The popular 'How It's Made' TV series visits the ROXUL factory in this 5 minute video http://youtu.be/clN-wB8Vl_k
You may also be interested in this video of ROXUL's "Test The Best" demo presented at building stores across the country. http://youtu.be/7rbRYs0XEAM
Showing posts with label Spray Foam. Show all posts
Showing posts with label Spray Foam. Show all posts
Monday, 13 January 2014
ROXUL Mineral Wool Insulation - Highly Vapour Open
Dr. John Straube of Building Science Corp dispels the misconceptions of mineral wool insulation and identifies some of the many benefits from choosing ROXUL in this 3.5 minute video.
http://youtu.be/Fc6sVrVjRks
Of particular importance is his comments regarding the vapour permeance of a mineral wool insulation in comparison with rigid or spray foam insulation and why this is so important.
"Some insulation products that have built-in vapour resistance can impede drying and this can become an important concern during design. The resiliency of a wall to built-in construction moisture or accidental flaws in water control needs to consider how that insulation will allow drying outward."
"There are many types of foam insulation but all of them are characterized by limiting vapour flow through them."
"If the design is not taking into account resistant properties of foam, you can trap moisture in a wall or roof assembly, and of course trapped moisture leads to damage such as mould growth, corrosion or decay."
"One of the unique features of stone wool is that it is very open to vapour flow" "This means there are some tremendous advantages if you are trying to dry a wall or roof out or in, because water vapour came move almost unimpeded through the actual insulation product"
http://youtu.be/Fc6sVrVjRks
Of particular importance is his comments regarding the vapour permeance of a mineral wool insulation in comparison with rigid or spray foam insulation and why this is so important.
"Some insulation products that have built-in vapour resistance can impede drying and this can become an important concern during design. The resiliency of a wall to built-in construction moisture or accidental flaws in water control needs to consider how that insulation will allow drying outward."
"There are many types of foam insulation but all of them are characterized by limiting vapour flow through them."
"If the design is not taking into account resistant properties of foam, you can trap moisture in a wall or roof assembly, and of course trapped moisture leads to damage such as mould growth, corrosion or decay."
"One of the unique features of stone wool is that it is very open to vapour flow" "This means there are some tremendous advantages if you are trying to dry a wall or roof out or in, because water vapour came move almost unimpeded through the actual insulation product"
Monday, 9 December 2013
It's All About The Air Barrier!
Building Science Corporation has just released their report (available here ) that confirms that if you give insulation a chance by air sealing the assembly, all insulation will perform the same from a thermal transfer stand point.
The report highlights the increasing level of importance attributed to getting the details right as you increase the performance of an assembly by adding more insulation. Loosing 10% of your nominal value when you have a R15 assembly is a lot less critical than when you have a R50 assembly.
In order to complete this study, BSC had to design and build a hot box that significantly improved upon past designs.
Key improvements include the ability to:
An interesting outcome of the air leakage measurements:
"Air leakage always increases the total heat flow through the building enclosure. However, air interacts with the materials in an assembly as it travels through. This interaction changes the temperature field in the assembly and through an assembly. The Thermal Metric wall test results provide strong evidence of the interaction between conductive and convective heat flows. This interaction results in heat exchange between the air and the materials inside the wall assembly and the total measured heat flow will be less than predicted by the commonly used discrete air leakage model"
Also of interest was the observation that "All of the reference test wall assemblies were subjected to significant temperature differences: up to 50°C or 90°F in the winter tests and up to 40°C or 72°F in the summer tests. Natural convective looping was not noted in any of the wall assemblies."
One of the most important confirmations for me was that "All wall assemblies experienced a loss in thermal performance due to air movement through the assembly. This is true for all of the assemblies tested regardless of the type of insulation material used (e.g. cellulose, fiberglass, ocSPF, ccSPF, XPS)". With the failure of an effective air barrier that I typically see on spray foam jobs, this research helps to confirm that without an effective AB, even the might spray foam has diminishing thermal resistance. The report also confirmed "spray foam insulation only seal areas where the spray foam is installed; significant leakage paths often remain at wood to wood connections" This confirms my conviction that spray foam is highly over rated. If it does not guarantee an air tight assembly (see 3.6.4 on pg 102 of the report to see air barrier failures that occurred even in these lab conditions), why use it when there are cheaper products of lower environmental impact available? I see attempting to use insulation as an air barrier as being just as foolish as attempting to use a poly vapour barrier to double as an air barrier. Both products are hard pressed to represent an effective and durable air barrier.
Finally, it was interesting to note that they were able to measure the various resistance to air flow that different insulation represent. In 1.1 the report confirms that wet sprayed cellulose has more resistance to air movement over various fibreglass bat products. It is too bad that they did not test mineral wool as it would be interesting to see how it compares to WPC. Maybe next time!
The report highlights the increasing level of importance attributed to getting the details right as you increase the performance of an assembly by adding more insulation. Loosing 10% of your nominal value when you have a R15 assembly is a lot less critical than when you have a R50 assembly.
In order to complete this study, BSC had to design and build a hot box that significantly improved upon past designs.
