Demilec Attic Air Sealing: The Dallas Owner’s Guide
If your Demilec spray foam attic air sealing has failed or is underperforming, we stock the materials and know-how to get it fixed. In Dallas, a Demilec attic air sealing repair or touch-up typically runs between $900 and $2,800 depending on square footage, access, and how much of the existing foam needs to be removed and replaced. Most jobs are completed in a single day, and we carry Demilec-compatible product on our trucks for same-week scheduling.
The way most homeowners discover a problem is subtle. You notice the upstairs runs five degrees hotter than the downstairs in August. Your energy bill ticks up month over month. Or you poke your head into the attic and spot areas where the foam has shrunk back from the rafters, leaving a visible gap. That gap is the whole story: air sealing only works when the seal is continuous. One open seam lets conditioned air escape and attic air pour in, and in Dallas, attic air in July can sit at 140 degrees. Glenn Hartley has walked enough Dallas attics to tell you the same thing he tells every customer: a failed air seal never fixes itself. It gets worse every summer.
Key Takeaways
- Demilec air sealing problems usually show up as uneven room temperatures, higher cooling bills, or visible gaps where foam has pulled away from framing.
- Repairs in Dallas generally range from $900 to $2,800 installed, and we give you the exact written price before any work starts.
- We are an independent installer and servicer of Demilec products, not a Demilec corporate entity, and we service what other contractors won’t touch.
- Most Demilec air sealing repairs take one day, and we can usually schedule within the same week.
- Every repair carries our 365-Day Done Right Promise, in writing, at no additional charge.
Which Demilec Models This Applies To
Demilec produces several spray foam lines that get used for attic air sealing, and compatibility matters more than most homeowners realize. The main product families we work with are Heatlok HFO, Heatlok Soya, Sealection 500, and Sealection Agribalance. Heatlok is a closed-cell foam, typically installed at one to two inches in attics to create an air and vapor barrier in one pass. Sealection 500 is an open-cell foam, more common in vented attics where the goal is air sealing at the roofline while still allowing some moisture movement. They do not behave the same way, and they are not interchangeable. If someone patches an open-cell job with closed-cell foam or vice versa, you can end up with moisture trapped where it should not be, and in a Dallas attic that cycles between dry heat and humid Gulf air, that mistake shows up as damp sheathing or mold within a couple of years.
Here is the compatibility gotcha that trips up a lot of homeowners: the foam itself is not the only part that matters. The air sealing system includes the foam, the ignition barrier or thermal barrier applied over it (often an intumescent coating), and the sealant used around penetrations like can lights, plumbing stacks, and electrical boxes. A failed Demilec air seal is often not a foam failure at all. It is a failure of the sealant bead around a penetration that has cracked or peeled. Before you pay anyone to re-foam a whole attic, someone needs to inspect the full system and identify exactly where the seal broke. That is the difference between a $900 targeted repair and a $6,000 re-foam.
On the OEM versus aftermarket question: Demilec foam is a two-part chemical system, and the company has a proprietary formulation. We do not substitute generic foam into a Demilec repair unless the homeowner specifically asks for it and understands the tradeoff. The reason is simple. When you patch Demilec with another brand, the adhesion and expansion characteristics will not perfectly match the original. You might get a bond that looks fine for a year and then separates. For a repair you want to last, we use the matching product. It costs a little more, and it is the only way we will stand behind it for 365 days.
Signs Your Demilec Attic Air Sealing Is Failing
- Upstairs rooms that never cool down evenly. This is the classic first sign. The air seal at the attic floor or roofline is no longer continuous, so superheated attic air is bleeding into the living space or conditioned air is escaping upward. Your AC works harder and the upstairs still feels swampy by mid-afternoon.
- Energy bills climbing with no change in habits. If your July electric bill jumped $40 or $60 compared to last year and your HVAC is in decent shape, the air seal is the first suspect. An attic air seal that has failed can add 20 to 30 percent to your cooling load in a Dallas summer.
- Visible gaps where foam has shrunk or pulled back. Closed-cell foam should look tight against the framing. If you see cracks, curling edges, or daylight coming through where foam should be, the seal is compromised. Open-cell foam can shrink slightly as it cures, but significant pull-back means the foam was not applied correctly or the substrate was too hot or too cold during application.
