I have inherited a 1950s house that has vinyl over original wood siding over old fiber board. Much of the house's siding is damaged and needs replacement. I'm thinking of replacing the full house's sheathing so I can re-insulate it and install new windows and Hardie siding or vinyl. The question is "is ripping off all the sheathing over doing it or the best option?" Also, what type of insulation and sheathing should I use? I'm located in Wichita, Kansas.
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Which layer of siding is damaged, the vinyl or clapboard? How is it damaged? How much is damaged?– James OlsonCommented Feb 20, 2017 at 2:51
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Also it is important to understand what the 'old' fibreboard sheeting is made of. I'm commenting from Australia where we use different terms but a lot of pre '70s fibreboard contains significant amounts of asbestos. If this is the case with your sheeting and it is damaged you should replace it for your familiy's safety. Also this is not a diy job (asbestos fibres will go right through a regular frspira– pHredCommented Feb 23, 2017 at 2:52
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... dam small keys. ... respirator's dust filter. Get the stuff removed by licensed removal guys.– pHredCommented Feb 23, 2017 at 2:54
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1 Answer
Fiberboard is flimsy and might be damaged in the process of removing the vinyl siding anyway. I'd replace it if the opportunity presented itself.
While you have the stud cavities open, replace whatever's in there with mineral wool. Then sheathe with plywood. Cover that with 2+ inches of rigid foam. Preferably polyiso (best R-value per inch) and preferably foil-faced (radiant barriers are nice, and you can use the foil surface as your water-resistive barrier if you tape the seams properly--no Tyvek!). Install your new windows on the foam, not the sheathing (outie windows). Install vertical furring strips over the foam, and nail your new siding into that. This creates drainage cavities that promote drying, and allow the foil surface of the foam to act as a radiant barrier.
Update: if after removing the sheathing and insulation, you discover that the wall was built with an interior-side vapor barrier (usually clear polyethylene sheeting right under the drywall), use a razor knife to cut it out. The wall assembly will be much more robust, especially in conjunction with the kind of exterior insulation I'm recommending.
answered Feb 19, 2017 at 3:57
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Using this system moisture from the outside cannot penetrate past the outer layer of the the rigid foam. Water vapor from the inside will penetrate to the innermost impermeable layer which would be the inside surface of the rigid foam. You don't want the water vapor to condense at that surface but at least if it would condense under extreme cold you'd want it to quickly dry out to the inside. So do the components of your system achieve this for the climate conditions in which you have tried it? Commented Feb 19, 2017 at 9:50
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99% of the time, there won't be an outward vapor drive in the first place but even if there was, the inner surface of the foam wouldn't be a condensation plane because it will be warm, above the dew point (foam is an insulator). What I've described isn't at all weird or experimental, and it's used for most new construction nowadays with a few modifications (putting the WRB layer between the foam and sheathing, for example). If you're unfamiliar with the foam-sheathed building approach, I recommend reading some of the documents available at buildingscience.com Commented Feb 19, 2017 at 15:57
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I wasn't questioning your system; basically just wanted you to explain in more detail how it functions. I'm aware that putting significant insulation and the outside water barrier and the inside vapor barrier all outside the structural framing and sheathing is a feature of a set of new building systems. Commented Feb 19, 2017 at 17:42