How Much Insulation for a 2,000 Sq Ft Attic?
Quick Answer
For a 2,000 sq ft attic targeting R-38, you need about 63 rolls of R-38 fiberglass batts or 60 to 80 bags of blown-in cellulose. Cold climates targeting R-49 need about 80 rolls.
- R-38 fiberglass batts: ~63 rolls
- R-49 fiberglass batts: ~80 rolls (cold climates)
- Blown-in cellulose (R-38): 60–80 bags
- Add 10% for irregular joist spacing and obstacles
Formula
Divide attic square footage by the coverage per roll from the packaging. For 16-inch OC joists, each R-38 roll covers about 32 sq ft.
Step-by-Step Calculation
- 1
Attic area
2,000 sq ft
- 2
R-38 batts (32 sq ft per roll)
2,000 ÷ 32 = 62.5 → 63 rolls
- 3
Blown-in cellulose
2,000 × 0.03–0.04 bags/sq ft = 60–80 bags
- 4
Add 10% waste
63 × 1.10 = 69 rolls
Insulation for 2,000 Sq Ft Attic by Type
| Insulation Type | R-Value | Depth | Quantity | Material Cost* |
|---|---|---|---|---|
| Fiberglass Batts | R-30 | ~10" | 53 rolls | $800–$1,300 |
| Fiberglass Batts | R-38 | ~12" | 63 rolls | $1,000–$1,600 |
| Fiberglass Batts | R-49 | ~16" | 80 rolls | $1,270–$2,000 |
| Blown-In Cellulose | R-38 | ~10.5" | 67 bags | $670–$1,070 |
| Blown-In Fiberglass | R-38 | ~14" | 73 bags | $870–$1,330 |
*Materials only. Professional installation adds $0.50–$1.50 per sq ft.
Pro Tips
- For 2,000 sq ft, blown-in cellulose is the clear winner over batts — the blower machine handles this area in 5–6 hours with 2 people. Laying individual batts over 2,000 sq ft of joists (often awkward attic spaces with low roof lines) would take 12–16 hours.
- Mark the target depth on every truss or rafter with a marker before blowing — for R-38 cellulose, that is about 10.5 inches. Without depth markers, you end up with uneven coverage: too thick in some areas, too thin in others.
- Check for and seal the top plates of all interior walls from the attic side before insulating. In a 2,000 sq ft house, there are typically 300–500 linear feet of top plates with gaps — sealing these with caulk or spray foam cuts air infiltration by 20–30%.
- In cold climates targeting R-49 to R-60 (14–16 inches of cellulose), ensure your attic ventilation is adequate. The thicker insulation leaves less clearance at the eaves — you may need to add baffles or increase ridge vent capacity.
Key Cost Factors
- Blown cellulose for 2,000 sq ft at R-38 needs 60–80 bags at $11–$15 each = $660–$1,200. For R-49 (cold climates), increase to 80–100 bags = $880–$1,500. The blower machine is free with purchase of 20+ bags at most big-box stores, so the only cost is the cellulose itself and a helper.
- Professional insulation for 2,000 sq ft costs $3,000–$6,000 installed. The DIY materials-only cost of $660–$1,200 saves $2,300–$4,800. With typical energy savings of $300–$600 per year, the DIY investment pays back in 1–3 years.
Common Mistakes to Avoid
- Using the wrong R-value for your zone. A 2,000 sq ft attic needs R-38 to R-60 depending on climate. Under-insulating a cold-climate attic wastes energy for the life of the home.
- Blocking soffit ventilation. Pushing insulation into the eaves chokes airflow, causing moisture and ice dams. Install baffles to keep the vent path open.
- Skipping air sealing. Blowing insulation over unsealed penetrations lets conditioned air escape past it. Seal gaps and top plates before adding depth.
- Compressing the insulation. Packing batts tighter than their rated thickness reduces the R-value; loose-fill needs to reach the correct settled depth.
Related Project Considerations
- Blown-in suits large attics. Over 2,000 sq ft, blown cellulose or fiberglass is faster and fills around framing better than cutting and fitting batts.
- Handle recessed lights safely. Non-IC-rated fixtures need clearance from insulation; box them out or upgrade to IC-rated units to avoid a fire hazard.
- Insulate and seal the hatch. The attic access is a common heat leak — weatherstrip it and add a rigid insulated cover.
Frequently Asked Questions
What R-value do I need for my attic?
R-38 for climate zones 1–3 (southern US), R-49 for zones 4–5 (mid-US), and R-60 for zones 6–7 (northern US and Canada). Check the DOE climate zone map for your area — your local code may exceed these minimums. Most existing homes have R-19 or less in the attic, so adding insulation to reach R-38 or higher is one of the most cost-effective energy upgrades available.
How many bags of blown-in insulation for a 2,000 sq ft attic?
Plan on 60 to 80 bags of blown-in cellulose for R-38 over 2,000 sq ft, depending on existing insulation depth and joist spacing. The exact count is printed on each bag as coverage at a target R-value, so check the label before buying. Most home improvement stores lend a blowing machine free with the purchase of 20+ bags — ask at checkout, as this saves $200–$400 in equipment rental.
Is it worth adding attic insulation myself?
Yes. Attic insulation is one of the highest-return DIY energy upgrades — you save the $0.50–$1.50 per sq ft installation cost, and the materials often pay for themselves within 2–4 years through lower heating and cooling bills. Many home stores lend a blower machine free with a qualifying bag purchase. The job is straightforward but dusty; wear a respirator, goggles, and long sleeves, and avoid stepping between joists.