Key improvements include the ability to:
- test higher R value enclosure assemblies (which have lower heat fluxes),
- expose enclosure wall samples to realistic temperature differences while maintaining the interior temperature at normal room temperatures, and
- measure the impact of imposed airflow at a given pressure difference across the specimen in both directions
An interesting outcome of the air leakage measurements:
"Air leakage always increases the total heat flow through the building enclosure. However, air interacts with the materials in an assembly as it travels through. This interaction changes the temperature field in the assembly and through an assembly. The Thermal Metric wall test results provide strong evidence of the interaction between conductive and convective heat flows. This interaction results in heat exchange between the air and the materials inside the wall assembly and the total measured heat flow will be less than predicted by the commonly used discrete air leakage model"
Also of interest was the observation that "All of the reference test wall assemblies were subjected to significant temperature differences: up to 50°C or 90°F in the winter tests and up to 40°C or 72°F in the summer tests. Natural convective looping was not noted in any of the wall assemblies."
One of the most important confirmations for me was that "All wall assemblies experienced a loss in thermal performance due to air movement through the assembly. This is true for all of the assemblies tested regardless of the type of insulation material used (e.g. cellulose, fiberglass, ocSPF, ccSPF, XPS)". With the failure of an effective air barrier that I typically see on spray foam jobs, this research helps to confirm that without an effective AB, even the might spray foam has diminishing thermal resistance. The report also confirmed "spray foam insulation only seal areas where the spray foam is installed; significant leakage paths often remain at wood to wood connections" This confirms my conviction that spray foam is highly over rated. If it does not guarantee an air tight assembly (see 3.6.4 on pg 102 of the report to see air barrier failures that occurred even in these lab conditions), why use it when there are cheaper products of lower environmental impact available? I see attempting to use insulation as an air barrier as being just as foolish as attempting to use a poly vapour barrier to double as an air barrier. Both products are hard pressed to represent an effective and durable air barrier.
Finally, it was interesting to note that they were able to measure the various resistance to air flow that different insulation represent. In 1.1 the report confirms that wet sprayed cellulose has more resistance to air movement over various fibreglass bat products. It is too bad that they did not test mineral wool as it would be interesting to see how it compares to WPC. Maybe next time!
Monday, 28 October 2013
Double Vapour Retarders are NOT Fine by Me!
Far too often, a poster on LinkedIn makes comments that defy good building science. As I am often busy, I try to bite my tongue and just move on, but often the posts push too many of my buttons and I find myself in the position where I MUST comment or commit hari kari!
A resent post titled "Double Vapor Retarders are Fine by Me!" was one such post that pushed me to reply:
I find it interesting that often when I see what (in my view) is bad building science, the individual in the conversation is almost always in the business of selling or pushing foam. The facts are that Physics has not changed – EVER- and the rules are not being ‘smashed’, only disregarded – often to the building owners peril.
Re OP - I believe this is propagating bad language and bad science and (wish) to review my view of the basics.
VB or vapour control layers are to address vapour movement by diffusion. The requirement for the ‘tightness’ of this control layer is based on the vapour gradient across the assembly and location is based on the direction of the pressure. The VB should always be on the high pressure side, so generally inside in heating climates, outside in most cooling climates, and carefully designed and managed in the rest of the climates. Diffusion is a very small vapour driver, and while it cannot be ignored, having a pretty good VB is more than adequate. You do not need to sweat the details on a VB and do not need to worry about holes and untapped seams. A 90% effective or even 80% effective VB is going to be just fine.
An AB on the other hand is critical, and even small holes in AB’s can move large amounts of moisture by means of convection. The AB can pretty much be anywhere in the assembly and many (myself included) like to detail this layer on the exterior of the sheathing, where the number of penetrations are reduced and much easier to detail. When on the exterior, the one issue to address from a thermal performance point of view, is to reduce convection currents within the stud bays by use of a denser insulation.
Can you build a wall assembly with two VB’s? Yes in theory IF you have a perfect AB always. But in practice this is foolish, in my view, and will come back to bite you a significant number of times, because AB’s are almost never perfect in the field and or do not stay so for long even if they start out perfect. So conventional wisdom, based on decades of experience by many, pretty much always recommend that the assembly is generally vapour open from the VB control layer towards the low pressure side of the assembly. Careful design using modeling may show that you get away with a barrier on one side high side and a retarder on the low pressure side, but (in) my opinion, this is only going to consistently work in dryer regions where the load is low anyway.
The reason a freezer works is because the two metal shells on each side of the foam are perfectly sealed as air barriers and the manufactures go to great lengths to ensure this during assembly with both sealants and gaskets.
The OP mentions “any mistakes are easily corrected by the air leaks”. Really? Are you promoting an ineffective AB? Are you promoting air movement that can move HUGE volumes of moisture into and through a wall??
The only time a dew-point does not exist, is when the temp and humidity of the air on both sides of an assembly never reach each other’s dew-point. Obviously, this is extremely rare. You can however negate a dew-point in various fashions. A) You can remove all of the air in and through an assembly so that there is no moisture to condense. (easy to do in a manufactured fridge – hard in a site built structure) B) You can design your assembly so that your thermal control layer is mostly/all on the low pressure side of the VB and WRB control layers (so that the condensing surface never reaches the dew-point temperature).
