Is it OK to put 1 inch of EPS under vinyl siding with no wall insulation?

Roger Smith Nov. 12, 2019Updated: Aug. 26, 2020

We have a cabin in the Bershires of Massachusetts ceilings and floor have been insulated, dense pack celluose in ceilings 4 in Amivic graphite EPS under floors.

Walls have no insulation, siding is T-1-11 from the sixties would like to put 1 inch EPS under vinyl siding. the building is pretty well built. no sagging parts no gaps no structural issues, drywall in good shape. would the 1 inch EPS under vinyl siding be a problem with condensation on inside of walls would vapor barrie paint help over the old paint.  What type of house wrap and where do you put it under EPS or over EPS.

Roger and Judy Smith  




Responses (7)

Trevor Prinz 3 years ago

I would consider choosing a different siding material or a different type of insulation. In the Incompatible Building Materials Research Report by the Canada Mortgage & Housing Corp. these materials are listed as incompatible. Vinyl siding has a high coefficient of expansion and the expansion of the siding over the EPS insulation (same goes for XPS) can cause a squeaking noise that can be heard through the walls. To fix this problem they suggest that you install a layer of house wrap between the two materials; However, if it were me, I would swap out one of the materials for something else.

Roger Smith 3 years ago

Hi Trevor

I think I am going to take Mikes advice and do a dense pack on the walls seeng I already spent the cash on the ceilings and the floors, May still use the 1 inch EPS under the siding with a house wrap.

Thanks Roger and Judy


Mike Reynolds 3 years ago

Thanks for your input Trevor, that was news to me about the sqeaking. As for the siding, Roger - given that you were in the middle of a reno, in my mind I had envisioned you already having the vinyl and 'reinstalling' it. Reusing exising vinyl is the only vinyl we would ever recommend, despite it being about as affordable and popular as siding can get. If you're buying new it's our least favorite given the ecological impact since 40% of chlorine gas manufactured goes towards producing vinyl

Since Trevor has broached the topic (Kudos to you Trevor), I'd second his motion to investigate other possible materials. Here is our page on Siding Types & Costs: Which is Best and How to Choose. For what it's worth, I have FSC painted wood on my house, which will require a coat of paint in the next 10 years or so, and if I could do it over again I'd be going with Shou Sugi Ban Carbonized Wood, if nothing else but for the look.

Are you reinstalling old vinyl or buying it new Roger? I'm not going to take a rip out of you either way because people have budgets they need to stick to, but I may try to twist your arm a little to discuss options if you're open to it :) 

Roger Smith 3 years ago

I was going to install new vinyl siding  primarily because I have some experience installing it , cost and fairly maintenance free also factor in. I also thought of going over the EPS with new T1-11 but the maintenance is an issue, as this may become the home I retire to do not want to repaint every few years.  I know vinyl is not Eco friendly in the short term but the fact that it will not need to be painted over its life time may offset some of the unfriendly eco concerns, And the vinyl may become widly recyclable some day.

Thanks fo keeping me on the eco track

Roger and Judy

Mike Reynolds 3 years ago

Just had to point it out in case, we don't like to preach but just open discussions.   And who knows, It may well become recyclable, certainly reusable. Best to you  both Roger and Judy, drop us a line for any other questions.