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Thread: New house! Eternal heater w/ solar preheat?

  1. #16
    In the trades Dana's Avatar
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    Quote Originally Posted by Steve29 View Post
    Excellent summary of singles vs a multi - thanks! I didn't realize the 3" lines were carrying refrigerant. I'll look into wall vs ceiling mounts and continue on the Taco expedition (am a little nervous of what it'll tell us....)
    The Taco heat loss tool will just tell you what you already know, but it'll put a number on it. Having a lot of glass is pretty lossy (gain-ey, if in direct sun). Finding the right balance between the aesthetics, thermal performance, and costs (capital & operating) is never simple- it's an iterative process. Cutting the glazed area 20% is usually far cheaper than increasing it's performance 20% with extra coatings, exotic gases, & extra layers. It's sometimes possible to cut the losses elsewhere with high-R wall & roof assemblies, but costing that out is also not simple.

    The last thing you'd want to do is keep the field of view large, but end up cutting out so much of the light with the high-performance windows that the view looks dull and it's so dark you need to turn on the lights to read your watch, as sometimes happens with some of the more serious heat-rejecting goods. The view out of a 15' x 8' wall of glass isn't much compromised by reducing it to 14' x 7', replacing that ~18% of U0.33 glass with R20+ (sub U0.05) wall is a 17%+ cut in total heat loss out of that wall. Then bumping the windows from U0.33-0.34 down to U0.29-0.030 buys you another ~10%, usually without breaking the bank or ruining the daylighting or view. Adjusting the size & shape of the windows to optimize the view using the minimum of total area counts for a lot- make the case for every square foot.

    The conduits housing the insulated refrigerant lines DO look a lot like high-velocity mini-ducts, but "ductless" is a key factor in the high efficiency of ductless systems. Without ducts there's no duct leakage losses or backpressure increasing loads to the air handler. If you literally never clean the filters on the interior units of split system it'll cut into efficiency measurably, but not as much as going to a ducted system. Using indoor units with continuously-variable speed blowers rather than some of the simpler 2-speed also improves average efficiency.

    The ceiling mount units tend to look like this:



    But there are flush-mounted versions too:



    Most of the ceiling mounted units are well north of 10,000BTU- finding one appropriately sized for a bedroom might take a few discussions with distributors or manufacturer's reps, since they're usually targeted at larger commercial installations that have far more ceiling than wall as opposed to single-office/room type installations.
    Last edited by Dana; 09-09-2011 at 02:55 PM.

  2. #17
    DIY Junior Member Steve29's Avatar
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    Dana, our Taco load results are intimidating compared to the numbers you've tossed around: 115KBTU/hr cooling, 109KBTU/hr heating. Despite the ton of detail we put into it, I'm not sure how correct they are, as I get no change to the cooling load when I add a huge overhang (to simulate exterior shading) over our expansive east side glass. We will try to get these numbers lower using your recommendations (less glass, more insulation, etc), but they'll still be high. (We input .5 ACH/hr in Taco, which seems pretty agressive.) I have cost estimates for four different HVAC approaches (but this guy hasn't done a load analysis, he has just reviewed our plans):
    1) conventional GFA/AC = $24.9K (two Carrier 16 SEER AC units, two 93%-eff. furnaces)
    2) central (ducted) heat pump = $34K (highest eff. Carrier, 21 SEER)
    3) geothermal = $47K before incentives, about $21.5K after incentives (30% fed credit plus an $11.4K after-tax estimate of the incentive from APS, our utility company, to be given to us by check)
    4) Evap and radiant = $30K, or $36K with gypcrete upstairs (2 evap units needed)
    5) ductless (minis) - I had to ask him about this as an option, and he said he does like them and will get me an estimate.

    Our energy unit prices are currently $1.17/therm, and 12.75 cents/kwh in winter, 15.1 cents in summer.

    Your thoughts at this point? (I've looked into possible tax credits for the high efficiency heat pumps but believe they are available only for existing homes.)

  3. #18
    General Engineering Contractor ballvalve's Avatar
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    Very interesting read especially without a fee!

    It takes a sharp pencil and good energy-use modeling of the house in-situ to determine where all of the crossovers are.
    And a few bottles of wine and finally some guesswork.

    I cannot imagine a house without radiant heat. You dont need those absurd systems with outdoor sensors, numerous automatic valve zones, and a mass of wiring that insures a lifetime repair profit to the installer.

    http://www.radiantec.com/systems-sou...pen-system.php

    Thats the system a lot of guys in the business hate because billy bob can install and adjust it. I find the cost estimate on the site terribly high.

    I feel the mini splits add a huge level of complexity in a large house also, not to mention the lack of a warm floor - the KEY to comfort in the winter. I see the splits as nice in motels and small rentals.

    I've been doing radiant for 30 years starting with polybutylene [no leaks yet] and always plumbed in with the potable hot water. 1 pump [or as you wish] and 4 to 10 valves, and a GOOD checkvalve, and you are ready to heat. The day-laborers sitting on the safeway parking lot can run the pex zones in a day. And another day for this cheap labor for mortar mixing to fill in betweeen the 3/4" wood sleepers on the second floor where the pex is tacked to the floor. Lay wood or carpet over it. The gyp crete guys are way out of line in cost. Call in a pro to make the manifold connections and pressure test it.

    I have laid out systems for many owner builders, and they have done it all with laborers and good instructions. And they still call back to thank me for a house they cannnot imagine living in without the radiant. I think the only callback was for a mouse in a Polaris vent.

    My vote is water cooler and radiant, hands down. Then you guys can duke it out about what water heater to use. I wouldnt trust the Korean infernal-eternal.

