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Musings of an Energy Nerd

Vermont House Uses Only Half a Cord of Firewood

In Ripton, Vermont, this fuel-stingy replica of Chris Corson’s Maine Passivhaus was heated last winter by a small wood stove

Last winter, Chris and Zoe Pike heated their 1,800-square-foot house in Ripton, Vermont, with just 1/2 cord of firewood. The house was designed by Chris Corson of Belfast, Maine. (The small roof that shades the first-floor windows on the south side of house has steel roofing. Although Chris Corson sometimes recommends the use of PV panels to provide shading in this location, PV wasn't in the budget for this house.)
Image Credit: Image #1, #3, and #4: Chris Pike

When my friend Laura Murphy mentioned that her neighbors in Ripton, Vermont, Chris and Zoe Pike, stayed warm last winter by burning just half a cord of firewood, I was intrigued. So I tracked down the Pikes to learn a few more details about their house.

It turned out — surprise, surprise — that the Pikes’ house was designed by Chris Corson of Belfast, Maine. In fact, the Pikes’ house is a virtual replica of the well-publicized Passivhaus that Corson built in Knox, Maine. (GBA has published two stories about the Knox house: Striving for Passivhaus Affordability and Cold-Climate Passivhaus Construction Costs. Chris Corson’s JLC article about the Knox house was titled An Affordable Passive House.)

Chris Corson, the founder of Ecocor, is one of two New England builders — the other is Carter Scott in Massachusetts — who have been justly praised for building high-performance cold-climate homes that don’t break the bank.

A tight thermal envelope with high R-values

The Pikes hired Alex Carver of Northern Timbers Construction to build their house. Construction was completed last fall.

The house sits on a slab-on-grade raft slab foundation that includes 12 inches (about R-50) of expanded polystyrene (EPS) foam. “Branch River Plastics delivered the EPS foam right to my shop, which is two miles away from the building site,” Carver told me. “We precut the four outside corners. I had to miter the corners, using a combination of hand saw cuts and a hot wire. The house is a rectangle, so that was easy.”

The 14-inch-thick walls are a variation of the Klingenberg wall, with 2×4 bearing walls sheathed with OSB and vertical TJIs attached to the exterior side of the OSB sheathing. The TJI bays were insulated with dense-packed cellulose, and the 2×4 bearing wall was insulated with 3.5 inches of Roxul mineral…

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  1. user-995931 | | #1

    wood stove chimney thermal bridge?
    How did they run the metal chimney through the roof and outdoors without creating a massive thermal bridge? I've often wondered how this is done.
    Switching to PVC on the fresh air side makes a lot of sense, but I'm sure you couldn't do this on the exhaust side.

  2. GBA Editor
    Martin Holladay | | #2

    Response to Zac Blodget
    Penetrations through the thermal envelope allow heat flow, and reduce the thermal performance of the envelope somewhat. Neverthess, every thermal envelope has penetrations: water supply pipes, sewage pipes, electrical cables, ventilation ducts, and sillcocks -- not to mention windows and doors.

    We make these compromises because of the benefits that these penetrations provide. I could seal you up in a rigid foam box if I wanted, and the box would perform well -- but eventually you would want some fresh air, a glass of water, and facilities where you could relieve yourself. And eventually you would also request a door.

  3. Expert Member
    Dana Dorsett | | #3

    How is a PVC air intake duct anywhere near code compliant?

    I doubt PVC is safety agency listed air-intake duct, thus falling under R1006.3:

    "R1006.3 Clearance.
    Unlisted combustion air ducts shall be installed with a minimum 1-inch (25 mm) clearance to combustibles for all parts of the duct within 5 feet (1524 mm) of the duct outlet."

    I've read elsewhere (a previous blog on this site?) than the Morsø combustion air kits are nowhere near air-tight to the firebox, which explains the backdrafting difficulties.

    I'm no rabbi, but this installation doesn't look kosher to me.

    A metal duct with code-legal clearances to the siding & sheathing and metal air barriers at the penetration points, wrapped in rock wool where it penetrates the cellulose might cut it. The thermal bridging of the metal duct penetration might add up to another 5lbs of wood consumption over a cold VT winter, but so be it.

    A backdrafted coal into the PVC from a big wind gust can become white-hot once the air-flow reverses, and will burn through PVC like a hot knife through butter. Counting on the fire-retardents in the cellulose to suppress a well-fanned flame for extended periods of time seems a bit optimistic.

  4. Expert Member

    Very interesting project. I'm a bit confused by the reference to the heating element in the HRV. Isn't that another source of heat? The climate here in the PNW and Vermont aren't comparable, but my electric bill for my Not Very Good House here, including resistance baseboard heat, are about the same as theirs.

  5. Marc Rosenbaum | | #5

    I'm soon to try this in my own renovated house. It's one story. I made the choice (which may be a poor one) to take the smoke pipe out horizontally out through the wall directly behind the stove, to an exterior stainless insulated chimney. I know I'll not get as good of a draft because the chimney is outdoors, but I thought I'd get less air leakage with the envelope penetration through the wall at about 2-1/2 feet above the floor than with a roof penetration, because the wall penetration has less pressure acting on it. We'll see next winter.

    My Zehnder 200 also has the electric preheat element for defrost. For the second half of the heating season (late Jan to end of May) the unit used 131 kWh in total and about 70 kWh of that is the preheater.

  6. ntisdell | | #6

    true cost?
    I'm intrigued by the price of the home (as an energy eng) - the price per foot is quite high (yet it alludes to not need to be a millionaire...). How do the fit and finishes of this house compare to an 'executive quality' home..? Also if one was to include a modest .3 acre lot what would that come to as a price per foot?

    Lets say...50k lot, added in that gets you at 190$ per sq ft. In my neck of the woods that ends up being a very costly house for new construction. New construction in a nice suburb, with a 'very nice' home ends up in the 140-150$/ft mark... Of course the NE is quite a bit higher in costs then MN, but would nice to see that comparison.

    Something like "Homes of similar style and acreage (besides efficiency items) are selling for on average 164$/sqft" Which then would allow some sort of investment conclusions (besides just warm and fuzzy feelings about icebergs and our children's children world, which I hope we all love). What would a code (plus a little maybe) built home in that region end up paying per year in utilities? ($1k in heat/cool annually around here for 2700sqft finished approx(+1000unfinsh basemt))

    I really like the idea of using a similar design of an existing super efficient home and then also not getting it certified to help somewhat control the amount of unnecessary money spent on the project.

