Replies

1. GBA Editor
   Martin Holladay | Jun 24, 2013 04:19pm | #1

   Geoffrey,
   Before jumping in to answer your questions, here are two general comments:

   1. Considering the range of your questions, I don't think that you should be designing a hydronic heating system. Hire an engineer or a qualified contractor to help you design and install your heating system.

   2. The cost of purchasing a boiler and the other parts necessary to install your hydonic heating system may not be the best use of your money. If I were you, I would concentrate on air sealing and insulation measures, and I would choose a simpler heating system.

2. 
   user-2423385 | Jun 24, 2013 07:25pm | #2

   I'm finding it hard to believe a forced air system with huge ducts running all over my house, air returns and outdoor condensers to be less complicated than a hydronic system...but I will consult an expert when the time comes. I've been consulting with experts throughout the entire process and I'd be fearful of any home where the DIY person did not.

   I will be hiring out a complete manual J when I get to that point.

   I guess I want to be more informed or extremely informed and know what I want. I'm sure you've found as I have that many "professionals", while being very skilled at what they know, stop learning when they get used to learning what works and aren't up on new technologies. Ask the city around here for a permit for solar panels and you will most likely find yourself on trial for witchcraft.

   The house is gutted and currently has no insulation. I'll be air sealing it to the best of my financial resources regardless of the heat source. That again is a bag of hornets with one question and a thousand answers.
   Thanks!!

3. GBA Editor
   Martin Holladay | Jun 25, 2013 08:33am | #3

   Geoffrey,
   The usual approach to heating and cooling an energy-efficient house is to follow the following steps:

   Work hard to make the building envelope as airtight as possible.
   Install above-code levels of insulation.
   Choose the best performing windows you can afford.
   Install a very small heating and cooling system to handle the small remaining load.

   A hydronic heating system like the one you describe is rarely the best choice for a green home. For more information, see these two articles:

   Heating a Tight, Well-Insulated House

   Choosing HVAC Equipment for an Energy-Efficient Home

4. Expert Member
   Dana Dorsett | Jun 25, 2013 02:30pm | #4

   In a full-gut rehab, spending the money you might have spent on the hycronic heating on building a tighter better insulated house can often put the heat load of the house within the range of mini-splits.

   R19 walls and R38 attic doesn't even meet current code-min for new construction in northern WI, but in a full gut you have a once-in-a-century opportunity address things like thermal bridging of the framing and air tightness.

   If your double-panes are sub-code clear-glass ~U0.5s rather than current code-min U-0.30 low-E gas-filled it's worth adding tight low-E storm windows on the exterior. (Harvey makes some of the tightest, but the better-grade Larsons sold through box stores don't suck.) It's far less expensive than swapping out serviceable code-min windows for high-performance versions, and the performance uptick is quite good- better than code-min replacement windows in most cases.

   Four squares have fairly modest glazing fractions and a fairly low ratio of exterior surface to conditioned space, and if you make it air tight you'd already be in the range of heating with a couple of mini-splits. The Fujitsu AOU 15RLS2-H puts out 15,000BTU/hr even at -15F, and the Mitsubishi MSZ-FE18NA puts out about that much at -13F. If it drops below -18F in your neighborhood the Fujitsu would be the better choice though, since the Mitsubishi actively turns off to self-protect when it's that cold. A pair of these would usually cut it for a 1450' house even at current code-min type construction. (You ARE going to be insulating the foundation, right?)

   If you were planning to hit R19 by spraying 3" of closed cell foam in 2x4 cavities, don't- the thermal bridging would pretty much waste the high R/inch insulation. Assuming it's balloon-framed with about a 20% framing fraction, the difference in whole-wall R (the net performances after factoring in the framing) between insulating with R3.7/inch cellulose or R4/inch rock wool vs R6.5/inch foam is the difference between ~R13 and ~R10, but the same performance could be had with a half-inch of rigid foam on the interior side under the gypsum.

   If you were planning on furring out the interior to 5.5" and using low density R19 batts, that's even worse. At the same thickness going with cellulose or R15 rock wool batts and 2" of interior foam would put you in the R20 whole-wall range.

   But to answer the questions you actually asked...

