How do I dec I'd love spray foam, but I doide what insulation is best?

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I'm starting to refurbish a ca. 1947 home. Weather-worn aluminum siding over the original wood clapboards. I want to strip the existing siding, replace the insulation, wrap, and re-side with HardiPlank. Which is the best way to insulate? Because of tight money (new divorcee), I'll be doing only one side of the house at a time.

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  • Seth Seth on Aug 04, 2018

    Are you stripping the sheathing down to the studs? If you are opening up the studs, fiberglass batts are easier to put in, are less expensive, have a higher R value, and you will have less waste. Spray foam is excellent at air sealing, but is the most expensive way to insulate. Living in a warmer part of the country, you probably don't need two layers as some people in colder regions would use batts in the walls and sheathe with rigid foam. Blown in cellulose has a slightly better R value than fiberglass, but is more trouble to install and costlier. Rigid foam in the stud bays is harder and costlier if you are doing it yourself as well. If you are keeping the existing sheathing in place and your stud bays are already insulated, then you could add a layer of rigid foam over the sheathing to increase your overall R value. This may change the depth of your window casings and you may need to add jamb extensions. Being a 1947 house, your stud bays may not be insulated, in which case blown in cellulose may be the way to go. You will also want to consider adding a rain screen under your siding. Are the wood clapboards in bad shape? You may want to consider keeping them and blowing in insulation.

    • See 1 previous
    • Sharon Sharon on Sep 07, 2021

      I would also test those clapboards for lead paint cause they may require special handling according to your state regulations. My 1940s house was insulated by removing the old wood siding, insulated with rigid foam and had new siding put on.

  • Jeannie wallace Jeannie wallace on Aug 04, 2018

    Spray foam usually is the best idea but it can get pricey. The newer white insulation is extremely thick so you can split its depth in half and do twice as much. It's way cheaper and won't cause you to itch and is allergy rated good. I used it when I redid the outside of my house and even noticed the muted sound of the interstate which connects to my property. Hope this helps and good luck.

  • Bijous Bijous on Aug 04, 2018

    Hi Alex. Too much insulation can be a bad thing. Houses need to breathe especially in the Gulf Coast states.


    • The main worry here is keeping the house cool. The main insulation should be in the attic -- both on the attic ceiling and the attic floor.
    • I used radiant barrier on the ceiling and the highest R value roll insulation I could find on the floor. Roll was easy to do and the barrier sheets are light enough for two people to handle. The link below recommends blown insulation and the equipment can be rented from Home Depot and the blown is cheap.
    • I did radiant barrier the one side wall where the setting sun hits but other than that, there's no insulation in the walls.
    • I did paper and HardiPlank. I recommend the sheets rather than the individual boards for beginners. It's heavy, but two people can handle it.
    • Rent or buy (you can always sell them on Craig's List when you no longer need them) the right tools for your job. Trying to "make do" never gets the job done right or in a timely manner.

    And congrats on the new house!! Insulation for a Hot Climate | The Craftsman Blog


    • Alex Alex on Aug 11, 2018

      Thanks for the info. I do want to use planks for the look of it. Radiant barrier sounds great, as the largest wall is west facing. Attic application is intriguing as well.

  • Zard Pocleeb Zard Pocleeb on Aug 04, 2018

    I think Tyvek wrap would be the best way to go for your project. It is easy to install, and it does a good job. It comes in a wide roll that you roll out and nail to the house using a product called ‘plastic cap nails’ (see pic). This is a two-person job though; one person unrolling the Tyvek, another nailing it to the house. One other thing I should mention; Tyvek is a brand name. You might find it called by another name.