The R-value of insulation is a measure of its ability to resist heat traveling through it, and higher R-values indicate better thermal performance. Exterior insulation can add additional R-value to the wall system by adding a small amount of thickness and eliminating thermal bridging that occurs where framing materials transfer heat. For most climates and building styles, an R-value of 12 inches is recommended for exterior walls.
There are three potential ways to insulate the walls of your home: external wall insulation, cavity wall, and internal insulation. Thicker walls generally have a lower U-value, meaning they offer better thermal efficiency. The goal of adding external insulation is to reduce the U-value, thereby improving thermal efficiency.
To increase the R-Value of the external walls, go beyond the standard R2.5-3.0 Batts that can be entered into most walls. Thicker insulation provides better thermal performance and energy savings, but adding too much insulation creates other issues that must be considered. External walls should be insulated to their full thickness, with 2×4 walls having 4″ insulation and 2×6 walls having 6″ insulation.
The type of insulation used should also be considered. Thick walls do not necessarily mean good insulation; usually between 1″ to 3″ is a good number. Most rigid foam installs limit the exterior drying capacity of the wall. Thicker exterior walls are beneficial because they allow for the use of denser insulation materials that provide higher R-values. Fiberglass insulation can also be used to improve the exterior wall’s R-values.
In new construction, the recommendation for wall thickness is double the current standard – 12 inches.
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Let’s talk wall assemblies. Bomber wall options to frame a REALLY good wall with 2×4-6-8’s and some thick insulation. A home …
What is the problem with too much thick insulation?
Over-insulating walls can cause issues like poor ventilation, mold growth, and condensation, as thicker insulation can block airflow and trap moisture, leading to indoor air quality issues and structural damage. It’s crucial to balance energy efficiency and proper ventilation when insulating walls. The maximum thickness for walls is around 4-5 inches, beyond which additional insulation won’t significantly impact energy savings. Adding extra insulation to your home can be a significant investment, but in most cases, it’s worth it. In most cases, the additional insulation is worth the cost.
Can your R-value be too high?
Over-insulation in an attic can negatively impact a home’s energy efficiency and comfort. In most of the United States, achieving an R-Value of 38 is sufficient for most attics. Proper attic insulation should have the optimal R-value based on the location and home requirements. Whether using blanket insulation, fiberglass insulation, spray foam insulation, or cellulose insulation, the goal is to achieve the proper depth and ideal R-value for your attic space.
While over-insulated attics are less common than under-insulated attics, it is possible to put too much insulation in your attic that negatively impacts its function. Understanding how your attic functions, why attic insulation is crucial for your home’s energy efficiency and comfort, and how much is too much insulation in your attic is essential for maintaining a comfortable and energy-efficient home.
What R-value insulation is recommended for exterior walls?
The necessity for insulation in a given residence is contingent upon a number of factors, including the geographical location of the property and the specific architectural elements comprising the dwelling. Exterior walls typically necessitate insulation with an R-value of between 13 and 23, while ceilings and attic spaces require insulation with an R-value of between 30 and 49. In order to ascertain the recommended R-value and insulation level, it is advisable to utilise the JM insulation calculator in conjunction with the Department of Energy’s map.
Can insulation be too thick?
Over-insulating a house can lead to mold growth and lower-quality air. The main purpose of home insulation is to tightly seal the interior, but if it becomes too tightly sealed, moisture can get trapped, causing mold growth. This can make it difficult to achieve consistent temperatures and breathe in lower-quality air. While it is possible to over-insulate a house, it is unlikely that you are in danger.
Does doubling the thickness of insulation double the R-value?
Doubling the thickness of insulation can double its R-Value, but it doesn’t necessarily reduce heat loss by half. In cold weather, insulation acts like a puffy parka, holding in body heat and reducing heat flow from inside to outside during winter and from outside to inside during summer. A continuous layer of insulation should be present on all sides of a home, including the floor, exterior walls, and ceiling or roof. However, doubling insulation from R-10 to R-20 will result in more energy saved per year due to the law of diminishing returns.