  7. GBA Editor
    Martin Holladay | | #7

    Response to Dana Dorsett
    I reported on the combustion air duct's transition from metal ducting to 2-inch PVC deliberately, because this detail caught my attention. When I interviewed one of the owners (Chris Pike) and the builder (Alex Carver), I mentioned the fire risk. Both responded that they weren't particularly concerned about the fire risk.

    I'm a journalist who is reporting on the details of this house, as it was built. Like you, I consider the use of PVC at this location concerning. Conceivably, a strong backdraft or a gust of wind could send a hot glowing coal into the PVC duct.

  8. GBA Editor
    Martin Holladay | | #8

    Response to Malcolm Taylor
    Q. "I'm a bit confused by the reference to the heating element in the HRV. Isn't that another source of heat?"

    A. Yes, it is. That's one reason why I asked Chris Pike about his electric bills.

    Zehnder documents are rather vague when it comes to providing information on the watt draw and control algorithms for the electric-resistance element in their ComfoAir 200 HRV. One Zehnder document states, "In order to ensure reliable operation even at extreme outside temperatures, an optional integrated, electrical preheater register is available."

    Another Zehnder document states, "Fitting the optional pre-heater in the ComfoAir gives the added bonus that balanced ventilation remains intact for longer." This isn't English. I think the document means, "Installing the optional pre-heater in the ComfoAir reduces the amount of time during which the appliance reduces the ventilation rate or ceases operation altogether in cold weather."

    When reporting on heating fuel data, it's important to remember that all indoor electrical appliances -- including the HRV, the refrigerator, the television, and the light bulbs -- give off heat that keeps a house warm during the winter. If these appliances were all turned off, either the indoor temperature would drop, or the consumption of firewood would necessarily increase.

  9. Robert Swinburne | | #9

    Others doing affordable Passive Houses.
    Don't forget and (Jesper Kruse) as others doing affordable Passive House level projects. (what is it with those Maine folks?)

    To Nick T: Here in Southeast Vermont $150/s.f. exclusive of land generally means some level of owner involvement in the construction or run of the mill factory housing or a very large house with low per square foot costs. A recent high end project came in at $270/ s.f. but when I added in the basement area - it cost an additional $20 to finish the basement on a $700k project - the overall cost was reduced to $210/s.f. A good lesson about not using cost per square foot in any but the most vague terms.

  10. jackofalltrades777 | | #10

    Window Size and SHGC
    The article mentioned that they used Intus triple pane PVC windows but what are the specs on the SHGC and the window sizes? That center window seems to be pretty large, maybe 6x5?

  11. GBA Editor
    Martin Holladay | | #11

    Response to Marc Rosenbaum
    Thanks for the kWh data on your Zehnder; that's useful.

    You wrote, "I made the choice (which may be a poor one) to take the smoke pipe out horizontally out through the wall directly behind the stove."

    Your parenthetical comment reveals that you understand the trade-offs involved. But I think you may rue the day that you decided to cut a hole in your wall instead of your ceiling.

    I've always been a chimney-in-the-center-of-the-house kind of guy, for several reasons. Warm chimneys certainly draw better, as you point out. But more importantly, warm chimneys collect less creosote and need less frequent cleaning.

  12. GBA Editor
    Martin Holladay | | #12

    Response to Robert Swinburne
    Thanks for your comments. If GBA readers want to read more about the Maine builders mentioned by Robert, here are some links.

    Homes by Jesper Kruse: Two Single-Family Passivhaus Projects in Maine.

    Homes by GO Logic:

    Michigan Gets Its First Passivhaus

    Cold-Climate Passivhaus Construction Costs

    A Cohousing Community Readies for Construction

    Unity College’s TerraHaus Aims for Passivhaus

    Gearing Up for a Passive House Residence at Unity College

  13. subahn | | #13

    HRV frosting / balanced ventilation problems
    It seems like in a northern climate it could have made sense to specify an HRV that had a core that wasn't susceptible to frost in the first place (or at least didn't have to rely on dampers/electric heating elements that cause imbalanced/restricted ventilation and preheater energy cost).

    The added complexity to these units also seem to be reflected in their cost that cause them to cost thousands vs. hundreds of dollars compared to units that are just as energy efficient but don't require defrosting hardware. (I'm guessing the Zehnder unit with heating element cost well over $2,000) Here's a similar house that took care of that issue with an inexpensive (<$600) passive-defrosting HRV unit:

    Our house uses a similar 90CFM HRV unit (EV90P) that stayed frost free on the coldest winter weeks in Wisconsin this past year and used about 25kWh from Feb-May with a ventilation rate of 30CFM. Also, I imagine the installation cost of some of these complex units are significantly more when you include the additional wiring of the defrost unit and plumbing of condensate lines.

  14. northerntimbers | | #14

    PVC Air inlet
    Ok I hear you all on the air intake. How about some sort of screen which would prevent a large coal from exiting the stove? Assuming we leave the intake as is.

  15. GBA Editor
    Martin Holladay | | #15

    Response to Peter L. (Comment #11)
    I have glazing-only information on the windows. I don't have whole-window (NFRC) specs.

    The glazing specs are orientation-specific.

    Orientation #1 [presumably, east- and west-facing]:
    Glazing only:
    U-factor = 0.088
    SHGC = 0.494

    Orientation #2 [presumably, south-facing]:
    Glazing-only specs:
    U-factor: 0.106
    SHGC: 0.62

  16. GBA Editor
    Martin Holladay | | #16

    Response to Alex Carver (Comment #15)
    When it comes to fire safety, I'm not inclined to suggest halfway measures or work-arounds. Instead, I suggest that (a) you contact Morso and make sure to follow the company's instructions for installing the outdoor combustion air kit, and (b) study the applicable codes to make sure that the combustion air duct complies with code requirements.

    This is a controversial topic. Many stove manufacturers have concluded that it's safer for a combustion air duct to terminate in the vicinity of the wood stove rather than to be connected directly to the wood stove.

