Foundation services
Crawl space insulation: walls or floor?
Crawl space insulation goes in one of two places: the floor above a vented crawl space, or the perimeter walls of a sealed one.
Find a Foundation Professional What it costs
Written by HyreFoundation Research Desk Primary-source research and fact checking
The short answer
Crawl space insulation goes in one of two places: the floor above a vented crawl space, or the perimeter walls of a sealed one. Mixing them up is the common mistake. In the model code, an unvented crawl space with exhaust ventilation has its perimeter walls insulated, which moves the crawl space inside the house.
Key takeaways
insulate the floor above.
insulate the walls and rim.
in vented crawl spaces trap moisture against joists.
What does crawl space insulation involve?
Vented or sealed decides where insulation goes.
Wet, fallen or moldy batts come out.
Rigid foam or spray foam on walls and rim joists, or properly supported floor insulation.
Air sealing, plus moisture control for sealed crawl spaces.
What moves the price
Strategy and area drive the price. We publish no price figures until we hold enough sourced, dated quotes; see what drives foundation costs.
| Factor | Why it changes the number |
|---|---|
| Wall or floor | Wall area is usually smaller than floor area. |
| Material | Foam board, spray foam or batts. |
| Removal | Old insulation tear-out and disposal. |
HyreFoundation publishes no national average price for this work. Depth to bearing, soil, access and method vary enough between two houses on the same street that a single figure would mislead.
Which strategy fits?
Decide whether the crawl space will stay vented or be sealed first. See encapsulation for the sealed route.
What to ask before you sign
The full checklist is on choosing a foundation contractor.
Where this goes wrong
Moisture condenses and wood can rot.
It splits the difference and usually works worse than either.
A big source of air leaks.
Get connected
Tell us about the work
Three short steps: the job, your home, and how to reach you. Nothing goes to a foundation company unless you agree.
A straight answer first. A person reads it and replies by email, free and with no obligation. Matching is not live yet, so this is not a quote. If a wall is moving or a door frame has racked out of square this week, call a structural engineer first.
Find a Foundation Professional
A person at HyreFoundation reads the request and replies. Matching is not live yet, so this is not a quote.
Questions
Should I insulate my crawl space walls or floor?
Is spray foam good for crawl spaces?
Why is my crawl space insulation falling down?
Does crawl space insulation save energy?
Written and audited by
HyreFoundation Research Desk
Primary-source research and fact checking
We read the model building code, the federal soil and moisture guidance and the insurer position ourselves, and we publish each figure with the document it came from and the date we retrieved it.
Where a number cannot be traced to a primary source, we say so instead of printing it. HyreFoundation does not inspect, engineer or repair foundations. Authorship is organizational: this desk, not a named persona.
- 40
- pages published on this site
- 12
- free tools, each showing its assumptions
- 0
- foundation repairs we perform or sell
- 0
- paid placements or rankings
How this desk works
- Primary sources only. Code statements come from the International Residential Code, Chapter 4, as the model code. Soil statements come from USDA and USGS. Insurance statements come from the policy language and the Insurance Information Institute. We open the source rather than cite a blog that cites it.
- The code is a model, and adoption is local. Your jurisdiction adopts an edition and amends it, and foundation chapters are amended more than most because frost depth and soil are local facts. Every code figure says so.
- We hold no job data. We have no dataset of bids, pier counts or invoices, so no page claims an average from one. Calculators show the arithmetic and the inputs they assumed, and label the result as an estimate.
- We do not diagnose your house. A crack guide can tell you which pattern to measure and when to call a structural engineer. It cannot tell you whether your foundation is failing. An engineer on site does that work.
- We do not repair foundations, and we take no payment for placement, ranking or a favorable mention. Nobody buys a position on this site.
Authorship on this site is organizational: the analysis belongs to the desk rather than to a named individual, and we do not publish credentials we do not hold. Our editorial policy sets out how we source, date and correct what we publish.
Sources & retrieval dates
Information on this page is general and varies with soil, climate, foundation type, building code, insurance policy and circumstance.
It is not engineering, insurance or legal advice, and no page can tell you whether your house has a structural problem: that needs a licensed professional on site.
HyreFoundation is an independent foundation resource, not a repair contractor or an engineering firm, and does not perform, supervise or warrant foundation work.