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Another retrofit tale

user-1135248 | Posted in Green Building Techniques on

If I have to phrase a post as a question, I guess this one boils
down to “so, whaddaya think?”

I managed a DER on my own house over the summer, and some of you
possibly saw some of my questions that stemmed from that. At the
risk of tooting my own horn a little, I’d like to start giving back
to the community by sharing the MONSTER writeup I’ve done about the
project — and there’s more to come, as I collect and compare energy
stats over the rest of this winter. At almost 120,000 words it’s
easily book-length, but right now it’s just a set of simple web-pages
with the story and plenty of detailed pictures and a decidedly informal
style. In effect it’s a resource *I* would have loved to find online
when I began my own research.

It’s also a complete geek-fest, dwelling heavily on technical aspects
and building science and HVAC fun as well as capturing some good
“action shots” of my contractors doing what they do.

While I’d rather not link to it directly for what are probably obvious
reasons, I have created an indirection step that only requires
following a couple of simple instructions in your browser:

and after that you can select any sections of particular interest.

Some of y’all at GBA have really helped me out over the last year
whether you know it or not, and this is the least I can offer
in return!


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  1. GBA Editor
    Martin Holladay | | #1

    I haven't finished reading yet... but it's fascinating.

    I hope you can contact me by e-mail. I'd like to republish some of your pages as guest blogs at GBA -- with your permission, of course. You've done a great job of documentation!

    My e-mail address is:
    martin [at] greenbuildingadvisor [dot] com

  2. homedesign | | #2

    .....Fascinating is a good description
    Thanks for posting...

  3. gusfhb | | #3

    I cannot even tell you how much I am laughing because you sound so much like ME.

    There needs to be a job in construction called 'anal retentive man'

  4. user-757117 | | #4

    I've barely put a dent in your material so far...
    But I'm looking forward to reading through it all.

    Thanks for taking the time to share your experiences in such detail.

  5. GBA Editor
    Martin Holladay | | #5

    I admire your attention to detail, and I understand your occasional frustration with the quality of work performed by local contractors. That said, it's remarkable that these contractors were able to work as well as they did with your camera so close.

    Anyway, here's what I'd love to see: a "lessons learned" essay summing up your experience. What would you do differently? What worked well -- and what would you have changed if you had to do the whole job again?

    You have written so many words that I may have missed a few details. But here's what I am curious about:

    1. How did you insulate the basement walls?

    2. Do I understand correctly that you have pressure-treated lumber in your return-air plenum?

    3. How do you feel about all that ductwork? If you had to do it again, would you choose a heating and cooling distribution method that didn't require ductwork?

  6. user-1135248 | | #6

    I guess one thing I'd change is to flatly disallow crew members
    from compromising parts they or others had already built, even
    if they intended to "patch" afterward. The roofing episodes
    were a prime example of the kind of cluster I'd rather avoid.
    A lot of the stuff I noted really seemed like no-brainers to
    think ahead and get right the first time.

    __ 1. How did you insulate the basement walls?

    The 1" white styrofoam was there when I moved in. Since it does
    help keep the chill off, even if relatively low R-value and not
    air-sealed, I left it in place and just patched up its missing
    parts and connected the sill sprayfoam job to it. I think I
    remember mentioning it in a prior post here and getting the
    expected comments about fireproofing; at one point my local
    building inspector looked straight at the bare EPS and didn't say
    a word. I know it's a mild compromise in terms of insulation
    value but see the discussion about passive freeze-down prevention.

    __ 2. Do I understand correctly that you have pressure-treated lumber
    __ in your return-air plenum?

    That's a really good point, that I didn't think about too much.
    Not that it's a whole lot of lumber in the AHU support frame...
    at the risk that quoting Wikipedia is the fastest way to lose
    a debate, it's got this to say on the matter:

    _ On December 31, 2003, the US wood treatment industry stopped
    _ treating residential lumber with arsenic and chromium
    _ (chromated copper arsenate, or CCA).

    The other potential issue is corrosivity to steel, and I just went
    to stick my head in there again and take a close look and there's
    no sign of anything bad happening yet ... but I can keep an eye
    on that. The air going through there should be fairly dry, as
    the coil and pan are up above all that.

    __ 3. How do you feel about all that ductwork? If you had to do it again,
    __ would you choose a heating and cooling distribution method that didn't
    __ require ductwork?

    I'm fine with ductwork, especially as most of it in this job
    already existed. The HRV additions were very easy. While air
    isn't the best heat-carrying medium it's likely the safest, so
    rather than muck with hydronics or worry about where to punch
    minisplits through perfectly good walls I'd likely do ducts
    again. I know a lot of the building-design wonks hate them.

    An alternative I might consider is something like a VRV system
    with small fancoils sprinkled around here and there and the
    distribution medium being refrigerant piping, all inside the
    conditioned space. *IF* I could have assurance that the pipework
    was done competently, that is...