  17. user-1026988 | | #17

    Chimming in
    For the record. I never lobbied for Not having a wood stove in an PH. I like wood. Biomass makes a lot of sense in Maine ,VT,NH.; largely heavily forested regions with small rural populations. We could take some lessons from the Austrians in this regard. Cut one tree plant three.The Austrians tend to employ biomass regularly in many PH's. Where as the Germans opt for PV.
    In our own PH ( enerPHit at 4.95kbtu/ft2yr) We have an airtight wood stove insert with no make up air. All appliances however that would depressurize the house are outside of the thermal envelope and we use a recirc hood in the kitchen. To get the stove lit we open a window light the stove then close the window. No biggy.

    On sundays and in the evenings the kids want to help Dad light fires and we snuggle in front of the fireplace and I drink PBR's and we watch football. (we are a classy bunch)
    I would not trade fire on the floor of the cave. I ; Ramapithicun as I am, like fire on the floor of the cave.
    BUT, in a Passive House or any well built super insulated airtight, resilient, home that has ultra low heating demands a wood stove is NOT needed. A primary heating plant IS needed .
    A wood stove IMO can not be considered a primary heating plant from a design perspective.
    Practically speaking, of course it can be.

    A wood stove in a PH is a luxury. Since it is not needed, it is a 4-5K luxury item that can be bolted on if it fits within the budget. When designing within strict budgets those discussions need to be had.

    I calculated the heating demand of the house at 5,820,480btu. I think this is pretty accurate. The difference in this metric v Martin's 7mill ( which is pretty darn close) is the wood.

    I predicted a 1/2 cord bases on these calculations with an additional factor for the wood. I am glad I was close and I applaud Chris and Zoe for their dedication to conserving electrical resources.
    I hope that minisplit gets fired up this summer!

    Metrics for the windows are correct. Uw for this project ranges between .14btu/hr*ft2*F for the smaller units to as low as .12btu/hrft2F for the lager ones.

    I concur with Dana and Martin about the PVC inlet.

    Chris and Zoe came to me with Alex and wanted to use the Knox house as a basis for designing and affordable PH. This is truly a bigger brother to that house. Chris, Zoe and Alex were fantastic throughout this project. As Alex I worked together to achieve passive house we have become what I consider to be very good friends.

    Hats off to you guys.

    Nice article Martin! Wood is good.

  18. kimcrow | | #18

    Electricity Costs
    Malcolm Taylor asked about the electricity costs because his household costs seem to be similar for a house that does not perform as well as this one does. I wonder if it is possible to discover the amount of energy that the house used during the colder months (kwh) and how that compares to warmer months. Electricity costs vary from location to location so a dollar amount may be misleading. This would make the energy consumption for supplemental heating question a bit clearer.
    Great house! Great house dwellers!

  19. jinmtvt | | #19

    nice stuff ...
    i don't want to sound pessimistic ( again ! )

    please tell me if i am getting it wrong :

    ~1800 sq ft X 165$ = ~ 300K$ + land

    Please list the expenses that brings this up to 300K$ house
    I just can't work it out in my head.

    Is the price difference of housing from here to USA really that much ?
    ( here = QC, Canada )

    Please do not get me wrong, but when i look at this nice project, i see a 2 story wood shack built using low cost materials ( cellulose, osb etc.. ) no basement, nothing expensive
    ( i get that it was not the point ..but i'm trying to push my 300K$+ argument )
    not especially beautiful in terms or architecture ( aka it feels neutral )

    How much will this kind of house worth for resale in 10 years?

    Out of my head, it is the kind of building i would see for sale in the high 100K to the low 200K
    ( ~ 190K - 230K maybe ) but 300K+ land ?

    If this would've been built to the code standard, using similar methods and the usa windows ( non PH approved ),
    how much would it cost to build it then ?

  20. GBA Editor
    Martin Holladay | | #20

    Response to Jin Kazama
    I would be interested to hear the owners, builder, or designer respond to your comments. In the meantime, I'll offer some observations.

    You are correct that this house was more expensive to build than one might guess from looking at it. This means that real estate agents and mortgage lenders may not properly understand its value -- a major problem with energy-efficient houses.

    Here are some elements of the house that cost significantly more than similar elements of code-minimum houses:

    - The 12 inches of sub-slab rigid foam cost a lot more than what is typically installed.

    - It cost more to frame the 14-inch thick walls than typical 2x6 walls.

    - The triple-glazed windows cost more than typical double-glazed windows.

    - The cost of installing R-52 wall insulation and R-100 ceiling insulation was more than the cost of typical insulation.

    - The Zehnder HRV probably cost at least $6,000.

    - The European membrane (Solitex Mento) and many, many rolls of European air sealing tape are expensive.

    Were the incremental costs worth it -- especially considering the fact that the Pikes ended up with a home with no basement, with very simple windows, with a concrete slab floor, and without many aesthetic flourishes? Only the Pikes can answer that question.

    The Pikes probably paid at least $350,000 for their house and land. For purposes of comparison, the house in the photo below is on the market in Ripton, Vermont now for $300,000. It is more than twice as big (4,267 s.f.) and has 4 bedrooms. The lot measures 7.5 acres.

    I am certain that the house in the photo costs a lot more to heat than the Pikes' house.


  21. Chris Pike | | #21

    Response to Martin (post #17)
    At least our non compliant air intake gave Dana a chance to use the rabbi quip! All kidding aside, we discussed the air intake with the chimney installer. Since air sealing was a big priority we wanted to think of a good way to close off the intake tightly when the stove was not in use, which is a majority of the time. He showed us a poorly sealing metal gate valve. We asked him about the PVC ball valve to metal duct and he didn't flinch. Guess he wasn't up on intake air codes.

    As Dana said, the Morso air intake is not tight to the stove. I asked the Morso dealer about this when I initially bought the stove. It is by design but he wasn't sure why. As a commenter in a previous post here says, something to do with EPA stoves cannot be completely closed off. I don't have a citation for this but here's the blog post:

    The code that Dana linked doesn't mention wood stove, unless manufactured fireplace means wood stove. I can see with a fireplace, manufactured or masonry, where the air inlet is directly to the firebox where a coal can easily be blown into the intake. When you trace the air path on our wood stove, to keep the glass clean and to burn clean, the intake air ultimately enters the firebox from the top.  A coal would have to be lifted up the front of the glass, into a channel over the top, down the back and into the air intake.  There are secondary reburn holes, again at the top of the firebox, that are 1/16".  Conceivably a small ember could make it back with a wind opposing the draft of the 30' of straight chimney.  Then it would land on PVC with internal air temperatures below freezing surrounded by fire retardant insulation.  

