R-8 Insulation Rolls
The lowest-cost R-value in the standard fiberglass line — built for metal building condensation control and unconditioned storage. 2.5 inch thickness, $0.48 per square foot wholesale.
What R-8 Insulation Is For
R-8 fiberglass insulation sits at the entry point of the wholesale fiberglass catalog. The R-value rating — 8 — represents the lowest thermal resistance in the standard product line, but the practical purpose of R-8 is not thermal performance. It is condensation control.
Metal buildings have a recurring physics problem: in cold weather, the inside surface of a metal panel drops below dew point and warm humid interior air condenses on it. Drips form along purlins. Water pools on the floor below. Tools rust. Stored materials get damaged. Vinyl-faced R-8 fiberglass installed against the panel solves this for a fraction of the cost of deeper R-values: the facing acts as a vapor retarder that keeps interior humidity from reaching the cold metal surface, eliminating the condensation cycle.
At Insulation Overstock, R-8 is available in every NAIMA-certified facing in the catalog. VR-R Plus is the cheapest option at $0.48 per square foot, with WMP-10, WMP-30, and WMP-50 facings running $0.54 per square foot for slightly higher tensile strength and perm rating flexibility.
R-8 Thickness and Composition
R-8 Nominal Thickness
R-8 fiberglass insulation has a nominal installed thickness of 2.5 inches. The thin profile fits shallow metal building purlin cavities and pole barn girt spaces where deeper R-values like R-13 (3.625") or R-19 (6.25") would not accommodate.
R-8 Roll Dimensions
R-8 rolls ship in 4-foot, 5-foot, and 6-foot widths. WMP-30 is also available in 8-foot wide rolls. Roll lengths run longer for R-8 than higher R-values (typically 50-100 feet per roll) because the thinner material packs more square footage per roll.
Facing Options for R-8
All four NAIMA-certified facings are available in R-8: VR-R Plus (PSP), WMP-10 (PSK-STD), WMP-30 (PSK-HD), and WMP-50 (PSKP). Black-faced variants are also available for aesthetic preference. Detailed facing selection guidance is on the facing comparison page.
Where R-8 Insulation Works Best
R-8 vs Higher R-Values
R-8 is the right pick for a narrow set of applications. For most occupied or conditioned buildings, stepping up to R-13 or R-19 produces a much better value despite the higher per-square-foot material cost.
| R-Value | Thickness | Wholesale (VR-R Plus) | Best For |
|---|---|---|---|
| R-8 | 2.5" | $0.48 | Condensation control, storage |
| R-10 | 3.0" | $0.52 | Light unconditioned |
| R-13 | 3.625" | $0.65 | 2x4 walls, occupied buildings |
| R-19 | 6.25" | $0.90 | 2x6 walls, conditioned |
Choose R-8 when: the building is unconditioned, the primary need is condensation control, the cavity depth is limited, or the budget cannot accommodate deeper R-values.
Upgrade to R-13 when: the building will be heated at any point, the framing is 2x4 with full cavity depth available, or you want code-compliant performance for Zones 1-2.
Upgrade to R-19 when: the building is heated year-round, the framing is 2x6, or the location is in Zones 3-4 where R-19 is the IECC wall minimum.
R-8 Insulation Cost
R-8 is the lowest per-square-foot fiberglass insulation in the catalog. Wholesale rates:
- VR-R Plus (vinyl-reinforced PSP): $0.48 / sq ft
- WMP-10 / WMP-30 / WMP-50: $0.54 / sq ft
- Black-faced variants: $0.52 to $0.58 / sq ft
Add freight ($395-$745 by state) and your offered service fee within the published acceptable range. Run the Insulation Calculator for your specific square footage and state.
R-8 Insulation FAQ
What is R-8 insulation used for?
R-8 fiberglass insulation is the lowest-cost R-value in the standard line, used primarily for metal building condensation control and unconditioned storage buildings. It is the right pick when the goal is preventing roof and wall sweating rather than maintaining tight indoor temperatures.
How thick is R-8 insulation?
R-8 fiberglass insulation is 2.5 inches thick at nominal installed depth. The thin profile fits shallow metal building purlin spaces and pole barn girt cavities that cannot accommodate deeper R-values.
How much does R-8 insulation cost per square foot?
Wholesale R-8 fiberglass insulation costs $0.48 per square foot for VR-R Plus and $0.54 per square foot for WMP-10, WMP-30, or WMP-50. It is the cheapest R-value in the catalog by a meaningful margin.
Is R-8 enough for a metal building?
Can R-8 prevent metal building condensation?
Yes. R-8 vinyl-faced fiberglass installed against metal panels with the facing toward the interior creates a vapor retarder that keeps warm humid air from reaching the cold metal surface where condensation forms. This is the standard low-cost condensation solution for unconditioned metal buildings.
What climate zones is R-8 appropriate for?
R-8 is not a code-compliant wall or ceiling R-value in any IECC climate zone for conditioned buildings. It is used specifically for condensation control in unconditioned buildings regardless of climate zone, where code minimums do not apply.
Order R-8 Fiberglass Insulation
Wholesale R-8 with every facing available. The lowest per-square-foot pricing in the catalog for condensation control and unconditioned storage projects.
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