Insulation · Project planning

Crawl-Space Insulation Calculator

Compare insulating the floor above a crawl space with insulating its perimeter walls. Add a separate rim-joist area and deduct measured openings.

By Alish Gautam, Software Developer · Updated · Calculation methodology

Start with the editable example below. Dimensions retain their physical size when units change. Region sets currency labels without converting currencies; confirm entered quotes after changing region. Thermal inputs labeled US R retain that unit in every region.

Basic settings
Choose the estimating method.
Choose an actual product quantity workflow after selecting the thermal boundary.
Editable arithmetic example. Replace with your project or product specification.
Editable arithmetic example. Replace with your project or product specification.
Product settings
Product and system dimensions
Editable arithmetic example. Replace with your project or product specification.
Editable arithmetic example. Replace with your project or product specification.
Editable arithmetic example. Replace with your project or product specification.
Optional supplier product name, chart revision or quote reference, saved in shared project state.
Advanced settings
Advanced planning settings
Planning allowance, not a code or industry requirement. Set zero to order the exact rounded takeoff.
Cost settings · USD
Optional quote prices
Optional supplier quote in the selected currency. Blank omits cost.

Project takeoff

Whole packages round up. Allowance is separate from purchased surplus. Prices omit labor, delivery, tax and other items unless explicitly entered.

Perimeter
100 ft
Gross selected boundary area
600 ft²
Rim-joist area added
0 ft²
Net selected boundary area
600 ft²
Net requirement
600 ft²
Allowance
60 ft²
Planned requirement
660 ft²
Unrounded package requirement
16.5
Packs / units to buy
17
Purchased coverage
680 ft²
Surplus beyond planned requirement
20 ft²

Supplier-ready material list

Packs / units to buy
17

Choose the thermal boundary with a project-specific moisture, ventilation and combustion plan. Neither strategy is universally correct.

How it works

Floor area = length × width. Wall area = 2 × (length + width) × wall height − openings. Net area plus rim area passes to coverage-pack, layered-sheet or board-foot kit rounding.

Assumptions and limitations

Choose the thermal boundary with a project-specific moisture, ventilation and combustion plan. Neither strategy is universally correct.

Whole packages round upward after the chosen allowance. Physical geometry and purchase reserve are separate. Manufacturer and project specifications override editable examples; the selected region does not establish a local code requirement.

Sources and boundaries

Natural Resources Canada: Keeping the Heat In — Section 6: Basements and Crawl Spaces

Open the source · Web guidance; edition not stated · Reference checked 2026-10-04

Scope: Foundation, moisture and crawl-space retrofit guidance

Used for: Floor versus wall strategy context.

Does not establish: One strategy applies to every crawl space; Moisture design certification.

Quantity calculations do not select the correct thermal boundary.