Ranch in NJ - Looking for more comfort

Discussion in 'HVAC Heating & Cooling' started by SatCat66, Oct 21, 2013.

  1. SatCat66

    SatCat66 New Member

    Messages:
    6
    Location:
    NJ
    Hello,

    I got a 1956 ranch house in central NJ. 1750 sq.f. above grade and 1000 sq f. in the partially finished basement.
    The rest is crawlspace. That 1750 sq.f. include 200 sq.f. of the room created in the garage. It is often too cold or too hot.

    The house has forced air (natural gas), something old, Kenmore-branded. Furnace is 100K BTU. Air conditioner works OK, just probably isn't efficient. Don't know how to tell the conditioner size.

    I have already spent $500 on the new exhaust fan for the furnace (emergency), and I know the sensor that tells if the exhaust fan is working well is shot ( contractor who replaced the fan discovered that but instead of replacing he shorted it out).

    I'm not happy with my heating. I think the furnace works for too short periods and temperature drops to uncomfortable levels in some areas between the runs. Also, there are uninsulated ducts in the crawlspace, so I'm getting cold air into the house when furnace starts running.

    Also, even with the new exhaust fan, I feel I'm getting a bit of exhaust gas into the house when it runs (not CO, that has been ruled out by my fire department and the furnace was checked by 3 people - no heat exchanger cracks).

    This is my second attempt to fix my heating. When I tried a couple years back, I saw no contractor I would trust. Most wanted to replace 100K furnace with a new 100K furnace. My own heat loss estimation (don't remember what software I have downloaded for this) was at 45K. Today I have read on this forum that I should be at 25K! I'm planning to double the attic insulation, but that's all I can do. Windows are already modern.

    So I would like the heater to work permanently and modulate. I would like to warm my hardwood floor, especially on top of the crawlspace. I would like to address the special needs of the room in the garage (BTW, it's 50 ft from the mechanical area). My mechanical area is the furnace and 50 gal water heater next to it. I could hang a wall-mounted boiler behind the water heater.

    I don't have more space and would ideally eliminate water heater and use its space for something else.

    So, here I am asking for advice. Am I unreasonable looking for a

    * smallest boiler I can find, direct vented. It will probably be at 50K BTU
    * if it had internal heater for the DHW, nice, otherwise - indirect WH
    * radiant heat for the floor - stapled up. No hope to heat the whole house, only warm the feet
    * a coil to heat the forced air (how this can be modulated? )
    * in the summer I would love to use same boiler to heat the pool up at bit

    If that is too much to ask for, I would probably settle on a new modulating furnace (does one exist though for my house)?


    Thanks!
  2. nukeman

    nukeman Nuclear Engineer

    Messages:
    711
    Location:
    VA
    It sounds like you are on the right track. People don't realize just how big a 100k furnace is. It is too big for most houses in most of the country. It sounds like the lowest cost option might be a smaller/modulating gas furnace with maybe some duct rework for the garage area (might be as simple as adding a return or might need a larger supply). You could also supplement the garage heat with something like resistance electric (cheap to install, expensive to run) or perhaps a mini-split (which would cost more to install, but less to run).

    Now, if you are willing to spend more (along with the work that goes with it), there are many more options. A boiler could work, but would be costly to retrofit (although could give some nice features like the indirect WH). You might also go with a couple mini-splits in the house and ditch the furnace and ductwork altogether. Mini-splits are very efficient and will heat and cool without ductwork. As an additional plus, you could pull out the old ductwork and maybe gain a bit of space in the house(remove some bulkheads/duct chases).

    I think that I would go for the mini-splits or a new gas furnace based on costs and your location. However, things the you want (like the heated floors) as well as any other renos that you were planning at the same time could put the boiler as a contender.
  3. Dana

    Dana In the trades

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    Location:
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    With the exception of radiant floors in mid-winter, gaining comfort comes primarily from improving the HOUSE, not the HVAC systems. Raising the interior surface temperatures of the walls/windows/ceilings when it's cold has a bigger effect on comfort than bumping up the air temp to compensate, no matter how quietly and efficiently that's done.