   1) O2 barrier PEX is the right stuff

   2) there are no problems using radiators from the salvage yard (but you'll probably want to put a pretty-good filter ahead of the boiler & pumps to protect them, especially if using refitted steam radiators)

   3) radiant is all about comfort, not economy or efficiency

   4) combining radiant in combination with radiators doesn't inherently affect the system efficiency

   5) you don't need to run two different temps- it's a design choice whether to do dual temps, but it can be done- not a subject readily treated in a web-forum though

   6) Staple ups work fine under hardwood floors (extruded aluminum heat spreaders can lower the water temp requirements in those apps)

   7)Yes there are good web sources, some more DIY-friendly than others- look for forums where they're not actually selling you the equipment. John Siegethaler's book is considered something akin to hydronic scripture by some newbies & DIY, but is probably far broader than actually necessary for most home systems: http://www.hydronicpros.com/publications/

   Free advice (well worth the price), if you're forging down this path, design the whole system to work at a single temp, and that temperature should something like 125F average water temp (135-140F out, 115-120F return). That simplifies the system design immensely, and allows you to use a condensing tank-type hot water heater (with an exterior plate type heat exchanger), and you can then micro-zone the hell out of it without running into short-cycling issues, and you'll still get real condensing efficiencies out of it. There's no way the heat load of this place would exceed the output of even the cheaper 76KBTU/hr Vertex, but the 100KBTU/hr Vertex (or a Polaris) might be more appropriate, if you have higher than average domestic hot water needs (big soaker tubs, etc.)

   All good heating system designs start with a room-by-room heat load calculation (Manual-J, or I=B=R methods are fine) at the local 99% outside design temperature:

   http://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/Outdoor_Design_Conditions_508.pdf

   From there you can work out how much radiation you need based on your design water temp. When trying to figure out what you can get out of scrapyard radiators at some random lower temp, references like this are useful:

   http://www.columbiaheatingsupply.com/page_images/Sizing%20Cast%20Iron%20Radiator%20Heating%20Capacity%20Guide.pdf

   When in doubt, go bigger, but if running the whole house or a whole floor as a single zone any oversizing of the radiation needs to be about the same for each room's calculated heat load. (not a problem when micro-zoning)

   Radiant heat spreader manufacturers will have nomographs plotting BTU per square foot of floor at some spacing across average water temp and R-value of the floor stackup. You'll have to estimate how much wood and rug you have to come up with the R-value of the floor stack and work it from there. You'll have to subtract some from the room totals for areas with low-clearance furniture like couches & beds, etc. but it's not rocket science to come up with reasonably close estimates with a lot of pencil-pushing and researching R-values of different wood species, etc. But it IS a real design problem- it'll take a whole bag of napkins, and a whole box of crayons to do it.

   Pay attention to total loop lengths too, use manifolds and balance-length parallel to keep the pumping head under control- a 1000' of PEX on a single loop is a pumping-power disaster, and may never deliver the performance you're looking for even with a monster pump behind it.

   In general, radiant floors under wood subfloors adds a LOT of expense, and in high-R houses it's not adding much cush-factor except for the 3 coldest weeks out of the year. High-R walls and oversized low-temp high-mass radiators &/or cast-iron baseboard (not fin-tube) reclaimed from the scrap yards and de-construction outfitters may be the better expenditure. But it's your money- just do the math first, and do it iteratively. Start with the room by room heat load calc at standard R values, and adjust them as you change the wall stackups & attic R, and any window upgrades. Don't bother with hiring out the Manual-J, since you'd have to adjust it with every tweak. Instead run an I=B=R spreadsheet that you can adjust the U-factors on as you go, and it'll tell you pretty well when & where you'll be making real progress, and what the relative cost-effectivness aspects are.

   But when your heat load at the 99% design temp drops under 36,000BTU/hr (which it probably is, even at code-min) the simplicity of heating with a couple of mini-splits make start to look really attractive, especially after you price out what a decent hydronic design with radiant floors costs, even as a DIY.

5. 
   user-2423385 | Jun 25, 2013 03:21pm | #5

   Wow...that's a lot of info to chew on. As far as the foundation...a stone wall foundation is something that needs to breath..the space above ground will be insulated to the 10x10 sill plate. The wall's are 2 feet thick...removing the dirt around them to insulate is by my understanding...not a good place to go.

   How would a mini split heat an entire house? Would I have to install one in every room?

   I was going to fur out the walls to 5.5 and go with batts. I understood mixing batts and foam was not a good idea as well? The walls are made up of 1" TNG and 1" orgiginal siding. I was going to side over this eventually. I'm not sure of the window values...how would I find out. They are newer replacement double hung?

   thanks much

6. GBA Editor
   Martin Holladay | Jun 25, 2013 03:40pm | #6

   Geoffrey,
   Q. "How would a minisplit heat an entire house?"

