Performance Walls for a Harsh Climate

The National Building Code of Canada is a prescriptive standard.  A prescriptive standard is one where instructional information is provided to ensure that the components are built to ensure longevity, safety and health of the occupants.  The end game is not necessarily energy efficiency.  For example, 2x6 stud walls 16" o.c. with double headers over windows is purely prescriptive.  We need prescriptive standards but we also need a way to ensure that homes are also energy efficiency.  Here's where performance standards are important.  A performance standard is one where the performance of a building as a whole is important and can be measured and compared against a set of standard metrics eg. air leakage, thermal performance, energy usage.  Mixing the two ensures that a home is energy efficient, safe, healthy and comfortable.

To ensure that structures are more efficient, Canada introduced the National Energy Code for Buildings.  This code is prescriptive but defines minimum building standards to meet energy efficiency requirements depending on your climate zone.  The adoption of this code has been fairly slow...too bad because it really aims to make a difference...energy efficiency translates to more money in the home owners pocket book and could lead to a large decrease in the rate of global warming.  Have a look at the map below and see if your province has adopted the Code:


If you said no, you're not completely alone!  There are only two provinces that have yet to adopt the standard!...and you're living in one of them!  Its not surprising that NL is one of them.  Imagine what implementing a new energy standard will do to power sales;  How will we pay off Muskrat Falls if we're using less energy?  Its not necessarily a conspiracy, but it does raise questions about our priorities as a province when the government mandate is to create more energy for consumption when we only have a population of 1/2 million.  And at what cost?  TWELVE BILLION DOLLARS!  I mentioned a hypothetical situation on a previous blog entry where I showed that for less than 600 million we could have outfitted every home in NL with heat pumps and it would have decreased our hot water heating requirements by the equivalent of shutting down the Holyrood generating station for 66 days or a total of about 790 GWh.  In 2011 total GWh production at Holyrood was about 1100 GWh.  Thats like decreasing production by almost 71%.  Heating with heat pumps could have been another option.  It would have decreased heating requirements buy up to 5 TWh or more (i.e. terawatt hours).  Given that in 2011 our total generation was about 40 TWh, heat pumps for heating and hot water could have decreased drain on the grid by a total of about 6 TWh.  That's an impressive conservation measure of 15%!!! and it would have generated about 1.2 billion dollars of economic stimulation rather than sinking 11.5 billion of taxpayers dollars into Nalcor assets.  It could have easily bought another 10-15 years at current rates of population increase.  Seems to me that conservation through good technology and more passive measures should be at the top of the list rather than filling the pockets of Nalcor.  My rant is over...lets continue!!

Did you know that the NECB defines that R23 walls are required for our climate?  When you drive around and look at new homes do you see exterior foam? Probably not.  To attain R23 with 2x6 stud walls, exterior foam really needs to be added to the building when its being constructed.

Enough about the NECB.  Lets talk about the Flatrock Passive House wall system.  Its different.  VERY DIFFERENT!!!  have a look below:


This envelope is built to perform in our climate.  The foundation has 2" of EPS on the outside and the inside.  Under the slab is 10" of EPS amounting to an R-value of about 40!!

The wall assembly is a fairly typical of stud wall construction comprised of a 2x4 stud cavity filled with fibreglass batt, 7/16 OSB taped and air sealed against the slab and rim joists and carried through to the wall system on the second floor.  Outboard there is a 2x8 stud wall filled with batt insulation, followed by another 3" of EPS.  The total R-value is about R50.  The effective R-value is a little less.  This is almost R-20 more than most people have in their attics in Newfoundland.  There is no vapour barrier.  A vapour barrier is actually a Class I vapour retarder meaning it perm rating is less than 0.1.  In a traditional house, the vapour barrier that everybody talks about serves two purposes:  An air barrier and a vapour retarder.  However, vapour diffusion is rarely an issue.  Moisture laden air infiltrating into the structure can carry with it almost 100 times more moisture than would normally diffuse into wall structure through painted drywall alone. This traditional vapour control layer has been replaced with OSB in this case creating a vapour open structure on either side of the vapour control layer so the wall can dry out via diffusion should moisture infiltration ever become an issue.

