Common Energy Assessment Findings in Maine Homes

After 20+ years of walking through homes in Greater Portland, patterns emerge. The houses are different - Capes, colonials, ranches, Victorians, split-levels - but the energy problems repeat themselves with remarkable consistency.

We have performed thousands of assessments since 2006. The specific details vary from house to house, but the core findings show up again and again. If you live in a Maine home built before 2000, there is a good chance your house has at least three or four of the issues on this list.

Understanding these common findings before your assessment helps you recognize what your advisor is talking about when they point things out. It also explains why homes that look fine from the outside can have significant hidden energy problems.

The Top 10 Findings (In Order of Frequency)

1. Inadequate or Missing Attic Air Sealing

How common: Nearly every pre-2000 home we assess

This is the number one finding because it is the number one energy loss in most Maine homes. Warm air rises. If the attic floor has gaps and penetrations that are not sealed, warm air from your living space flows directly into the attic - carrying your heating dollars with it.

The culprits are specific and predictable:

• Plumbing vent pipes that pass through the attic floor with gaps around them
• Electrical wire penetrations - every wire that passes from a wall or ceiling into the attic creates a small gap
• Recessed light housings that are open to the attic above
• The attic hatch or pull-down stairs - often the single largest air leak in the house
• Bathroom and kitchen exhaust fan housings that penetrate the attic floor
• Chimney and flue chases with gaps between the framing and the masonry or metal
• Top plates of interior partition walls - the double 2x4 at the top of every interior wall often has gaps where it meets the attic floor

Even homes with decent insulation often have terrible air sealing. Insulation slows heat transfer by conduction. Air sealing stops heat transfer by convection (air movement). You need both, and air sealing should come first.

2. Insufficient Attic Insulation

How common: 80-90% of pre-2000 homes

Maine's climate demands R-49 to R-60 in the attic (roughly 14-18 inches of blown-in cellulose). Most older homes have far less:

• 1950's-1970's homes: Often 2-4 inches of old fiberglass batts (R-7 to R-13), sometimes nothing
• 1970's-1980's homes: Often 6-8 inches of fiberglass batts or early blown-in (R-19 to R-26)
• 1990's homes: Sometimes 10-12 inches (R-30 to R-38) - better, but still below current recommendations

The difference between R-13 and R-49 in a Maine attic is not marginal. It is the difference between a cold ceiling that radiates discomfort into the rooms below and a warm, even living space.

3. Uninsulated Rim Joists

How common: 70-80% of homes with accessible basements

Rim joists (also called band joists) sit at the top of the foundation wall where the floor framing begins. In most homes built before 2000, these are completely uninsulated and unsealed. The rim joist area is essentially an open seam around the entire perimeter of the house at the first-floor level.

You can feel this on a cold day by putting your hand near the bottom of a first-floor exterior wall, right above the floor. If you feel cool air, your rim joists are likely uninsulated.

4. No Wall Insulation

How common: 40-60% of homes built before 1970

Many Maine homes built before 1970 have empty wall cavities. There is siding on the outside, drywall or plaster on the inside, and nothing but air in between. Some homes from this era were built with minimal insulation that has settled or deteriorated over time.

Homes built in the 1970's and later are more likely to have some wall insulation (fiberglass batts were standard by then), but the quality and coverage varies. Gaps, compression, and missed cavities are common.

Dense-pack blown-in cellulose insulation can be installed in existing wall cavities without removing the interior or exterior finish. Small holes are drilled, the cellulose is blown in at high density, and the holes are patched. This is one of the most effective retrofits for older Maine homes.

5. Drafty Basement or Crawlspace

How common: 60-70% of homes with unfinished basements

Beyond the rim joist issue, basements in Maine homes often have multiple air leakage paths:

• Sill plate gaps where the wood framing sits on the concrete foundation
• Foundation cracks - small cracks in poured concrete or gaps in block walls
• Utility penetrations - where pipes, wires, and ducts pass through the foundation
• Bulkhead doors that do not seal well
• Crawlspace vents that are open or poorly sealed

A drafty basement affects the entire house. Cold air entering the basement rises through floor penetrations, interior wall cavities, and stairways, making first-floor rooms colder and driving up heating costs.

6. Aging Heating System (Low Efficiency)

How common: 30-40% of homes assessed

We frequently encounter boilers and furnaces that are 20-30+ years old, operating well below their original efficiency ratings. Common scenarios:

• Oil boilers from the 1990's originally rated at 82% AFUE, now operating at 65-72%
• Older gas boilers that are non-condensing, running at 80% even when working properly
• Furnaces with standing pilot lights and single-stage burners

The heating system is not always the first priority - insulation and air sealing typically deliver a better return. But when a boiler is 25+ years old and showing signs of declining performance, replacement makes sense as part of a whole-home plan.

7. No Basement Wall Insulation

How common: 50-60% of homes with unfinished basements

Foundation walls below grade lose heat to the surrounding soil. In winter, an uninsulated basement wall in Maine can have a surface temperature of 50-55 degrees - cold enough to make the basement uncomfortable and to sap heat from the floors above.