The spray foam crowd claim that filling stud bays with foam meets strategy 1. But I have yet to see a spray foam stud cavity where the foam has not pulled away to some degree from the studs (ore probably has been compressed away from the studs as the studs expand and contract into a material with no elasticity). SO, in these circumstances, the ‘air tightness’ has been lost and you better have a Plan B.
In my Linked-IN Post I also commented:
Of course, I should have also added a third method to my post for negating a dew-point, and that is to ensure that all materials down stream of the high pressure side and VB control layer are vapour open enough to allow drying to the low vapour pressure side.
It really frustrates me, that in order to sell foam (spray or rigid) to the building industry, manufacturers, vendors, and installers all try to twist the science to meet their objectives. While this will help them sell their product or service, it will often leave the building owners with assemblies containing much higher risk for condensation, rot, and mould.
I feel it is up to the rest of us to cry foul when we come across these inaccuracies and try to provide some protection to potential victims of bad science.
A resent post titled "Double Vapor Retarders are Fine by Me!" was one such post that pushed me to reply:
I find it interesting that often when I see what (in my view) is bad building science, the individual in the conversation is almost always in the business of selling or pushing foam. The facts are that Physics has not changed – EVER- and the rules are not being ‘smashed’, only disregarded – often to the building owners peril.
Re OP - I believe this is propagating bad language and bad science and (wish) to review my view of the basics.
VB or vapour control layers are to address vapour movement by diffusion. The requirement for the ‘tightness’ of this control layer is based on the vapour gradient across the assembly and location is based on the direction of the pressure. The VB should always be on the high pressure side, so generally inside in heating climates, outside in most cooling climates, and carefully designed and managed in the rest of the climates. Diffusion is a very small vapour driver, and while it cannot be ignored, having a pretty good VB is more than adequate. You do not need to sweat the details on a VB and do not need to worry about holes and untapped seams. A 90% effective or even 80% effective VB is going to be just fine.
An AB on the other hand is critical, and even small holes in AB’s can move large amounts of moisture by means of convection. The AB can pretty much be anywhere in the assembly and many (myself included) like to detail this layer on the exterior of the sheathing, where the number of penetrations are reduced and much easier to detail. When on the exterior, the one issue to address from a thermal performance point of view, is to reduce convection currents within the stud bays by use of a denser insulation.
Can you build a wall assembly with two VB’s? Yes in theory IF you have a perfect AB always. But in practice this is foolish, in my view, and will come back to bite you a significant number of times, because AB’s are almost never perfect in the field and or do not stay so for long even if they start out perfect. So conventional wisdom, based on decades of experience by many, pretty much always recommend that the assembly is generally vapour open from the VB control layer towards the low pressure side of the assembly. Careful design using modeling may show that you get away with a barrier on one side high side and a retarder on the low pressure side, but (in) my opinion, this is only going to consistently work in dryer regions where the load is low anyway.
The reason a freezer works is because the two metal shells on each side of the foam are perfectly sealed as air barriers and the manufactures go to great lengths to ensure this during assembly with both sealants and gaskets.
The OP mentions “any mistakes are easily corrected by the air leaks”. Really? Are you promoting an ineffective AB? Are you promoting air movement that can move HUGE volumes of moisture into and through a wall??
The only time a dew-point does not exist, is when the temp and humidity of the air on both sides of an assembly never reach each other’s dew-point. Obviously, this is extremely rare. You can however negate a dew-point in various fashions. A) You can remove all of the air in and through an assembly so that there is no moisture to condense. (easy to do in a manufactured fridge – hard in a site built structure) B) You can design your assembly so that your thermal control layer is mostly/all on the low pressure side of the VB and WRB control layers (so that the condensing surface never reaches the dew-point temperature).
The spray foam crowd claim that filling stud bays with foam meets strategy 1. But I have yet to see a spray foam stud cavity where the foam has not pulled away to some degree from the studs (ore probably has been compressed away from the studs as the studs expand and contract into a material with no elasticity). SO, in these circumstances, the ‘air tightness’ has been lost and you better have a Plan B.
In my Linked-IN Post I also commented:
- Both OSB and Plywood are a Vapour retader in dry conditions, but only plywood opens up to over 6 perms in a wet-cup environment, that for instance all sheathing sees in my region.
- My vapour diffusion holes question was a bit of a trap. Only way they work is when you have air movement through them, which is obviously something you do not want happening. I did a lot or research before posting on this subject http://goo.gl/0SAiSJ
Of course, I should have also added a third method to my post for negating a dew-point, and that is to ensure that all materials down stream of the high pressure side and VB control layer are vapour open enough to allow drying to the low vapour pressure side.
It really frustrates me, that in order to sell foam (spray or rigid) to the building industry, manufacturers, vendors, and installers all try to twist the science to meet their objectives. While this will help them sell their product or service, it will often leave the building owners with assemblies containing much higher risk for condensation, rot, and mould.
I feel it is up to the rest of us to cry foul when we come across these inaccuracies and try to provide some protection to potential victims of bad science.
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