Demilec Attic Air Sealing in Sunnyvale: What to Know First
We seal Demilec-insulated attics across Sunnyvale, and most jobs are done in a single day. Air sealing typically runs $850 to $2,400 depending on attic size, access, and how many penetrations need work. If your Demilec spray foam is underperforming, the problem is usually not the foam itself - it’s the gaps around top plates, can lights, and duct boots that were never sealed before the foam went in. This page covers what actually goes wrong in Sunnyvale homes and how we fix it. Call (669) 215-4805 any time - a real person answers.
Key Takeaways
- We’re an independent Demilec service provider - not a factory rep, not a franchise.
- Sunnyvale attics fail most often at top plates, can lights, and attic hatches, even with Demilec foam in place.
- Most Demilec air sealing jobs are completed same-day.
- Every job is backed by our Done Right Promise: if it’s not done right, we make it right. For life.
How Demilec Products Fail - and How We Fix Them
Demilec makes good foam. We install it. But after 25 years of crawling through Sunnyvale attics, we know the failure points are rarely the foam itself. Here’s what we actually find:
- Bypass gaps around top plates on Demilec Heatlok HFO jobs. The foam seals the cavity, but the seam where drywall meets framing stays open. Air moves freely from wall cavities into the attic. We pull back existing insulation, seal the top plate with foam or caulk, and re-cover. This is the single most common issue in older Sunnyvale ranch homes near Murphy Avenue.
- Recessed can light leaks in homes with Demilec Sealection 500. Can lights are Swiss cheese for airflow. Older non-IC-rated fixtures get scorching hot, which is why sealing them wrong is a fire hazard. We install rated covers and seal them properly - never just foam over an unrated can. If you have old cans, this is the first thing we check.
- Sunnyvale’s dry-summer heat cycling causes foam shrinkage at penetration points. Around plumbing vents, electrical conduit, and flue pipes, we see hairline gaps open up as the house moves through 90-degree days and 50-degree nights. The Demilec foam is fine - the gap is around it. We re-seal every penetration with a compatible sealant and verify with a thermal camera.
- Attic hatches with Demilec Heatlok spray jobs but zero weatherstripping. Builders spray the attic but skip the hatch. The hatch becomes a big open hole. We build up the jambs, install compression weatherstripping, and add an insulated cover so the hatch actually seals. If your upstairs hallway feels hotter than the rest of the house, this is often the culprit.
- Duct boot disconnects in homes with Demilec open-cell foam. When the register boot loosens from the drywall, conditioned air dumps straight into the attic. Open-cell foam doesn’t stop that. We re-secure boots, seal them with mastic and foam, and re-insulate around the connection. It’s unglamorous work that saves real money on PG&E bills.
Our Demilec Attic Air Sealing Process
Here’s what a Demilec air sealing job looks like from your first call to the final walkthrough:
- 1
You call (669) 215-4805. A live person answers - no voicemail, no answering service, no call center. We ask about your house, your attic, and what’s been bugging you.
- 2
We schedule an assessment. Walt’s team shows up on time, in uniform, background-checked. We inspect the entire attic: top plates, penetrations, hatch, duct boots, can lights.
- 3
We give you a written estimate with real numbers. No vague ranges, no pressure. You’ll know exactly what needs sealing and what it costs. Also, we do free second opinions on any written estimate you already have.
- 4
We do the work. We use Demilec-compatible materials when OEM is required for warranty reasons, and quality aftermarket sealants where they perform the same or better for less. We never gamble with your warranty.
- 5
We verify. Thermal camera check before we leave. If the air movement is gone, we’re done. If it’s not, we’re not.
- 6
You get the Done Right Promise. Lifetime workmanship. If it’s not done right, we make it right - no runaround, no re-quote, no fine print. That’s been the deal since 2000.
What Demilec Attic Air Sealing Costs in Sunnyvale
Here are straight numbers for common Demilec air sealing jobs in Sunnyvale:
- Basic top plate and penetration sealing in a standard 1,500 sq ft ranch: $850-$1,300
- Full air sealing including duct boots and can lights: $1,400-$1,900
- Attic hatch rebuild with weatherstripping and insulated cover: $450-$700
- Whole-attic air sealing plus Demilec foam touch-up on a larger two-story home: $1,900-$2,400
What moves the price? Attic accessibility, how many recessed lights you have, whether duct boots need re-securing or just re-sealing, and how much existing insulation has to be moved and then put back. No trip charge inside our service county, and seniors and veterans always get 10% off. Call (669) 215-4805 for an exact quote - estimates are free.
Why Sunnyvale Homeowners Call Walt’s Insulation for Demilec Work
We’re the one down the road. Walt Brenner has been doing this since 2000, and unlike the franchise outfits, he’s the one whose name is on the truck and the license. When you call, you get a real person - 24/7, including weekends and holidays. Our techs know Demilec products because we install them. We also work with Owens Corning, Rockwool, Icynene, Johns Manville, CertainTeed, Knauf, GreenFiber, and Reflectix - so if a job calls for something besides Demilec, we’re not stuck. Good insulation should be invisible - you only notice it when it’s missing. We make sure it stays invisible.
FAQs
No. Air sealing does not void a Demilec foam warranty. In fact, it often improves real-world performance. We use materials compatible with Demilec chemistry and follow manufacturer installation guidelines to keep your coverage intact. If you’re unsure about a specific warranty clause, call (669) 215-4805 and we’ll walk through it with you.
We use Demilec products when the job calls for it - especially on warranty-sensitive areas - and quality aftermarket sealants where they perform as well or better for less money. We’ll always tell you which we’re using and why before we start. No surprises.
Most Demilec air sealing jobs are done in one day. Larger homes with multiple can lights, duct boot issues, or a hatch rebuild can take a second day. We schedule around your life - not the other way around. Call (669) 215-4805 and we’ll give you a straight answer.
Sealing is almost always cheaper than adding foam, and it’s the better first move. Adding foam over unsealed gaps is like putting on a heavier coat without buttoning your shirt - you’re still losing heat through the openings. Air sealing typically costs $850 to $2,400, while adding new Demilec foam can run two to three times that. We’ll tell you honestly which makes sense for your house.
It means we install and service Demilec products, but we’re not a Demilec factory outlet and we’re not authorized by Demilec to act on their behalf. We call things as we see them without a corporate sales target hanging over our heads. If Demilec foam is the right answer, we’ll tell you. If something else fits better, we’ll tell you that too. That’s been the Walt’s way since 2000.
Often, yes. We keep our crews close to Sunnyvale, and same-day assessments are common depending on scheduling. Call (669) 215-4805 - a live person will tell you exactly when we can be there.
Written by Walt Brenner, Owner, Walt’s Insulation at Walt’s Insulation, serving Sunnyvale and nearby areas.