InstaBidsFor homeowners
Spray foam vs fiberglass insulation: which fits your home?
Choose Spray foam for sealing air leaks while insulating (DOE, 2012); Fiberglass (batts and rolls) for relatively easy installation (DOE, 2012).
The right choice depends on whether you want a relatively easy install or can hire a trained installer, how much air leaks through the wall, attic or ceiling, and where it goes: open walls and attic floors, or cathedral ceilings, roof decks and walls with the siding off.
| Factor | Spray foam | Fiberglass (batts and rolls) |
|---|---|---|
| Sealing air leaks while insulating (DOE, 2012) | an excellent air barrier; can eliminate the need for separate air-tightness detailing | not air-tight; careful installation is necessary to reduce air leaks around edges, which significantly reduce R-value |
| Relatively easy installation (DOE, 2012) | installation requires a trained installer; limited attic access may impede proper installation | DOE lists relatively easy installation among its advantages |
| Irregular spaces and obstacles (DOE, 2012) | fills even the smallest cavities, including spaces around electrical boxes, wiring, plumbing, and nails | hard to fit into irregular spaces; loses R-value when compressed |
| Where DOE lists it for use (DOE, 2012) | the perimeter of vented attics; roof deck of cathedralized attics; vaulted ceilings; flat roofs; basement walls; walls with siding removed | open walls; attic floor and kneewalls; basement or crawlspace ceiling in dry climates only |
| Exterior walls, cathedral ceilings and standard framing (DOE, 2022) | DOE: "Use higher R-value insulation, such as spray foam, on exterior walls and in cathedral ceilings to get more insulation with less thickness." | available in widths suited to standard spacing of wall studs and attic or floor joists |
| Moisture (DOE, 2012) | very resistant to moisture, especially when treated with sealant | DOE lists batts for a basement or crawlspace ceiling in dry climates only |
| Fire protection (DOE, 2012) | plastic foam insulation must be covered with a thermal barrier to retard the spread of fire | batts with flame-resistant facing are available for basement walls in which the insulation will be left exposed |
| What it is made of (DOE, 2022) | two types, closed-cell and open-cell; both are typically made with polyurethane | flexible products made from mineral fibers, such as fiberglass and rock wool |
InstaBids is an AI-run marketplace for homeowners and property managers: describe a home job once, by chat or through your own AI assistant, add photos, and get multiple written quotes on the same scope, compared apples to apples, with no phone calls or home visits before you pick.
Post your job on InstaBids, and contractors can bid in writing on one written scope.
- Describe it onceBy chat, or through your own AI assistant, and add photos.
- Post it and send itContractors bid in writing on that scope.
- Compare line by lineEvery quote is written against the same scope.
- You chooseContact details stay hidden until you pick and they confirm.
For your AI assistant
MCP connector · REST API · plain HTMLHand any of these to your assistant and it can help you write this job's request; you send the request yourself. What you type in the job box above goes into the prompt these buttons carry. The connector asks you to sign in to your InstaBids account the first time.
- MCP connector URL
https://instabids.ai/api/agent/mcp - Agent API (OpenAPI)
https://instabids.ai/openapi.json - Start-request link
https://instabids.ai/intake?from=options-compare--spray-foam-vs-fiberglass-insulation&utm_source=us&utm_medium=page&utm_campaign=options&page_type=options#job=insulation%20installation - Prompt for any AI, with your job
- ChatGPTOpens with the prompt
- ClaudeOpens with the prompt
- GrokOpens with the prompt
- GeminiCopies the prompt, then opens
Every page is plain HTML. Steps for every assistant: add to your assistant.
| Priority | Choose |
|---|---|
| sealing air leaks while insulating (DOE, 2012) | Spray foam |
| filling a cavity around electrical boxes, wiring and plumbing (DOE, 2012) | Spray foam |
| relatively easy installation (DOE, 2012) | Fiberglass (batts and rolls) |
What does attic insulation cost?
For attic insulation prices, see How much does attic insulation cost?
Get written bids
Contractors who take part bid on one written scope card, so nobody visits before you see any prices.
Contact details stay hidden until the homeowner picks a contractor and they confirm the connection.
Sources for the facts on this page
- U.S. DOE Building America Best Practices Series Vol. 17, Energy Renovations: Insulation (PNNL-20972, prepared by Pacific Northwest and Oak Ridge National Laboratories, May 2012), government, read 22 October 2026.
- U.S. Department of Energy, Energy Saver Guide (2022), government, read 22 October 2026.
- U.S. Department of Energy, Building Science Education Solution Center, Types of Insulation, government, read 22 October 2026.