http://shrinkthatfootprint.com/average-electricity-prices-kwh
This is one of the reasons why energy efficient dwellings are not as popular in North America than say Germany. When power is cheap, we love to waste it.
Will we ever see 30¢/kWh electricity? Probably not in my lifetime.
Thursday, 26 September 2013
Saturday, 7 September 2013
Designing walls that are not vapour permeable - A good idea?
I have been having a discussion on a LinkedIn Passive House forum regarding the choices one can make in regards to insulation and the effects of these choices.
http://goo.gl/1vGTyI
The poster was asking for experiences within the building community with Wood Fiber vs. Cellulose insulation and I suggested that neither may be desirable depending on your climate conditions and instead suggested continuous exterior mineral wool fibre insulation. This then morphed the conversation towards what constitutes a durable high performance wall.
I posted my thoughts on the perfect wall (which just happens to match my walls in my upcoming build) and other who are builders of PassivHaus (PH) structures posted their perfect wall details. This led to a discusion about the merrits of designing a wall that is vapour open to the low pressure side, where one of the posters stated:
"I've been indoctrinated with the Bau-biology "Breathable Wall" idea with nearly 10 years now and spent many years preaching that gospel. But then I found the Spokane and Tsong studies where they opened the walls of 250 houses, that were built wrong in terms of 5:1 breathability but no decay was found. The walls had no membranes, no decay was found, its the same for SIPs houses, ICF houses and most other construction methods, the walls don't breathe as per the 5:1 rule and the houses aren't falling down."
The two studies can be found here:
1) http://www.viking-house.ie/downloads/Tsong79.pdf
2) http://www.viking-house.ie/downloads/Spokane.pdf
I read the two studies the poster provided and was somewhat shocked at the jump in logic that is represented by the statement that we do not need to make walls permeable and that impermeable walls will not rot. This is such an important subject, I though I would reproduce my comments here to a larger readership.
The Tsong study is discussing the lack of VB, and not a wall that is vapour tight. A wall that does not have a VB is by definition VERY vapour open and in fact most of the assemblies studied were quite vapour open (poorly insulated wood frames). It is also important to note that the study occurs in 1979 and the levels of insulation discussed are far below what we are talking about in today's high performance homes (the study does not state the R value but we are talking about poorly filled 2x4 walls, so probably an effective average of below R7). Therefore these walls all had a lot more drying potential due to thermal bridging than high performance homes of today and certainly a lot less drying potential compared to a PH. It is also important to note that these houses had an average ACH50 of 16.2, which is more than enough to also help dry the assembly when it was experiencing very high RH levels. I have been unable to locate the permeability of Urea Formaldehyde insulation so do not know how permeable those walls were if detailed perfectly – but per the study, these foam walls had a lot of air leakage due to foam shrinking and cracking. The average foam shrinkage was 8% and the report states that as a result of the shrinkage of this foam, there was a 70% increase in heat loss (heat loss dries walls, so even these walls could dry easily).
It should also be noted that areas of high moisture content were found at many locations on these homes where bulk water entry was occurring (in other words control layers regularly fail and you should design your assemblies for such to the extent possible).
What I do love about this study is their remark at how the mineral wool insulation had an ‘extremely low average moisture content’ when compared to the other insulation (in no case was the moisture content of the mineral wool above 2%). The study went on to say this is “probably attributable to the fact that mineral wool is not hygroscopic, whereas the cellulose and U-F foam both tend to retain moisture”. Go ROXUL!
I then went on to say that relying on this dated research to state that a wall should not be vapour permeable to the low pressure side is grossly flawed in my view, does not come close to lining up with the current recommendations of the building science community and their experience in repairing failed structures, and in my view also miss-interprets the studies results and compares conditions that are grossly miss-aligned with the high performance structures we are building today.
All this study can really claim is that there was no significant moisture damage associated with diffusion observed on any of the homes that generally had no or minimal insulation and high levels of thermal bridging. And as we know today, this results in assemblies with built in drying safety factors. The study was also was clear to specify that these results could not be related to colder climates.
The second study was by the same author but took place in a colder climate. The same arguments above apply. It should also be noted that colder climates generally have less problems with moisture damage to wall assemblies than milder climates. In climates with cold winters and hot summers, the moisture typically exists as frost all winter and then quickly dries out in the late spring as the temps rise. In a location like the Pacific North West (3000 DD), moisture will stay in liquid form for months at a time as is able to cause a LOT more damage as the moulds take hold and flourish.
