Quick Answer
Insulating all internal walls in a home can provide some benefits like improved thermal comfort, reduced noise transmission between rooms, and lower heating and cooling costs. However, it may not make financial sense in all cases depending on factors like climate, existing insulation levels, and budget. A tailored approach evaluating each wall on a case-by-case basis is recommended.
What are the benefits of insulating internal walls?
Some key benefits of insulating internal walls include:
- Improved thermal comfort – Insulation helps maintain comfortable temperatures in each room by reducing heat transfer through walls.
- Noise reduction – Insulating walls decreases noise transmission between rooms, creating quieter spaces.
- Energy savings – Less heat transfer means your heating/cooling system doesn’t have to work as hard, lowering energy bills.
- Condensation reduction – Insulated walls are less prone to condensation buildup and associated mold growth.
Insulating walls is an effective way to increase the overall comfort, energy efficiency, and air quality of a home.
What factors determine if internal wall insulation is beneficial?
Several key factors play a role in determining if insulating an internal wall will provide meaningful benefits:
- Climate – Insulating walls in very cold or hot climates leads to higher energy savings compared to temperate climates.
- Existing insulation levels – Homes with little existing insulation stand to benefit more than those with adequate insulation already.
- Wall construction – Solid brick walls provide more insulation value than framed stud walls by default.
- Adjoining rooms – Insulating between rooms with very different functions (e.g. home theater and bedroom) is more impactful.
- Budget – Upfront costs may not justify small energy savings depending on insulation cost and energy prices.
Knowing these factors helps determine which walls are good candidates for insulation upgrades.
How much does internal wall insulation cost?
The cost to insulate internal walls depends on the insulation material and installation method:
Blown-in insulation
Blowing insulation into wall cavities costs $1-$1.50 per square foot.
Batts/rolls
Installing batt or roll insulation ranges from $1-$3 per square foot.
Rigid foam boards
Rigid insulation board costs $1-$5 per square foot installed.
Spray foam
Spray foam insulation runs $3-$7 per square foot professionally sprayed.
Additional labor costs apply if drywall must be removed and replaced to access wall cavities. Insulating existing finished walls is more expensive than insulating during new construction.
How much money can internal wall insulation save annually?
Annual heating and cooling cost savings from insulating internal walls depends on several factors:
- Existing wall insulation levels – Less existing insulation means more potential savings.
- Insulation material and thickness added – More effective or thicker insulation saves more energy.
- Climate where home is located – Cold and hot climates see higher savings.
- Home size and wall area insulated – More walls equal more savings.
- Energy costs – Higher energy prices lead to increased savings.
Typically, homes see 5-15% in total heating and cooling energy savings from comprehensive internal wall insulation. With average residential energy costs, this translates to roughly $100-$400 in savings per year.
Individual walls may save $10-$60 annually depending on size and use. Payback periods range from 2-20 years.
What are the best materials for insulating internal walls?
Here are top insulating materials for interior walls:
Fiberglass batts
Fiberglass batt insulation is inexpensive, effective, and common. It rates around R-13 for a 3.5″ thick batt. Sound absorption is fair.
Mineral wool batts
Mineral wool batts have similar insulation properties as fiberglass but are denser and provide better sound blocking.
Cellulose
Blown-in cellulose offers good insulation value (R-13 to R-22) and excellent noise reduction for a moderate price.
EPS foam boards
Expanded polystyrene (EPS) foam boards give insulation values from R-4 to R-5 per inch of thickness. They cost slightly more than other options but give the best noise blocking.
Spray foam
Spray polyurethane foams provide the highest R-values (up to R-6.5 per inch) and air sealing, but have the highest cost.
Many factors like climate, budget, noise needs, and existing insulation determine the optimal choice.
Should interior structural walls be insulated?
Structural walls like those between levels or holding up the roof should usually be insulated. Here’s why:
- They take more heat/cooling load – Structural walls are often external facing or separate unconditioned spaces.
- They’re often uninsulated – Structural walls are installed before finishes so lack insulation.