The ceiling assembly will have 26" of loose fill insulation giving an R-value of almost 90 in the attic space. Our plan of attack for building the wall system is fairly simple and pretty much the same as any other house.  The 2x8 stud walls will be built flat with window bucks attached.  It will be erected on the foundation and sheathed with foam on the outside.   The second floor will be constructed in the same fashion.  Trusses will be erected on the roof and the roof shingled.  Attic baffles will be installed before sheeting the ceiling in OSB.  All OSB joints will be air sealed using 3M 8067 tape.  The air seal will follow around the rim joist using tape and spray foam.  We will air seal all buck corners and install and air seal the windows according to the prepared drawings.  Once the tyvek is on the building we'll insulate the inside 2x8 stud bay and then apply the interior OSB and air seal all seams. At this point we'll bring in my energy advisor, Brad Dunn with Amerispec to complete the blower door testing. (http://energyevaluationstjohns.com/newfoundland-energy-advisors/)

Once we're sealed up  as good as we can get (hopefully 0.05 cfm/sqft of gross envelope area or better) construction will continue.  We will bring in Brad several times to envelope for air tightness.   There will may be a need to spot check air sealing as we go so Brad is aware that we will need his services as we move forward.  I am planning on doing 5 tests total during the construction to ensure we meet the air tightness specifications.  Air tightness does several things:  It decreases random infiltration which can lead to long term durability issues and it increases energy efficiency.

So there's the wall....and the plan...now I just have to cross my fingers!

Comments

  1. Hi David
    As to your comments on Muskrat and Holyrood, I did some analysis in 2012 that was published as letters to the Telegram as to energy efficiency for existing house stock, as a component of alternative to Muskrat.......and has addressed the issue with the PUB, but it seems to go no where, but thousands of Nflders are moving to efficiency for heating, but a bit late to counter the 12 billion being spent.
    I wanted to let you know as to my research on mini-split performance here. With dual heat units we see a COP (compared to baseboard electric) of 2.5 for a R2000. However with a single head unit,at a cottage, attic mounted, we appear to get a COP of 4.1 at around 0C,nightime, and expect about 2.5 at -15C And the baseboard heaters are mounted on the inside walls, if they were on the usual location , under windows, I would expect a COP of about 4.5 would apply to many existing houses, as those baseboards use more electricity at the window location. Daytime COP would be higher than so far recorded, as the attic temperature is warmer in the daytime.
    For attic mounting, for energy savings: you knock out most of the defrost cycles; your black roof acts as a low grade solar collector improving performance for the heat pump, and any heat lost through the ceiling is recaptured by the heatpump; and at that location the unit spends more time at part load operation, which improves performance. Not sure if you are aware of these benefits, as it greatly improves performance over regular installation methods, outdoor. Added bonus, and this probably the most important is that it weather proofs the unit from storms, and also protects against our salt environment. I am now operating 6 years with a unit in the attic, and just 3 days ago started detailed monitoring........but from meter reading I determined I got 268.00 per year energy used for heat, for 1000 sq ft.
    Winston

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  2. David, I had two Nfld Power Conservation team employees at my place today to see my setup and performance data. I mentioned to them of your passive house and location but they showed little if any interest.
    Likewise, as to informing best practices for efficient electric heating systems to installing contractors,,,,,,practises that really work, evidence based, it is not a priority with them, they will not even publish a list that Nova Scotia has on their web site for good systems for our climate,,,,,,,,so contractors have little guidelines and performance here is usually half of that one should get.
    They do a lot PR, promoting a lot of ineffective measures that save customers very little. I guess passive is just too energy efficient for Fortis shareholders whose dividends increase when electricity sales and revenue increase.
    Efficiency NL........not happening here it seems. Inefficiency NL is the preference, INL instead of ENL. A lot of money being spent, many billions to promote INL. Think Take Charge would be promoting your project as how future housing should be, but in fact Nfld is the second worst in the country for Conservation and Efficiency performance, yet they argue they do a good job!
    What they are good at is PR, like the latest scallywag TV ad. These are cute little cartoon figures, with evil intentions of stealing your energy. Never before realised they were so numerous.......and sure the Take Charge crowd, a joint operation by Nfld power and Nfld Hydro are infested with scallywags, me thinks. Sneaky creatures,..... take Ed Martin, walked off with 6 million...., a scallywag for sure, but I need to check the dictionary meaning....if only you had a fraction of that 6 million to go toward your (Nfld`s) first passive design house. Make sure you get your air tightness really good, as those scallywags are cunning creatures.
    Winston

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  3. Hey Winston, Sorry I haven't commented yet...been a busy week, tomorrow is my blog day.

