Older homes in Ottawa hold undeniable charm — but they also often come with a hidden problem: air leaks. Drafty walls, poorly sealed windows, and outdated siding systems lead to significant heat loss during frigid winters, driving up energy bills and making homes uncomfortable. Modern siding installation isn’t just about aesthetics; it’s a critical opportunity to air-seal the building envelope effectively, stopping drafts and improving year-round energy efficiency.
This comprehensive guide explains how new siding projects can integrate air-sealing strategies, the building science behind it, and why Ottawa homeowners should consider these upgrades now.
Why Older Ottawa Homes Are So Drafty
Many Ottawa houses built before the 1980s lack modern air and moisture control layers. Common issues include:
- Uninsulated or poorly insulated wall cavities
- Sheathing gaps and cracks behind outdated cladding
- Degraded caulking and flashing around windows and doors
- Absence of house wraps or weather barriers
These gaps allow cold air to infiltrate in winter and warm air to leak out, increasing energy use and causing discomfort. The Government of Canada notes that air leakage can account for up to 25% of total heat loss in older homes — an enormous opportunity for savings during siding replacement.
The Science of Air-Sealing During Siding Replacement
When homeowners invest in new siding installation, they gain access to the exterior wall — the perfect moment to integrate modern air-sealing techniques. Proper air-sealing involves three main layers:
- Continuous Sheathing: Provides structural support and forms the base for sealing.
- Air and Weather Barrier (House Wrap): Prevents uncontrolled air movement while allowing moisture vapor to escape.
- Flashing and Sealants: Close gaps around penetrations, windows, and edges to stop drafts.
These layers work together to create a tight building envelope, critical for cold Ottawa winters.
House Wraps and Weather Barriers: The First Line of Defense
Modern Air Barriers vs. Old Felt Paper
Older homes often used tar paper or minimal barriers that degraded over time. Modern house wraps, like Tyvek or similar products, are engineered to resist air infiltration while remaining vapor-permeable. When properly installed behind new siding, they:
- Block wind-driven drafts
- Prevent moisture ingress
- Allow trapped humidity to escape, avoiding mold growth
During a siding replacement, contractors can wrap the entire exterior in one continuous layer, sealing seams with special tapes to prevent leakage — a significant upgrade for Ottawa homeowners looking to winterize.
Sealing Wall Penetrations and Edges
Drafts commonly occur at wall penetrations — think plumbing vents, electrical outlets, or old cable entry points. Best practices include:
- Installing gasketed covers or sealed boots
- Applying high-quality, cold-weather-rated sealants
- Flashing penetrations with self-adhering membranes
These details might seem small, but collectively they eliminate dozens of mini air leaks that add up to major heat loss.
Rigid Foam Sheathing and Exterior Insulation
Adding rigid foam insulation boards beneath siding is one of the most effective ways to air-seal and insulate simultaneously. This strategy, sometimes called “outsulation,” involves:
- Placing foam boards (e.g., XPS or polyiso) directly over the sheathing
- Taping all seams to act as a continuous air barrier
- Installing furring strips to create a rainscreen before attaching siding
This technique can dramatically reduce air leakage and thermal bridging. It aligns with Ontario energy codes and is a popular choice in Ottawa retrofits where interior insulation upgrades are costly or disruptive.
Upgrading Windows and Siding Together
If windows are drafty or nearing end-of-life, combining window replacement with siding upgrades is ideal. Integrating new energy-efficient windows with properly flashed and sealed siding layers eliminates common leak points. Learn more about window replacement services in Ottawa to plan a cohesive upgrade.
Proper integration includes:
- Sealing the rough opening with spray foam or backer rod
- Flashing window flanges with self-adhered membranes
- Overlapping the house wrap correctly to shed water and block air
Choosing the Right Siding Materials for Airtightness
Not all siding materials perform equally when it comes to sealing. While the air barrier typically lies beneath the cladding, the siding itself influences durability and water resistance:
- Vinyl siding is affordable but requires careful detailing at seams and corners.
- Fiber cement siding offers durability and pairs well with foam sheathing systems.
- Engineered wood and aluminum siding can provide excellent wind resistance when installed with sealed trims.
For cold climates like Ottawa, insulated vinyl siding is an especially attractive option. It adds a thermal break and helps minimize air infiltration at the panel edges.
Professional Installation Is Key
Even the best materials fail if improperly installed. Air-sealing success depends on:
- Continuous taping of house wrap seams
- Proper integration of flashing and membranes
- Tight fitting at corners, soffits, and penetrations
- Avoiding tears or gaps in barriers
Homeowners should always work with experienced siding contractors familiar with Ottawa’s freeze-thaw cycles and building codes. Quality workmanship ensures that the new siding system performs as intended for decades.
Energy Savings and Comfort Improvements
The benefits of air-sealing with new siding extend far beyond aesthetics:
- Lower heating costs — Homeowners can expect up to 20–30% reductions in heating energy use.
- Warmer walls and reduced drafts — Improved comfort during long Ottawa winters.
- Improved durability — By managing air and moisture movement, wall assemblies stay drier and last longer.
- Higher resale value — Energy-efficient upgrades are a major selling point in today’s real estate market.
The Canada Greener Homes Initiative even provides rebates for exterior insulation and air-sealing work, making it financially attractive to tackle these improvements during siding replacement.
Common Mistakes to Avoid
Skipping the Air Barrier
Some contractors still treat siding replacement as a purely cosmetic job. Without installing or repairing the air barrier, drafts will persist.
Improper Sealing Around Openings
Relying solely on caulk without flashing leads to leaks. Always integrate flashing properly.
Not Extending Air-Sealing to Roof and Foundation Junctions
The top and bottom of walls are major leakage points. Proper detailing where siding meets soffits and foundation walls is crucial.
Timing Your Project for Maximum Impact
Fall is often the best time for Ottawa homeowners to tackle siding and air-sealing projects. Temperatures are moderate enough for proper sealant curing, and upgrades can be completed before winter heating season. Learn more about winter siding preparation tips to plan effectively.
Partnering with Experts in Ottawa
Air-sealing is both a science and a craft. Working with a reputable Ottawa siding company ensures the right materials, installation techniques, and sequencing. Whether you’re restoring a 1920s brick home in Centretown or updating a 1970s suburban house, the right retrofit approach can make your home warmer, quieter, and more energy-efficient for years to come.
👉 Contact Kaloozie Comfort today to schedule a siding and air-sealing consultation.
