Hello All. My family and I live in a small (1000sqft) home in the Hudson Valley of NY. The home was originally built as a summer cabin in the 1920's. There is existing wood siding nailed directly to the 2x3 wall studs, considering its age the shell is in good shape, it is straight and square and rot free. I would like to begin insulating and it seems like 2 inches of rigid foam (taped) on the exterior of the building is a good place to start. I am thinking of nailing the rigid foam directly to the existing siding then attaching furring strips and then attaching the siding to the furring strips. Does this sound proper? Do I need one of those house wraps also?

depends on the siding. If it's clapboards, then you're better off removing the siding, installing plywood & then the foam, But if it's novelty siding which is probably likely, then yes, use the fabric, but detail it as an air barrier which means that it will need to be sealed with a high quality caulk all around the edges; seams taped etc. The foam is another issue. There is a real danger of creating serious problems - mold & rot - if you apply the wrong type & wrong amount.

Thank you for your input Bob. here is a pic of the siding. It looks like the siding is 5 inches wide, but it is actually 10 inches with a detail that makes it look like two pieces of wood. It has a shiplap groove on the bottom and top. Is this the type that you would recommend removing?

cannot open your picture, but if there are gaps between the back of the siding and the studs, as there would be with clapboards, remove it. If it is nailed flat against the studs, you can leave it. Many camps were sided with a pine board molded into a pattern, so it acted as a one piece structural sheathing and siding. The shiplap,,or sometimes t&g joint is installed in a way that allows it to drain.

Thanks again Bob. You might not be able to see this either, but it is a side profile of the siding from a wall that was removed when the porch was enclosed. It doesnt look like there is a space. Preventing mold and rot are of primary concern. So your opinion is much appreciated. I was hoping to insulate with 2 inches of rigid, side and change the windows. then add cellulose from the inside on a room by room basis. I should add we are living in the home during this process.

keep in mind that if any exterior air gets into those "clapboard" style grooves, it will defeat whatever insulation you have outboard of that. Think about using a layer of EPS which is very permeable, or, if you want to use polyiso for a higher R value, (and which is impermeable) you'll need a minimum amount. I'd guess you want 3" minimum, but others here (Dana) can be more specific. You can also use sheets of ROXUL which is permeable, but availability, and hence, pricing, is an issue.

Understood about outside air getting behind the rigid foam. I want to create a thermal and pressure barrier with the foam. I will take my time and make sure it is done well. I am hoping to use polyiso for its r value but also because it is available locally in slightly used condition at almost half price. I usually see it in 2 inch so I was hoping that would be a good fit.
That said EPS is certainly not out of the equation yet. I guess the house wrap is still good. It's just that I am used to seeing it flapping in the wind and pieces together hastily under vinyl. I guess if it's done right it is still worth the time. So should the wrap go under the rigid or over?

you basically have to decide where the air barrier will be around the house. If you choose the sheathing/siding plane, which is the usual place, then seal it there. Tyvek may not be the best material (I'd look at www.foursevenfive.com/ for that) but it will probably work if detailed correctly.

Thank you for the link. the membrane products certainly look more robust than Tyvek. It makes sense to me to have these two products (WRB and PolyIso) aligned. I am also thinking that I want to minimize the penetrations through both. Ideally just my fasteners that are securing my furring strips. So do you feel themembrane would work equally well on either side of the PolyIso? or is one side better?

It looks like you have ship lap siding, pretty common in upstate NY on camps. It is not only the siding but also the sheathing. It's flat with a grooved top. I've installed exterior insulation on these. All you have to do is remove the corner and window trim to get down to a flat surface. Pay attention to your corner laps, extend the window and door jambs out the thickness of your insulation. If you reside with vinyl then no need for a drainage plain.

Thanks Smartwall. I am still deciding on siding product. But I am pretty sure it wont be vinyl. I was thing about a Hardie product. If anyone knows of a good siding product, I would love to hear about it.