    I'm a professional firefighter by trade with over 20 years in the service. I have not seen or been able to find any reports where the air intake was determined to be the cause of a structure fire. I can't say that one does not exist. They wrote the code for a reason. The risk is small but is still there. If I can easily eliminate a risk to my family I do it. The metal transition slides off and I now have an easily sealable proximity air source. I may not even use it and try burning this winter as Chris Corson does. Martin, I can send you an updated photo so the focus can be back on how amazing this house is.

    I can't say enough how happy we are with the house. This was an especially cold winter up here and all of our neighbors ordered more firewood. I felt kinda bad telling them we haven't gone through even a 1/3 of a cord at the time. Everyone has been amazed. Many thanks to Chris Corson for the design and to Alex for making it happen. Everyone should build like this.

  22. GBA Editor
    Martin Holladay | | #22

    Response to Chris Pike
    Thanks very much for the added information on the outdoor air duct that provides combustion air to your wood stove. The details are useful and help us understand the situation.

  23. GBA Editor
    Martin Holladay | | #23

    Updated photo
    GBA readers,
    Chris Pike just e-mailed me the photo below, with the title "Updated air intake photo."


  24. Expert Member
    MALCOLM TAYLOR | | #24

    Jin, the per sq footage costs used by mortgage lenders here in the PNW as representing the average house is $150, so 165 is by no means unusual. To my eye the finished house does look more like the projects I design that come in around $130, however that the owners have decided to put that difference into increased performance rather than finishes is surely a legitimate choice.
    There definitely is a difference between Canadian and American costs. Look at FHB's Annual Housing Awards Issue if you want a shock.

  25. Expert Member
    MALCOLM TAYLOR | | #25

    response to Chris Pike
    You are right. Getting lost in this is that it is a very well built house that performs exceptionally at a price that dispels the idea of Passive Houses being Boutique Green. Well done.

  26. STEPHEN SHEEHY | | #26

    Construction costs
    The real monetary value of a house like this is in the money saved every year, for the life of the house.

    When we see a per square foot cost of $165, does that include design? Architect fees are typically around 8-12 per cent, money well spent as far as I'm concerned, but still need to be counted.

  27. kevin_in_denver | | #27

    Less Expensive Alternative to Zehnder?
    A regenerative-style ERV is potentially much cheaper and more efficient than a Zehnder:

    Approximately $1600 for a 3 bedroom house. And a whole lot less scary to look at.

  28. jinmtvt | | #28

    Malcolm Taylor: is 150$
    Malcolm Taylor: is 150$ including the land ?? that changes the price significantly

    I believe we all understand the impact on the building energy consumption .

    But, how can you justify for monetary value, the price difference between the new cost
    and the resale value ?

    I do not believe that this building will gain 30%+ of value solely based on its energy performance in the near future.

    Let's quadruple the energy consumption of this building ... that would put it at near 2 full cords of wood!! representing a superb 100-200$ of value saved.
    ( ~ 225$ using 3.0cop with a mini @ 0.1$/kw/h and 65% stove eff . )

    The point here neway is not the performance of the building, as it looks superbly efficient and well built for this kind of system.

    The new cost is the problem.

    If the owner accepts to pay more for the efficiency , then there is no problem.
    But that situation will only represent a very low % of new homeowner who places eco-efficiency before money etc.. ( it is a positive point but not one many can afford )

  29. Chris Pike | | #29

    Response to Jin Kazama

    We just converted the construction loan to a conventional mortgage. The bank assessed the house at 400K. We have just under 17 acres of useable land that cost 105K. I say useable because we looked a 30 acre lot for 30K. A few acres were flat the rest went straight up a mountain.

    We had to find a builder that would build Chris Corson's design. Builders weren't comfortable with the construction method. One wanted to do a double stud instead. Price quotes were still $200-$220 sqft. Alex was willing to take on the project on both fronts of design and cost. We did it.

    We could have done it for less if we bought a less expensive lot, did laminate instead of granite countertops, hollow core instead of solid wood doors, cheaper appliances and a few other upgrades. From what I know $165 sq ft plus land is very good for the northeast. We were under budget. The bank would not have agreed to the mortgage if they thought the house wasn't worth it.

  30. Expert Member
    MALCOLM TAYLOR | | #30

    No, the land is extra as is the design, although all services, septic and a rudimentary road are included.
    I'm not sure that comparing new construction to existing houses that are on the market is all that instructive. Right now the price for used houses around here is well below the cost of building a comparable new one. The two often bear no logical relation to each other.
    You would think that if new builds were more expensive construction would slow down until the scarcity in the market drove all prices up. To some extent this happens, but there must be something else in play because there isn't any direct correlation I can see. Proving, yet again, that applying a logical analysis to real estate markets can lose you a lot of money.

  31. wjrobinson | | #31

    Malcolm, used homes... should
    Malcolm, used homes... should cost less.... you don't make sense to me.

  32. jinmtvt | | #32

    ok, thanks for the info
    Have you guys been able to establish some kind of "cost list" ??
    Total material price, total labor pricing etc..

    Having to chose cheap inside materials in a new house worth 300K$+ is a bit disconcerting to me,
    but again my references might be biased .

    Please do not believe i am trying to bash your project , only trying to analyze the build and its cost to better understand the relationship between all the different factors.

    And i thought that materials were cheaper in US of A than in Canada
    ( judging from HD website they still are )

    Have you made a list of prices for the different components of the building ?
    ( total material cost, labor cost, professional fees etc.. ?? )

    Why do you think other builders were reluctant toward your project ?
    Would it be more of a monetary issue or a capability ??

  33. Chris Pike | | #33

    Response to Jin (post #33)

    Yes, for the construction loan every expense had to be accounted for. The bank required periodic draws with an itemized list to make sure their money was being spent appropriately. Whether it was the windows or a porta potty rental it was on the list. Again, the bank thought the costs were appropriate for our locale. If I walk away from the house they need to know they can sell the house and recover their money. I know I could have moved to southern US areas like the Carolinas and have built for much less. But Vermont is where I want to live. If you're interested in more specific numbers Alex would have better details on individual costs.