Can you build vapour tight assemblies that work in the Pacific North West? Yes, but you then need to sweat the details.
An ICF IS a wall that works. It is often quite vapour tight but because there is no air movement through it at any point in the structure, there is generally no opportunity for condensation to occur (I have heard of isolated events where condensation has occurred between the foam ICF and concrete core leading to mould build-up). The typical foam materials of the ICF are also highly resistant to vapour diffusion, all but eliminating that risk as well. From a building science standpoint a typical foam ICF structure makes a lot of sense, but where it fails in my view is the very high embodied energy that it represents both in terms of the volume of concrete used in these homes and the foam used in the typical ICF blocks.
As far as SIP construction (structural insulated panels), which are typically fabricated with OSB sandwiched on each side of a foam block, I personally feel that the jury is still out. There is a multitude of reports of SIPs failures across North America and once again, this style of construction represents a high embodied energy.
For me, I will stay true to my stick frame, plywood sheathed structure wrapped in a nice continuous warm blanket of highly vapour permeable and fire/rodent/bug proof Roxul mineral wool insulation thank you very much.
http://goo.gl/1vGTyI
The poster was asking for experiences within the building community with Wood Fiber vs. Cellulose insulation and I suggested that neither may be desirable depending on your climate conditions and instead suggested continuous exterior mineral wool fibre insulation. This then morphed the conversation towards what constitutes a durable high performance wall.
I posted my thoughts on the perfect wall (which just happens to match my walls in my upcoming build) and other who are builders of PassivHaus (PH) structures posted their perfect wall details. This led to a discusion about the merrits of designing a wall that is vapour open to the low pressure side, where one of the posters stated:
"I've been indoctrinated with the Bau-biology "Breathable Wall" idea with nearly 10 years now and spent many years preaching that gospel. But then I found the Spokane and Tsong studies where they opened the walls of 250 houses, that were built wrong in terms of 5:1 breathability but no decay was found. The walls had no membranes, no decay was found, its the same for SIPs houses, ICF houses and most other construction methods, the walls don't breathe as per the 5:1 rule and the houses aren't falling down."
The two studies can be found here:
1) http://www.viking-house.ie/downloads/Tsong79.pdf
2) http://www.viking-house.ie/downloads/Spokane.pdf
I read the two studies the poster provided and was somewhat shocked at the jump in logic that is represented by the statement that we do not need to make walls permeable and that impermeable walls will not rot. This is such an important subject, I though I would reproduce my comments here to a larger readership.
The Tsong study is discussing the lack of VB, and not a wall that is vapour tight. A wall that does not have a VB is by definition VERY vapour open and in fact most of the assemblies studied were quite vapour open (poorly insulated wood frames). It is also important to note that the study occurs in 1979 and the levels of insulation discussed are far below what we are talking about in today's high performance homes (the study does not state the R value but we are talking about poorly filled 2x4 walls, so probably an effective average of below R7). Therefore these walls all had a lot more drying potential due to thermal bridging than high performance homes of today and certainly a lot less drying potential compared to a PH. It is also important to note that these houses had an average ACH50 of 16.2, which is more than enough to also help dry the assembly when it was experiencing very high RH levels. I have been unable to locate the permeability of Urea Formaldehyde insulation so do not know how permeable those walls were if detailed perfectly – but per the study, these foam walls had a lot of air leakage due to foam shrinking and cracking. The average foam shrinkage was 8% and the report states that as a result of the shrinkage of this foam, there was a 70% increase in heat loss (heat loss dries walls, so even these walls could dry easily).
It should also be noted that areas of high moisture content were found at many locations on these homes where bulk water entry was occurring (in other words control layers regularly fail and you should design your assemblies for such to the extent possible).
What I do love about this study is their remark at how the mineral wool insulation had an ‘extremely low average moisture content’ when compared to the other insulation (in no case was the moisture content of the mineral wool above 2%). The study went on to say this is “probably attributable to the fact that mineral wool is not hygroscopic, whereas the cellulose and U-F foam both tend to retain moisture”. Go ROXUL!
I then went on to say that relying on this dated research to state that a wall should not be vapour permeable to the low pressure side is grossly flawed in my view, does not come close to lining up with the current recommendations of the building science community and their experience in repairing failed structures, and in my view also miss-interprets the studies results and compares conditions that are grossly miss-aligned with the high performance structures we are building today.
