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Keeping your home warm in winter is more of a matter of keeping heat in, to start with. This is where insulation comes in. Insulating exterior walls in winter is one of the most efficient means of making your home warm and decreasing energy costs.
But what’s the best exterior wall insulation in cold climates? Most experts prefer to use closed-cell spray foam because it is a heat retainer, keeps cold air out, and keeps excessive moisture build-up in check. This keeps your home warmer for a longer period of time and reduces such issues as dampness and mould.
Best Insulation for Exterior Walls
When keeping a house warm in cold weather, it is a matter of using the right insulation materials. Some of these hold heat better, whereas others seal up air leaks and dampness. Some of the best of these are:
1. Fiberglass Insulation
Fiberglass is made from tiny glass fibers and comes in rolls or batts. It is a low-cost product usually placed between wall studs. It resists heat well but does not block airflow. This can lead to heat loss over time.
One downside is that it sags after a period of time, hence it is not that useful anymore. Also, it is irritating to the skin when applying. However, it is a popular option due to it being easy to install and it is also low in price.
- Pros: Low cost, easy installation, reasonable thermal resistance.
- Cons: Can sag over time, allows air movement, can be irritating to the skin when installing.
2. Foam Board Insulation
Foam boards, or rigid foam, are manufactured using polyurethane or polystyrene material. The foam boards can be installed externally or between studs, making them convenient to use.
This insulation is more expensive than fiberglass but is a more resilient thermal barrier that is also more permanent. Sealing is also necessary to plug up the air leaks around the perimeter, though.
- Pros: High per-inch ratio of resistance, water resistant, durability.
- Cons: You need to close it up tight to prevent air leaks. It is more expensive than fiberglass.
3. Spray Foam Insulation
It is applied to close gaps and cracks to give a tight air-tight seal. This is excellent in preventing heat loss and maintaining a constant interior temperature. Close-cell spray foam is a high R-Value product that is also a vapor barrier, while open-cell spray foam is more flexible and used in applications for soundproofing.
This insulation is expensive but highly effective. Professional installation is frequently a requirement, adding its high price to it. However, it is one of the most energy-efficient options available.
- Pros: Excellent thermal insulation, prevents air leakage, increases strength of structure.
- Cons: Expensive, professional installation is necessary.
4. Cellulose Insulation
Manufacturers make it from recycled paper, making it an environmentally friendly product. People usually blow cellulose into wall cavities. It is a great option for existing homes because there is no need to remove drywall.
Although it is a great thermal resistor, it can settle in the long term which also creates gaps in the insulation. It is also a moisture absorber, and hence it is somewhat ineffective. Despite these deficiencies, it is one of the most eco-friendly to use to insulate.
- Pros: Environmentally friendly, great thermal resistance, ideal for use in soundproofing.
- Cons: Can settle over time, and possibly requires a vapor barrier to prevent moisture issues.
5. Rigid Foam Board
Rigid foam panels exhibit high thermal resistance and restrict heat loss in walls. The panels can be installed externally or between studs to supply a solid layer of insulation.
They provide great resistance to dampness and also great insulation, though more costly is rigid foam board in comparison to fiberglass and cellulose. Though it is more energy efficient and more resilient.
- Pros: Long-lasting, moisture-resistant.
- Cons: Higher in price, requires accurate installation.
6. Rock Wool Insulation
Rock wool, or mineral wool, is manufactured using natural minerals and is fireproof and soundproof in character. The product is a high-grade heat retainer that is resistant to dampness, making it a durable option.
This type of insulation is more expensive than fiberglass and harder to cut and install. However, its fire resistance, durability, and resistance to dampness make it a wonderful choice for exterior wall insulation.
- Pros: Fire-resistant, water-repellent, excellent to apply in applications of noise reduction.
- Cons: More expensive than fiberglass, harder to cut and fit.
Check your Eligibility Now
If you are receiving benefits from the UK Government then you might be eligible for free insulation grants.
Insulation for Different Wall Types
The right thickness of insulation is a function of the home framing of walls. The two most prevalent wall frames in homes are 2×4 walls and 2×6 walls. Each of which needs a different thickness of insulation to be most energy efficient.
2×4 Walls
Homes built with 2×4 construction need insulation to create a 3.5-inch stud cavity. The most suitable options are:
- R-13 or R-15 fiberglass batts – Low-cost, easy to install, and is a kraft-faced vapor barrier
- Mineral wool (rock wool) insulation – Is more fire resistant and more soundproof than fiberglass but is more costly.
2×6 Walls
Homes with 2×6 studs need to be insulated in a 5.5-inch stud cavity. The preferences of choice are
- R-19 or R-21 fiberglass batts – The higher the R-values, the more they insulate to resist heat loss
- Mineral wool insulation – The thickest of the three, extremely fire resistant, and of high durability in the long term.
So, What Is the Best Insulation for Exterior Walls?
The best exterior wall insulation is a matter of budget, house design, and climate. In cold climates, you obtain maximum energy efficiency when you apply closed-cell spray foam or rigid foam boards. Alternatively, you can apply mineral wool or fiberglass batts if you prefer something more affordable.
Minimum Insulation Thickness for Exterior Walls
The thickness of the insulation must be between 80 mm to 140 mm depending on the material you use and the amount of insulation you need.
The minimum thickness of approximately 50 mm is recommended in UK building rules, though it is recommended to use a minimum of 100mm to get a U-value of 0.3W/m²K.
The actual thickness you need is dependent on construction and the type of insulation of your wall. The thicker it is, the better its R-factor will be, meaning that it is more efficient in winter and in summer.
R-Value for Exterior Wall Insulation
The R-value is a measurement of a material’s resistance to heat transfer. The higher the R-value, the more insulated it is. The walls in a house in the UK must be approximately 3.30 m²K/W in terms of their R-value.
