Indoor Environmental Risk in Cold-Climate Buildings

Lead is a building science problem (not a “lead paint problem”)

If you manage, renovate, buy, or live in older housing in Greater Portland, you already know the headline: lead-based paint is common.

But here’s the deeper (and more useful) truth:

Lead exposure in homes is usually a building performance issue—driven by pressure, airflow, friction, moisture, and maintenance—more than a “paint exists” issue.

Paint is the reservoir. Dust is the delivery system. And buildings—especially cold-climate buildings—are exceptionally good at making and moving dust.

The “by the numbers” section (the part everyone forwards)

• There is no safe level of lead exposure. CDC uses a Blood Lead Reference Value (BLRV) of 3.5 µg/dL to identify children with higher blood lead levels than most kids. CDC+1

• CDC estimates ~500,000 U.S. children have blood lead levels at or above that BLRV. CDC

• HUD/EPA estimate tens of millions of U.S. homes still contain lead-based paint (EPA cites ~38 million permanently occupied housing units). Environmental Protection Agency

• Maine is old-house country: one Maine public health resource notes that about 80% of Maine homes/apartments built before 1978 could have some lead paint. Maine Indoor Air Quality Council

• Maine’s statutory definition of a “lead poisoned child” (under Maine law) still references ≥ 5 µg/dL; a Maine legislative report notes that in 2023 an estimated ~300 children (1.7% of tested children) met that threshold. Maine State Legislature

• On the building standard side: EPA tightened dust standards over time—and then tightened again in 2024, announcing strengthened standards (with floors/sills/troughs dropping significantly). Environmental Protection Agency+1

• Renovating pre-1978 housing? EPA’s RRP Rule generally requires lead-safe certified contractors when paid work disturbs painted surfaces in pre-1978 homes/child-occupied facilities. Environmental Protection Agency+1

  
  

So: big reservoir + old housing stock + dust movement + renovation = persistent risk.

Why lead behaves like a building science hazard (especially in cold climates)

Think like a building:

1) Friction makes dust (windows and doors are dust factories)

Old double-hungs, painted sashes, jambs, stops, door edges—these are high-friction interfaces. Every open/close cycle can generate microscopic dust from layered coatings. Maine’s indoor air resources explicitly call out opening and closing windows as a routine dust generator. Maine Indoor Air Quality Council

2) Pressure moves dust (stack effect is the unseen conveyor belt)

Cold climate = long heating season = stack effect:

• Warm air rises and exits upper levels

• Lower levels pull in replacement air (often from basements, rim joists, leaky entries, porch cavities, wall chases)

• Dust rides the airflow pathways

Add bath fans, range hoods, dryers, or unbalanced HVAC and you’ve got mechanical depressurization that can pull dust from the places you least want it.

3) Moisture + deferred maintenance turns paint into powder

Lead isn’t dangerous because it exists. It’s dangerous when paint deteriorates into dust/chips—often because water management is failing: bulk water at sills, flashing gaps, ice dams, wet basements, humid interiors with condensation, etc.

4) Weatherization can unintentionally concentrate hazards

Air sealing and insulation are great—until they’re done without source control and compartmentalization:

• You tighten the box

• Dust stays inside longer

• Small reservoirs (a window, a stair rail, a porch entry) become more consequential

  
  

5) Renovation is the “dust event”

Sanding, cutting, demo, window replacement, trim work—these create orders of magnitude more dust than day-to-day living if controls aren’t used. That’s why RRP exists. Environmental Protection Agency+1

Three anonymous Greater Portland case studies

(Real-world patterns. Details altered for privacy. The building physics is the point.)

Case Study A: “The drafty triple-decker with the perfect nursery”

Building: ~1900–1920s multifamily, original windows, steam heat, finished attic unit.

Complaint: “We cleaned constantly—why is dust coming back daily?”