    As I said, the builders that weren't willing to take on the project either not comfortable with the construction method or were not able to meet the price per square.

  34. Expert Member
    Dana Dorsett | | #34

    EPA wood stove air supply (response to post #22)
    From K Willet's post on the other blog piece:

    "As I understand it, an EPA stove can't be completely closed off. The various joints and seals in the stove are airtight, but the air supply has to be sufficient to keep the stove burning cleanly"

    The reason EPA wood stoves air supplies are not allowed to be completely cut off is due to high particulate & CO emissions potential when brought down to a true smolder condition. Many/most manufacturers deal with this by using a perforation in the draft control valve- even with the valve fully closed there is a minimum cross-section of area for combustion air defined by the size of the perforation, always provided at least a minimum amount of combustion air to limit the depth of smolder.

    But that's inherent to the the stove design, not the combustion air ducting, and orthogonal to the how tight the combustion air duct is to the stove. (Except in this case with the addition of an un-bypassed ball valve on the PVC duct the smolder potential is still there even if the draft valve on the stove has the EPA approved minimum bypass.) Other vendors use reasonably air-tight connections between duct & stove on the combustion air kits, and it's unclear to me why Morsø chose to implement it as a (very-close) proximity duct rather than a tight connection. I haven't seen Morsø units close-up to figure out their drafting design, which may (or may not) provide insight to why they did theirs that way. I'm glad that the drafting design is makes it difficult for backdrafting to ever move embers into the air intake duct (this is not universally true for wood stoves.)

  35. user-995931 | | #35

    Question for Chris Pike: Chimney Envelope Penetration
    Hey Chris,
    I tried this earlier (see comment #1) but Martin's response didn't quite get to my question: How did you handle the chimney / building envelope penetration of your woodstove? Thanks!

  36. user-1006269 | | #36

    Electric HRV
    Wonderful building, but the electric heater in the HRV system colors the 1/2 cord of wood consumption, as does the electric bill.
    All things considered, it is a fine home.

    As one who sells and uses a lot of foam, is anyone else a little concerned about 12 " of foam under the slab and the potential for critters to move in?

    I am not saying it is a bad thing, but if one is building an R-50 floor system, why not move it up off the ground to minimize the hidden pathways of insects and rodents. This foundation scheme has to last for a very long time. Plastic foam is inert, but one would have to imagine a time when some nuclear medicine is needed to knock back some sort of infestation in 2, 5, 10 or 20 years.

  37. jimblodgett | | #37

    Spinning numbers
    I'm wondering if the 1800sq ft is measured outside framing? Or is it inside the exterior walls? At 14" thick, it matters, and here in Western WA building departments measure from the exterior.

    Another thing - all this talk about cost/square ft - according to Chris Briley and Phil Kaplan's "Green Architect's Lounge" podcast (don't remember which one, they're all worth listening to) initial construction costs only account for...what was it...11%?, 15%?...of the total cost of owning and operating the average home over it's life. Pretty shocking.

    But things have to change. We can't keep stifling advances in our building techniques based on initial construction costs. Maybe it's time to look towards longer mortgages, I don't know. But I do believe the value of these well built homes is over their lifespans, not necessarily how well they hold their resale value, or fit into common bank lending metrics.

  38. user-1026988 | | #38

    To Tom G.- I am not sure how the electric post heater colors things? Nor am I sure what is so outrageous about the electric bill as some other posters have mentioned. It is impossible to model occupancy behavior. Dollars are NOT a metric for energy consumption. The post heater a 500 dollar bolt on appliance is used solely to temper incoming air in extreme conditions. It is a back up heating plant that takes the place of electric baseboard heat as a secondary heating source at a fraction of the cost. I would be surprised if it was even on at all in this house. That being said it is not a perfect devise. I could write a blog on pros and cons of redundant heating methods in PH's.

    The foam is type 9 or 29 ( depending on who you talk to) Geofoam EPS. It is infused with boric acid and is not not only pest resistant but also fire resistant. How long does that treatment last below grade? Good question. Nobody knows. I mean really knows. Alternatives, foamglass, foamglass aggregate at 1"minus (not available in the US) or building on piers. I have been working through this for 5 years and foam is still the most cost effective IMO. This will and should change soon....i hope. Working on it.

    et al......................COST......................Investing in a home is just that. An investment. For the vast majority of us, it is the single largest capital investment we make in our lives. For some that investment is made more than once. Family's have a way of growing( we have that going for us).

    Investments need to be made upfront, not on the back end. Investing in a super insulated, airtight, mechanically ventilated home , that is comfortable to live in and healthy at the same time, is just a no brainier for some, for others it is a different story.

    I agree with Jims Bloggetts comment " things have to change. We can't keep stifling advances in our building techniques based on initial construction costs" This is one of the tenants of our mission as a company.
    However, longer death pledges are not the answer.

    The answer is far more complicated that . Starting with a total cultural shift in what we perceive as important, and ending with redefining the culture and best practices of a construction industry, that has not evolved in 50 years. Can you imagine driving to work in a 72VW bug on the 405 in cali? Or any other modern situation? This again could be a blog post.

    Energy prices increase at a rate of 5.68% annually ( DOE). This exceeds cost of living increase's. A larger problem is that energy prices do not behave in "averages" they spike and fall, spike and fall (another blog post) . In 2008 we went from 45-90$/barrel for crude. That will happen again and again; and more and more frequently as this finite resource continues to be consumed by an endlessly growing (and way more complex global economy) than I grew up with. It was already bad then. #70-80's

    i'll sum with a statement and then a question then a statement:

    I live and work and raise my family in Maine. We have not only one of the oldest existing housing stocks in the country but one of the oldest population's as well.
    80% of New England heats with oil ( Diesel fuel)

    What happens to the value of the existing housing stock when energy cost's exceed the the means of homeowners to pay them?

    My grandfather taught me to buy the best tools that I could afford, to take care of them, and to use them carefully, diligently, and patiently.

    Invest wisely. Invest in the best that you can afford to. Have respect and care for that investment, and don't expect immediate returns, the universe just doesn't work like that.

  39. user-1006269 | | #39

    More comments
    Hi Chris,
    Thanks for your comments. I do not disagree with any of them.
    Having lived in Maine for 40+ years, anyone in New England understands the cost of living with old housing stock.
    My old home in Searsport has been retrofitted to R-65 with polyiso foam and heats with a good mood.
    I guess about half of my heating load for most of the year is from electric use waste heat.