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  4. Hi Winston, It is unfortunate that there is so little interest. Often it is a lack of understand/information that leads to this. It appears that when people hear "Passive House" they think passive solar. As you know, these are two completely different beasts: One is a standard, the other is a type of house. I have told several people about my house and they have said comments like "Oh yeah, theres a guy up there on the hill in Torbay that built one of those homes." I have to correct them. I tell them that even if it does heat part of the time with solar, unless modelling is done, most of the heat maybe going right out the windows on cloudy days and most likely it is.

    Nova Scotia is up on their game with respect to energy efficiency. Mainly because they have to. A large component of their power is generated by burning coal. They have even had Passive house pilot projects where they have offered people money to build passive houses. Its pretty impressive. I agree that energy efficiency is not at the top of the list for NL power. A lot of money is being spent on scraps....light bulbs, insulation, etc....Insulating a drafty space is useless. Unless you can control random air infiltration, exfiltration, adding insulation goes right out the window. Even retrofits are a little misunderstood. Adding insulation does very little. Intact, I just read a book that said that if one were to change windows and adding insulation for a retrofit they wouldn't be able to expect much more than a 25% savings on heating costs. mainly because adding insulation and new windows, doesn't address air tightness. To address air tightness you have to re-establish the air tight barrier. to do this, the house really has to be stripped. You'll get better satisfaction by purchasing a heat pump in this case as the cost factor is much less. I think retrofits can work but to do it right they are expensive....but the energy bill savings would be huge.

    I have long thought that a lot of our dollars are being wasted promoting things that don't matter. A lot of times these are things that people have very little understanding about. Having little understanding leads to bad decisions.

    If I can reach 0.6 ACH 50 ill be pleased. As I have my air sealing plan on paper, mapped out by the architect, I plan on doing it all myself. above 0.6 ACH 50, the energy penalty (cost) is approximately proportional to infiltration/exfiltration. Below that number it starts to level out and the cost benefit is less. I am hoping that something will come of all of this. If not anything, at least I will have a passive house.

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    Replies
    1. Indeed airtightness is so important, especially in Nfld, we have one of highest average wind speeds in the world, good for wind generators, bad for houses not very airtight, and is 99 percent of them.
      And is Nova Scotia much ahead of us because it is NEW Scotland, I wonder. Here we are mostly Irish and English, and Scots are known to be trifty, whereas we waste our resources it seems.
      If we had more Scotish heritage here , maybe the boondoggle of Muskrat might have been avoided.

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  5. Hi David
    I posted a comment on your most recent piece that never got posted, maybe it got lost.
    But on this construction, I compare with what I read on construction using panels as for refrigeration rooms, which seems cost effective and quick to install (4 days with walls up , 2 story, and roof on), and they generally say it can meet passive standards with 6 in thick panels for everything, unless in the Arctic region.
    You use R60 for wall, R49 for floor and R90 for the attic, walls overall some 16 in thick, and attic insulation 26 in and floor 12 in thick.
    For the wall, we see extreme of -23C as low temperature,but this is rear, but -15C is more common ,this being +5 F. The ground gets to about 43F but under the house may be stable at about 48 or 50F. So the temperature differential for the floor is only 22 or 24 F , For the wall the differential is 72F inside to 5 outside, so 67F. The wall temperature differential is almost 3 times that of the floor......so it suggests that 12 inch of floor insultion is about double of what is cost effective., and I wonder if overkill,......and that the panel manufactures may be right. I have used 4 in panels that are pretty good, and believe 6 in is better. R2000 used to have just 2 in insulation under the slab, just 4 ft in from the perimeter, but now continous I think. Contractors who install in floor hydronic heating are upset over Ontario standards now requiring 3.5 or 4 in, saying the cost is too much. Certainly 4 in is not too much.
    Again R 90 for the ceiling......good if there is some air leakage, and maybe necessary to avoid convective currents........but any better I wonder than 6 in, or 8 in panels.
    Just tossing this to you, wondering which way I would go if building a passive house
    Winston