What we found (building science):

• High-friction windows in the nursery + painted stops = consistent dust generation

• Strong stack effect (warm air exiting upper levels) + leaky basement = dust transport upward

• Entry vestibule acted like a dust “mixing chamber” every time the door slammed shut

Fix approach (not “paint panic”):

• Treat windows/trim as a friction-surface hazard: stabilize, reduce abrasion, consider window strategies that eliminate rubbing

• Air-seal bypass routes (basement to attic chases) to cut dust conveyance

• Upgrade cleaning to HEPA + wet methods (dry sweeping = dust redistribution)

• When work occurs, use containment + negative pressure in work zones

  
  

Takeaway: the lead source didn’t change; the airflow network did.

Case Study B: “The ‘energy upgrade’ that accidentally amplified exposure”

Building: 1950s Cape, partial basement, blower-door-driven air sealing, new bath fans.

Trigger: Post-weatherization, family noticed more settled dust + toddler hand-to-mouth behaviors (classic risk window).

What we found (building science):

• Air sealing reduced fresh-air dilution but didn’t address a basement dust reservoir

• New fans increased intermittent depressurization, pulling air (and dust) from the lowest-pressure pathways

• Old bulkhead + rim area leakage created a direct line from basement → living space

Fix approach:

• Compartmentalize the basement (air-seal rim/bypasses, improve door/gasketing)

• Balance ventilation so fans don’t turn the home into a dust vacuum

• Address reservoirs first, then tune ventilation

  
  

Takeaway: energy work is good work—when it’s paired with IEQ hazard control.

Case Study C: “The condo renovation that went ‘Instagram clean’… except the dust”

Building: 1890s condo conversion, new kitchen, old stairwell/common areas remain.

Trigger: Renovation next door + common stair traffic; repeated dust wipes failed in the same locations.

What we found (building science):

• Common stairwell acted as a shared dust highway

• Negative pressure in the renovated unit pulled dust from the hall/stairs under door undercuts

• Dust deposition hotspots matched airflow patterns, not “where paint looked bad”

Fix approach:

• Building-wide thinking: corridor cleaning protocols, entry mats, stairwell stabilization

• Temporary door containment during work + pressure management

• Post-work verification where air actually carries dust (not just where it “looks old”)

  
  

Takeaway: in multifamily, lead control is often a systems problem, not a unit problem.

A practical “Lead = Building Science” playbook (for owners, PMs, and renovators)

Reduce dust generation

• Prioritize friction surfaces: windows, doors, stair rails, trim edges, porch entries

• Stabilize peeling paint early—don’t wait for “reno season”

Reduce dust transport

• Air-seal the big bypasses (basement-to-attic chases, rim joists, plumbing/stack penetrations)

• Compartmentalize basements and common areas when they’re reservoirs

Reduce occupant exposure

• HEPA vacuuming + wet cleaning beats dry dusting

• Upgrade entry systems: walk-off mats, shoe policies, stroller/gear management

Renovate like dust is the hazard (because it is)

• Use RRP-compliant lead-safe practices in pre-1978 buildings when paid work disturbs paint Environmental Protection Agency+1

• Containment, minimization of dust creation, thorough cleaning, and clearance aren’t “nice-to-haves”—they’re the whole game

  
  

Bottom line

Lead sticks around because buildings keep making and moving dust.

So the winning mindset is:

Stop treating lead like a “paint problem.” Treat it like a cold-climate building science problem:

• reservoirs (old coatings, soil, common areas)

• mechanisms (friction + deterioration)

• transport (stack effect + depressurization)

• exposure (dust on hands, floors, sills, entry zones)

How HarborLight Property Inspections Helps Close the Loop

At HarborLight Property Inspections, we approach lead the same way we approach buildings: systematically, defensibly, and in full alignment with Maine DEP requirements.

Our comprehensive lead-based paint inspections use state-approved XRF lead paint detection technology to accurately identify lead reservoirs without damaging finishes, paired with risk-based evaluation of friction surfaces, dust pathways, and building conditions that actually drive exposure.

When corrective work is complete, we perform clearance testing and documentation to support issuance of a Maine DEP Limited Lead-Safe Certificate—giving owners, property managers, and residents confidence that the building meets Maine’s lead safety standards.

In short, we don’t just test for lead—we help you understand how your building behaves, verify compliance, and document lead safety the right way.