- They transfer more noise – Hard structural materials readily transmit noise.
Adding insulation helps structural walls resist heat flow, absorb noise, and prevent moisture issues like condensation. This provides better comfort and energy efficiency.
Insulating structural walls does not compromise strength when done properly. Building codes require maintaining certain R-values for structural walls.
Should partition walls be insulated?
Partition walls are non-structural interior walls dividing a single level. Insulating these is not always necessary but can provide benefits:
- Between frequently used rooms – Insulation improves comfort and noise.
- Between heated and unheated rooms – Insulation resists heat transfer to unconditioned spaces.
- Rooms with different functions – Insulation contains noise between units in apartments.
- Rooms with HVAC issues – Insulation compensates for inadequate system sizing or supply.
Light partition walls with existing insulation or between closets/hallways likely don’t need additional insulation. Prioritize insulating partition walls between commonly occupied rooms.
Should basement interior walls be insulated?
Insulating basement wall interiors provides similar benefits as upstairs rooms:
- Increased thermal comfort and energy efficiency
- Lower moisture and condensation
- Reduced noise transfer between rooms
However, several factors make insulating basement walls extra beneficial:
- Basements are underground – Earth contact lowers temperatures.
- Most remain unfinished – Open framing lacks insulation.
- Floors amplify noise – Sounds easily transmit below.
Insulating basement wall interiors brings them closer to upstairs comfort and usability levels. Prioritize insulating frequently used spaces like bedrooms, theaters, and playrooms.
Should garage interior walls be insulated?
The decision to insulate garage interior walls depends on how the garage is used:
- Garage workshop or living space – Insulate walls for thermal comfort and noise control.
- Storage garage – Insulate walls bordering conditioned rooms.
- Enclosed but uninsulated garage – Insulate walls to prevent freezing pipes and condensation.
- Detached uninsulated garage – Insulation provides minimal benefit.
It is not cost-effective to insulate all garage interior walls. Focus on shared walls with occupied spaces or zones seeing frequent use. Insulating garage attic spaces has a bigger impact.
Should interior walls with existing insulation be upgraded?
Upgrading insulation in walls with existing insulation can potentially be beneficial in these situations:
- Insulation level is R-5 or less – Added insulation greatly improves performance.
- Walls border extremely cold/hot spaces – Added insulation boosts energy savings.
- Existing insulation has settled – Topping off compression restores insulation value.
- Controlling noise is a priority – Extra insulation absorbs more sound.
- Planning other remodeling – Convenient to add insulation while walls are open.
Otherwise, the small comfort and energy savings from upgrading may not justify the costs for adequate existing insulation like R-11 batts. Priority should go to uninsulated walls first.
What are the main methods for insulating interior walls?
Common interior wall insulation techniques include:
Batt insulation
Fiberglass and mineral wool batts are fitted tightly into wall stud cavities before drywall.
Blown-in insulation
Loose cellulose or fiberglass blown through holes drilled into the walls fills cavities fully.
Rigid foam boards
EPS, XPS or polyiso boards glued over wall surfaces add continuous insulation and damping.
Spray foam
SPF seals cracks and completely fills cavities for the highest R-values.
Injection foam
Foam is injected with hoses into wall cavities through small holes for less mess.
The optimal method depends on insulation type needed, existing construction, and installation considerations.
What are the main considerations when insulating interior walls?
Key considerations for interior wall insulation projects include:
- Vapor barriers – Proper vapor retarders must be installed to prevent moisture issues.
- Draft prevention – Sealing any gaps is crucial to prevent convective loops.
- Wiring issues – Blown-in insulation requires moving or protecting wires.
- Blocked cavities – Plumbing lines, ducting, etc can obstruct full cavity filling.
- Finish restoration – Matching drywall mudding, texturing, and painting takes skill.
- HVAC sizing – Added insulation may require resizing furnace/AC for proper airflow.
Careful planning and execution ensures insulation projects go smoothly and safely with optimal results.