    You're right- a heat load of 45K for a rancher house at NJ type mid-teens 99% outside design temp with 1740' of conditioned space + 200' garage room + 1000' of conditioned basement is actually bit on the high side at well over 20 BTU/ft for the above-grade stuff. Most 2x4 framed houses can be cost-effectively brought in to the ~15 BTU/ft range with a combination of air-sealing and spot insulation, and maybe some window improvements. (Replacement windows aren't very cost effective, but tight low-E storm windows over pre-exisiting single-panes can outperform some code-min replacement windows at a fraction of the installed cost.) Getting it down to 25K or less may still be cost effective, but it takes a pretty careful analysis on where & how to say for sure.

    You can probably get some insights as to where to start by breaking down your heat load calculations to see where the heat leakage really is.

    If it's typical 1950s construction with typical improvements you probably have NO foundation insulation, R11 batts in 2x4 walls that leak air and maybe R30 batts in the attic, with copious air leakage at the foundation sill & band joists and at the ceiling plane. In the crawl space you can usually lay down a ground vapor barrier lapped up the wall by about a foot then air-seal and insulate the foundation walls right up and over the sill and band joist with 2" of closed cell spray foam, followed by intumescent paint. (If it's possible to get sheet-goods in there, it can also be done with 3" of EPS or 2" polyiso at lower material cost but higher labor cost.) Earth coupling the crawlspace will raise your average wintertime floor temps by a few degrees, and your coldest-night floor temps by several degrees. Even if you're going to insulate between the joists after installing radiant floor this is a very worth while measure, and often necessary to protect the joist edges from summertime mold conditions in NJ climate in an air-conditioned house with insulated floor joists.

    How to insulate the semi-finished basement kinda depends on what's already built next to the walls, (and possibly how much you're willing to rework or scrap & start over.) There are several approaches that can work without creating a mold farm, and several that would.

    Typical conducted losses out of the foundations would be on the order of 10-15KBTU/hr plus air-leakage, so this would likely be the lions-share of the total load reduction.

    Air leakage at the ceiling has both obvious and less-obvious locations. Recessed lighting fixtures and plumbing/electrical chases extending from basement to attic are usually pretty straightforward to fix, flue-chases take some special considerations (any fireplaces), but the air leakage of all the electrical & plumbing penetrations can be pretty subtle to chase sometimes. When you think you've hit all of the obvious stuff, it's worth getting a blower door test with infra-red imaging to highlight the leakage paths, and to figure out where all the gaps in the insulation are.

    If the heat load is under 25K it means your average mid-winter load will be under the minimum-modulated output of a modulating-condensing boiler, and it's kind of silly to pay for modulating equipment that doesn't actually modulate much to track your load. In these situations using a condensing hot water heater for both heat and hot water (isolating the potable from the system water) often makes more sense, and has greater design-forgiveness built in. Going to hydro-air using the same ducts as the AC probably isn't the way to go if comfort is your goal, and would likely require a new air handler. Low-temp panel radiators are far more comfortable and quiet, and would be dead-easy to micro-zone if you used a condensing hot water heater as the heat source. (Even the comparatively-cost Vertex has better than 70K of burner output, which is probably more than your current HW tank plus your reduced heat load. The smallest stainless steel Polaris has a ~100K burner.)

    Heating & cooling the mis-behaving garage zone with a ductless mini-split may be the right solution there. If the floor plan for the whole house is pretty open it might a reasonable solution for there too. It really depends on how the room-by-room loads break down. It's definitely more comfortable and quieter than the smallest ducted-air gas-burner. If you heat the doored off spaces with panel radiators or radiant floor, heating & cooling the open common areas with a mini-split is comparable in operating cost to mid-efficiency gas hydronic system, and CHEAPER than heating with condensing gas in a leaky unbalanced duct system.
  4. SatCat66

    SatCat66 New Member

    Messages:
    6
    Location:
    NJ
    Thanks, nukeman. Yes, resistance heat supplements the garage room now... It already has two supply ducts and one return duct. The issue is that it's not a separate zone. It gets heat/cooling only when the rest of the house needs it. But the rest of the house is heated by the people, couple south-facing windows, kitchen... Kitchen-living room area is large and open. So mini-split for the garage room is viable option. Whole house I can't imagine with mini-splits. That's 3 bedrooms, 2 bath, kitchen, LR-DR. That looks crazy to have a unit in each.
  5. SatCat66

    SatCat66 New Member

    Messages:
    6
    Location:
    NJ
    Thanks, Dana. I didn't realize how big impact the basement has. 50% of the perimeter is insulated (2x4 with fiberglass). Basement windows are leaky ( it was OK with me so far. Combustion air should enter somewhere). If I install everything direct-vented, I can seal the windows.

