Seven spray foam myths Central Ohio homeowners still hear

Spray foam draws strong opinions, and much of what Central Ohio homeowners hear at the hardware store or read online is half right. Here are seven claims that come up again and again, with what building science and the Residential Code of Ohio actually say.

Myth 1: A house needs to breathe, so sealing it is bad

Half true. A house needs fresh air, and the people in it need it far more than the framing does. The trouble with relying on leaks is that leaks deliver air in the wrong amounts at the wrong times: too much on a windy January night, almost none on a still day in May, and always by way of dusty attics and damp crawl spaces. The Residential Code of Ohio answers this directly for new homes by capping air leakage at 5 air changes per hour at 50 pascals and making whole-house mechanical ventilation mandatory. The modern rule is build tight and ventilate on purpose, and a retrofit that tightens an older house should follow the same idea with a planned fresh air path.

Myth 2: Spray foam rots roofs

Foam does not rot anything; water does. Roof sheathing gets into trouble under foam in three situations: open-cell sprayed against a cold deck without a vapor retarder coating, closed-cell that is too thin under added batts, and foam sprayed over a leak or a wet deck. The Central Ohio code handles the first two directly. In Climate Zone 5 an unvented roof needs foam that is a Class II vapor retarder or is coated to become one, and when fibrous insulation is added below, the foam against the deck must reach at least R-20. The third is a process step: a moisture reading and a sound roof before any spraying. The roof deck moisture FAQ goes deeper.

Myth 3: Foam off-gasses forever

Properly mixed and cured foam is an inert plastic. The exposure concern is during spraying and curing, when isocyanates are in the air. OSHA identifies them as a cause of occupational asthma, which is why applicators wear respirators and occupants leave until the manufacturer re-entry time has passed. A strong fishy or chemical smell that hangs on for weeks is not normal curing. It points to foam mixed off-ratio or sprayed outside its temperature limits, and it should be reported rather than waited out.

Myth 4: More R-value is always the answer

In most older Columbus houses the bigger loss is air, not thin insulation. Stacking more loose fill over an attic floor riddled with open chases and a gap around the chimney leaves those leaks untouched, and warm air keeps carrying heat into the attic, which is also how ice dams get started. Seal first, then add depth. A blower door test tells you which problem is bigger in your house.

Myth 5: Closed-cell is always better than open-cell

Closed-cell delivers roughly twice the R-value per inch and slows vapor, so it is the right call at rim joists, crawl walls, steel buildings, and many roof decks. Open-cell costs less per board foot, fills deep cavities well, and absorbs more sound, so it makes sense in deep new-construction roof framing, 2x6 walls, and interior walls. The right product depends on the surface, and a good quote explains the choice for each one. The closed-cell versus open-cell comparison lays it out.

Myth 6: Spray foam makes a house impossible to sell

Most of the frightening stories online come from the United Kingdom, where lenders and surveyors objected to foam on roof timbers. Around Columbus the practical issue is documentation. An inspector who cannot see the roof sheathing will note it, and buyers want to know what sits behind the foam. Photos of the deck before spraying, the product and its evaluation report, the thickness, and a written warranty turn that note into a routine line. Selling a house with spray foam covers what to keep.

Myth 7: There is still a federal tax credit for insulation

Not for 2026 work. The Section 25C Energy Efficient Home Improvement Credit ended for property placed in service after December 31, 2025, and the IRS treats an improvement as placed in service when installation is complete. In Central Ohio the remaining help is income-qualified, through Columbia Gas WarmChoice, the AEP Ohio HELP program, and the state weatherization program. For most households the return now comes from lower bills and a more comfortable house.

Where these myths come from

Most of them started with something real. Early open-cell roof decks in cold climates were sometimes sprayed without the vapor control the code now requires in Zone 5, and a few of those decks did get wet. Off-ratio jobs do smell, and the owners who lived through one tell the story loudly. UK lending problems were genuine for the people caught in them. And the advice that houses need to breathe dates from an era when houses leaked so much that nobody had to plan for fresh air. The lesson running through all of it is the same: the problems trace back to design and installation choices, which is why the questions you ask before the job matter more than the product name on the drum.

The short version

Seal before you stack, match the foam to the surface, follow the Zone 5 roof rules, keep the paperwork, and plan for fresh air. If you have been told something that does not sound right, send us a message or give us a call and we will talk it through.