Upgrading your home’s insulation is one of the most effective ways to improve energy efficiency, lower utility bills, and prevent air movement that causes discomfort. Spray foam insulation is widely regarded as one of the most advanced insulation systems on the market.
It provides an airtight seal that traditional materials simply cannot match. However, one of the most common mistakes homeowners and even some contractors make is applying spray foam insulation over existing materials like fibreglass batts or cellulose.
In this blog, we’ll explore why it’s essential to remove old insulation before installing spray foam and the potential risks of skipping this step. See how professional insulation contractors in Edmonton ensure your home is sealed properly and performs at its best.
What Really Happens When Spray Foam Is Applied Over Old Insulation?
Applying spray foam insulation without removing existing materials can lead to several serious issues. Here’s what can go wrong:
1. Incomplete Air Sealing
Spray foam works by expanding to fill all gaps, cracks, and cavities. If old insulation is left behind, it can block the foam’s path, leaving air pockets untouched. These hidden air leaks mean:
- Reduced thermal performance
- Persistent drafts
- Uneven room temperatures
- Lower energy savings
Essentially, you’re investing in a premium product but not getting the full value because the foam can’t bond to the necessary surfaces.
2. Condensation
Traditional insulation materials can cause condensation. When covered with spray foam, these damp areas become enclosed, creating a hidden breeding ground for:
- Mould and mildew
- Wood rot in framing and sheathing
- Deterioration of structural integrity
Spray foam is designed to seal air. In Edmonton’s climate, where condensation is already a challenge, this mistake can result in costly repairs down the line.
3. Voided Manufacturer Warranties
Most reputable spray foam manufacturers require a clean, debris-free substrate before application. Leaving behind old insulation can:
- Void your product warranty
- Lead to poor adhesion and cracking
- Increase the risk of insulation failure
This becomes a legal and financial liability if the insulation fails and damages occur.
4. Fire Risk And Code Compliance Issues
Old fibreglass and cellulose materials are often not up to current fire safety standards. Spray foam applications over these can:
- Create layers of flammable material behind the foam
- Fail to meet local Edmonton building codes
- Increase the risk of combustion spread during a fire event
If you’re renovating or building a custom home, skipping insulation removal can result in inspection failures or insurance problems.
Why Professional Removal Matters
Removing existing insulation isn’t just about tearing out the old and spraying in the new. It requires specialized equipment, safety protocols, and proper disposal practices. Professional insulation contractors use:
- Negative air machines and vacuums to remove debris and airborne particles
- Thermal cameras to identify moisture issues or gaps
- Vapour barrier removal is needed for correct substrate access
- Substrate cleaning and prep for foam adhesion
In Edmonton homes, especially older or custom-built ones, this meticulous approach is critical. Spray foam insulation is an investment that pays off for decades, but only when applied correctly.
Common Places Where Removal Is Essential
Not all areas of a home are treated equally when it comes to insulation upgrades. Here’s where removal is typically non-negotiable:
Attics
Attics often contain layers of outdated, dusty, or degraded blown-in or batt insulation. Leaving it in place prevents spray foam from properly adhering to the roof deck and joists, which can result in:
- Poor R-value performance
- Ongoing ice dam issues
- Temperature swings in the upper floors
Basement Rim Joists
Old fibreglass in rim joists may look harmless, but it harbours moisture and mould. Spray foam insulation is one of the only solutions that effectively seals rim joists and prevents cold drafts and condensation.
Crawl Spaces
Crawl spaces are typically dark, damp, and neglected. Any leftover insulation can hide structural issues and block foam coverage. Professionals clear out old material, apply foam to the foundation walls and floor joists, and create a sealed, insulated environment.
Signs That Your Old Insulation Needs To Go
Here’s how you’ll know it’s time for a complete insulation upgrade:
- Visible sagging or discoloured insulation
- Rodent droppings or nesting in the attic or crawl space
- High energy bills despite recent furnace upgrades
- Cold drafts and uneven heating in winter
- Musty odours in upper or lower levels
Any of these are red flags that your current insulation has failed and must be removed before spray foam insulation is installed.
About Classic Spray Foam
At Classic Spray Foam, we specialize in premium spray foam insulation services for custom-built homes across Edmonton. We use industry-leading products like Insulthane® 450 NM, DC315, and Hygrothane to create airtight, high-efficiency thermal barriers.
Our team doesn’t cut corners; we remove old insulation properly, prep every surface, and apply foam to perfection. Whether you’re upgrading an attic, sealing basement rim joists, or insulating new construction, we’re your go-to team for quality and performance that lasts.
Ready to insulate right the first time? Contact us today to book a professional assessment.