   A. Here are two articles for you to read:

   Just Two Minisplits Heat and Cool the Whole House

   Massachusetts Owner-Builders Complete a Superinsulated Home: This passive solar saltbox is heated by a single ductless minisplit

7. 
   user-2423385 | Jun 25, 2013 04:05pm | #7

   That's pretty cool..I'd love to insulate my home to that degree...but the foundation cannot be insulated as it is and I have nowhere near the space to fur out to that degree. Thanks for the information and the more the better. Looks like Mini-splits are available to sizes that would work for me but need to find out the energy usage. Electricity by us keeps going up as we have a monopoly and the Nukes are shutting down. NG is the cheapest (for now) but need to think about the continuing development of solar options down the road. I looked into the goodman furnace mentioned on one of your other posts...so many options.

   I did love the idea of heating with a Hot water heater like the polaris...but as I mentioned in my original post. The local codes do not allow for anything like that.

8. Expert Member
   Dana Dorsett | Jun 25, 2013 04:31pm | #8

   A stone foundation does not need to "breathe". Most stone has far lower wicking potential and inherently drain better than poured concrete foundations. Touch up all the pointing, and use 2-3" of 2lb spray polyurethane right up to and over the foundation sill, and paint it with an intumescent paint for fire protection. (It's done all the time in my neighborhood, on everything from fieldstone to quarried granite to any type of brick foundation.) Stone foundations typically DO breathe, in the sense that they leak copious amounts of air, but that's generally a bad thing, for both indoor air quality and for the heating & cooling loads.

   If you have very wet subsoil you might even take it as far as Joe L. did on his place, with an EPDM capillary break/vapor barrier:

   http://www.buildingscience.com/documents/insights/bsi-041-rubble-foundations

   See the picture on page 28 of this document for another discussion:

   http://www.buildingscienceconsulting.com/services/documents/file/20100615_Foundation_Insulation_Options_Neuhauser.pdf

   In drier sandy soils with good drainage you can spray the foam directly on the stone without the EPDM membrane and it'll be fine.

   Foundation losses are a large fraction of the whole house heat load in climates as cool as yours, even if you're not heating it directly. In an otherwise code-min house an uninsulated foundation with a semi-conditioned basement is typically 15-25% of the heat load, but with a leaky stone foundation with better than code insulation on the rest of the structure it could easily be more than half, between the air leakage and the conductive losses.

   No house, and particularly a high-R house doesn't need a mini-split per room (which would be overkill for the room by room heat loads anyway.) Open floor plans or leaving the doors open to the areas with the heads can make it easier to do it one head-per floor, but a doored-off room with larger heat load may deserve it's own, or have supplemental radiant-cove heaters (under thermostat-limited occupancy sensor control is best ) to cover the shortfall when it's truly cold outside.

   Concentrate on getting the heat loads down first, then we'll worry about what it takes to handle those loads. Starting with the heating system first is the wrong order, and fraught with error.

   With plank sheathing and low density R-19s you'd end up with about the leakiest cavities in WI. R19 batts have the same amount of fiberglass as R13 designed for 2x4 framing, which tells you about how resistant they are to air movement. With t & g sheathing and a 40mph north wind it's performance is WAY less than R19. In fact, R19 is a barely-legal fiction even with tight walls, given that they're only R19 at their full 6-1/4" loft. Installed perfectly to spec in a 5.5" deep cavity they perform at only R18, according to the manufacturer's own compression charts:

   http://www.owenscorning.com/literature/pdfs/10017857%20Building%20Insul%20Compressed%20R-Value%20Chart%20Tech%20Bulletin.pdf

   To air seal the t & g plank sheathing you have a few options. A flash-inch of closed cell foam would do it for air sealing, wouldn't be sufficient R for dew point control for the remaining 4.5" of depth, assuming you furred-out the framing. But if you put either open cell foam or dense-packed cellulose in the 2x4 cavity, and installed 2" of unfaced 2lb density Type-IX EPS on the interior instead of furring it out, the vapor retardency of the EPS would be about 1-perm, a minimal class-II vapor retarder (ergo, no poly necessary), and at a 20% framing fraction you'd be at about R18.5-R19 for a whole-wall R, compared to about R14-ish with low density R19 batts. The air-retardency of cellulose is quite good at 3,5lbs per cubic foot dense-packing- though not quite as tight as open cell foam, the difference is academic. Unlike spray foam, cellulose gets blown into every exfiltration path during installation, clogging it, and in rare instances would be even tighter than spray foam. But either would be a good choice.

   If you use only unfaced EPS you re-side you can still use more insulating foam on the exterior when it's time to reside, but not if you went with something more vapor tight, like XPS or foil-faced polyiso. When that day comes it's still better to use something more vapor open than foil-faced goods on the exterior though. If EPS you could drop back to 1.5lb density (Type-II) goods, which is too permeable for the interior side application. If polyiso, fiber faced goods designed for roofing insulation would cut it at about 0.5-1 perm, and would give you a higher R/inch than with EPS.

