Should I Insulate Interior Walls (Umm, No…)?

by Erik North on October 17, 2011

should i insulate interior walls


Another question that crops up in audits (have you gathered that questions about almost everything come up?), is whether it makes sense to insulate the interior walls in your home. Heat is escaping everywhere, so it makes sense to slow it down as much as possible right?

Short answer: No.

Longer answer: Noooooooooooo.

Much longer answer: No, but there are some cases you may want to.

Why Shouldn’t I Insulate Interior Walls

The case for not insulating the interior is simple: the building envelope is the dividing line between the warm, cozy interior and the chilly exterior. The interior walls are inside the building envelope so they’re warm on both sides. Barring a desire to subsidize your poor local insulation contractors and spend twice as much on your home’s insulation work, there’s no need – the keyword here – to do so.

Interior wall insulation can cause problems in some instances. Usually, this involves some combination of the words: insulation, vapor barrier and/or moisture.

During one training program conducted by Maine Housing, we toured a home which included an indoor pool which had been filled in. Don’t ask. There were no heating elements in the space, since the pool had provided plenty of heat when in use, and the interior walls and ceiling had been insulated. By insulating these walls, the owners had eliminated enough radiant heat that they’d inadvertently reduced room temperatures below the dew point. There was a dehumidifier in the space that fell woefully short of handling the huge level of humidity. End result: loads of condensation on the ceiling and walls. Now this is a pretty egregious combination of factors and unlikely to normally occur but illustrates the issues you can run into.

Why Should I Insulate Interior Walls

And the advantages to insulating interior walls? First, it would be quite a generous support of the insulation workers industry. Times are tight in construction-related fields and your generous doubling of the project size would be most appreciated.

Beyond contributing to recovery from the recession, there are times when interior insulation, not to mention a full air/vapor barrier assembly, to control heat and moisture movement are warranted. Vivariums, indoor pools or hot tubs put out massive heat and vapor loads, making thermal and especially vapor controls prudent.

A universal benefit to interior insulation is sound proofing. Rockwool, fiberglass and cellulose are commonly used in this capacity, allowing homeowners to deaden sound between rooms, soundproof home theaters or reduce street noise.

And In Conclusion…I’m Not Insulating My Walls, why?

Insulating interior walls have negligible, if not quite zero, savings and comfort benefits. Considering the potential but negligible benefits, you create odd, potentially problematic heat dynamics. You may want to soundproof one room from another and that is a legitimate reason to consider interior insulation. It can make your home quieter and more audibly comfortable.

{ 4 comments… read them below or add one }

Travis Johnson October 14, 2014 at 6:13 pm

I have a 3,300 sq ft home in sunny ca. with insulated interior walls & my highest electric bill during hot months was $160 with winter months around $50. So, umm yes


Ed Stephens December 12, 2014 at 1:11 am

Um….yes or at least it should be an option as it’s partly personal, partly beneficial for sound as well as keeping relatively unused rooms more controlled regarding heat loss. More expensive? Sure but considering the way vast amounts of money is thrown around on such heat loss and noise producing materials like granite, marble and even hardwood floors; I’ll take insulated interior walls thank you very much. It sure beats the alternative. Silence is golden and too often in short supply.


Kathy April 27, 2015 at 7:15 am

You didn’t address the issue of insulating an interior wall that separates 2 apartments, or an often-used room and an occasionally-used room such as a guest room. My home is in Northern New England and I am considering insulating the wall between a an often used bathroom and a guest room that is not heated unless there is a guest staying in it (which is not often). Thanks for your help.


B May 16, 2015 at 9:15 am

OK, so insulating between walls is terrible for heat purposes, but is ok for noise purposes?


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