    My comment about heating loads is based by the fact that the inherent electrical usage will become part of the heat contribution to the home. There is always that anecdotal aspect to comparing projects.
    Certainly a 700w heater is of some consequence.

    While I admire the 12" foam foundation base, my concern is if any compromise comes of that thickness of foundation foam, there are could be major structural issues.
    Hopefully borates will do the trick, but as you say, we just do not know.
    It is certainly the most cost effective way to get that high insulation value, but I wonder if that would be acceptable south of the Mason-DIxon line where foam in contact with soil is not an accepted practice.

    Unfortunately, there has been some reports of ants and termites in borate treated materials. I hope that was a fluke. I am sure you do too.

    All things considered, an important project that people should learn from.

  40. hallie17 | | #40

    foundation foam in slightly warmer climates?
    Since these houses are in the really cold areas of Maine & Vermont, my understanding is that termites and carpenter ants are less of an issue. Would you make the same choices with the foam in contact with the ground in zone 5, such as northeast Ohio? We aren't prime insect territory, but termites do happen here.

  41. Chris Pike | | #41

    Response to Chimney penetration and Electrical usage
    Zac, the chimney installer used what I believe is called a fire stop spacer at the envelope penetration. There is also an attic insulation shield.

    For questions about our electrical usage, we have a SiteSage monitoring system that was installed March 4th by Efficiency Vermont. It monitors each circuit individually. The HRV used 146 kWh in March. April 35 kWh and May was 28kWh which correlated to outdoor temps. The HRV draws about 40 watts durning normal use, setting #2. The unit has four speeds (absent, 1, 2 and 3). 3 is used when cooking, showering or other times when a boost is needed. We set it to 1 or absent if we're not home. When the heating element is on, the draw was recorded at just under 800 watts. We had a data logger monitoring CO2, humidity and indoor temperature. The CO2 monitor helped us tune in our HRV usage. The last 30 days with moderating outside temps the HRV cost $4 to run.

    Some things we learned with the electrical monitoring system:

    Our old stand alone upright freezer is never turning off. It's supposed to cycle. It is constantly drawing around 100watts costing about $13 dollars a month. We need to replace it with a efficient chest type freezer, predicted to cost only $6-$7 a month.

    My wife has a home office. The computer peripherals were drawing a minimum 80-100watts mostly in standby. More when functions like printing were actually happening. We now unplug items that we don't use often like the printer. But internet and back up systems cannot be shut down. About $15 to $20 a month.

    We have two young kids. Most every night one of them gets up to use the bathroom and leaves a trail of left on lights. We have all LED lighting, it's not a lot of usage but it still drives me nuts.

    There definitely are places where we can get the electrical bill down. We have an electric dryer but we mostly use a clothesline. Like Chris Corson said, it has a lot to do with occupant behavior.

  42. jimblodgett | | #42

    "...has not evolved in 50 years"
    (quote from christian corson in cooment #39)

    But they have. Building practices have clearly evolved over the past 50 years. But things change slowly in an industry that produces something (houses) that last far longer than the original mortgage, or builder's career, or original homeowner's life.

    The thought is deeply ingrained in me "well, it will last my lifetime, that's for sure". As if that should be "good enough", some measure of quality. But it's not. Over 40 years I've been at this and it seems like only yesterday I started. Those carpenters who built all that "old housing stock" in Maine? I bet for the most part they were doing their level best, according to the standards of the day, and that's what you and I have to do today.

    We have to make tough choices what to invest in initially, but I agree that the shell and thermal boundry are great places to start.

    But there also has to be a cultural shift in how we view homes. At a minimum they should last 200 years (like many of those old places up your way). We have no way of forseeing how homes will be lit, or heated, or cooled 200 years from now. But the bones should remain strong and the shell should be easilly maintained so as to protect those bones.

    And the true "cost" of home ownership over that 200 years should not be higher than average so that the original building can have more curb appeal, stimulate more potential buyer's egos, resell at a profit within 10 years.

    A good start would be a cultural shift in thought about what constitutes "good home investment". And thanks to the internet, this too is evolving as we exchange ideas from far flung locals.

    Evolution is slow in our industry, no question. But evolve we have, and those building long after you and I are gone will continue to innovate and change. I just hope to leave something that someone with similar values will respect when they tear into it 100 years from now and think "...yeah, well, at the time these folks did the best they knew how. Not what we'd do today maybe, but for it's day..."

  43. Expert Member
    Dana Dorsett | | #43

    Response to christian corson (#39)
    "80% of New England heats with oil ( Diesel fuel)"

    Not even close to fact.

    According to EIA data, in the northeast heat (with NY/PA/NJ included) more than half of all homes heated with natural gas:

    Maine's fraction of homes heated by oil is about 77%:

    But Maine is sparsely populated compared to neighboring NH, where the fraction is only 47%:

    In (even tinier population) VT, heating oil has less than a 60% share:

    VT has recently been heavily subsidizing cold-climate mini-splits for those heating with oil & propane. That program is soon to become expanded, pending signature of a recently passed legislative amendment.

    In MA ,RI, & CT the gas grid is more developed, and the number of houses greater, but natural gas is the dominant heating fuel in those states. Even before crude hit $100/bbl heating oil's share in MA (the most populous New England state) had drop to 1/3, and since 2009 it's been dropping faster:

    Oil is DEAD as a heating fuel. To sustain the current levels of oil production requires increasing tight-oil production to increase just to stay even (let alone grow), which has a price floor of about $75/bbl to remain profitable. Oil is currently trading at $100/bbl. Heating oil tracks crude prices fairly closely, so the price floor of heating oil is going to be about $3/gallon, which is far more expensive heat than ductless mini-splits.

    As a region, the raw economics are favorable to rapidly displacing heating oil & propane with high-efficiency ductless.

    But in Maine wood pellets (stoves & boilers) and cord-wood are is also viable fuels for many.

