Homes aren’t just built differently over time; they carry the personality flaws of the era in which they were built.
The materials builders had access to, the amount of insulation knowledge that existed, and what building codes required (or didn’t) all shaped how homes perform today. That’s why roughly 89 percent of homes are underinsulated, even if insulation is technically present.
If you’ve ever wondered why your house is drafty, has uneven temperatures, high energy bills, or persistent comfort issues, the answer often lies in when your home was built.
Let’s travel decade by decade, from the 1920s to today, and break down the most common home insulation problems, why they happen, and what they mean for your comfort.
• Older homes(1920s to 1940s) often have little to no effective insulation, leading to drafts, highenergy bills, and musty basements.
• Mid-century homes (1950s to 1970s) usually have insulation, but poot air sealing causes comfort issues and cold rooms.
• Homes from the 1980s to 1990s may meet old code standards but still suffer from air leakage and inconsistent insulation coverage.
• New homes (2000s to present) are tighter, but complex designs and ventilation issues can lead to hot or cold rooms, humidity, and condensation.
• A poorly insulated house doesn't always mean "no insulation" -- it often means insulation that doesn't stop air movement.
Homes built between the 1920s and 1940s are what we lovingly call part of the creative insulation era.
Builders used whatever materials were available at the time, including:
And no, that’s not an exaggeration. Other items homeowners would put into their walls are dolls, photos, and even hay.
These materials offer little to no thermal resistance, and after decades, most have completely broken down.
That means many wall cavities are now essentially empty, allowing air to move freely in and out of the home.
The 1950s brought mass home construction – and with it, fiberglass and cellulose insulation became common.
Insulation was added, but air sealing wasn’t a concept yet.
Over time, fiberglass thins and settles, reducing its effectiveness. When air moves through traditional insulation, its performance drops dramatically, creating a myriad of problems.
This era saw greater use of cellulose and the emergence of the earliest forms of foam insulation, but fiberglass still dominated.
Building codes improved slightly, but air sealing still wasn’t addressed, and R-Values remained low.
Once air moves through insulation, its ability to resist heat flow drops further, leading to comfort issues that homeowners still experience today.
The 1980s brought higher R-Values and fiberglass installed everywhere – attics, walls, crawl spaces, and basements.
Fiberglass can’t stop air movement.
Areas around pipes, wires, and penetrations were often left uninsulated, creating pathways for cold air to enter the home.
Homes in the 1990s technically met code, but code doesn’t mean optimal.
More complex home designs created insulation blind spots.
Combine that with inconsistent installation quality, and you end up with homes that meet minimum standards but still feel uncomfortable.
This era saw more spray foam, rigid board, and blown-in materials, as well as greater architectural complexity.
Even with better materials, some areas simply weren’t insulated properly due to complex rooflines and design challenges.
Modern homes are built tighter than ever using high-density fiberglass, cellulose, spray foam, injection foam, and air-sealing techniques.
When a home is sealed without proper ventilation or a correctly aligned building envelope, moisture and comfort problems follow.
Tight homes require smart system design, not just better insulation.
Every home carries the fingerprint of the era it was built.
Understanding those era-specific challenges helps homeowners:
If your home feels uncomfortable, drafty, or inefficient, chances are it’s not random; it’s predictable.
Every home tells a story, and once you understand the era it was built in, you’re better equipped to fix the problems that come with it.
And if you’re ready to tackle those era-specific insulation issues, checking out a contractor who understands how homes were built over time can make all the difference. When you’re ready, take a look at our Dealer Finder to locate a RetroFoam dealer near you.
A Journey Through Time: The Fascinating History of Home Insulation
How to Insulate an Old House with RetroFoam without Damaging the Aesthetic
Knob and Tube Wiring and RetroFoam: Can You Add Insulation to an Older Home?
Drafts, uneven temperatures, high energy bills, cold walls or floors, and rooms that never feel comfortable are all common signs of poor insulation.
Yes.
A poorly insulated house often has insulation that allows air movement, has settled, or was never installed correctly.
Most older homes are underinsulated by modern standards, especially those built before air sealing and high R-Values became common.
Knowing when your home was built helps predict problem areas like walls, attics, crawl spaces, rim joists, and bonus rooms.
Start by identifying comfort issues and understanding your home’s construction era.
From there, targeted insulation and air sealing solutions can dramatically improve comfort.