Insulating basement walls with rigid foam board (polyiso) reduces this heat loss and makes the basement noticeably warmer. For rubble or stone foundations that are not flat enough for rigid board, closed-cell spray foam (which we subcontract for this specific application) provides both insulation and air sealing.

8. Ice Dams (Caused by Attic Heat Loss)

How common: 25-35% of homes assessed report ice dam history

Ice dams form when heat escaping through the attic melts snow on the roof. The meltwater runs down to the cold eaves (which are not heated from below) and refreezes, creating a dam that forces water back under shingles and into the house.

Ice dams are not a roofing problem. They are an insulation and air sealing problem. When we properly air seal and insulate the attic floor, heat stays in the living space instead of warming the roof. The snow stays frozen. No melt, no dams.

If your assessor notes ice dam risk, it usually means the attic air sealing and insulation are the first priority.

9. Inadequate Ventilation in Tight Homes

How common: 15-20% of homes assessed (more common in recently weatherized homes)

This finding applies mostly to homes that have already had some insulation or air sealing work done, or newer homes built to tighter standards. When a house is well-sealed, natural air exchange drops. Indoor air quality can suffer if mechanical ventilation is not installed.

Signs include:

• Excessive window condensation in winter
• Stuffy or stale air
• Humidity that feels too high
• Odors that linger

The solution is controlled mechanical ventilation - an ERV (energy recovery ventilator) or HRV (heat recovery ventilator) that brings in fresh outdoor air while recovering heat from the exhaust air.

This is not a reason to avoid air sealing. It is a reason to pair air sealing with proper ventilation. A drafty house is not a ventilation strategy - it is an uncontrolled energy leak.

10. Oversized Heating Equipment

How common: 20-30% of homes with newer heating systems

When a heating system is replaced, contractors sometimes install the same capacity as the old system or round up "just to be safe." The result is equipment that is too large for the home's actual heating load.

An oversized boiler short-cycles (fires up and shuts down repeatedly). An oversized heat pump runs in short bursts. Both waste energy and reduce comfort. Proper sizing based on a load calculation, not a guess, is essential.

This is why we always evaluate the building envelope during an assessment, even when the homeowner called about their heating system. The envelope determines the heating load. The heating load determines the right equipment size.

Findings by Housing Era

Different eras of construction have characteristic patterns. Here is what we typically find:

Pre-1940's (Victorians, Four-Squares, Early Colonials)

• No wall insulation at all
• Minimal or no attic insulation
• Single-pane windows (though these are rarely the primary problem)
• Balloon-frame construction in some cases (open wall cavities from basement to attic)
• Stone or rubble foundations with significant air leakage
• Often the most impactful homes to insulate - the improvement is dramatic

1940's-1960's (Post-War Capes, Ranches, Split-Levels)

• Wall insulation hit or miss (some have early fiberglass, many have nothing)
• Attic insulation typically inadequate (3-6 inches of fiberglass)
• Poured concrete foundations - better than stone, but rim joists still open
• Heating systems often replaced once or twice since original construction
• Cape Cod knee walls are a particular challenge - insulation and air sealing behind the knee wall is frequently missing or poorly installed

1970's-1980's (Colonials, Garrisons, Early Energy-Aware)

• Wall insulation usually present (fiberglass batts) but often poorly installed (gaps, compression, missed cavities)
• Attic insulation present but insufficient (6-10 inches)
• Some early air sealing awareness, but inconsistent execution
• Heating systems from this era are now 40-50 years old and well past their useful life

1990's-2000's (Code-Built, Better Insulated)

• Wall insulation standard (fiberglass batts, R-13 to R-19)
• Attic insulation typically R-30 to R-38 - better, but still below R-49 recommendation
• Air sealing improved but still has gaps at penetrations
• Heating systems approaching replacement age (25-30 years old)
• Often the most cost-effective era for targeted upgrades (less work needed, good returns)

What These Findings Mean for You

If you recognize your home in several of these descriptions, that is normal. Most Maine homes have multiple energy improvement opportunities. The assessment process prioritizes them so you know where to start.

The good news: every one of these findings has a proven solution. Air sealing and insulation are not experimental. Condensing boilers and cold-climate heat pumps are proven technologies. Efficiency Maine rebates offset a significant portion of the cost for many homeowners.

About Horizon Homes

Horizon Homes has been assessing and improving Maine homes since 2006. Efficiency Maine Top Contractor for 10+ years, with 4.9 stars across 64+ reviews.

Curious what your home's findings would be? Schedule a free home energy assessment or call (207) 221-3221. It takes 30-60 minutes, costs nothing, and tells you exactly where your home stands.

Related Guides

• What Happens During a Home Energy Assessment
• Understanding Your Energy Assessment Report
• After Your Energy Assessment: What Happens Next
• Home Energy Assessment vs Audit: Which Do You Need