The Short Answer

Spray foam costs more upfront than fiberglass batts, blown-in cellulose, or rigid foam board. But in Michigan’s cold climate (Zone 5/6), it outperforms every alternative on air sealing, moisture control, and long-term energy savings — by a margin that typically justifies the investment within 5–8 years.

This page walks through how spray foam compares to each major alternative on the factors that actually matter for homeowners in Michigan.

Spray Foam vs Fiberglass Batts

Fiberglass batts are the most common insulation type in existing Michigan homes — the pink or yellow rolls you see stapled between wall studs or laid in attic floor joists. They’re inexpensive to install and easy to work with, which is why they’ve been the default for decades.

The problem: fiberglass batts don’t air seal. They insulate, but gaps around outlets, pipe penetrations, ceiling light fixtures, and framing seams still allow conditioned air to escape — and unconditioned air to enter. Studies from the Building Science Corporation estimate that air leakage accounts for 25–40% of heating and cooling losses in a typical house. Fiberglass batts do nothing to stop this.

Spray foam addresses both problems simultaneously. Because it expands to fill every gap, crack, and penetration as it cures, it creates an air barrier and an insulation layer in a single application.

In Michigan — from Detroit and Ann Arbor to Grand Rapids and Lansing — homes were commonly built with R-19 fiberglass batts in the walls and vented attics. These homes work reasonably in mild weather but hemorrhage heat during Michigan winters when temperatures drop into single digits and wind chills go negative.

Spray Foam vs Blown-In Cellulose

Blown-in cellulose (recycled newsprint treated with borate fire retardant) is a popular attic top-off material and a common choice for wall cavities in retrofit projects. It achieves higher R-values per dollar than fiberglass batts and settles into irregular spaces better than rolls.

The limitations are similar to fiberglass: cellulose doesn’t air seal, and it’s hygroscopic — it absorbs moisture and can compact over time, reducing its effective R-value. In Michigan’s cold climate (Zone 5/6), cellulose attic insulation that gets wet from roof leaks or condensation can become a substrate for mold growth.

Spray foam in attic applications creates an unvented conditioned attic — the roof deck itself becomes the air and thermal barrier, and the attic space is treated as part of the conditioned envelope. This is more effective than any amount of blown-in at the floor level because it eliminates the attic as a thermal buffer entirely.

Spray Foam vs Rigid Foam Board

Rigid foam board (XPS, EPS, or polyiso panels) achieves high R-values and does resist moisture — making it a legitimate choice for specific applications like exterior wall sheathing, under-slab insulation, and some crawl space applications. It has some legitimate advantages.

The limitations: rigid foam board must be cut and fitted by hand, leaving gaps at seams, edges, and penetrations that require tape or caulk. In crawl spaces, it must be mechanically fastened and can separate from surfaces over time. It doesn’t seal irregular or complex geometry as effectively as spray foam, and labor costs for a quality rigid foam installation are often comparable to spray foam anyway.

Michigan crawl spaces face the harshest combination: frozen ground in winter, condensation-heavy summers. Fiberglass batts in joist bays absorb moisture from below, compress, and lose R-value — often by 30-40% within a decade. Closed-cell spray foam in a Michigan crawl space pays for itself faster than almost any other application because the heating savings in a Zone 5/6 climate are so significant.

What Spray Foam Is NOT the Right Answer For

Spray foam isn’t the answer to every insulation problem. It’s not cost-effective as an attic floor top-off if your attic already has adequate R-value and no air sealing issues. It’s not the right choice for a quick landlord-class rental repair where the goal is minimum upfront cost. And it requires professional installation — it can’t be a DIY project like fiberglass batts.

The applications where spray foam consistently wins in Michigan homes:

• Attic air sealing and roof deck insulation — especially if HVAC equipment or ductwork is in the attic
• Crawl space encapsulation — eliminating moisture at the source
• Rim joist and band joist sealing — one of the most air-leaky spots in any house
• New construction walls — capturing the full R-value benefit during initial build
• Unvented roof assemblies — cathedralized ceilings and open-plan designs

Getting a Real Quote

The right insulation choice for your home depends on your specific situation — the age of the home, your current insulation type, your DTE Energy / Consumers Energy bills, and your goals. If you’re comparing options and want to understand what spray foam would actually cost and save for your home in Michigan, reach out for a free consultation.

We work with homeowners across the Michigan market to evaluate whether spray foam makes financial sense for their specific project — and to give you the numbers you need to make a confident decision.