The required R-value is dependent on climate, material of insulation, and building regulation. Always check the local code to meet your home’s specifications and requirements.
Different materials carry different R-values per inch, so be sure to check the material you choose before determining the proper thickness.
Best Insulation for Soundproofing Exterior Walls
Mineral wool (Rock wool) is one of the best options when it comes to soundproofing. It is heavy, a wonderful sound absorber, and a good thermal insulator. Soundproof insulation is a lifesaver if you need to reduce noise from traffic, neighbours, or other outside sounds.
Here are a few other great options:
- Mineral wool (rock wool) – Sound-absorbing and excellent at blocking noise.
- Spray foam insulation – Insulates gaps and prevents penetration of sound through walls.
- Rigid foam boards – This is a sound reducer, though works best when combined with other forms of insulation.
For the best soundproofing, employ a double-layered insulation system with both acoustic mineral wool and rigid foam panels.
Best Rigid Insulation for Exterior Walls
Rigid insulation boards are highly suitable for exterior wall insulation due to their high thermal resistance properties and durability in the face of moisture. The most suitable options are
- EPS: Cheap, yet light in weight, and also resistant to water. Overall a fantastic all-around material.
- XPS: It is stronger and more water-resistant, making it ideal for rainy areas.
- Polyiso: It has the highest R-value per inch. So it is used in tight spaces to provide maximum insulation.
Advantages and Disadvantages of External Wall Insulation
External wall insulation is a great way to make a house more energy efficient, but it also has pros and cons.
Advantages
- Better Energy Efficiency – Less heat loss, warmer home in winter, cooler home in summer
- Lower Energy Bills – Reduces heating costs by insulating homes
- Improved Soundproofing – Adds a secondary barrier to help block exterior noise.
- Weather Protection – Shields your home against wind, rain, and temperature swings.
- Enhanced Appearance – Update the look of your home with a new finish.
Disadvantages
- High Upfront Cost – More expensive than internal insulation.
- Changes the Outside Appearance – This is not always permitted in conservation areas or in listed buildings.
- Complex Installation – Professional installation is needed and it is time-consuming
- Potential Planning Constraints – There may be controls in some areas over altering exterior walls.
Installation Methods: DIY vs Professional
DIY
If you are confident in your skills, you can save money by installing it yourself. However, DIY is better for simpler insulation methods.
For rigid foam board insulation, attach the panels to the exterior wall with adhesive and secure them mechanically.
For weatherproof insulation panels, use prefabricated systems that make installation easier.
Pros of DIY:
- Saves money on labor costs.
- Flexible timing – you work on your own schedule.
Cons of DIY:
- Requires skill and the right tools.
- Mistakes can also lead to bad insulation performance and to moisture issues.
Professional Installation
For the best results, please hire a professional to undertake it for you.
- External wall insulation systems – Typically installed by experts using insulation boards, mesh, and a protective render.
- Spray foam insulation – Professional installation is required using specialist tools.
Pros
- Guaranteed quality and adherence to building regulations
- Less risk of making mistakes, and more energy-efficient
- Faster and hassle-free process.
Cons
- Higher cost of material and labour
- You may have to wait until a contractor is free.
If you require a high-performance, long-lasting system of insulation, professional installation is always a better bet. Alternatively, you can also install rigid insulation boards yourself if you have a tight budget and you know you can manage it.
Right Insulation for Your Exterior Walls
Picking the ideal insulation for your exterior walls is a function of your home’s structure, budget, and desired insulation. Consider the following:
- Wall Type – Solid walls need a different insulation to that of a cavity wall. Solid walls can be insulated externally, whilst cavity wall insulation is used in homes that have a gap in between the brickwork.
- Energy efficiency – Demand high R-value insulation to reduce heat loss and gain maximum energy savings.
- Moisture resistance – In a humid area, use a material that is resistant to moisture, such as closed-cell spray foam or rigid foam board.
- Soundproofing – Both mineral wool and high-density cellulose function well to cut down on noise.
- Fire resistance – One of the great fire protection options is mineral wool.
- Installation method – Some materials, like rigid foam boards, are DIY-friendly, while others, like external wall insulation systems, require professional installation.
- Cost – The cheapest option is fiberglass, though more expensive spray foam and mineral wool options deliver better performance.
Exterior Wall Insulation Grants
If you’re concerned regarding affordability, you can be eligible for government grants to finance external wall insulation. In the United Kingdom, there is an ECO4 scheme that funds free exterior wall insulation grants. To find out if you qualify, you can check the government’s website or contact a licensed energy supplier.
The Bottom Line
External wall insulation is a great way of reducing heat loss, and energy bills and improving home comfort. As a more costly upfront expense, though, the long-term return in money saved and comfort is more than worth it.
With grants that you can obtain, you won’t even have to pay for it in total yourself. With whatever you choose to use – rigid boards, mineral wool, or spray foam – just be sure to pick the right one for your home and budget.
Frequently Asked Questions
Yes, you can also insulate exterior walls from the inside, a useful option when exterior insulation is not feasible. Some of the more common methods are blown-in cellulose (it’s a great option to use to fill cavities in walls) and spray foam (it’s great to use to air-seal).
Closed-cell spray foam is used on exterior walls. Closed-cell spray foam is a highly insulated, highly air-tight, and highly water-resistant material. Nevertheless, it is more expensive than other insulations.
PIR boards are one of the more appropriate options in that they provide high thermal resistance in a thin thickness. EPS is also a low-cost material that is also a good insulator.
Yes, but it is not recommended. There is a do-it-yourself option in the form of spray foam or rigid foam panels for small use. Professional installation of large exterior wall insulation is needed, though. So please hire a professional.
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