   If the replacement windows met code at some point in the past 10 years they're probably U0.34, which isn't an energy disaster, but would still be much-improved with low-E storms. If you know the manufacturer and model you can probably look it up. But adding low-E storms is a decision that can wait, since they can go up even after the place is occupied. Getting the tightest & best-insulated walls, foundation, and attic should take priority during the full-gut.

9. 
   user-2423385 | Jun 25, 2013 05:17pm | #9

   Again...thanks....that's a whole ton of info to chew on. I like the idea of insulating the fieldstone foundation and letting it "leak" into a sump pit. What about mold in between the insulation/epdm and wall? And I'm pretty sure all the motorcycles will have to go just to put a down payment on all that spray foam? I had discounted the spray foam a few times due to it's amazingly high cost. 3 inches in my walls was going to be almost 15K while bats were closer to 1500.

10. Expert Member
    Dana Dorsett | Jun 25, 2013 06:24pm | #10

    There are other ways to skin that foundation insulation cat, and even 2" of closed cell foam would be a huge improvement, which should run about $2-2.50/square foot. While ccSPF would be pretty much a waste in a wall cavity (where it's thermal performance is undercut by the thermal bridging, it's moisture resistance and air tightness is valuable when applying it to a moisture-bearing uneven surface like a stone foundation.

    Closed cell spray polyurethane foam bonds pretty well to EPDM- even better than it does to wood. It's chemically very similar to Gorilla Glue. And with EPDM on one side ( less than 0.05 perms) and 2-3" of closed cell foam on the other (0.4-0.6 perms), there isn't sufficient moisture to support mold growth. Between the EPDM and stone there is, but that's outside the pressure & thermal boundary of the house, and not feeding on structural wood, so who cares?

    If the interior surface of the foundation is fairly even you could build it out as if it were an above-grade cavity wall, with an inch or two of space between the stone and a couple inches of rigid foam as the sheathing of a non-structural batt insulated 2x5 studwall with unfaced R13s or rock wool R15s. In your climate (presumably the Climate zone-7 part of WI?) it takes R10 (~2.5" of EPS ) for dew point control on wood-sheathed above-grade structures, but without the wood sheathing and the warmer average temps below grade you're just fine at 2" which is R8.4 at 75F average temp, R9+ when it really matters.

    Put a couple of inches of foam under the bottom plate of the studwall as a capillary and thermal break for the framing, as well as on the underside of the joists between the foundation sill and the top plate of your insulating studwall. After thermal bridging that ends up at about R18-R20 whole-wall, just like the 3" of spray polyurethane, and totally appropriate for zone 7. It's harder to make that approach perfectly air tight though, and air tightness is important. Caulking the wall board to the studs helps, as does a bead of can-foam underneath the bottom plate. The harder spot to air seal will be the joist cavity between the studwall and foundation sill. You may be in for a few FrothPak kits (1.5lb closed cell DIY foam, available at box-stores) rather than a case of can-foam. The detailing between the studwall an any basement windows/doors can be leak points too. It's possible to get there, but you have to pay a lot more attention to detail than the "stand back and spray" approach to insulating stone foundations.

    It's true that none of this is going to be super cheap, but a full-gut rehab is a once in a century opportunity to get it right. If you can find a local source for reclaimed rigid roofing foam (or insulationdepot.com ) you can often save many thousands over conventional methods. (A full-gut rehab/deep energy retrofit I helped manage last year saved well over 10 grand compared to virgin-stock that way, but it involved 4-6" of rigid foam over the entire exterior of a circa 1890 3-story balloon framed house.) I have multiple vendors handling reclaimed and factory-seconds rigid foam in my area, some even advertise on craigslist, etc. YMMV.

11. 
    user-2423385 | Jun 25, 2013 08:14pm | #11

    So putting up a wall made up of foam (another question below) and batts with a couple inches of barrier between would work? Without the EPDM? What about the mold possibility?

    I see tons of foam on Craigslist all the time...but most is exterior foam taken off of roofs or walls..is this foam appropriate for interior use?

    Would putting up ridgid foam towards the exterior of the main walls then finishing off with batts (after caulking and spray foaming the gaps) be a good compromise? Then maybe adding an inch or so on the exterior when I re-side as to lessen thermal bridging?

    You have to realize there is a plethora of contradictory info when it comes to this..thanks so much for your time and your answers..they are very informative and generating creative ideas.

12. Expert Member
    Dana Dorsett | Jun 26, 2013 12:19pm | #12

    Any of the surplus rigid foam would be appropriate for the basement, but if it's polyiso you have to keep the exposed edge from getting wet.

