Demilec Crawl Space Encapsulation & Vapor Barrier in Sunnyvale: What to Know First
If you own a Demilec spray foam system in your Sunnyvale crawl space and it’s failing, delaminating, or letting moisture through, we can fix it. As an independent Demilec service provider, Walt’s Insulation handles crawl space encapsulation and vapor barrier work on Demilec installations across Sunnyvale, typically completing most jobs in one to two days. Honest pricing runs from about $2,100 for a straightforward vapor barrier replacement to $9,500+ for a full encapsulation with Demilec-compatible foam reapplication. Call (669) 215-4805 and a real person answers, day or night.
This page is for Sunnyvale homeowners with existing Demilec products, whether you know the exact product line or just know the foam in your crawl space is failing. We’ll walk you through what goes wrong, what it costs, and how we approach the work.
How Demilec Products Fail - and How We Fix Them
Demilec makes solid foam products, but no spray foam survives a wet Sunnyvale crawl space forever. Here’s what we actually see on service calls around town.
- Heatlok HFO delamination from trapped moisture. We’ve pulled back Heatlok HFO panels in older Sunnyvale ranch homes near Murphy Avenue where the foam looked intact from the outside but had separated from the subfloor above. The cause is almost always condensation trapped between the foam and the framing when the crawl space wasn’t properly dried before application. Our fix: remove the delaminated section, dry the substrate, and reapply a compatible closed-cell foam before wrapping the space with a new vapor barrier.
- Sealection 500 open-cell foam saturation. Open-cell foam absorbs water like a sponge. In Sunnyvale’s clay-heavy soil, standing water after winter rains wicks up and saturates Sealection 500 in low-clearance crawl spaces. Once saturated, it loses R-value and becomes a mold risk. We cut out the wet foam, address the drainage issue, and switch to a closed-cell product suitable for below-grade contact.
- Vapor barrier failures around piers and plumbing penetrations. This is the most common Demilec-related issue in Sunnyvale homes of all ages. The original installers foamed the field cleanly but left gaps around support piers, drain lines, and the sewer cleanout. Moisture finds every gap. We re-flash every penetration with Demilec-compatible foam sealant and run the vapor barrier up each pier a minimum of 6 inches, sealed with vapor tape, not duct tape.
- AGP and Heatlok Soya rodent damage. Demilec’s soy-based formulations attract rodents more than petroleum-based foams. In the older neighborhoods off El Camino Real, we regularly see squirrel and rat tunnels chewed through Heatlok Soya panels in just a few seasons. After repairs, we recommend encapsulation with a reinforced 12-mil vapor barrier and, if needed, exclusion work to keep them out for good.
- Improper thickness on original installs. Demilec specs call for specific thicknesses by climate zone. We’ve measured Heatlok HFO at half an inch in Sunnyvale crawl spaces that should have double that. Thin foam underperforms on both insulation value and air sealing, and it’s more prone to cracking. We document the deficiency, remove what’s failing, and reapply to the correct depth before encapsulation.
Our Demilec Crawl Space Encapsulation & Vapor Barrier Process
We follow the same six-step sequence on nearly every Demilec job, whether it’s a simple vapor barrier swap or a full encapsulation.
- 1
Assessment call. You describe the symptoms. We tell you if it sounds like a Demilec product failure, a barrier failure, or drainage problem. No charge for the conversation.
- 2
On-site inspection. A background-checked, uniformed tech crawls the space, documents foam condition, measures humidity, and photographs everything. You see every photo.
- 3
Parts and materials decision. We recommend Demilec OEM products when the warranty is still active, and quality aftermarket alternatives when it isn’t. You get the choice, with our honest take on each.
- 4
Prep work. We remove failed material, dry the space, address any drainage or grading issues, and clean out debris so the new system has a clean surface.
- 5
Installation. New foam applied where needed, vapor barrier sealed at every penetration, piers wrapped, seams taped, and a dehumidifier recommended only if your humidity numbers justify one.
- 6
Walkthrough and guarantee. We show you the finished work, review before and after photos, and cover everything under the Done Right Promise. If it’s not done right, we make it right. No runaround, no fine print, ever.
What Demilec Crawl Space Encapsulation & Vapor Barrier Costs in Sunnyvale
Here’s what Sunnyvale homeowners typically pay for Demilec-related crawl space work, based on jobs we’ve done across the city from the Cherry Chase neighborhood to the newer developments near Lawrence Expressway.
- Reinforced 12-mil vapor barrier replacement (1,200 sq ft typical Sunnyvale crawl space): $2,100 to $3,200
- Spot repair of delaminated Heatlok HFO or saturated Sealection 500: $800 to $2,400, depending on square footage
- Full re-foam of rim joists and band board with Demilec-compatible closed-cell: $2,800 to $4,500
- Complete crawl space encapsulation with new vapor barrier, foam, pier wraps, and sealing: $6,500 to $9,500 for most Sunnyvale homes
- Add-on drain line or sump pump installation for chronic moisture: $1,400 to $3,800
The big price movers are crawl space height (low-clearance spaces under 30 inches cost more in labor), how much foam needs to be removed, and whether drainage work is necessary. Call (669) 215-4805 for a free estimate. We’ll give you a number before we leave, not three days later.
Why Sunnyvale Homeowners Call Walt’s Insulation for Demilec Work
We’ve been at this since 2000, and we’re the one down the road, not a 1-800 franchise. Walt Brenner built this business on doing thorough assessments before recommending anything, because the wrong product installed perfectly still wastes your money. Our techs know Demilec foams, but they also know Reflectix and every other major brand, so you get an honest recommendation, not a brand pitch.
Every job carries the Done Right Promise. Every call gets a live person, 24/7, no voicemail trees. And every tech who walks through your door is background-checked and in uniform. We’re not the biggest outfit in Sunnyvale, and that’s the point. We’re accountable to you, not to a regional manager in another state.
FAQs
Demilec warranties cover the foam product itself, not the installation labor. Since we’re an independent Demilec service provider, not an authorized contractor, manufacturer warranty terms apply to the product from the original install. Our work is covered separately by the Done Right Promise, our lifetime workmanship guarantee. If we fix it and it fails, we make it right.
In most Sunnyvale homes, yes. We can source Heatlok HFO, Sealection 500, and other current Demilec lines. If your original product has been discontinued, we’ll recommend a compatible closed-cell foam that meets or exceeds the performance spec. We always tell you what’s going in and why before we spray.
For failed encapsulation or active moisture intrusion, we typically schedule within 3 to 7 days. Same-week appointments are common outside of peak winter rains. Call (669) 215-4805 and we’ll give you a real date, not a two-week window.
For isolated delamination or saturation under 30% of the crawl space footprint, spot repair is almost always cheaper. When failures cover more than half the space, or when the vapor barrier is also compromised, full encapsulation usually costs less per year of service life. We’ll show you both numbers and let you decide.
Sunnyvale’s clay soil holds water close to the foundation, and some homes will always need drainage correction before any encapsulation will hold up. During inspection we check grading, downspout discharge, and standing water. If drainage work is needed, we’ll recommend a licensed excavator and coordinate the work so the encapsulation is done right the first time.
Written by Walt Brenner, Owner, Walt’s Insulation at Walt’s Insulation, serving Sunnyvale and nearby areas.