What happens if your walls are not insulated?

Author: Theron Kunze  |  Last update: Saturday, February 14, 2026

Insulation slows the movement of heat through the walls, roof, and floors, maintaining a more consistent indoor temperature. Without insulation, the interior surfaces of a home can become significantly cooler than the air inside, leading to condensation when moisture in the warm air condenses on these cold surfaces.

What happens if you don't insulate walls?

Exterior walls are one of the primary barriers between your home and the outside environment. Without proper insulation, this barrier is compromised, allowing cold air to seep into your home during winter and letting cool air escape in the summer.

How do you know if your walls are poorly insulated?

Areas where you can feel a draft, or cold spots on your walls can indicate poor insulation. Drafts indicate panel gaps and openings that need to be sealed, cold spots in walls and floors indicate insulation clumping or areas where the material is too thin.

Is insulation necessary in walls?

Insulating the right interior walls can regulate temperatures from room to room and between floors in your home. This is especially beneficial if your home has rooms used infrequently or closed off for parts of the year. Noise control. Soundproofing interior walls is an additional benefit of interior wall insulation.

Are interior walls required to be insulated?

State and local codes don't mandate interior insulation, so usually only in interior walls if the homebuyer specifically asks the builder to include it. If you weren't included in the building process, there's a very good chance your home's interior walls are not insulated.

I’m recommending we NOT INSULATE This Old House

Do you need to insulate internal walls?

Whether you're aiming to improve thermal regulation, reduce noise pollution, prevent moisture-related issues or enhance structural integrity, insulation plays a pivotal role in elevating the overall quality of your living space.

Why do builders not insulate interior walls?

Usually, the answer is no. Interior walls are frequently left uninsulated during construction because the energy efficiency benefits aren't as great as insulating exterior walls, floors and ceilings.

What is the cheapest way to insulate internal walls?

Thermal lining paper is among the cheapest ways to insulate internal walls. This thick, insulating wallpaper can be easily applied directly to walls, making it a quick and straightforward solution. Costing around £10 per square metre, it effectively reduces heat loss and is perfect for smaller DIY projects.

How much does it cost to insulate interior walls?

The average cost to insulate a wall is $2,400, but it often ranges between $1,150 and $6,000, depending on the project scope and materials your installation pro uses.

Can you add insulation to existing interior walls?

There are Two Ways to Insulate Existing Walls (That Are Empty) Under the right circumstances, certain types of insulation can be installed directly into a wall through small holes, including injection foam and blown-in cellulose.

How to deal with poorly insulated walls?

Tips to Keep a Poorly Insulated Home Warm
  1. Cover your windows with plastic window seals. ...
  2. Hang thermal curtains over your windows.
  3. Put a draft stopper in your door to the basement or garage. ...
  4. Make sure your heating system is maintained and has a clean air filter. ...
  5. Consider installing a ductless mini split system.

How much heat is lost through insulated walls?

About 35% of the heat will escape through the walls and through gaps, in and around windows and doors, and about 10% of heat will disappear through the floor. Taking action to make sure your home is energy efficient has many benefits. For your pocket, for your comfort and for the environment.

How do you know if a wall isn't insulated?

If you don't have an inspection scope, you can put an old wire hanger to good use. If you put the wire through the hole and can hear it tapping on the other side, then there isn't insulation in that area of the wall.

Where should you not put insulation?

Never place insulation close to water heaters, oil burners or anything hot. The backing is especially flammable and will be a major fire hazard for your home.

Can lack of insulation in walls cause mold?

Insulation can help to maintain indoor temperature conditions which can help to control factors leading to mold growth so not having it where it counts can be a big problem.

What happens if your house is not properly insulated?

The lack of insulation in homes can lead to condensation and mould growth, creating unhealthy living environments and potentially causing structural damage. Insulation slows the movement of heat through the walls, roof, and floors, maintaining a more consistent indoor temperature.

Is it a good idea to insulate interior walls?

Insulated interior walls will prevent large temperature swings that can crack drywall. These insulated rooms will also hold their temperature longer. For rooms that aren't used frequently, like guest rooms or storage rooms, interior wall insulation can reduce heat transfer and help you save on your utility bill.

What is the cheapest way to insulate a wall?

Here are the three cheapest ways to insulate internal walls:
  1. Insulation Boards. Insulation boards are a popular choice for internal wall insulation because they are relatively affordable and easy to install. ...
  2. Battening the Walls. ...
  3. Building a Stud Wall.

Why don t builders insulate interior walls?

A house where the interior walls have been insulated sounds much more “dead” and still. Cost is a huge issue on insulation. If you look at various building codes, you will see that insulation in noisy areas is not in the requirements.

Can I insulate my walls from the inside?

Internal insulation can be fitted when you're planning to redecorate anyway, or to fit a new kitchen or bathroom. You can also spread the cost by tackling one room at a time. External insulation will also cost less if you fit it when you're having other work done to the outside.

Can you insulate interior walls without removing drywall?

The best, and most common, method for adding insulation without removing drywall is through the drill-and-fill method. Using the drill-and-fill method, the insulation is blown directly into a closed wall through small holes drilled into the wall.

What are the disadvantages of internal wall insulation?

Cons:
  • It is less effective than external wall insulation.
  • It is more likely to cause damp problems (so needs careful planning)
  • You will lose internal floor area.
  • It is a more disruptive process (you may need to move out of the rooms being worked on)

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