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Is new residential construction in CA required to have AC?

gustave_stroes | Posted in Building Code Questions on


We are planning the build of a home in Paso Robles CA.

Although summer day temps can get over 100 deg, it still will cool down to the 60’s at night, even the 50’s. Large diurnal temp swings (which apparently is good for the vineyards).

We plan to build a very well insulated house, with much effort given to reducing solar absorption during the day. At night we plan to cool the house using whole house fans drawing in cool outside air. We also plan to use radiant floor heating in the winter.

We think we can get away without needing to install AC. Just keep the house shut during the day and seal in the cool air.

Does anyone know if not installing AC is allowed by CA code? We are in San Luis Obispo County btw.

Thanks – Gustave

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  1. Peter Yost | | #1

    Hi Gustave -

    Section 4.3.2 "Prescriptive Requirements for Cooling Equipment" states that a "cooling system" is not required. (

    California tries to promote ventilation cooling such as you describe: see section 4.7.12.


  2. gustave_stroes | | #2

    Thank you Peter.
    You reference the 2013 Residential Standards. I have been studying the 2016 Standards.
    I am not done studying, but one section in the 2016 Standards leaves me uncertain. Namely:

  3. exeric | | #3

    Hi Gustav,
    I think Peter is correct and knows what he's talking about. I live in a similar climate to yours in California and I think you are wise to do this. I use a WHF and even before I insulated the attic floor with loose fill cellulose I put up a radiant barrier on the bottom of the roof rafters. In combination with the WHF it kept the house below 80F even on days reaching above 100F. Radiant barriers do nothing for cold weather but my experience is that they really work in hot.

    Also, invest in ceiling fans for most rooms as it can get up to the high 70s in the house just before the outside evening temps cool below ambient inside temps, which is when you can turn on the WHF. You have made a very energy efficient choice.

    1. exeric | | #9

      "A radiant barrier on the bottom of the roof rafters ... In combination with the WHF it kept the house below 80F even on days reaching above 100F."

      In the interest of accuracy that isn't quite right. Sorry. It kept it below 85F. Radiant barriers help but not THAT much. Maybe about 10F lower than otherwise. You still need normal attic insulation in addition to keep it to a tolerable situation.

  4. gawdzira | | #4

    Paso Robles gets pretty hot. It depends on the lifestyle of the occupant but A/C is not a bad consideration.

    The couple with the A/C there is an innovative new product worth checking out. The sales guys email is included. I just did some quick research on it and I am very intrigued.
    [email protected]

    1. Expert Member
      Dana Dorsett | | #5

      Thermal storage as ice is beneficial for time shifting the cooling load away from peak load hours, but it still uses about the same amount of cooling energy. If there are subisidies or programs that pay the homeowner to put it under utility or grid operator control for demand-response/ grid control purposes it may be worth it compared to conventional cooling systems, but the Ice Cub is not cheap, (though cheap compared to battery storage of equivalent capacity).

  5. gustave_stroes | | #6

    My original question was whether it was even allowed by code to construct a new home without AC in CA. Peter answered that for me. Some might wonder why I would ask this question. If you don't want AC, why would the State not allow you to build that way? Because they might be concerned about a future homeowner, should you sell your house. They might want AC, but now be stuck with the cost of retrofitting. The same situation applied in a town I used to live in next to an airport. They had strict STC ratings for windows, which allowed only a few types of windows to comply. But if I am intensive to the noise from the airport, why should I be limited in my window choice? Because the potential next owner may be very sensitive, and would then be stuck with your substandard windows. That was the town's reasoning.

    In any case, after getting the first part of my question settled, I then started to investigate what type of credits might be available for a "ductless" home. For those not in CA, we have to comply with Title 24, Part 6, which prescribes increasingly stringent rules for a home's construction in an effort to make it more energy efficient. You can comply by following prescriptive solutions, but almost all new homes comply using a performance approach.

    In this method the basic characteristics of the home are entered into a computer model which compares the energy efficiency of the home to one of the prescriptive methods. It's pass/fail. If you are 1% better you pass, if you're at 99% you fail and have to change something and try again. The results of this computer modeling must be officially logged with the State and submitted when you go for a permit.

    You would think that a home with no ducts, no AC, whole house fans, and conditioned attics would score well. But I am not so sure. The codes were written around the average type of home for the average type of home builder. The codes do not (yet) seem to accommodate those willing to build a home towards the leading edge of energy efficiency. At least that's my impression so far.


    1. ar_t | | #7


      2015 IRC R303 Light, Ventilation and Heating

      R303.1 Habitable Rooms
      ...openable area to the outdoors shall not be less than 4 percent of the floor area being ventilated.
      See R303.4 Mechanical Ventilation

      I think if you meet the minimum ventilation requirements by the code, you do not need mechanical ventilation for the whole house.

      1. gustave_stroes | | #11

        Hi Robert. I think you are taking about how much area can be created by opening windows? In any case, in CA open windows are no longer allowed to be considered in meeting indoor air quality (IAQ). Some type of "active ventilation is required, which can be bathroom fans blowing out, with air leaking in. But preferably some sort of HRV or ERV system, which is what I plan to do. This would be important in the winter when the whole house fans are not used.

  6. brendanalbano | | #8


    Have you talked to your local code officials yet? I'm sure every building department is a little different, but at least in the city where where I work, they are very helpful and seem to be happy to answer questions.

    Give them a call and ask them what the process is for getting help on code issues for a new project. It may be something you do by email or phone, a drop-in thing where you show up and wait your turn, a meeting you set up, or something else.

    While Peter seems to have answered your initial question, getting into the nitty gritty of the process of complying with your local energy modelling requirements without an AC system may be the sort of question that you'll get the best answer by talking directly to the folks who are going to be reviewing your building permit application.

    1. gustave_stroes | | #12

      The code folks in question here are at San Luis Obispo County, and they are very friendly. It's never very busy so waiting in line is rare. They will have the last word when our plans go through plan check. It may be worthwhile asking them. But we're working with a fairly experienced engineer in town, and we'll see what he says first. His shop does it all, grading plans, structural, architectural plans, and Title 24 Part 6.

  7. gawdzira | | #10

    I can not remember the architects name but when I was in school he gave a lecture on houses he was designing that were passively cooled. Also passive heat.

    These were earth bermed houses in a triangular (or oblique pyramid) shape with 2 stories. He ran culverts out at the lower points of the plan and buried them. This created a vacuum of air being drawn in which was cooled by the below grade temps. There was a vent at the apex which if opened would help move this air through the house. He was getting close to 20 deg. temp drops.

    Please do something similar and let me know if it works so you can be the guinea pig.

    1. gustave_stroes | | #13

      On our last home we put an opening skylight at the top of a two story staircase in the center of the house. This worked great as a thermal chimney. But that house was a mile from the ocean and the breeze blew all the time, which helped. Here our home will be single story. I like your architect's idea, but I'm not sure my wife wants to live in a pyramid!

    2. STEPHEN SHEEHY | | #14

      A common concern with earth tubes is that unless they can be easily cleaned, they get nasty with mold, various critters and miscellaneous gunk. And unless they are pretty large, the volume of cool air is minimal. Given CA strict rules regarding IAQ, would they even be allowed?

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