Rim joist spray foam insulation in Drumheller is the single best-value item on the great majority of houses in this town, and the reason is in the stock. About 76% of homes here predate 1991 and much of it is older still, built for mining families along the valley, and in houses of that age the joint between the wood structure and the top of the foundation was never sealed and frequently never insulated.
What the joint actually is
At the top of the foundation wall sits a sill plate, and on the sill sit the ends of every floor joist with a rim board closing them off. That band is a few inches tall and it runs the whole perimeter of the house. On the inside it is warm house; on the outside it is a few inches of wood and whatever cladding is on it. Three things meet there: concrete, wood and the exterior wall above. In older construction that junction is dry-laid, with no gasket under the sill and no sealant anywhere, so the gaps are continuous and they run the full way round the building.
Why it is not a straight gap here
This is what makes a Drumheller rim joist different from one in a newer town. The valley is cut into bentonitic shale and clay, which swells with moisture and shrinks as it dries, and differential foundation movement is a familiar condition on houses in this area. Many of these houses have been jacked, shimmed, relevelled or had a section of wall rebuilt at some point in a long life. The result is that the sill is not sitting flat on the foundation. There are tapered gaps, shims with voids beside them, parged patches, and places where the sill is hard down and places where you can see daylight. Nothing cut to a dimension seals that, because there is no dimension. A sprayed liquid that expands into the void it finds and bonds to concrete, wood and shim alike is the only thing that does.
The stack effect, and why this band is the bottom of it
Warm air rises, so a heated house is slightly pressurised at the top and slightly depressurised at the bottom. That means the ceiling plane is being pushed out of and the rim joist is being pulled in through. Every cubic foot that leaves through the attic has to be replaced, and it comes in through the lowest openings available. On a house here that is the rim joist and the crawl space. Sealing the top without sealing the bottom removes the exit but leaves the entrance; sealing the bottom removes the supply, and that is why the rim joist is the item that changes how cold a floor feels.
The valley makes the air it pulls in colder
Cold air drains off the prairie above the valley on still nights and pools on the valley floor until the sun clears the valley wall. A house on the bottom is therefore drawing its make-up air from the coldest air in the municipality during exactly the hours the heating is working hardest, and it is drawing it in at floor level. That is the physical reason floors feel cold at dawn in these houses and the thermostat reading does not explain it.
Why this detail belongs to foam
Fibreglass stuffed into a rim bay is the standard old treatment and it does nothing, because air passes straight through it and then condenses on the cold rim board behind, which is how a joist end rots. Closed-cell at roughly R-6 to R-7 per inch is adhered, fills the irregular voids, and becomes its own vapour retarder past about two inches, so the warm moist air never reaches the cold wood. It is a small quantity of material and a short job. We quote the job, schedule it and stand behind it, pricing follows the board feet sprayed, and this is the item we would recommend first if a household can only do one thing.
Rim Joist Spray Foam Insulation Drumheller: Common Questions
Why is this the first thing to do? Because it is the leakiest reachable surface in a house of this age, it is where make-up air enters, and it is a small quantity of material.
Our house has been relevelled. Does that matter? It is the main argument for foam here. The sill-to-foundation joint is irregular and tapered after movement, and only a sprayed material seals a gap with no fixed dimension.
Can we just stuff batt in the rim bays? It will not work. Air passes through it and condenses on the cold rim board behind, which over years is how the joist ends get damaged.
How much does rim joist spray foam insulation cost in Drumheller? It follows the sprayed area, and the rim band is a small area, so this is usually one of the least costly items. Access matters most: a finished basement ceiling that has to come down adds more than the foam.
How do I choose a rim joist spray foam contractor in Drumheller? Ask whether they intend to go all the way round, including behind any ductwork and under the stairs. A partial perimeter leaves the supply path open and most of the benefit on the table.
Check quantities with the R-value calculator, then get a free Drumheller quote. More on Rim Joist Spray Foam Insulation Alberta province-wide.