    Thanks for the thought-provoking feedback, it's discussions like
    this that everybody learns from...


  7. user-1135248 | | #7

    Oh, and ...

    While the guys did seem a little nervous about me chasing them
    around with a camera, that really didn't make sense to me.
    For a crew that prides itself as, in the GC's own words,
    "possibly the best deep energy retrofitters in the country"
    ... you would think that they should be *proud* to show off
    their work and how they do it, not look away and hope I
    didn't notice deficiencies. But the results and the process
    sort of speaks for itself, and being totally candid about
    the good, the bad, and the ugly I really hope to work toward
    *improving* the industry as a whole. That's one reason
    I thought it so important to get the writeup out there
    in front of some of the people who matter. The GC has the
    opportunity to read it and pass the lessons to the relevant
    subs, it's just a question of whether it becomes a positive
    thing for everyone concerned or just another bitchy homeowner
    who was hard to satisfy.

    ps: Martin, check your spam-box or whatever...


  8. BillDietze | | #8


    A great read. Thanks so much for this treat: funny, nerdy & informative.


  9. homedesign | | #9

    Hobbit wrote: "While I'd rather not link to it directly for what are probably obvious reasons, I have created an indirection step that only requires following a couple of simple instructions in your browser:"

    Hobbit, I found your story to be very interesting....
    I am curious why you felt the need to create the "indirection step"... the reasons are not-so-obvious to me.

  10. nvman | | #10

    Hobbit, I admire the way you are going about your reno.
    I think you are somewhere between a genius and a mad scientist, with a little bit of Bob Villa mixed in.

    Keep up the writing!

  11. user-1135248 | | #11

    Mr. Brooks asks why the indirection ...

    It's sort of explained in the indirection file. This is something
    I *don't* want the search-engine spiders to rip through, at least
    not yet. If you're the type of person that just hangs all the
    details about their life out on the internet that's one thing;
    not everyone is like that.

    If things go well parts of the piece may find their way here, which
    would not only make the content searchable, it will carve out
    a lot of the in-between personal fluff that some folks may not
    care about and work toward being a more condensed reference.

    Thanks for understanding.


  12. Expert Member
    Dana Dorsett | | #12

    Having skimmed the whole thing and looked pretty closely a some of the pics I'm a bit concerned about where & how the Daikin compressor is mounted. With the slippy-slidey steel roofing the likelihood of a massive cornice-fall after some random nor'easter burying or bashing the compressor at some point seems pretty high, even with the mini shed-roof dog house built over it.

    Assuming your in eastern or central MA more than 20 crow miles from saltwater, the 20 year high-point snowpack depth over is probably something about as deep as the compressor is tall, even without considering snowdrift potential. Wouldn't be too surprised if you had to dig it up once or twice a year to keep it running. (I know for certain that would be the case for ground-mounted units at my home in central MA, even with 24" overhangs.)

    On a recent DER I was involved with in Worcester the mini-split compressors got bracket-mounted to the wall about 4' off grade, hugging the wall as deeply under the eaves as possible to mitigate those potentials, and the roof pitch is flatter, roofing shingles far grippier than what you have going. Bracket mounting solves ground settling/frost heaving flex issues too. (Not that you're looking to crack open the R410 lines again, I'm just sayin'... )

    Adding snow anchors designed for metal roofing can keep it all coming down in one big chunk, but wouldn't solve the snowpack depth and snow drift dept issues, and there would still be some cornice fall accumulation around the compressor. It would have to be a fairly wide & deep open-shed to fully protect it from all snow accumulation issues. (I've seen them tucked under well ventilated porches in VT, but near walkways that always get dug out after storms, preserving access to good air flow.)

  13. user-1135248 | | #13

    Thanks for that feedback, it's interesting stuff to think
    about. Which I hopefully have done enough in advance.

    So far, the gutter catches the sliding pack enough that it
    breaks off in fairly small chunks. But a different quality
    and/or quantity of snow might behave in some other way; I'll
    have to wait and see. I'm pretty confident in the ability
    of the hutch to withstand heavy stuff falling on it, as its
    structure is pretty sturdy. I think it would be hard for
    anything to fall *inward* enough from the 24+ inch overhang
    to get in between it and the wall, even if a cornice curled
    itself fairly far in before breaking.

    I'm expecting to have to shovel out the compressor once in
    a while; I factored that into placement. I didn't want to
    go farther from the house, but didn't want to tuck it in too
    close as I wasn't sure at its installation time how far the
    wall was going to get bulked out toward it. Wall mounting
    would require custom brute-strong brackets lagged into the
    old framing through strapping and foam like everything else,
    and would still be quite a lever-arm hanging off the wall
    structure. The ground back there is quite stable and has
    never exhibited any "heaving" problem even back when the small
    gutterless shed-dormer roofline was constantly dripping water
    on the area, so I don't think it's going to move a whole lot.

