Building codes generally require exterior walls and walls between shared dwellings to be insulated. Adding more insulation than the bare minimum required by the building codes – even to the home’s interior walls – can be beneficial both for the home itself and the people living inside it. I wanted to know more about the topic of wall insulation with the purchase of our new home in Lewes, Delaware. I did some research to understand if all walls need insulation and what the benefits are to have all walls insulated.
Exterior Walls
Almost all building codes require insulation for external walls, and codes in many parts of the country require insulation values of R-19 or higher.
What does R-19 mean? In essence, the R-value measures how much heat the wall can sustain with the existing insulation. The higher the number, the better the insulation is working to prevent heat transfer.
You may live in an older house that predates these codes and are happy you don’t have to do extra work. However, making sure that your exterior walls are well insulated will go a long way to increasing your comfort and decreasing your energy bills.
Blow-in insulation or injectable spray foam insulation is likely the easiest way to add insulation to an existing home. Using the dense pack technique to add this kind of insulation provides effective air sealing, and you can do this without disturbing the finished areas of your home or opening up the walls.
If your walls will be opened for other remodeling work, you may want to consider wet-spray cellulose insulation or two-part spray foam. These will provide the tightest seal and most insulative properties. If you are on a tight budget, batt-and-roll (blanket) insulation is more economical. It will not provide as tight of an air seal as the foams, but it will definitely increase the insulation in your home.
When you are building a new home, you have lots of options for effective, economical insulation. Insulating concrete forms, insulated concrete blocks, and structural insulated panels all contain built-in insulation. This will reduce thermal bridging and provide superior insulation. Advanced wall framing techniques and insulated wall sheathing are also effective and efficient.
Party Walls
You typically find party walls (shared interior walls) in apartments, duplexes, condominiums, and townhouses. Most building authorities require owners to insulate these party walls. This means that you may need to consult these authorities and probably your Homeowners Association (HOA) if you are planning to modify these walls.
Whether or not building codes require insulation in shared party walls, it’s an excellent idea to ensure that they are adequately insulated. Insulating party walls decrease sound transmission, reduces thermal transfer, and significantly diminishes fire spread between units.
In this case, proper insulation must be fire-rated, and the compound, tape, and drywall used to construct the party wall need to be fire-rated as well.
Interior Walls
It is rare for building codes to require insulation for interior walls; therefore, most of us live in dwellings without insulated interior walls. Even if the code doesn’t require it, it can be very beneficial, and homeowners may want to consider adding insulation to their interior walls.
Properly insulated interior walls:
- Decrease sound transmission
- Increase energy efficiency
- Prevent walls from cracking
- Reduce dampness and condensation
- Reduce the risk of fire spreading
Sound Barrier
Insulating interior walls helps to create a sound barrier between rooms. Drywall alone provides a minimal barrier to sound transmission. Adding insulation underneath the drywall in a typical home can help control the transfer of sound between rooms. Many people appreciate this in bedrooms and bathrooms especially.
Energy Efficiency
Adding insulation also dramatically increases energy efficiency. It can reduce the thermal bridge or heat transfer between rooms. It also reduces temperature fluctuations between rooms, which means that your HVAC system won’t have to work as hard to maintain even temperatures.
You and your family will feel more comfortable in an evenly heated and cooled house. You will also pay lower energy bills as a bonus.
Moisture Control
Properly insulating your interior walls also helps with interior moisture control. Nearly every home experiences fluctuations in humidity from showering/bathing, cooking, and doing laundry.
If this humidity accumulates and condenses in the walls, it can lead to water stains, rot, mold, and mildew. The last two can especially be serious health hazards. Insulating the interior walls reduces moisture collection, and you can also add vapor-resistant membranes to minimize condensation as well.
Preservation of the Walls
Insulating your interior walls and lessening temperature fluctuations help preserve the interior walls themselves, especially in less-used areas such as storage rooms and guest rooms.
When there are dramatic temperature differences, the framing can expand and contract, and the drywall can crack. Keeping the temperature consistent throughout the house will lessen the chances of this happening.
As mentioned above, insulated walls can help to prevent the spread of fire between rooms. You will need to make sure that the insulation, the drywall, and other materials are fire-rated. But insulating bedroom walls is just one more thing that you can do to protect your family as they sleep at night.
Interior Walls Insulation Options
You have several options when it comes to insulating interior walls.
If you’re doing most of the work yourself, fiberglass batt insulation is relatively inexpensive and moderately handy people can usually install it on their own.
It comes in rolls, which you will have to cut to accommodate the most common stud spacings. In general, fiberglass and mineral wool batts help you minimize noise.
When you’re working with professionals, you can also choose expandable foam insulation or blown-in cellulose insulation. Both of these require installers to work around your walls’ existing structure, including outlets and other fixtures.
Blown-in cellulose also requires installers to drill holes in the walls and then patch them afterward. However, it’s often worth the trouble because cellulose insulation is eco-friendly (made from recycled materials) and is resistant to insects, mold, and fire.
Bottom Line
In most areas of the country, building codes require exterior walls and party walls to be adequately insulated. Some people prefer more insulation than what authorities require. Adding insulation to most walls significantly increases the comfort and safety of the people living in the home.
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