The rim joist is the band of framing that sits on top of the foundation wall and closes off the ends of the floor joists. It is a strip only as tall as the joists, it runs continuously around the entire house, and in Devon's older housing it carries no insulation and no air seal whatsoever. Rim joist spray foam insulation in Devon is the smallest piece of work with the largest effect on how the main floor feels, and it is first on the list for a reason.
Why this strip loses so much
It is the one line in the building where three things coincide. It is at the very top of the foundation, so it is the warmest part of the wall and the point from which rising warm air is trying to escape. It is the thinnest assembly in the whole envelope — on an older house, often nothing but the band board and the exterior cladding. And the joist ends break it up into dozens of separate pockets, each needing its own seal, which is exactly the kind of work a batt cannot do.
Bearing on block changes the detail
Much of the pre-1991 stock here sits on concrete block, and where joists bear on a block wall the top course is frequently left open. That means the rim joist pocket is not a dead end; it is connected to the hollow cores running down the inside of the foundation wall. Air that enters at the sill does not stop there, it travels. Sealing the pocket face without closing the connection to the top course leaves half the circuit intact, so the foam is carried down onto the top of the block and across the sill bearing, not just sprayed on the band board.
What closed-cell does here that nothing else does
Two inches of closed-cell is roughly R-12 and is its own vapour barrier, which matters because this is a cold surface with warm humid interior air available to it. It adheres, so there is no gap behind it for air to circulate. And it is sprayed, so it fills the irregular joist pocket, the gap over the sill plate, and the space around any pipe or wire passing through — the places a cut rectangle of anything cannot reach.
Fibreglass stuffed into a joist bay is the usual previous attempt. It does nothing about the air, it holds moisture against the band board, and it has to come out before the pocket can be sealed properly.
A cheap job that proves the rest
Because the whole band is reachable from an unfinished basement, this is work that can be done in a day on most Devon houses with no demolition and no disruption upstairs. Owners report the difference at floor level the same evening. That makes it a reasonable way to judge whether a contractor's diagnosis of the rest of the house was sound.
What the crew looks for while down there
Rot or staining on the band board, which indicates water has been getting in and needs its own fix first. Gas lines, dryer vents and hose bibs passing through, each of which gets sealed around rather than buried. And any fuel-burning appliance venting nearby, because combustion air has to be accounted for when a basement gets tighter.
Who quotes it and who sprays it
We do rim joist spray foam insulation Devon ourselves. We scope and quote it, we book it, and our own installers spray it -- one company, one point of contact.
Rim Joist Spray Foam Insulation Devon: Common Questions
Is this really the first job on an older Devon house? Usually, yes. Tiny area, continuous all the way round, at the top of the coldest wall, and reachable without taking anything apart.
Our joist bays already have fibreglass in them. Is that enough? No. It slows heat and does nothing about air, and against a cold band board it holds moisture. It comes out first.
Does a block foundation change the work? It extends it. The foam gets carried onto the top course of block so the hollow cores are closed off, not just the face of the band board.
How much does rim joist spray foam insulation cost in Devon? It is priced per board foot, so the perimeter length and the joist depth set the quantity. It is the lowest-quantity job in the house, which is why it is usually the first one recommended.
How do I choose a rim joist contractor in Devon? Ask whether they intend to remove existing fibreglass and whether the foam will reach the top of the foundation wall. Both answers should be yes on this stock.
Size the job with the R-value calculator, then get a free Devon quote. More on Rim Joist Spray Foam Insulation Alberta.