Spray Foam for Older Michigan Homes: What 1890s-1920s Construction in Detroit and Pontiac Actually Needs

Drive down any block in Hamtramck, or through the older residential grid of Pontiac near the Woodward corridor, and you are looking at houses that predate building insulation by several decades. The workers who framed those places in the 1890s were not thinking about R-values. Warmth came from the coal furnace. Coal was cheap.

That was then. DTE rates have climbed, Michigan winters have not gotten shorter, and those same homes — brick two-stories in Ferndale, woodframe workers’ cottages in Pontiac, foursquares on Detroit’s east side — are leaking heat through wall cavities that have been open to the air for over a century.

Spray foam can fix it. But a balloon-frame house from 1905 needs a different approach than a 1978 ranch in Macomb County. The framing is different. The risks are different. And what turns up during inspection will probably surprise you.

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What balloon-frame construction means for your walls

Most homes built after World War II use platform framing. Each floor is its own platform, with separate wall studs sitting on each level’s subfloor. Fire stops are built in at every floor.

Pre-1920 construction in Detroit and Pontiac is almost all balloon-frame. The studs run from the sill plate at the foundation straight up to the roof rafters — one uninterrupted cavity, two or three stories tall. No fire block. No break. That open cavity is also why these homes are so drafty: air can travel the full height of the house inside the wall with nothing stopping it.

When a spray foam crew comes to a pre-1920 house in Oakland or Wayne County, tracing those cavities should be among the first things on the list. Where does air enter at the bottom, and where does it exit at the top? On balloon-frame, the answer is usually the attic — and sometimes everywhere.

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What the inspection will show

Air movement, not just heat loss

A thermal scan on a pre-1920 Detroit home will show cold streaks running vertically up exterior walls. That is air moving through the cavity, not just conduction through wood and plaster. Blown-in insulation slows conduction but does not stop air movement. Spray foam does both, which is why it performs differently in these houses.

No vapor barrier — anywhere

Polyethylene sheeting did not exist in residential construction in 1905. The interior wall finish is usually plaster over wood lath. The exterior is original brick, original wood clapboard, or aluminum or vinyl siding added in the 1950s through 1980s over the original wood.

This matters because changing the thermal profile of the wall moves the dew point. Michigan winters drive interior vapor pressure toward the exterior. If you close-cell the wall cavities without thinking through the wall assembly, you can trap moisture. A contractor familiar with this housing stock will work through this before recommending a product.

The attic hatch problem

Pre-1920 homes in Hamtramck, Ferndale, and the older sections of Royal Oak were usually built with attic access through a small hatch — sometimes just a trap door in a closet ceiling. That means spray foam crews work in a tight space, and it also means some of these attics have never been properly insulated because nobody could physically get into them.

Open-cell spray foam in those attics is one of the better investments you can make on a pre-1920 house. Sealing the top of the balloon-frame cavities where they meet the attic floor cuts a major infiltration path. Open-cell in a Wayne County attic runs roughly $1.50 to $2.50 per board foot. A 1,200-square-foot attic floor at 5 inches deep comes out to $900 to $1,500 in material cost.

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How to approach the project

Start with the basement rim joists

The rim joist — where the floor framing meets the foundation wall — is where balloon-frame wall cavities begin. Two inches of closed-cell foam on the rim joist seals the bottom of those cavities and breaks the stack effect pulling cold air up through the walls. On a typical Detroit-area two-story, this is a half-day job, and it runs $600 to $1,200 depending on perimeter and how much junk is in the basement.

Do the rim joists before you touch the walls. It is the lowest-cost move and often produces the most immediate change in comfort.

Wall cavities require a decision

Two realistic options: drill-and-fill from the exterior, or open from the interior.

Drill-and-fill means boring holes through the exterior at each stud bay, injecting insulation, and patching. On a brick Hamtramck two-flat, this typically means drilling through the mortar joint — softer than the brick and easier to patch. On original wood siding, the holes go through the siding and get plugged. The catch is that balloon-frame cavities run 18 to 20 feet tall, not the 8 feet you would expect in a newer house. Incomplete fill in a tall cavity creates a cold zone at the top where condensation can accumulate. Whoever does this work needs to understand what they are actually filling.

Opening from the interior — pulling the plaster or drywall, spraying, patching — costs more and requires finish work, but it gives you full visibility into what is in the wall before anything goes in. On a pre-1920 house, that visibility matters. Budget $4,000 to $8,000 for a full exterior wall treatment on a 1,500-square-foot two-story if you go this route.

Attic air sealing before adding insulation

If your house has existing blown-in cellulose or fiberglass in the attic, it has air gaps. Insulation without air sealing reduces conduction but the wind still gets in at every penetration.

Foam every top plate, every plumbing stack, every electrical box, the tops of the balloon-frame cavities. Then add blown-in on top. This costs more upfront. It is also what actually moves your DTE bill.

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What to ask before hiring

Balloon-frame wall cavities in Pontiac and Detroit sometimes contain things nobody documented: old knob-and-tube wiring, abandoned gas lines, plumbing that wanders through the cavity. Before any injection work, someone needs to understand what is in there.

Ask for specific references from pre-1930 housing in Oakland County or Wayne County — not just “older homes,” but this housing type. What did they find? How did they handle the cavity height? The answer tells you whether they have actually done this before or whether your house is a learning experience for them.

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FAQ

My Hamtramck home has original brick. Can insulation still be injected into the walls?

Yes. The standard approach on brick two-flats is drilling through the mortar joint rather than the brick face — the mortar is softer and patches cleanly. Holes run in a horizontal line at mid-height of each floor. A careful mortar patch is nearly invisible. If you are not comfortable with any exterior drilling, opening from the interior is the other option, though it requires more work inside.

Does DTE Energy offer rebates for spray foam on a pre-1920 home?

DTE’s Home Energy Efficiency Program includes rebates for attic and wall insulation, and spray foam qualifies when it meets the R-value thresholds. The attic rebate has applied at R-49 or better; wall insulation has typically required R-13 minimum. The amounts and eligibility rules change, so pull the current schedule before your project starts. A contractor who works regularly in Wayne and Oakland County should know the current tables.

I have knob-and-tube wiring in my walls. Does that block spray foam installation?

Spray foam cannot go in direct contact with active knob-and-tube wiring — that is a Michigan fire code issue. It does not mean the walls cannot be insulated, but the wiring question has to be resolved first. An electrician needs to evaluate whether the circuits are live and carrying load, then either decommission or reroute before insulation goes in. On pre-1920 housing in Detroit or Pontiac, expect to find some. Build it into your budget rather than treating it as a surprise.

What is a realistic payback period for a Wayne County home from this era?

For a properly done wall and attic project on a pre-1920 two-story in Wayne County, payback typically runs 7 to 12 years at current DTE rates — depending on how bad the existing condition is and how much air sealing is included. The rim joist treatment alone on a drafty basement usually pays back in 3 to 5 years. These are not guarantees; gas prices move and winters vary. But they are the ranges that show up consistently on this housing stock.