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Pourquoi les vieilles maisons de Longueuil cachent souvent un air toxique (et comment le détecter)
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Why Old Homes in Longueuil Often Hide Toxic Air (and How to Detect It)

An Invisible Truth: When Indoor Air Becomes the Greatest Danger Inside Your Own Home

On the South Shore, and more specifically in Longueuil, our team at AirGreen is increasingly being called in for issues related to indoor air quality in older homes. These properties, often full of charm, can hide a silent enemy: stale, unhealthy, sometimes toxic air that impacts the health of the occupants every day—without them even knowing it.

We were recently called to inspect a home built in 1954, located in the Saint-Hubert sector. The owners, a couple in their 60s, were experiencing constant fatigue, recurring headaches, and mold that kept coming back in the corners of windows and the basement—despite regular cleaning.

Why Do These Homes Become Toxic?

Once-Beneficial Insulation… Now a Problem

Older homes in Longueuil, as in many South Shore municipalities, have gone through multiple renovations over the years. Among them: added fiberglass insulation, vapor barrier membranes, and double-glazed windows. The result? A home that’s better insulated, but often poorly ventilated.

Without a controlled mechanical ventilation system, these homes trap humidity and pollutants. It’s something we encounter frequently during inspections: a perfectly renovated house with indoor air more polluted than the outdoor air in downtown Montréal.

Older Materials and Invisible Contaminants

  • Wooden floors treated with varnishes still emitting VOCs

  • Walls coated with lead-based paint or containing asbestos

  • Semi-buried basements prone to radon accumulation

  • Outdated heating systems emitting fine airborne particles

The AirGreen Intervention: Diagnosis and Solution in Saint-Hubert

Following the couple’s call, we performed a full indoor air quality analysis using our specialized instruments. Here were the results before any intervention:

  • CO₂: 1,480 ppm (dangerous level for concentration and sleep)

  • Relative humidity: 71% (ideal for mold proliferation)

  • VOCs (volatile organic compounds): 490 ppb (above Health Canada’s recommendations)

  • Mold index: high, with presence detected behind low furniture

We recommended the installation of a heat recovery ventilator (HRV): the Venmar EVO5 700 HRV, a unit specifically designed for medium-sized homes with basements, offering excellent airflow and energy efficiency.

Technical Specs of the Installed HRV:

  • Model: Venmar EVO5 700 HRV

  • Type: HRV (heat recovery ventilator)

  • Max airflow: 120 CFM

  • Thermal recovery efficiency: up to 70%

  • Installation: wall-mounted in the basement with rigid ductwork

  • Smart wall control with continuous or intermittent ventilation options

  • Subsidy eligibility: Yes (Hydro-Québec’s LogisVert program)

Installation Timeline: Adapting to an Older Structure

One of the main challenges in this house was the lack of existing ducts. So we proceeded with:

  • Strategic mapping of air intake and exhaust points

  • Installation of insulated ducts through the basement ceiling and attic

  • Preservation of existing finishes, with no need to open walls

  • Discreet integration of air grilles, custom-painted to match the décor

Post-Installation Results: Noticeable Changes Within Days

Three days after the installation, we returned to conduct a new air quality test, along with a follow-up inspection:

  • CO₂: dropped to 560 ppm

  • Relative humidity: stabilized at 45%

  • VOCs: reduced to 90 ppb

  • No visible mold after surface cleaning

  • Immediate reduction in odors in bedrooms and basement

The couple reported more restful sleep, easier breathing, and even improvement in their elderly dog, who used to cough frequently before the intervention.

Our Recommendations for Owners of Older Homes in Longueuil

  • Get your indoor air tested at least once

  • Avoid temporary fixes like portable purifiers that don’t solve the root cause

  • Don’t wait for visible signs (mold, condensation, unpleasant odors)

  • Invest in a certified mechanical ventilation system, professionally installed

Similar Cases Across Other Longueuil Neighbourhoods

We’ve completed similar interventions in Vieux-Longueuil, LeMoyne, Greenfield Park, and Saint-Hubert, each time with immediate improvements in the occupants’ quality of life. These installations are now eligible for major subsidies, significantly reducing upfront costs.

Conclusion

Old homes in Longueuil are beautiful… but they can also hide toxic air, especially if they’ve been renovated without integrating modern ventilation. At AirGreen, we have the expertise, the equipment, and the right HVAC solutions to make these homes as healthy as they are warm and welcoming.

Own a house built before 1985 in Longueuil, Laval, Montréal, the North Shore, or the South Shore? Contact our team for a free inspection and find out what a well-calibrated air exchanger can do for your health.

At AirGreen, we reveal what you can’t see—so you can finally breathe with peace of mind.

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