    On the interior side of your studwalls upstairs you have to be careful not to make it too vapor tight (if you hope to add exterior foam later) or too vapor open, which means you're probably better off going with virgin-stockType IX EPS with known permeance rather than random foam of unknown specification.

    Yes, you CAN take a "cut'n'cobble" approach using cut up rigid foam to air-seal the exterior sides of the stud bays. If you plan to put up exterior foam later use 2-3" EPS (any density), or 1-2" of XPS, or fiber-faced iso (any thickness.) Cut it somewhat loose, and use can-foam or FrothPak to seal the edges to the framing. The remainder of any depth should be filled with fiber- if splitting batts, make sure that it's a compression fit, carefully tucked at the corners and edges to ensure it completely fills the space. This is a place were unfaces R19s can be useful- split in half into two low-density 3-inchers, you can fill a 1.5-2" depth and be at a reasonable density, and guaranteed a compression fit. With even 1.5" " of any type of foam you will be fine from a dew point control point of view with 2x4, but if you're furring it out to 5.5" you'd need 2" min.

    If furring out is still in the plans, running the furring laterally and putting it 24" o.c. reduces the thermal bridging. This is sometimes referred to as a "Mooney Wall" in some quarters. See: http://www.builditsolar.com/Projects/Conservation/MooneyWall/MooneyWall.htm

    It may be worth putting rosin-paper or a highly permeable housewrap on the studs before installing the furring, to provide a secondary air-barrier, given how leaky the t & g sheathing is. Unlike poly, it would still allow drying in both directions, should you later opt to put up less-permeable foam on the exterior later.

13. 
    user-2423385 | Jun 26, 2013 12:29pm | #13

    man that Mooney wall is brilliant..and will save me many...many hours as the house is of course not square (name a hundred-thirty year old house that is) and I was cutting angled strips out of old 2x4's running vertical (huge pain)...now I can stop and just run solid strips across..BRILLIANT. I have a line on 6" wide Dow, Blue 3" insulation strips for the stud bays...what's your thoughts on those. There will be some waste but I can put the strips in smaller areas and bunch them together before foaming along the sill plate pockets in the basement..or something.

    what about using strips of sill plate foam between the mooney wall and the studs...would that have any benefit?

14. Expert Member
    Dana Dorsett | Jun 26, 2013 02:17pm | #14

    Only 6" wide, 3" deep? Ideally you'd want to start with goods much wider than the stud bays and cut down to fit. With 6" wide stock you'd have 2-3x as many seams to seal.

    The blue styrofoam is XPS, which at 3" would be about 0.3-0.4 perms (depending on density) which is on the low-permeance side of ideal, but still OK.

    I've seen pictures of Mooneywall done with 1x furring 16" o.c. screwed to the studs with 3" bugle-heads, through 1.5" foam blocks as spacers (for 2-1/4" of total added depth) at the intersection with the studs for lower thermal bridging but that was with blown insulation, not batts, and I wondered if those fasteners wouldn't eventually split the furring, but some variant on that might work for you. Compressing a 3" split-batt under the furring would leave lateral air channels at the furring edges- it's hard to get a perfect fit, but I s'pose cutting the fiber after the fact at the edges of the furring could get it to fluff for a more- perfect fill. There are lot's of creative variations one could work out, but fitting without air gaps or channels is key to getting the performance out of batt insulation (which is why performance builders prefer blown.)

15. 
    user-2423385 | Jun 26, 2013 05:22pm | #15

    OH....sorry...I meant 16" wide..my bad

16. 
    user-2423385 | Jun 26, 2013 05:54pm | #16

    By "blown" insulation do you mean the regular gray, shredded newspaper stuff...I have bags and bags of that sitting around. I rented the blower once and got pretty frustrated with the mess on another project. But with the walls out I could compartmentalize the stuff and use what I have like in that link you sent me. Is the shredded stuff better? I was under the thought it settled and created voids?

17. 
    user-2423385 | Jun 29, 2013 01:05pm | #17

    Ok...I picked up the insulation for a smoking good deal. I delivered the first bunk to the house and started cutting it to size. A couple questions:

    Is there any prep to the outside wall surface? I've heard of a anti-mold spray but can't recall the name, is this a good idea?
    Is spray foam (can) the best sealing method between the stud and the foam and between foam pieces or will a high quality caulk (sold by the 5 gallon bucket) just as good. I'm trying to balance cost and performance.
    What are your thoughts on vapor barrier. I plan on adding an inch or so of insulation to the outside over the original wood siding but that will not be until after one winter.

    Thanks much