    Based on the insulation goals you have set, radiant floors alone should be enough. I recall the floor limit was about 20 Btu/sq ft. I have 3/4" plywood with 3/4" oak on top. Garage room would get a radiant panel to help with extra loss.

    Crawlspace is vented now. I know it's legal to seal it.. I will consider.
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,059
    Location:
    New England
    Once you have radiant floor heating, you won't want to go back! Retrofitting with solid wood may mean you need higher temperatures, but if you have access to the floor below, is possible, regardless of the end temperature you need to feed it. And, if you have a cat or dog, they'll love you for it, too!
  7. Dana

    Dana In the trades

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    Location:
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    Insulating below grade with 2x4 & fiberglass is a recipe for mold. Above grade, with caveats.

    Concrete below grade will wick moisture up from the footing, even if the exterior of the foundation has been waterproofed. The temperature of the concrete below grade in NJ is also well below the dew point of summertime air, and in winter the near-grade portion of the wall and above grade portion run below the dew point of the INTERIOR air, which means the wood always runs at a high moisture content, making it conducive to mold growth.

    The solution is to put a layer of air-impermeable insulation (rigid foam or closed cell spray foam) between the concrete and the stud edge, at an R value sufficient to keep wintertime moisture from accumulating in the studs or the foam/fiber interface, and use UNFACED fiber with no interior side vapor retarder (other than standard latex paint on wallboard) in the studwall. Most of NJ is in US climate zone 4, in which case R4 (1" of EPS) would be sufficient for dew-point control. The colder parts in the NW are in climate zone 5, which means it takes R5 (1" of foil-faced polyiso would give you some margin, and would be preferable to XPS for several reasons, both performance & environmental.) The stackup (dimensions of foam aside) looks like this:

    [​IMG]

    Note the detail for using rigid foam to insulate the band joist & foundation sill too.

    Since moisture can wick up through the slab, and the slab is also below the summertime dew points, it's useful to slip an inch of EPS (but not polyiso) under the bottom plate of the studwall as both a thermal break (raising the temperature of the susceptible wood) and capillary break/vapor retarder. You can TapCon the stud plate to the slab to keep it from kicking out over time. Since it's not structural, the studwall only needs to hold up the gypsum & insulation, you need not use doubled top plates. If using EPS, seal the seams & edges with 1-part can-foam or 2-part closed cell (the 12 board foot FrothPak kits available at box stores are useful if you have a lot of seam-sealing to do.)

    If you use polyiso on the walls, make sure the cut edge of the bottom is not in contact with the slab, since polyiso is mildly hygroscopic and has the potential to slowly wick moisture over time, losing some of it's effectiveness.

    The high thermal conductivity of poured concrete compared to the 2x4/R11 wall it's supporting means every square foot of exposed foundation loses the same amount of heat at 10 square feet of insulated wall above, and every square foot of uninsulated band joist loses as much heat as 5 square feet of insulated studwall. Even with 2x10 joists and 18" of foundation exposure the heat loss through the foundation will often exceed that of the heat loss through the above grade walls of a 1-story rancher, even if you let the basement run cold.

    Regarding mini-splits- you should NEVER have one ductless head per room. If a room doesn't have a design heat loss of at least 5000 BTU/hr even the smallest ductless heads will be oversized. The smallest ductless heads will usually be rated for over 7000BTU/hr at +5F outdoor temps, more at your more likely +12F to +15F outside design temp.

    A low temp panel radiator sized to deliver the calculated room loss with 120-130F water is usually possible, and cheaper than a ductless head to boot. Since you're on a gas main but in a cool climate, the operating cost of heating with low-temp panel radiators off a gas hot water heater will be comparable to heating with ductless. (Which is actually cheaper will vary by season and your actual gas & electricity rates.) Look up the specs while designing the system, but the output at 130F is typically about half the 180F output ratings.

