Is it OK to put 1 inch of EPS under vinyl siding with no wall insulation?
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
It seems like you have gone to some effort and expense to insulate the rest of the house, so of course you should do the walls, but I’m wondering why only 1 inch? Being in the Berkshires of Massachusetts you’re likely in Climate zone 5A, which is not Arctic by any means but you’d certainly benefit from a bit more than an inch at R4.
And I say that largely because its a lot of effort to remove and replace siding to insulate and seems a wasted opportunity to not shoot for more R value than that. I would point you to this page before you make a final call on the amount :
How much insulation do you need for green home construction?
I would certainly propose more insulation, and to specifically answer your question about vapor – yes, adding vapor impermeable materials to the outside of a wall assembly can cause problems during the cold season. But, the vapor permeability of EPS could be used to your advantage in this case – 1 inch may be a problem, but several inches may solve your problem as it can begin to act like a SIP wall (structural insulated panel). EPS begins to act like a vapor barrier at 2 inches as it is then approximately 1 US Perm.
All that to say, I’d consider a few more inches if you can swing it, is that a possibility? Let us know if so, there are a few ways you could then go about it.
Thanks Mike
I was thinking the same thing I did the ceiling and floors with decent insulation coverage.
I was tring to cheap out on the process but I may retire here so I should do it right the first time. dense pack the walls and 1 inch EPS under siding to solve the thermal bridgeing issue.
Adding more EPS would be an issue for the fairly new front door and the new rather large pictue window in the front might look a bit funny if the siding is way out past the window.
I am replacing the other windows so they are not a problem to shim out.
I doubt condensation in walls would be an issue with this plan
Roger and Judy
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.
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
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 :)
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
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.