    As heat pumps become a more popular solution, I'm sure that
    placement engineering will play a more prominent part. This
    is always going to be a problem with any chunk of equipment
    left out in the weather... The hutch rooflet could have
    arguably been a little larger than 2 x 4 feet, but it's sort
    of what I had on hand and so far has been performing just as
    I wanted. I could always build a bigger top for it later, but
    the matching roof panels are just too much fun at the moment
    to make that a priority. If snow piled up sufficiently to
    disable the heat pump's ability to run I'd have a comfortable
    margin of time to get out there and tackle the situation
    before the place cooled down enough to endanger the plumbing.

    I thought about snow anchors. The only ones I'd accept would
    be types that don't involve penetrations, and I'm not entirely
    confident about long-term holding power of adhesives. Should
    I be? I am also leery about how much junk they'd doubtless
    retain outside of snow season. Picking the stem-in-first oak
    leaves out of the screens is PITA enough for now. Nobody is
    likely to be walking along under the roofline with any regularity
    except me on my daily ventures out to the electric meter.

    Speaking of which, we're pretty much into "design days" in the
    Boston area right now and I'm into the resistance-heating-only
    test mode with the heat pump part shut down completely. The 3 kw
    heater and other plug-loads are holding the place at an average
    about 60F inside, the same as when I was doing the furnace-burn
    timing to determine the previous baseline. [I'm hunkering down
    in one warmer room like in prior winters.] That's against maybe
    3 F average overnight, and it's going colder before this snap is
    over. Early figures show somewhere around 11,000 btu/h overnight
    seen at the power company's meter which is the only energy source
    coming into the house and all of which is being turned into
    interior heat in some manner. The envelope is not at a uniform
    interior temp, as corners upstairs will invariably lose a little
    more heat than the first-floor walls and the basement is undoubtedly
    adding some nonlinearity to the whole picture. And at these temps
    the polyiso is probably into its diminished R-value curve a bit, so
    I'm not expecting miraculous heat-holding. If y'all think of any
    other specific testing I should be doing, please suggest it!


  14. Expert Member
    Dana Dorsett | | #14

    I thought most Daikin compressors still had a rated output capacity at -20C/-4F (albeit at a pretty crummy , but still >0 COP.) Is there something about the control/feedback that precludes having the resistance coils and compressor run at the same time? (It got pretty close to -20C at my house last night, but it didn't break that mark.)

    Enameled steel roofing with riveted-in snow anchors holds up pretty well, but I'd be wary about drilled-through add-ons to aluminum roofing, especially if it's located anywhere near salt water.

    The concern about cornice falls and roof avalanches is really about volume- on a slick metal roof with a dense & deep snowpack once it all starts moving it can come down all at once, and if deep enough, it could bury the thing. If a nor'easter dumps 18" of the wet & heavy you could easily be looking at a 3'+ berm of compressed crud directly in front of the compressor after the roof slides, even if you started with bare ground at the beginning of the storm. You get some benefit out of the fact that it's a sub-25 degree angle. Natural slab-release avalanches on much grippier mountain substrates than metal roofing can occur on angles barely steeper than 25 degrees. ANY kind of snow anchor would probably be able to keep it in place at the angle of your shed roof, and a glue-on anchor is probably a good option (though I have no experience with them.)

    The 1.5lbs density iso rated R6/inch over the ASTM C518 conditions would be derated to about R5.6/inch (average) when it's 60F on the warm side, 0F on the cold side. If it's 2lb roofing iso it's ASTM rated values will be a bit lower, as will the derated numbers, but IIRC it's somewhat less derating with temp, albeit a lower starting point. Whatever, it's still pretty good stuff, and inch-for-inch performs comparably to or better XPS under these conditions, substantially better at the average winter temps of eastern MA.

  15. user-1135248 | | #15

    This is a special heating mode where the compressor is
    deliberately disabled and I'm heating purely on resistance
    and plug-loads, for a COP of exactly 1.0000 so I can measure
    the energy input to the whole system. It's a hack. And I'm
    giving far more credence to nighttime figures to try and
    eliminate the solar aspect during the days. It's also the
    expensive way to heat but only temporary while I study how
    the new envelope is doing in this weather.

    As mentioned in the writeup, the Daikin does *not* fall back
    to resistance heating by itself in the event of compressor
    unavailability, which has gotta be one of the stupidest
    engineering decisions I've run into in quite a while. This
    is why I have to crock in an auxiliary thermostat and lash
    up all that "integration box" mcguyvered control wiring. Per
    the concurrent "Japanese walls" discussion going on here, I
    guess they don't get noreasters and ice storms that could
    drop a log or an avalanche on their minisplit.

    I suppose it would have been safer to locate the compressor
    next to a gable wall instead, but we'll see how this goes and
    in the meantime I'm sure the neighbors are happier not getting
    blasted by colder-than-cold air across their driveway.

    With the number of other compromises noted in the whole job,
    this seems on the minor side...


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