Understanding IECC Climate Zones

qbrt | Posted in General Questions on

I’m a new homeowner trying to wrap my head around how all of this works. One thing that’s tripping me up is understanding climate descriptions. People throw around terms like “cool and dry” and “hot and humid”, but from my perspective NYC is both! We get 10F/40%RH in the winter and 95F/80%RH in the summer.

What kind of climate does NYC qualify as? When someone says “for cool, dry climates do X, but for hot, humid climates do Y”, which one should I be considering?

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  1. Expert Member
    PETER G ENGLE PE | | #1

    NYC is considered a "mixed-humid" climate. That means exactly what you would think - it is cold and dry in winter, and warm and damp in summer. There's enough precipitation in all seasons that you need reasonably aggressive bulk water control for the rain, and it is damp enough that you need to design for drying. That said, the climate is reasonably gentle compared to others. It is not too hot, not too cold, not too wet, etc. That all changes within a mile of the coast where coastal storms can change everything.

    1. qbrt | | #2

      Thanks! I probably should have figured that out from the description of CZ 4a as "mixed-humid". I guess I should be considering dehumidification advice from CZs 2/3 and the heating advice from zones 5/6? I don't see a lot of people talking about "mixed-humid" when giving advice. It's usually just "hot, humid" and "cold, dry".

      Also, I totally get what you're saying about "reasonably gentle compared to others", but when I'm freezing my butt off at 10F with a driving wind, it sure doesn't feel reasonably gentle!

  2. nynick | | #3

    As a non HVAC professional, I don't have much to add, but I've been living just north of NYC for over 50 years and know the climate.
    It's cold (and sloppy) in the winter and can get too hot/humid in the summer (July/August/September). The best NY seasons are Spring and Fall. I've been leaving for warmer weather in the winter and cooler weather in the summers for decades. I'm not a fan of hot or cold weather.
    Any normal A/C set up will take care of the summer heat and humidity. Same with heating. RH inside the house can get too low in the winters, but a humidifier can help a lot.
    If you're actually in NYC itself, the city setting can get hotter in the summers. Many people flee for the shore or the Island.
    BTW, a relatively unknown fact is that NYC has the best water in the world. Don't be sucked into the bottled water BS. The tap water is excellent.
    Welcome to the Big Apple!

  3. mgensler | | #4

    We're in 4a as well although not in NYC. We're in a heating dominated area with much more heating degree days. When we replaced our gas furnaces, we focused on the efficiency of the heating from cold climate heat pumps. (We typically only cool the house 3-5 weeks a summer as the night time temps drop enough to be comfortable.) We also focused on air sealing which eliminated our need to run humidifiers in the winter. Additionally, we paid close attention to the specifications for how to insulate an unvented cathedral ceiling so we minimized the opportunity for moisture to condense in the assembly.

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