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  6. Sorry about that winston. I read all comments, but I may have forgot the publish. things have been extremely busy with estimates and finalizing the plans. Passive house does take insulation a little beyond but it has been climate optimized...at least the PHIUS standard is. the Passive House standard is not. Foam is much more expensive than the other insulation required. For example R 90 in the attic will be about $1300. THis is a pretty small cost really. I agree that 4" is not too much and for a typical sized home 4" of foam under a slab is a small cost which will lead to a larger life savings. As for air leakage, i wouldn't say that insulation should be considered as a way to promote air tightness...ensuring a good air tight barrier and an internal service cavity needs to be defined from the get go. My sources tell me don't assume that walls will be air tight after insulation. So I am going for the gold...0.6ACH with the airtight barrier before insulation is applied. Work onside will cease until I reach better than that goal. As for thickness of insulation, at this point I need to follow the drawings to get the performance. My foam cost will be about 4% of the project cost. while the other insulations are about 2% or so. so 6% for the total cost of insulation is pretty good i figure....we'll see if it all pays off!

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  7. Your text says 12 inch foam under the slab, but the dwg seems to show 8 in, maybe it is not to scale, and hard to read the notes, the slab is 4 inch.
    you show vapor barrier under the slab, I assume the foam is not a sufficient vapour barrier. Is rebar for the whole slab or just some areas. Not sure if you will dowel slab rebar to the concrete wall.......if not the floor at the perimeter may drop some over time, unless compaction of the soil there is extremely good, I had that happen, a slow slab drop over 20 years needing the floor to be later leveled. it dropped almost a inch over 20 years.

    Winston

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  8. Hi WInston, there have been some updates to the plan that need to be uploaded. The slab foam was labeled as 12 but is, in fact, 10". the vapor barrier serves duel purpose in this case, a vapour barrier and an air barrier. without it, the house would be as leaky as a outhouse. They typically don't add rebar into the walls. the ground in the middle of the slabs will be, for the mostpart undisturbed ground. this ground will mvoe very little. However, around the periphery, we will be using structural fill... about 3' of it to bring it up to grade. It will be compacted with a large plate compactor as we fill. finally 6" of crush rock will be added as a leveling base for the foam. the top of the crush stone will be about 14" below the top of the foundation. It may settle a bit. this has been known to happen especially without compaction and proper fill. If the soil is "soft" we'll excavate the whole thing and fill it with structure fill. I estimated about 9 single axle loads to bring up to the point where we'll add the crush stone. THis will amount to about $1500 I believe....I dont' care as much about the garage.

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  9. Just to give my experience: I added to my house 30 years ago and had a 4 ft deep foundation for the new part and concrete slab, I compacted with a plate vibrator, yet this settled 1 inch over 20 years, so not compacted enough I guess. When I built my shed with a slab, I put rebar dowels every 2 ft about 2 or 3 ft long, just 3 in into the wall, 25 years and perfect, thought the soil may have dropped , the floor has not. My summer house is aslab on grade, and I did not use the dowels, and it dropped over 30 years in some areas about .75 inch.
    I bought a shed 30x 90 acroos from my cottage, it was built over a swamp area. The floor rotted out, and I removed the floor. There was all water and mud there. I put 6 tandem loads of 1.5 inch stone in there, then vapour barrier, no compaction, but rebar at 2 ft spacing all over and tied as dowels to the perimeter foundation. That was 20 years ago, and I stove vehicles etc in there, and perfect. In my young days I used to look for 95 percent compaction to avoid settling, by standard methods of checking that. Other wise you never know. With the dowels , sufficent compaction do not matter that much. When I had to remove carpet and put down hardwood 10 years ago, contractors would not quote me, as the floor was not level, and they would not do leveling.I had to do it myself. No more settling in the last 10 years! Thought it worth mentioning.
    I can see vapour barrier around the perimeter sealed to the rigid floor insulation say a foot in, but all over the floor......for air sealing, maybe to be sure, as sealing is so important.

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