What are the main health and safety concerns with internal wall insulation?
Key health and safety considerations include:
Respiratory hazards
– Dust from some insulation materials can irritate airways without proper masks
Skin and eye issues
– Fibrous insulations especially can cause skin itching and eye irritation upon exposure
Electrical risks
– Drilling into walls risks hitting live wiring if care is not taken
Fire hazards
– Some insulation gives off toxic fumes if exposed to fire, requiring proper fireproofing
Pest risks
– Organic insulations like cellulose provide food for rodents if left exposed
Moisture accumulation
– Condensation from improper vapor barriers leads to mold growth
With safe handling procedures and work practices, insulation risks can be minimized. Proper personal protective equipment is essential.
Does internal wall insulation present any fire risks that need consideration?
Some types of insulation pose greater fire risks than others:
- Polyurethane spray foam – Produces toxic fumes when burned without fireproof barriers
- Cellulose – Densely packed cellulose accelerates fire spread compared to other insulations
- Polystyrene foam – EPS and XPS foam melt and can drip when exposed to high heat
- Fiberglass and mineral wool – Do not sustain flames or produce much smoke
To manage risks:
- Use fire-rated insulation in high-risk areas
- Install thermal insulation barriers for foam and cellulose
- Seal insulations completely behind gypsum wallboard
- Use non-combustible insulations in fire-prone rooms like kitchens
Adhering to building codes and best practices minimizes any insulation-related fire hazards.
How can you determine if existing internal walls are already sufficiently insulated?
Here are some ways to gauge if existing internal wall insulation levels are sufficient:
- Refer to building codes – Current standards like ICC R-13 batts provide a benchmark.
- Inspect wall cross-sections – Directly observing insulation type and thickness during renovations.
- Thermal imaging – Scans detect colder uninsulated areas and air leaks.
- Energy assessments – Performance testing identifies building envelope deficiencies.
- Wall probes – Specialized tools can measure insulation depth in finished walls.
- Remodel history – Home remodels indicate if updated insulation was likely installed.
In older homes especially, walls may lack insulation entirely or be under-insulated by today’s standards. Testing helps identify problem areas to focus improvements.
Should you remove existing siding before installing interior wall insulation?
In most cases, existing wall siding like brick, vinyl, or wood does not need to be removed to add interior wall insulation. Interior installation is far less disruptive.
Reasons siding removal may be required:
- No interior access – Some wall constructions have no interior cavities.
- Insufficient cavity depth – Small framing spaces restrict insulation thickness.
- Pre-1930s home – Interior lath and plaster needs removal before accessing cavities.
- Moisture damage – Siding removal allows wall drainage system installation.
- Siding deterioration – Opportunity to replace damaged siding.
For straightforward drywall insulation, keep existing siding intact. Removing siding should only be done if absolutely necessary.
What are the main disadvantages to insulating interior walls rather than exterior walls?
Interior wall insulation has some downsides compared to exterior insulation:
- Lower insulation value – Exterior insulation is continuous.
- Thermal bridging – Framing still conducts heat through studs.
- Air leakage – Interior insulation does little to seal drafts.
- Moisture risks – Vapor barriers must be meticulously installed.
- Lower curb appeal – Does not improve exterior aesthetic.
- Access difficulties – Finished walls create installation challenges.
- Loss of space – Cavity insulation slightly decreases room area.
However, interior insulation also has significant advantages in cost, convenience, and minimizing disruptions to the home. The optimal choice depends on the specific home.
Conclusion
Insulating all interior walls provides thermal, acoustic, air quality, and efficiency benefits. However, it involves considerations in existing insulation levels, insulation materials, installation methods, costs, and home construction.
A tailored approach evaluating each wall individually helps determine where insulation upgrades are most beneficial and cost-effective. Prioritizing rooms with high occupancy, noise issues, or thermal comfort problems provides the biggest return on investment.
While insulating every interior wall is not always necessary, strategically planning insulation improvements during renovations or retrofits can significantly enhance home comfort and performance.