    [​IMG]

    A good designer could set up the low-temp hydronic system to run off your exisiting water heater without destroying it, but when using non-condensing water heaters you have to pay attention or destructive condensation can occur on the heat exchanger, rusting it out in short years. With condensing hot water heaters that condensation is GOOD, since it improves the overall combustion efficiency.

    As stated in my prior post, one advantage of using a hot water heater & panel radiators is that you can micro-zone even very tiny rooms with low loads, whereas with a boiler at your likely room-by-room loads even at min-mod the boiler would be way oversized for any indivitual rooms. Micro-zoning gives you huge control over the heating season comfort without having to carefully balance the radiation room-by-room, though getting it to all work a domestic hot water temperatures or lower would be ideal from an efficiency point of view. The odds are pretty good that with decent windows (or low-E storms) and air sealing on the zone you intend to heat with radiant, if you use extruded aluminum heat spreaders you'll be able to deliver enough heat to cover the 99% outside design condition with 120-130F water too, but that needs to be calculated, not assumed.
  8. SatCat66

    SatCat66 New Member

    Messages:
    6
    Location:
    NJ
    Thanks Dana, especially for the basement insulation insight. Maybe I will have to tear these basement finishing walls down (oh). I will check behind tonight to see if there's any mold. Floor joists are dry, I have worked with them recently.
    (At one point it is going to be cheaper to move or rebuild this house from scratch, but I have already heavily invested in it... and like the area)

    I have decided on radiant floor heating off existing 50K BTU atmospheric water heater (i.e. 40K BTU in the water). As soon as the prototype works, I will replace it with a direct vent solution, which may be a wall-hung boiler with a buffer tank. I was researching the advanced tank water heaters before and I'm not impressed. Existing forced air will stay as a backup.

    I will go with extruded plates, 4 loops by 300', for the crawlspace rooms. And, that radiant panel above will go to the garage room at the window.

    Since apparently there are no available contractors in my area, I will be doing it all myself. If a contractor in Monmouth county reads this and is interested, please feel free to PM.
  9. Dana

    Dana In the trades

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    Location:
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    If running the radiant off the atmospheric drafted tank it needs to be isolated with a heat exchanger, and the flows & temps adjusted so that the return water to the tank out of the HX never drops below 120F (130F is better). Condensation dripping onto the burner can become a hazard pretty quickly.

    There are thousands of long-standing combi heating/hot water systems running off the Polaris series hot water heater, and isn't a bad way to go if you can get somebody with the hydronic design smarts to actually design the system for you.

    If you have to design the system yourself you're probably better off going with the HTP Versa series though since it's a pre-engineered integrated high performance package. Even if it's totally overkill for your application it doesn't take as much math to design around it- it's a lower-risk solution. It's a hefty price tag, but so is a mod-con + buffer tank solution by the time you add in all the stuff that comes pre-fitted in a Versa Hydro. A Polaris based solution would be cheaper than either, but would have to be designed. (There are pros posting on this site with substantial experience designing around the Polaris who might be willing to design it for you.)
  10. SatCat66

    SatCat66 New Member

    Messages:
    6
    Location:
    NJ
    I was thinking of Taco X-Pump Block for isolation.
    Polaris and even pricier HTP Versa will never pay for themselves with the current NG prices. That's not mentioning they can break and need a $1000 circuit board, etc. The tank I have installed costs $600 and there's nothing to break in it. It needs no electical power. It will corrode in 10-15 years, and will be disposed. If a pump goes in the Taco block, I will replace it in a moment. If anything breaks in HTP Versa, I'm dead in the water.

    Regarding the basement insulation. Does it make noticeable difference that my basement is not concrete but hollow blocks?
  11. Dana

    Dana In the trades

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    Concrete masonry unit foundations run only modestly higher R than poured concrete, and they leak quite a bit more air (both above & below grade). Insulation methododology remains the same- you may want to inspect and repair any cracks before closing it all in.