In some cases, like attics, more insulation may be necessary due to ample space, but it’s more expensive to add more insulation to exterior walls. Overall, a continuous layer of insulation is essential for a home’s thermal barrier.
How thick should exterior insulation be?
External wall insulation should be 0. 3W/m2K or better, typically around 60mm or up to 100mm, depending on the material of the existing wall. To ensure the right thickness and the highest standard installation, it is recommended to hire a professional EWI Installer. They can provide a range of finishes and minimize disruption, as the entire work takes place on the exterior of the property, unlike interior wall insulation. This allows you to continue living as usual while your home is being insulated. Therefore, it is essential to choose a professional for your insulation needs.
What are the downsides of external wall insulation?
External wall insulation is a crucial component in creating comfortable living spaces and enhancing home energy efficiency. However, it is important to note that not all insulation types are created equal. Traditional methods, such as using insulative boards like fibre cement and polystyrene, can enhance thermal performance. A render is applied over these boards to protect them and create an aesthetically pleasing finish. Rockwool, a type of mineral wool insulation, is also popular in the UK.
8 disadvantages of external wall insulation types include impermeability, size, cost, insulation issues, irritation to the skin and respiratory system, weight, limited insulation value, and environmental impact. While these types can be effective, they come with several disadvantages, such as impermeability, size, cost, insulation issues, irritation to the skin and respiratory system, weight, limited insulation value, and environmental impact.
Is R-value dependent on thickness?
Insulation is rated in terms of thermal resistance, or R-value, which indicates the resistance to heat flow. The higher the R-value, the greater the insulating effectiveness. The R-value depends on the material, thickness, and density of the insulation. The effectiveness of an insulated ceiling, wall, or floor depends on how and where it is installed. Compressed insulation will not give its full rated R-value, as it can be added to denser insulation or placed into thinner cavities.
Thermal bridging occurs when insulation placed between joists, rafters, and studs does not retard heat flow through those areas. The overall R-value of a wall or ceiling will be slightly different from the insulation itself. It is important to cover the tops of joists and use insulative sheathing on walls.
To ensure the product is suitable for the intended application, check the information on the product label. The Federal Trade Commission has clear rules about the R-value label that must be placed on all residential insulation products, whether they are installed by professionals or purchased at a local supply store. Take time to read the label before installing the insulation and insist that contractors provide product labels from each package. Some materials require a greater initial thickness to offset eventual settling or ensure the rated R-value under a range of temperature conditions.
Does thickness affect insulation?
Insulation in a home increases its resistance to heat flow and R-value. However, loose-fill insulation’s R-value does not change proportionately with thickness due to compression. Consult a local contractor to determine the necessary insulation for your climate. The effectiveness of insulation’s resistance to heat flow depends on its installation method and location. Compressed insulation may not provide its full rated R-value. The overall R-value of a wall or ceiling may differ from the insulation itself due to thermal bridging.
Insulation that fills building cavities reduces airflow or leakage, saving energy. Radiant barriers, unlike traditional insulation, are highly reflective and re-emit radiant heat, reducing cooling loads. They have no inherent R-value.
Are thicker walls better for insulation?
The effectiveness of insulation depends on various factors, including volume of insulation material, type of insulation material, structural design, external factors like wind speed and temperatures, and the age of the structure. Thicker walls can accommodate more insulation material, offering better resistance to heat flow. Structural design with fewer thermal bridges also results in better insulation. Environmental conditions like wind speed and temperatures can influence insulation effectiveness.
Older structures may have settled or shifted over time, affecting wall thickness and insulation efficiency. Partnering with a trusted provider like Premier Insulation ensures that walls are optimized for Massachusetts weather conditions. Maximizing wall insulation requires planning and wisdom.
What is the best thickness for external wall insulation?
Insulation systems (EWI) are typically installed using 100mm insulation boards, which can be impractical for certain areas. Thinner systems offer better U-value savings but are more expensive. Installation takes a few days depending on the property’s size, with most completed within 5-7 working days. EWI costs can range from £4, 000 for smaller terraced properties to £14, 000+ for larger detached homes, depending on the size of the house and the number of walls needed.