- Dust, attic smell, or pest evidence in the living space. A proper air seal keeps more than air in and out. It blocks the fine dust, insulation fibers, and whatever else lives in your attic. If you are suddenly noticing attic dust on your baseboards or catching a whiff of the attic when the AC kicks on, you have a breach.
- Moisture stains or musty odor near the roofline. This one is serious. When an air seal fails at the roofline in a humid climate like Dallas, warm, moisture-laden air can reach the underside of the roof deck, condense, and soak the sheathing. If you see stains, deal with it quickly before the roof deck needs replacing too.
Replacement Cost & What’s Included
We have given the broad range above: $900 to $2,800 for most Dallas-area Demilec air sealing repairs. Let us break that down so you understand what drives the price. A targeted sealant-and-patch repair around a few failing penetrations, where the foam is largely intact, runs $900 to $1,400. A repair that involves removing failed foam from a section of the attic and re-foaming, say a 200 to 400 square foot area, typically runs $1,500 to $2,200. A full attic re-seal where the original foam has failed broadly or was installed wrong to begin with runs $2,500 to $2,800 and up depending on square footage and access difficulty. Attics with low clearance, existing blown-in insulation that must be temporarily moved, or extensive electrical work to work around will land at the higher end.
Every price we quote is a written price delivered before any work starts. That is the Kingswell Way and it is not negotiable at our shop: you know the number, we honor the number, and there are no door-step surprises. We do not price by the square foot with hand-waving. We walk the attic, measure the failed areas, and write a specific scope. The price includes removal of failed material, surface prep, new Demilec foam or Demilec-compatible sealant, any required protective coating, and full cleanup. You get a written guarantee on the repair, 365 days, and if anything fails within that year we come back and fix it at no charge. That is not a marketing line. It is the same promise in writing on every job we do in Dallas.
DIY or Call Us?
Spray foam air sealing is one of the few attic improvements we actively recommend against doing yourself, and we say that knowing full well it sounds self-serving. Here is the honest version. Working with two-part spray foam requires proper respirator protection, skin coverage, and an understanding of how the foam expands and cures. Mess up the mix ratio or apply it at the wrong temperature, and you get foam that never cures properly, off-gasses, and fails within months. There is also a real fall hazard in attics, and a real risk of overspray landing on wiring or recessed light housings where it can create a fire hazard if not handled correctly. The safe DIY work is inspection: go up with a flashlight on a cool morning, look for visible gaps, and take photos. That is genuinely useful. Then call us at (469) 916-4622 and talk through what you found. We will tell you straight whether it needs a repair or whether it can wait. Sometimes the answer is it can wait, and we will tell you that too.
FAQs
Properly installed Demilec closed-cell or open-cell foam should hold its air seal for 20 to 30 years or more, even in Dallas’s temperature swings. What shortens the lifespan is installation error, UV exposure (foam must be covered with a thermal or ignition barrier), and physical movement of framing. If a seal fails within five to ten years, it was almost always installed wrong rather than a product defect.
Most failures are repairable. If the foam is largely intact and the failure is limited to seams, penetrations, or small shrink gaps, a targeted repair is perfectly durable and far less expensive than re-foaming. Full replacement is only warranted when the foam has delaminated broadly from the framing or was applied at the wrong thickness throughout.
Most repairs in Dallas homes take four to eight hours from arrival to cleanup. Larger re-seal jobs may run a full day or spill into a second morning. We give you a committed arrival window before the job, and we leave the attic cleaner than we found it. Call (469) 916-4622 and we will give you a realistic time frame for your specific situation.
We stock Demilec Heatlok HFO, Sealection 500, and the compatible sealants and coatings on our truck, so most repairs do not require a second trip or a material order. We also carry Reflectix products for radiant barrier applications. If you have an unusual Demilec product line, we will confirm availability before scheduling. Call (469) 916-4622 for a free estimate, and we will give you the exact written price before any work begins.
Written by Glenn Hartley, Owner, Woolsey Insulation Dallas at Woolsey Insulation Dallas, serving Dallas and nearby areas.