Rough-in penetrations when plugging up basement windows
I live in an 1850s farmhouse in upstate NY, Climate Zone 5A. I’m planning to hire a contractor to apply closed-cell spray foam to the interior of the rubble foundation and sill. In anticipation, I’d like to close off at least 2 of the 4 small windows in the basement (see photos). Once they’re closed off, spray foam will be applied continuously with the rest of the foundation.
In addition to plugging up these air and thermal leaks, I think these spaces could provide valuable space for penetrations for systems we’ll want to install in the future, without having to disturb the foundation wall or the sill. I’d like to rough some of these in now, including:
– Radon mitigation: 4” Schedule 40 PVC pipe-stub with a slight inward tilt to allow for eventual condensation drainage
– ERV fresh-air intake and exhaust: in different window wells to ensure adequate separation (I’m unclear on what size/material these should be, and whether they should be stubs or sleeves)
– Minisplit refrigerant lines (one or more): sleeves that are wide enough to fit an insulated line
– PVC electrical conduit to feed a subpanel in the detached garage
– HDPE pipe, or a sleeve for such a pipe, for seasonal garden irrigation (I would drain in winter along with hose bibs)
I’m also anticipating some eventual exterior work around the foundation and window wells—filling some of them in, re-grading the soil surface away from the foundation, and installing a perimeter French drain to divert surface water.
If this overall approach seems reasonable, I have a few questions:
- How should I construct the “window plugs” themselves? A concrete pour with stubs built into the forms? Or a mostly-brick wall with some all-mortar sections surrounding the round penetrations? Or is there an easier way? Here’s an example of the brick-and-mortar approach from mason Mike Haduck: https://www.youtube.com/watch?v=VzbJPqZiubA
- Are there any design considerations (sizing, spacing, sloping etc) for roughing in so many penetrations for different systems in close proximity to each other?
- What should I do to keep the stubs and sleeves sealed/insulated/critter-guarded before using them? (Realistically, the timeline could be months for some projects, years for others.)
Thanks in advance!
Doug
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Doug,
I don't think you can go wrong with a few PVC 4" sleeves. They can be insulated with batts and each end loose capped. When you come to use them you can drill out the appropriate sized hole in the cap, run the lines, and replace the batts with spray foam.
Thanks, Malcolm! This approach makes sense.
I would build a sort of mini-SIP here: sandwich some polyiso (or EPS, whatever is handy) between two sheets of plywood and glue it all together. You can now easily cut whatever size hole you need with a holesaw by going through the plywood, then the insulation, flipping to the other side of the mini-SIP and then using the pilot hole to come in with the hole side from the opposite side to avoid a blow out at the end. This gives you unlimted flexibility for future services to be added. I'd use AT LEAST 2" rigid foam in the mini-SIP, and ideally a bit more. This would be less R value than the wall probably is, but it would be a whole lot better than the glass it replaces in that window.
If you can find a "real" SIP for cheap, that would work even better.
If you don't want to try the mini-sip, I'd go with Malcolms suggestion, and I'd seal them with the step-type boots made to seal pipe penetrations in roofs when you add a pipe to them. I'd just use a a "quick cap" (rubber endcap with a stainless pipe clamp) until you're ready to add a service. I have found that PVC end caps can get stuck on the pipe stubs pretty well and become difficult to remove, so those won't work as well here. You could use threaded cleanouts though, but those usually cost more than the quick caps.
BTW, this is a common application in the telecom industry (where I do most of my work), they are used to seal multiple conduit entries in telecom switch sites. There are various manufacturers, some examples from one that I found quickly with google is here:
https://polywater-haufftechnik.com/products/?filter=inside-the-pipe
Note that these systems are very elegant and easy to change out in the future, but they tend to not be cheap.
Bill
Thanks Bill! I like the mini-SIP idea. Thanks also for the "quick cap" and Polywater suggestions.
If I go the mini-SIP route, do you have any suggestions for how to frame it? Would I remove all of the existing window frame and install the mini-SIP with a surrounding frame of treated lumber with a capillary break? For the plywood on the exterior, what kind of protective layer should I apply? Could a section of ZIP-R sheeting work instead to provide more weather resistance on the exterior?
Am I correct that if I'm planning to fill in a window well with soil, I should stick to masonry approach? Or is there a way to make a mini-SIP work with direct soil contact?
I'd frame it with treated lumber as you descibe. If it was exposed, I'd just paint it with a heavy coat (which means multiple actual coats!) of exterior paint. I like PPG Permanizer for this sort of thing.
If you want to backfill the entirety of the opening so that the "mini-SIP" is against earth, I'd laminate a piece of plastic to the exterior face of the mini-SIP. My preference for endurance would be a sheet of HDPE, but many/most adhesives don't adhere to that very well, so some PVC sheet may work better. You would want an even layer of adhesive (think "apply the adhesive with a putty knife as if you were about to tile the surface"), so that you have no voids where water could sneak in.
Using Zip for the outer face may work, but I don't think it's intended to be used below grade, so being in essentially constant contact with moisture may be a problem. Thinking about that, using marine grade plywood for the outer face, and sealing the edges, would probably also be a good idea. You could just use a sheet of PVC trimboard for the exterior face though, which would then completely solve the "in contact with wet earth" problem. I'd probably try a spray polyurethane adhesive for laminating these layers together.
Bill
Thank you Bill!
This is brilliant. I just came across this and am going to follow this mini-SIP technique as well for closing up some foundation holes but keeping options for future foundation intrusions.
All this talk of closing up basement windows makes me want to remind everyone that code requires egress windows in many cases, so that people have a way to escape the basement in case of fire. Keep that in mind when considering closing things up in basements.
Bill