All this study can really claim is that there was no significant moisture damage associated with diffusion observed on any of the homes that generally had no or minimal insulation and high levels of thermal bridging. And as we know today, this results in assemblies with built in drying safety factors. The study was also was clear to specify that these results could not be related to colder climates.
The second study was by the same author but took place in a colder climate. The same arguments above apply. It should also be noted that colder climates generally have less problems with moisture damage to wall assemblies than milder climates. In climates with cold winters and hot summers, the moisture typically exists as frost all winter and then quickly dries out in the late spring as the temps rise. In a location like the Pacific North West (3000 DD), moisture will stay in liquid form for months at a time as is able to cause a LOT more damage as the moulds take hold and flourish.
Can you build vapour tight assemblies that work in the Pacific North West? Yes, but you then need to sweat the details.
An ICF IS a wall that works. It is often quite vapour tight but because there is no air movement through it at any point in the structure, there is generally no opportunity for condensation to occur (I have heard of isolated events where condensation has occurred between the foam ICF and concrete core leading to mould build-up). The typical foam materials of the ICF are also highly resistant to vapour diffusion, all but eliminating that risk as well. From a building science standpoint a typical foam ICF structure makes a lot of sense, but where it fails in my view is the very high embodied energy that it represents both in terms of the volume of concrete used in these homes and the foam used in the typical ICF blocks.
As far as SIP construction (structural insulated panels), which are typically fabricated with OSB sandwiched on each side of a foam block, I personally feel that the jury is still out. There is a multitude of reports of SIPs failures across North America and once again, this style of construction represents a high embodied energy.
For me, I will stay true to my stick frame, plywood sheathed structure wrapped in a nice continuous warm blanket of highly vapour permeable and fire/rodent/bug proof Roxul mineral wool insulation thank you very much.
Sunday, 1 September 2013
The Enclosure - Updated Exterior
I thought it might be time to provide an updated design photo showing the exterior of the dwelling as it is now modelled. I will use the through cavity window sill and head flashing to create borders around the windows (and doors). The infill will probably be simulated stucco cementitious panels.
Temporary Accommodation Road blocks!
As part of my desire to direct our budgeted monies toward a high performance home, I had always planned to request permission to live on site in a large vacation trailer (something like this). Rent in my region is expensive, with 1 bedroom basement suites renting for $1100/month. With an expected build time of 18 months, the avoidance of rent would allow $20k+ to be redirected to important components like windows and insulation. Instead, I could buy a trailer for $20k-$25K and then sell it when we were done for $5K less, resulting in a $5K living costs for the 18 months.
Two obstacles have been working against this plan from the beginning and it turns out both were insurmountable.
When I approached the District of North Vancouver in March, I was told this just was not done, with the manager citing safety concerns for the occupants of the trailer as well as the District services. This lead to investigation with BC Safety Authority (advised no jurisdiction in North Van, but a pretty common situation in rural building lots) and WorkSafeBC (advised no concerns beyond siting trailer in area where debris could not fall of the dwelling under construction and onto the roof of the trailer. The District manager had also sited concern for neighbour complaints, so I petitioned and received support for 4 of the 5 effected neighbours (three in writing) with no response from the 5th neighbour. I went back recently to the District with all of this additional information only to now be told that "A zoning bylaw prohibition cannot be varied" which I am not sure I understand because many other aspects of the zoning bylaw like roof height, setbacks, etc, can be varied under special circumstances. I tried to make a case for making this a test, because the District council are always looking for ways to make building more affordable in the District to allow those that have grown up here to stay here once they move out of the family house. I am also aware that the planning staff are soon to be proposing alteration of the neighbourhood zoning bylaw to allow lane-way carriage houses (which would further support a 'second' accommodation on the property). The mistake I made was asking in the first place. You see, there have been other owners in my neighbourhood that have lived in a trailer during their build. The difference is that they did not ask and no one complained, so the District was not forced into action. Because I did ask, in the end, it came down to one person with the authority to say no. If I had more time and did not have the second obstacle, I would have pushed for a text amendment to the zoning bylaw.