    Energy price inflation broadly cannot sustain year-on-year 5%+ levels- the rapidly falling price of PV solar (and grid storage) may even induce broad energy price deflation before the year 2030, according to Sanford Bernstein analysts, and both Barclays & CitiGroup seem to concur. (These are investment bankers, not green-power cheerleaders.) That's not to say it isn't worth building higher performance houses- quite the contrary, but the issue of space heating affordability in older lower performing homes is more about replacing the incumbent space heating fuels with existing technology & sources that is already less expensive. Since 2002 the price of oil has quadrupled, and there aren't any credible scenarios for that to turn around. But in the same period the cost of PV solar energy has dropped by over 60%, and is continuing to drop. Wind power has also had significant cost reductions, with year-on-year reductions in lifecycle-output cost, though not as dramatic as PV.

  44. user-1044645 | | #44

    Another 1/2 cord a year home
    FWIW my wife and I live in a 500 sq. foot SIPs octagon (one large room yurt-inspired floorplan) and burn 1/2 cord or less per year. We are off-grid so mini-split is not an option and it is in fact more efficient to open up windows for ventilation than run HRV through most of the winter. Ours is no fancy designed home, just small, and we self-financed and built it ourselves. No especially awesome windows or doors, but, the SIPs (Winter Panels) do a lot to keep it cozy inside. If we fill our fire box too much it'll be 80+ degrees in the wintertime.

    - Fred

  45. GBA Editor
    Martin Holladay | | #45

    Response to Fred Greenhalgh
    What is your climate zone or location? What is your typical minimum winter temperature?

  46. user-1044645 | | #46

    We're in Maine
    Reply to Martin - Whoops, guess knowing temp zone would be important! We are in Southern ME, York County, so I would imagine similar temps to the people featured in this article. We are inland from the coast so typically experience more snow and more bitter temps.

    As you know we all had a 'propah Maine wintah' this year, we are nerds with our solar PV / off-grid usage (by necessity) but not as strict monitoring wood consumption. But, anecdotally, I remember one night we had the house night and warm (75 or so) and so did not stuff the firebox and let it go out overnight. When we woke in the morning, it was chilly for us (62'ish) and when I checked our outdoor temp (remote temp sensor) it was -15F outside. Oh. So then I lit up a fire.

    We installed an outdoor wood-burning sauna which we run once a week. We literally will consume more wood in that sauna than we do heating the house the rest of the week, and indoor temps are never below 65F.

    - Fred

  47. Expert Member
    Dana Dorsett | | #47

    Update to a comment in post #44
    Where I wrote:

    "VT has recently been heavily subsidizing cold-climate mini-splits for those heating with oil & propane. That program is soon to become expanded, pending signature of a recently passed legislative amendment."

    Apparently it has been signed:

    It remains to be seen the level of subsidy, and for whom, and which models would qualify. In prior years it was only for those heating with propane or oil, and only the -FExxNA Mitsubishi or -xxRLS2-H Fujitsu or the Daikin Altherma air-to-water hydronig system, to the tune of $1000 rebate for the first unit, $700 for a second.

    There is greater value to the utility AND the ratepayers to subsidize retrofits for those heating with resistance electricity, since that reduces the grid load. Under the amended rules those heating with electricity (and natural gas/biomass) will have access to the subsidy as well.

    Since VT has NO fossil-fired power generation large enough to fall under the recent EPA carbon emissions rules (the only state exempted!), and electricity demand in VT is shrinking dramatically under recent efficiency efforts, this is a pretty green move!

  48. designthis | | #48

    Indoor humidity
    I'm really curious what the indoor relative humidity readings are in this house right now. We've had a pretty wet and cool spring in the northeast and I've discovered in my own very tight, new cottage in upstate New York indoor humidity readings of 60-70%. People have to breathe right? So I'm running the HRV 20 minutes on 40 minutes off, the minisplit is off because the indoor temp is a very comfortable 68-70 degrees--and you can forget the "dry" mode in the minisplit--with these conditions it will just reduce the indoor temp thereby increasing the relative humidity. It seems like in the "shoulder seasons" in the northeast, when you don't need heat or ac--which must be close to a half year--a stand alone dehumidifier seems to be the only solution for keeping indoor humidity levels to a point that you won't have mold or comfort issues. Could someone please address this? And if the case is that a dehumidifier is essential, they take energy to operate and that should be factored in as well for energy consumption.

  49. GBA Editor
    Martin Holladay | | #49

    Response to David Metzger
    If you want to lower your indoor humidity by operating a ventilation system, all you need is for the outdoor temperature to be cool (which you claim it has been). "Cool and wet" is almost as good as "cool and dry" when it comes to ventilation, because cool air doesn't hold much moisture. (Check out the psychrometric chart.) So just ventilate your problems away -- especially at night.

  50. designthis | | #50

    Indoor humidity
    I wish is was that easy to "ventilate your problems away." In tight houses in Upstate NY, climate zone 6a, my real-life experience begs to differ. That's why I was curious to hear from the folks spotlighted in this article.
    I realize the article is about using a tiny amount of fuel to heat their home in the winter, but isn't the bigger story always about energy consumption? Besides, we're beyond the heating season now and on to the more complicated season: Spring. People building passive houses can always brag about how little they spend on fuel in the winter, but nobody ever talks about the shoulder seasons and managing indoor humidity when there is little differential between the inside and outside air temperature and generally high humidity outside.
    I took your advice and ventilated (HRV set to high) last night. The indoor humidity shot up to 73% by this morning (up from 63%) and the temperature remained a steady 72 degrees indoors. Comfortable, but moist. So the question is, how much indoor moisture is acceptable to live with, and for how long before it becomes a problem? In the winter, one can always live with a little less heat, but in the Spring--in a super tight house--one should probably not live with too much moisture. We've heard over and over how bad that is. This time of year ventilation brings in excess moisture. I know this because if I turn off the HRV, the humidity goes down, but then I can't breathe :) So it seems like mechanical dehumidification is the only solution. And that's never talked about. It's not even in the letters HVAC. And not only does it use energy to run, it raises the indoor temperature.
    Perhaps this could be a topic for another article. How ironic that a house could require little energy in the winter only to use more in the temperate months to keep the indoor air fresh and dehumidified--while people in leaky houses are spending nothing!

    BTW, Here's my cottage:

  51. GBA Editor
    Martin Holladay | | #51

    Response to David Metzger
    Once the weather heats up -- especially if you live east of the Rocky Mountains -- then ventilation tends to raise indoor humidity levels. Under these circumstances, the less you ventilate, the better.