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Are you starting a DIY insulation project and not sure which type to choose? In this video I’ll go over the difference between pink …
6. 2×6 w/ zip R-3 (or R-6, R-9, R-12) and batt Rockwool R-23 insulation * Effective R-value of opaque assembly = 22 * $3.62 per sqft 1:19 7. 2×6 w/ plywood, Delta Vent SA, Rockwool Exterior comfortboard 80 (1.5″), and batt Rockwool R-23 insulation * Effective R-value of opaque assembly = 25 * $5.82 per sqft – (60% more than previous assembly) 3:35 8. 2×4 w/zip sheathing, Atlas energy guard 2″ polyiso (R-13), and batt rockwool R-15 * Effective R-value of opaque assembly = 27 * $ 4.05 per sqft – (30% less than previous assembly) 5:53 9. 2×8 w/ zip R-6 (or R-6, R-9, R-12) and batt Rockwool R-30 insulation * Effective R-value of opaque assembly = 30 * $4.82 per sqft – (19% more than previous assembly) 10:52 10. 2×8 w/ plywood, Prosoco R-guard, 3″ of Polyiso (2 @ 1.5″, offset seams), and batt Rockwool R-30 Insulation * Effective R-value of opaque assembly = 45 * $7.13 per sqft – (48% more than previous assembly) 12:29
I do blower door tests etc on new homes here in Wisconsin and I often see large homes that perform so-so. Not terrible compared to many fast-built tract homes but could be a lot better. My advice to people who have the luxury of planning a home build is to eliminate some square footage and put that savings into performance. Also, simpler designs are easier to make tight and to perform better.
Matt, You are costing me a lot of money. My home, which my wife and I love, was built in 1961. My utility cost is crazy high and I am repairing on stripping my home down to the studs from the outside, using new insulation between the studs, adding zip sheathing and an additional 2″ outside of that then furring then siding. I have built only 16 homes in my life, thought I knew it all, it through perusal your content and studying the building science behind your thoughts I didn’t know much. Thanks for the knowledge and keep it coming.
On my old house there is 2 by 4 walls and only sheething innside, cold climate in Norway. Doing renovation on it and changing the wall siding, put 2×2 laying on the whole wall and insulated the outside with rockwool then Tyvek vapor permable fabric and then one more layer pressure treated 2×2 for air flow and then the siding. Love the tought of insulated house framing where it stays at a nearly constant temperature all year around
Here’s the complete overview of all the assemblies: First Assembly: R-22 effective 2×6 R-23 Rockwool batting Zip System (R-3) Liquid Flash w/ foundation $3.62/sqft Second Assembly: R-25 effective 2×6 R-23 Rockwool batting Plywood Delta Vent SA Rockwool Comfortboard Tape w/ foundation $5.82/sqft Third Assembly: R-27 effective 2×4 R-15 Rockwool batting Zip System Atlas Energy Shield 2″ Polyiso (R-13) PT bug plate Liquid Flash w/ foundation $4.05/sqft Fourth Assembly: R-30 effective 2×8 R-30 Rockwool batting Zip System (R-3) PT bug plate Liquid Flash w/ foundation $4.82/sqft Fifth Assembly: R-45 effective 2×8 R-30 Rockwool batting Plywood Prosoco Fluid Apply (R-Guard & Joint and Seam Filler) Two layers (3″ total offset) of Atlas Energy Shield 1.5″ Polyiso (R-9.8) PT bug plate Prosoco Joint and Seam Filler w/ foundation $7.13/sqft
Drives me nuts how content is presented for the sponsor benefit. My experience and calcs say the best approach is to do a conventional frame; 2×4 or 2×6, depending on wind loading for your area, then sheathing of choice (ps guys, OSB is not horrendous vs plywood, which has all sorts of QC issues of its own). Then, 100% liquid applied or self-adhered with liquid applied as required (such as outie windows, and bucks fully coated, unlike Matt’s own build). And I use Barritech VP liquid applied, from Carlisle, for good reasons. Then, MAX OUT the continuous exterior insulation. It all comes down to the entirety of the delta temp that any part of the assemble, and its insulation materials, are seeing. Once inside the continuous layer, the heavy lifting (thermally speaking) is DONE. And bear in mind that the cost of a rain screen/ furring is ignored in the ZIP R versions shown here, despite being promoted incessantly here as the “right stuff”. Can’t walk both sides of the street, in my world. And, if one is going to perseverate about the cost of fasteners, keep firmly in mind that Rockwool is a good product, but is about half the R-value of polyiso, per inch. That means you need a LOT thicker blanket and finished wall assembly, for the same thermal performance (hint: look at fastener schedule and costs carefully). Law of Diminishing Returns says put the most you can in the continuous exterior layer, have an awesome air seal, and don’t waste time and money on the cavities; FG batts have a better return on money spent.