My second obstacle was my wife. She categorically refused to live in a holiday trailer even though it could be argued the accommodations would have been nicer than where we live now. She was making arrangements to stay with family. My hope was that once the trailer was in place and she saw that it would not be that bad, she would soften and move back 'home'. But I fear, this was just a pipe dream on my part and was never going to happen despite how nice I could make the living conditions.
So with a source of accommodation dried up and with a build looming, I needed to find a place for us to live, and fast. This is slightly complicated by the fact that my oldest cat is a resident of the neighbourhood FIRST! and our pet second. You see, he has grown up in the neighbourhood and used to live about 300ft NW from where I live. He is also an outside cat and just graces us with his presence at his direction. The requirement was to find an affordable place within his current 'stomping grounds' or fear an abandonment if we went someplace new (he did after-all abandon his first owners). I also wanted to be close so I could go 'home' at lunch and keep tabs on the job site. Fortunately, after I received the final correspondence from the District on Thursday, I went on line that night and checked the local Craigslist ads and lo and behold, the basement suite across the street was available as of Sept 1 (I had not even realized that the previous renter had left a month ago). Today, the neighbour and I shook on a deal that would see us move in March 1 2014 and move out September 1 2015. The two bedroom will set us back over $25K for the 19 months including a signing bonus so that he will hold it from now till we need it next March.
This will be a big hit to the budget (represents 8%) and I will need to cut costs or expend our budget accordingly, but in the end will make my wife much happier and you know what they say.
Happy Wife - Happy Life!
Two obstacles have been working against this plan from the beginning and it turns out both were insurmountable.
When I approached the District of North Vancouver in March, I was told this just was not done, with the manager citing safety concerns for the occupants of the trailer as well as the District services. This lead to investigation with BC Safety Authority (advised no jurisdiction in North Van, but a pretty common situation in rural building lots) and WorkSafeBC (advised no concerns beyond siting trailer in area where debris could not fall of the dwelling under construction and onto the roof of the trailer. The District manager had also sited concern for neighbour complaints, so I petitioned and received support for 4 of the 5 effected neighbours (three in writing) with no response from the 5th neighbour. I went back recently to the District with all of this additional information only to now be told that "A zoning bylaw prohibition cannot be varied" which I am not sure I understand because many other aspects of the zoning bylaw like roof height, setbacks, etc, can be varied under special circumstances. I tried to make a case for making this a test, because the District council are always looking for ways to make building more affordable in the District to allow those that have grown up here to stay here once they move out of the family house. I am also aware that the planning staff are soon to be proposing alteration of the neighbourhood zoning bylaw to allow lane-way carriage houses (which would further support a 'second' accommodation on the property). The mistake I made was asking in the first place. You see, there have been other owners in my neighbourhood that have lived in a trailer during their build. The difference is that they did not ask and no one complained, so the District was not forced into action. Because I did ask, in the end, it came down to one person with the authority to say no. If I had more time and did not have the second obstacle, I would have pushed for a text amendment to the zoning bylaw.
My second obstacle was my wife. She categorically refused to live in a holiday trailer even though it could be argued the accommodations would have been nicer than where we live now. She was making arrangements to stay with family. My hope was that once the trailer was in place and she saw that it would not be that bad, she would soften and move back 'home'. But I fear, this was just a pipe dream on my part and was never going to happen despite how nice I could make the living conditions.
So with a source of accommodation dried up and with a build looming, I needed to find a place for us to live, and fast. This is slightly complicated by the fact that my oldest cat is a resident of the neighbourhood FIRST! and our pet second. You see, he has grown up in the neighbourhood and used to live about 300ft NW from where I live. He is also an outside cat and just graces us with his presence at his direction. The requirement was to find an affordable place within his current 'stomping grounds' or fear an abandonment if we went someplace new (he did after-all abandon his first owners). I also wanted to be close so I could go 'home' at lunch and keep tabs on the job site. Fortunately, after I received the final correspondence from the District on Thursday, I went on line that night and checked the local Craigslist ads and lo and behold, the basement suite across the street was available as of Sept 1 (I had not even realized that the previous renter had left a month ago). Today, the neighbour and I shook on a deal that would see us move in March 1 2014 and move out September 1 2015. The two bedroom will set us back over $25K for the 19 months including a signing bonus so that he will hold it from now till we need it next March.
This will be a big hit to the budget (represents 8%) and I will need to cut costs or expend our budget accordingly, but in the end will make my wife much happier and you know what they say.
Happy Wife - Happy Life!
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