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Mid-Ohio renovation

Matt Bierlein | Posted in General Questions on

Hi all. We own a home in Columbus, OH (climate zone 5) and are evaluating renovation options. We have an architect engaged and have a rough set of plans to start the conversation with contractors and iterate/VE with the architect to get to CDs.

A few house details. It’s an old house (1926) with an original footprint of 864 sf and a subsequent 144 sf addition. The original house is balloon construction over a basement, 2×6 exterior walls with vinyl siding, shingle roof over 1x boards on 2×6 rafters, with four total floors of usable space (per our neighbors, some poor soul dug out the basement 20 years ago to add a few inches of headroom…and proceeded to cover it with a rat slab). The addition is one-story over crawl space. We have relatively new forced air central HVAC. It’s a 100,000 BTU gas furnace and 3.5 ton AC unit. It was purchased when our old unit failed mid-winter and the sizing reflects the rush (i.e., judging by the breeze when it runs, it’s oversized, though our home itself isn’t particularly well air-sealed). We have a GeoSpring HPWH and gas appliances in our kitchen. Finally, we have a detached garage with a south facing roof. I’m in the early stages of soliciting proposals from solar providers, but the first pass is a 4.50 kW system with 12 panels on the garage for around $9k (after applying the federal tax credit).

The renovation would add about 333 s.f. on the first floor, with slightly less SF on the second floor and significantly less on the third floor (owing to the sloped roof). Right now it’s planned as a crawl space foundation – unfortunately our yard is setup in such a way that it would be prohibitively difficult to get an excavator back to dig a basement, though I’m waiting for contractor feedback on that issue.

I’m an avid reader of the site and have Martin’s “Energy Nerd” compendium next to my laptop. I received loads of helpful feedback from the forum a few years back when I was considering options for renovating our flooded finished basement. I thought I would jump on again and ask for any thoughts and feedback. I’m happy to upload the plans if it would be helpful. Any thoughts are welcome.

The high level question is what’s going to be the best bang for the buck. My desired envelope would be:

-Exterior walls (existing and reno): 2×6 walls w/cellulose insulation -> OSB sheathing -> -Housewrap -> 1.5” XPS -> rain gap -> new fiber cement siding

-Roof: 2×6 rafters w/fiberglass batts -> OSB (new)/1x (existing) sheathing -> 6” XPS -> sheathing -> underlayment -> shingles [Note, I’m mindful of that my ratio skews heavier toward the exterior in considering the ratio referenced in Dana’s comment to this article. I’m trying to work around the minimal space I have in the rafters.]

-HVAC:  2 or 3 minisplits, probably 1 ducted to account for the bedrooms/layout on the 2nd floor

-ERV or pair of Lunos on 1st and second floor

-Solar mounted on the garage

Obviously, much of this is interrelated, but the basic question is whether or not the above is worth the cost over the alternative:  skipping the rigid foam, putting cellulose in the existing/new walls along with some air sealing work, using the existing HVAC (since it’s a sunk cost), and foregoing the solar.

Cost isn’t the only factor, as I like the “signal to the market” of solar and heavy insulation (unfortunately this approach seems pretty atypical in Columbus, though at least the Zip system is starting to appear more); but it’s always a factor.

Apart from the envelope, I’m trying to maintain a sensible number of windows and if possible reuse as much of what we have as possible. One issue – our existing double-pain windows have plastic lifts on the lower rail and virtually all of them are significantly cracked (photo attached-bad design idea). I hate to dump windows over that, but I’ve also not had much luck in searching for a viable fix. Does anyone know of a good fix for this situation?

Finally, if anyone has recommendations for good contractors/trades to talk to in central Ohio for a project like this – feel free to let me know. I have it on my to-do list to reach out to Energy Smart Home Performance, as this seems in their wheelhouse. I ran into it when working through my basement, but it can be hard to find folks willing to work on something that veers away from what’s typical. Also, if recommendations are outside the etiquette of the forum, sorry, and one of the moderators can let me know.

Any feedback/questions are welcome. Cheers…Matt

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Replies

  1. GBA Editor
    Brian Pontolilo | | #1

    Hi Matt,

    It sounds like you are weighing a pretty major energy retrofit plus renewable energy vs. doing the minimal amount of insulating and air sealing and skipping the PV system and you want to know whether the former is going to be cost-effective. I'm glad cost isn't the only factor in your decision because often deep energy retrofits are not cost-effective in terms of a reasonable payback period. Sometimes they have excellent return on investment, sometimes it's not so great. But if you hire a professional to help you model the options, and prioritize where to spend your money, you'll get more bang for your bucks. Just as an example, take a look at this article, which discusses the balance of insulation upgrades vs. spending on renewables. And keep in mind that the details, particularly air sealing, may have a greater impact on performance and comfort than the big-ticket items. Finally, if you have more specific questions, please ask.

    https://www.greenbuildingadvisor.com/article/energy-efficiency-retrofits-insulation-or-solar-power

  2. Expert Member
    Dana Dorsett | | #2

    >"It’s an old house (1926) with an original footprint of 864 sf and a subsequent 144 sf addition. The original house is balloon construction over a basement, 2×6 exterior walls ..."

    That's a fairly dubious description. A 1920s vintage 2x6 balloon framed wall is about as common as seeing the tooth fairy riding on a unicorn. Measure it. Odds are pretty good that it's rough-sawn full dimension 2x4s.

    >"-Exterior walls (existing and reno): 2×6 walls w/cellulose insulation -> OSB sheathing -> -Housewrap -> 1.5” XPS -> rain gap -> new fiber cement siding"

    The warranteed performance of 1.5" XPS is no more than R6.8, which would be insufficient for dew point control and a code violation on 5.5" deep milled 2x6/R20 celloulose wall in zone 5, but would probably cut it for full dimension 2x4s. Change the foam spec to 1.5" of foil faced polyiso and it'll make it, and it'll be a heluvu lot greener too, since it's blown with relatively benign hydrocarbons (usually a variant of pentane) rather than the extreme climate damaging HFC134a (~1400x CO2 @ 100 years), the predominant blowing agent used for XPS (among other high-impact HFCs used in combination.)

    >"-Roof: 2×6 rafters w/fiberglass batts -> OSB (new)/1x (existing) sheathing -> 6” XPS -> sheathing -> underlayment -> shingles"

    That's expensive and perhaps overkill on dew point control. Swapping out the XPS for RECLAIMED 2lb roofing (or foil faced) polyiso would take a lot out of the material cost of the system. ( It's available from multiple sources in your region: https://columbus.craigslist.org/search/sss?query=rigid+insulation ) Installing a fully adhered membrane (Grace Ice & Water Shield or similar) over the roof sheathing would provide substantial air sealing benefits comparable to or better than shooting foam on the underside of the roof deck

    >"Finally, if anyone has recommendations for good contractors/trades to talk to in central Ohio for a project like this – feel free to let me know. "

    I don't know if he'd take on a project as far afield as Columbus, but you're on the right track with Energy Smart. Nate Adams does a GREAT job at retrofitting older houses up in Cleveland (despite the arguable overuse of closed cell polyurethane & XPS, and perhaps not the most ideal or best bang/buck heat pumps for his climate- everybody's a critic, right? ;-) )

    http://energysmartohio.com/case-studies/

    It's worth a call.

    And when you do call him, let him know that some of the newer mid-static ducted mini-splits will outperform the heat pumps he's been using at cooler temps, with a lower upfront cost, much wider modulation ranges, and more appropriate sizes available at the low to moderate heat loads he's typically dealing with.

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