I’m sure there’s all sorts of research on this but I would be worried about shear resistance with the thicker Zip System sheathing. My inclination would be to just say no in the most serious earthquake areas. As an aside, the exterior rockwool insulation sounds awesome for use in a fire area. This seems like it could be part of the construction of a nearly fireproof house.
There is nothing wrong with using foil faced or otherwise vapor impermeable exterior insulation in northern climates – but it’s very important to put enough of it to keep the interior side of the sheathing warm enough to be above the dewpoint. And let the assembly dry to the interior – which means no interior vapor barrier.
Why complicating? 6×6 poles, spread every 8ft, with 2×4 cross beams internally and externally. Cross beam offset vertically to elongate thermal bridging. You have 6in of solid rockwool insulation with cross-pattern of 2in on either side giving total of 10in with lowest (thermal bridge) case of 2in (external insulation) + 6in (timber post) + 2in (external insulation) combo every 8ft! This is basically a passive house construction in every climate!. In most climates you can easily go with 6in if central rockwool and 2in free air voids both inter and externally. Or reduce beam thickness to 1×4 and pack them with 1in insulation or air void. This is on 6×6 post which allows you built 3 stories up. Posts every 8ft give cheap foundations. Total timber volume is less. Total building weight is less. Framing time is less. And you totally open internal space which can be arranged and modified freely. Only external walls/post are weight bearing !!
I think ease of construction should also be a major consideration, especially if you’re contracting out. So set-up 10 although it has a high R-value, if not built properly (which is likely in the uk lol), the R-value definitely won’t be that high. Whereas set-ups 6 and 9 is should be (should be!) difficult to screw up
Can you show examples of 2×6 and 2×8 houses that have already been built? I can imagine, that they look and feel more rich and sturdy, because of the deeper window sills and thicker walls and door frames. Would you use the thicker studs only for the exterior walls? Would there be any good reason other than the look to use 2×6 or 2×8 studs for interior walls?
I’m curious, in the last article you also talked only about rockwool. Why are you choosing that over fiberglass? Is it really worth the cost increase? I’m thinking of doing post frame and how I would make it efficient. My thoughts are a combination of post frame, the monopoly house zip-r, and attaching overhangs separately. 2″ of spray foam on the inside, and then fiberglass batting. I’m assuming 2×6 framing. My goal: very cost efficient build yet still effective.
“5 Ultra-Insulated Framed Walls” I’m surprised one of the 5 examples didn’t include closed cell spray foam. One respectable builder here is doing good detail work with sprayed in cellulose and is getting .03 blower door numbers injunction with OSB sheeting. I’m assuming 0.03 is a good number for those types of products?
What climate data do we look at to determine if we need a vapor permeable sheathing on the outside of a home? You gave examples of not wanting vapor permeability in a cold climate and wanting vapor permeability in Austin, which can be a humid environment. Can you reduce it to specific facts that we can check for a specific build location?
Matt, I would love to get an opinion on some of the sip like panels out there that are less mainstream. Companies like Thermobuilt, Insulsteel, Raycore, Thermasteel and Structall. They all have unique systems that have no plywood/OSB/sheathing and they claim to be more energy efficient and structurally sound than other sips and traditional framing methods. What are your thoughts?
Let’s say you live in zone 6, with fire hazard as a variable you should contend with. Considering ICF with additional 1.5″ insulation on the exterior or say option #8 or #9 from this article? Which would you choose? I like the simplicity of the ICF, but the cost of the options in this article are very appealing to the wallet.