    A 34 gallon Polaris with a 100KBTU burner runs $2500 to have it bounce off your door from a number of web-vendors. There is no way that any sub-components such as control boards cost a grand- the thing is as dumb as a box o' rocks, no more complex than an ~80% combustion efficiency power-vented water heater. It's stainless, practically bulletproof, and by the time it gives up you will have gone through at least 2 and possibly 3 low-efficiency power-vents, even if you DON'T abuse them with with condensing temperatures. (The Versa on the other hand has quite a bit of internal complexity.) A 100K burner and 34 gallons of buffering mass is plenty for most homes. Only if you had fairly substantial hot water needs would you need anything more, in which case your current water heater wouldn't be providing satisfactory results.

    The fact that the atmospheric drafted tank needs no power to fire up isn't much of a benefit- it's not as if your X-Pump Block runs without power, eh? Very few heating systems made after 1930 or so actually function without power. (Even the millivolt control gas valves on steam boilers don't meet current US code.)

    Polaris + Taco X-Pump Block is a standard approach:

    [​IMG]
  12. SatCat66

    SatCat66 New Member

    Messages:
    6
    Location:
    NJ
    Dana, are you kidding me? My water heater was the only heat source in the house during the Sandy storm exactly one year ago. Should that repeat, sure no radiant heat but still hot water in the tub. Difference between life and death.

    Polaris would be grossly oversized. If you google 'polaris water heater short cycling' you will see people had issues with larger houses than mine.
    I have completed my heat loss and loop design with LoopCAD. All my radiant above the crawlspace is going to use 13.7K BTU on the design day (including back losses). Total house loss 38.5K BTU. That's assuming additional layer of R30 in the attic and basement insulation per your suggestion.
  13. Dana

    Dana In the trades

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    Location:
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    It's true that the Polaris works better with high-mass radiation like radiant slabs, but the control modifications to increase the differential are not really very radical (but do involve soldering irons) and with 34 gallons of buffering mass it doesn't take a huge differential to establish a decent minimum burn length. A lower output (and less expensive) alternative would be the Vertex, which has ~70K of burner output, but it's not stainless- good for maybe 12-15 years. Morgan Audetat (Posts as BadgerBoilerMN) would be able to advise on how to best deal with it.

    38.5K is more than the output of most 50 gallon hot water heaters, which won't leave you much headroom for domestic hot water even at your average mid-winter heat load.

    Though smart grid technology going into the rebuild is improving grid reliability in NJ, if you're really concerned about another mega-storm like Sandy buy a generator and set up a crossover switch to run the critical items like heating systems & refrigerators. Or, if you have a reasonable place for it, a small air tight wood stove with ducted combustion air can work well as auxilliary heat (which has become the solution to storm related grid reliability issues at my MA house.)

    Regarding the additional R30 in the attic, it's worth renting a blower and using cellulose rather than fiberglass solutions for attic insulation, since it's far more air-retardent and far more opaque to infra-red than fiberglass. Air-sealing the ceiling/attic floor is a critical first step prior to insulating, to avoid running into moisture issue in the now-cooler attic. Wet insulation at air leak points doesn't work very well, and leads to localized mold/rot conditions. Preserving the code required clearances between the roof deck and insulation often leads to thin lower-R spots over the top-plates of the exterior walls too, and sometimes it's necessary to cut & stack higher R/inch foam board to eliminate the heat leak at that point, which is a common starting point for ice dams, etc. If your attic joists are 2x8s you may only have 5.5" of space do deal with and still have 1.5" clearance to the roof deck, but you can still get better than R30 at that point using cut up rigid polyiso.

    Air leaking from the interior into studwalls with low-density R11s often makes the top plates of 2x4 walls major leak points. If IR imaging shows gaps or hot spots in the wall insulation, retrofit cellulose blown from the exterior can often be achieved without ripping out the pre-existing batts or stripping the siding. Air sealing the wallboard can be a partial solution, which will also lower the amount of wintertime moisture accumulation in the sheathing.

    If you have existing fiberglass batts in the attic, if you pay attention when peeling them back very often the less obvious air leaks are visible as dusty or moldy spots on the batt where the batt filtered 50 years of air leakage:

    [​IMG]
    Last edited: Oct 23, 2013
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