    In some climates, tight houses definitely need a stand-alone dehumidifier. If the dehumidifier makes your house too warm, then you will have to run your air conditioner. However, your energy bills may still be affordable.

    Passivhaus builders are beginning to acknowledge these facts, and Katrin Klingenberg referred to these facts (obliquely) in her recent blog, New Passive Building Standards for North America, where she wrote, "We learned that latent loads really need to be accounted for in the [Passivhaus] standard."

    In your case, I would make sure that you have identified all the possible moisture sources in your home, including construction moisture (from damp concrete, damp framing lumber, and drywall mud) and any possible problems with your basement or crawl space.

  52. Expert Member
    Dana Dorsett | | #52

    "I took your advice and
    "I took your advice and ventilated (HRV set to high) last night. The indoor humidity shot up to 73% by this morning (up from 63%)"

    That was the night of 17/18 June, right? As it turns out that night coincided with the HIGHEST dew points of the season for most New England/New York locations, averaging in the mid-60sF, and peaking in the high 60s.

    The dew point of 72F / 73% RH air is 63F , which was probably the overnight outdoor air's dew point average at your house. If you pull up a dew-point history graph for say, Albany NY you'll see that the overnight average dew point outdoors was about 65F- go figure!!dashboard;q=albany%20ny%2C%20USA

    The dew point of the 72F / 63% RH air you started with is 59F, so unless they were forecasting overnight outdoor dew points averaging below 59F you would not be able to reduce your interior RH by increasing the ventilation, but you can limit the gain by limiting the ventilation rates.

    The forecast dew point for tonight for Albany is about 60F, but Thursday night/Friday it'll be below 50F, which is dry enough to bring your interior RH down below 50% RH without mechanical dehumidification.

    This is a location problem, not a house-tightness problem, and not likely to be a residual construction moisture issue, given your reported humidity & temp relative to the outdoor moisture levels. If you want drier summertime air you'll have to move the house to a location with lower dew points- say the western slope of the Tetons (Driggs ID, mayhaps? :-) ). If you keep the house (any house) in upstate NY you'll need mechanical dehumidification (such as dehumidifiers or air conditioning) to keep the interior air RH under 70% @ 72F. If you zoom back on your Weatherspark dew point history graph, you'll notice that the historical average year June-July mean outdoor dew point is about 63F, which is as noted above, translates to 73% RH when that air is at 72F.

    If your house had enough summertime solar gain that you needed air conditioning to keep it under 75F the air conditioning would do the dehumidification for you. But otherwise you'll need a dehumidifier. The tighter the house and lower the ventilation rate, the less dehumidification power it would take. And since a dehumidifier just takes the latent load (moisture) and converts it to a sensible load (temperature), a tight house and low ventilation rate is what you want, since the dehumidifier raises the indoor temp.

    This online psychrometric calculator is easy enough to use, and easier than reading a psychrometric chart. Click on the "IP" units to see it in F-degrees.

  53. designthis | | #53

    Humidity conversation
    Thank you both very much for your thoughtful responses.
    Room-sized dehumidifiers are problematic. And anyone who lives in a super-tight house knows that interior noise is greatly amplified--you hear everything from the ice dropping from the ice-maker to the ecm motor on the ERV. Then there is the issue of drainage, heat, energy consumption, and where to put the thing. Whenever I see a dehumidifier in someone's house I think, gee this person has a mold problems. And since I'm in the vacation rental business, first impressions are important. And since I'm also a designer, I like everything neat, organized, and well thought out. Nothing about a room-sized dehumidifier speaks to that need. I've also learned that installing a dehumidifier in a basement does nothing to dehumidify the living space above.
    Having said all that, I wonder why there isn't more talk about this issue--especially considering all the talk of ventilation. Clearly ventilation isn't enough to create a safe and comfortable interior atmosphere in a tight house, year-round. I'll admit I knew nothing of a psychometric chart when I designed this cottage, but I live in a house I designed and built that's twice the size and built very similarly. So with moisture in mind I was excited to finally install a mini split that would be a cure-all: Heat, ac, and dehumidification--all-in-one neat package. The HRV would solve the ventilation issues (and be invisible). So i was caught off-guard to learn that the dehumidification in the minisplit can actually make it more humid inside if the conditions are right. Like Dana says, it needs to be HOT and humid, not comfortable and humid--as it is often in upstate New York. My 2500 sq/ft house has an ERV--the RecoupAerator 200DX and rarely hits 60% so I was astonished to see readings of 70% in the cottage. But now I'm thinking the size of the space must be a factor. The cottage is only 1000 square/ft so the HRV--even on the lowest setting, must be over ventilating. I also noticed in the winter it was dry as a bone in there--a double wammy of ventilation and the forced air from the mini split. I guess we're always learning.
    So again, good topic for an energy nerd article. I think it's common for people to skimp on ventilation--which is clearly a terrible idea. All I have to do is turn my ERV off for a few hours and I feel claustrophobic. But dehumidification is something that rarely gets discussed--and I read a lot of green building articles.
    Thanks again!

  54. GBA Editor
    Martin Holladay | | #54

    Response to David Metzger
    The issue is disguised in many older houses -- the AC runs for more hours in poorly built houses, and therefore handles the humidity as a side benefit. Of course, energy bills are high.

    In a tight home, your energy bills are lower, but you still have to think about dehumidification in hot, humid weather. Ventilating during the summer (east of the Rocky Mountains) ALWAYS raises the indoor humidity level, no matter whether your home is tight or leaky. It's always important to minimize ventilation during the summer, no matter what type of house you live in.

  55. Expert Member
    Dana Dorsett | | #55

    ... right now this minute ventilating in New England would be quite drying. The dew point bottomed out at my house at 33F last night, and has been in the 40s all day, which is western-slope-of-the-Rockies type dry air, quite unusual for this region in June! Don't expect to see dew points this low on a regular basis until half-past October.

    I wish there were dehumidifiers with scroll compressors and ECM drive blowers, which would take that rattle, buzz & hum down to a whisper, like a 3/4 ton inverter drive mini-split.

  56. GBA Editor
    Martin Holladay | | #56

    Response to Dana Dorsett
    "Always" was an exaggeration, as you correctly note. My intended meaning was that ventilating during hot, humid, weather raises indoor humidity levels -- whether you have a tight house or a leaky house.

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