Insulation 101: How to Pick the Right Material & Save Big on Energy
Oct 8
4 min read
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Keeping your home comfortable without breaking the bank on heating or cooling starts with choosing the right insulation. The wrong insulation or poor installation can cost you in comfort and utility bills. In this post, I’ll walk you through what “R-value” means, the best insulation materials in different situations, their pros & cons, and what makes the biggest difference when picking insulation.
What is R-Value & Why It Matters
R-value measures how well a material resists heat flow. Higher R = more resistance = better insulation.
Different areas of the country (and even different parts of your house) need different R-values (attic vs wall vs crawl space). For example, under the 2021 International Energy Conservation Code (IECC), recommended R-values for attics in uninsulated wood‐framed homes vary by climate zone: in cold/hot mixed/humid zones, you might need R-49 to R-60 in the attic.
Types of Insulation: What’s Available & How They Compare
Here are the main types of insulation homeowners use, with typical R-values, cost, pros/cons, and best use cases.
Insulation Type | Approx R-Value per Inch | Approx Cost / Sq Ft* | Pros | Cons | Ideal Uses | |
Closed-Cell Spray Foam | ~ R-6 to R-7 per inch | High upfront cost | Great air sealing + high R per inch + moisture resistance + adds structural strength | Expensive; needs professional installation; may outgas; not great when budget is tight | Tight spaces, irregular cavities, walls, or roofs where space is limited; basement walls; sealing leaks | |
Open-Cell Spray Foam | ~ R-3.5 to R-4 per inch | Less than closed-cell spray foam, but still premium | Better for sound control; fills gaps; more flexible; cheaper than closed cell | Less moisture barrier; lower R; may absorb water; not as rigid | Interior walls; soundproofing; when budget won’t stretch to closed cell | |
Fiberglass (Batts and Rolls) | ~ R-2.9-4.3 per inch for batts; blown-in a bit lower in some cases | Moderate to budget friendly | Widely available; DIY-friendly; good for standard framed walls/attics where cavity depth is decent | Gaps or compression reduce effectiveness; moisture can be an issue; performance drops if installed poorly | Standard walls with 2×4 or 2×6 framing; accessible attics; retrofit where budget matters | |
Blown-In Cellulose | ~ R-3.2-3.8 per inch | Often similar to fiberglass but sometimes more expensive depending on access | Good eco credentials; fills odd shapes; good thermal performance. | Settling over time can reduce R value. moisture issues if exposed; may require thicker layers for high R | Attics; retrofit walls; places with irregular or obstructed cavities | |
Rigid Foam Panels (Foam Board) | Varies: Polyisocyanurate ~ R-6 per inch; XPS ~ R-5; EPS ~ R-4 | Higher cost, especially for thicker slabs | High R per inch; durable; good moisture resistance; builds continuous insulation layer (reduces thermal bridging) | More expensive; installation requires precision; edges/seams must be sealed; sometimes bulkier or more difficult to retrofit | Exterior walls; basement walls; roof decks; situations where wall cavities are shallow but you still need high R | |
Mineral Wool (Rockwool) | ≈ R-3.0-3.3 per inch | More expensive than fiberglass; somewhere between mid & high range | Fire resistant; good sound control; moisture tolerant; holds its R value better if wet than some others | Higher cost; batts are heavier; cutting/handling can be messier; fewer size options sometimes | Fire-rated assemblies; soundproofing; damp areas; when you want durability and safety as well as insulation |
*Cost varies heavily by region, labor, accessibility, and material availability. Always get local quotes.
Key Factors That Determine Best Choice
You pick insulation material, sure—but these other things often matter more in real savings and comfort:
Professional Installation: Even the best insulation can underperform badly if there are gaps, compression, or improper sealing around edges/windows. Air leaks are a huge loss.
Climate & Local Code Requirements: What climate zone you’re in affects what R-value is cost-effective. In hot and humid zones, moisture control matters more; in cold zones, high R for walls/attic is more important. Also, local building codes may require certain minimums.
Space available: If your wall is shallow or there are framing constraints, you might need high R per inch options (spray foam, rigid foam).
Moisture control & ventilation: Poor moisture management ruins insulation and creates mold, rot, etc. Some materials resist moisture better (closed cell foam, mineral wool, rigid boards); with others you must ensure vapor barriers, ventilation, etc.
Cost vs Long-Term Payback: Upfront cost is one thing; utility savings over years is another. Sometimes a more expensive insulation (higher R or high performance) pays off via lower heating/cooling cost, increased comfort, maybe even resale value.
Ideal R-Values in Dallas / North Texas
Here’s what local builders, energy experts, and code guides generally recommend for Dallas / DFW homes:
Area of the Home | Recommended R-Value (Dallas – Climate Zone 3) | Common Materials & Notes |
Attic | R-38 to R-60 | The attic loses and gains the most heat. For most Dallas homes, R-49 (about 17" of blown-in fiberglass) offers the best value. Open-cell spray foam at ~R-23 (5.5") also performs well when applied to the roofline. |
Walls – 2x4 Construction | R-13 to R-15 | Standard batt insulation or 3.5" open-cell spray foam (R-15) fits these cavities. Many older Dallas homes have under-insulated 2x4 walls—worth checking during renovations. |
Walls – 2x6 Construction | R-19 to R-21 | Thicker walls allow 5.5" open-cell spray foam (R-23) or R-21 fiberglass batts, improving soundproofing and comfort. Ideal for newer builds or remodels. |
Floors Over Crawl Spaces | R-19 to R-25 | Especially important in pier-and-beam homes around DFW. Proper floor insulation prevents drafts and reduces winter energy loss. |
AtticProsTX Recommendation
At AtticProsTX, we recommend aiming for R-49 in the attic for most homes in the Dallas–Fort Worth area. It’s the ideal balance between energy savings and cost efficiency for our Climate Zone 3 conditions.
For walls, we typically suggest:
2x4 construction: R-15 open-cell spray foam or R-15 fiberglass batts
2x6 construction: R-23 open-cell spray foam or R-21 fiberglass batts
These levels help homeowners maintain comfortable indoor temperatures year-round while keeping monthly utility costs under control. We’ve found that open-cell spray foam performs exceptionally well in DFW homes—it seals air leaks, reduces noise, and holds up against our humid summers.
If your insulation is older, uneven, or compacted, upgrading can make an immediate difference in comfort and HVAC performance. Our team offers free attic inspections and will walk you through the best insulation options for your specific home and budget.