    Every unvented flat roof I have cut into gives me a blast of hot wet air and the smell of mould... How are you insuring against this?
    I am just now adding flat roof vents to my home. Hard to do a perfect vapor barrier. And ANTS! be sure your insulation has some borax or D-earth in it. Around here it snows styrofoam in the spring in houses with open beams and the old styrofoam above. And my ants love the yellow "toxic" foam too.

    You seem quite quick with numbers - can you calc 8 cent per KW winter and 12 cent summer KW against $2.50 per gallon Propane on a say, 85% efficient water heater?
    Last edited by ballvalve; 09-24-2011 at 02:37 PM.

  4. #19
    DIY Junior Member Steve29's Avatar
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    Thanks for the info, and for your vote! Shoot, just when I was getting radiant out of my mind.... (And here I thought Californians didn't care about heating.) You've probably gathered we have a slab downstairs (not a basement, it's just the first level), so what do you suppose our cost could be to do that slab and upstairs? The slab is ~1650 SF, but maybe we'd have to heat only 60% of it or so. Upstairs is 2179 SF, but we would need to radiate maybe only 75% of it or less.

    I hope/think I understand what you're suggesting - you mortar in the pex inside channels that are created with 3/4" wood strips? Not sure why this done - better radiant heat distribution? And I still wonder how radiant can work well when it has to heat through a wood floor. That's why I thought about gyp ($6200 for 1 1/2" thick upstairs).

    I'm not sure of the flat roof construction method. The roof will be a combination of trusses and TJI's. Perhaps some blown fiberglass on the bottom, and on top of the roof sheathing a couple inches of rigid foam (to combat thermal bridging). So we could also spray a thin layer of open-cell foam at the top of the trusses/TJI's, to fight infiltration. Suggestions? If you used a vapor barrier, where would you put it? I assume under the blown fiberglass. There's a lot of dispute about using vapor barriers. And it doesn't have to be near-perfect to be very effective.

    What type of insulation are you suggesting putting Borax or D-earth in? Googling it shows that cellulose has 10-15% Borax and Boric acid, both non-toxic fire retardants. Dana suggested staying away from cellulose in the roof in case there is an undetected leak in the "flat" roof.

    I calculate that your propane, in an 85% efficient water heater, equates to 10.9 cents/kwh if using an electric heater (100% efficient).

  5. #20
    General Engineering Contractor ballvalve's Avatar
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    I can't figure out vapor barriers - not enough time or wine.

    The boric acid is more toward bug killing than fire. By the time a fire gets to the blown insulation, its time to start planning the rebuild.

    You need foam with boric acid in the board. Not carried usually by the lumber yards. The main ingredient of Terro ant killer is boric acid.

    Sedona likely has my climate, hotter summers I might guess. I have about 1/4 of the house with thick pine floors over the hand set cement or mortar, but I rarely even turn this zone on, as the heat from an adjacent 800 foot slab keeps that area warm enough. Heat transfers through wood quite well. put a piece on your electric hot plate. Or use a thin engineered flooring. I use 1/2" pex on 300 to 400' zones, and with sleepers, mortar, and pex, and all the unemployed workers, you should be able to do the upstairs for $3000 MAX. Were you going to leave the gyp exposed? Your gyp cost did not include the pipe, I suppose.

    On my third floor, I have carpet over the pipe set in cement. Almost all windows. No problem with heating.

    These idea might not work in Northern wisconsin, however.

    On one job, I got the exterior stuccoers to don knee pads and mortar and trowel a great finish right over the pipe without sleepers. Stained and varnished the floor. Even got them to thinset plaster the walls for less than the cost of garbage sheetrock mud.

    The most important issue of radiant heat is the entire mass of the house becomes warm, and the comfort feel is irreplaceable. Not like warm air blowing out of a chinese or Korean box on the wall.

  6. #21
    DIY Junior Member Steve29's Avatar
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    Was your $3000 estimate excluding whatever controls, pumps, manifolds, check valves, and heater that we'll need? (Shows my ignorance - I'll have to spend some time looking into radiant systems) Correct, my gyp cost of $6200 was just for the gyp. If we did gyp, we expected to tile over it, as I didn't realize there was a way to make exposed gyp look decent, and to wear OK. Is there?

    You didn't mention doing our slab downstairs. You would do that, too, right? One water heater for each floor's radiant, or one boiler for all? The calcs show a pretty high heating load. (stupid view windows!)

    I'll read some of your previous discussions from Feb 2010 on using the same heater for the radiant and domestic, as it seems odd to me right now. Seems you'd want the water for each to be at different temps.

    Great tips on the other things, too. Thanks!

  7. #22
    In the trades Dana's Avatar
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    A ~110-115KBTU heating or cooling loads for a 3800' house in that climate seems kinda insane, but I s'pose anything is possible with an insane amount of glazing. Are you sure you're entering the right U-values for the glass? Have you tried changing the amount & type of glass in the tool to see just how far you'd have to cut back to get it at least under 50K? (Seriously, I see bigger houses than that in places with -10F design temps and half the heating load, but perhaps not the view!) Without higher performance glass &/or less raw glazed area you probably won't be able to get there with insulation.

    With those kinds of incentives for geothermal, you might want to consider a geothermal-hydronic radiant solution rather than gas-fired, but try to cut the heat load in half first. With water-to-water and the low water temp requirements of radiant slabs you'd be able to beat the true system average COP of any water-to-air system, since hydronic pumps would use less power than the air handler(s), and with a lower temp output the geothermal heat pump itself will run at higher efficiency.

    I would NOT recommend trying to support a 110K heating load with just a condensing HW heater but an HTP Versa or Flame combi would get you there in a code-legal fashion. Some models are set up with solar-thermal heat exchangers already in place as well. Radiant & hydronic "open systems such as those recommended by radiantec are a code violation in most places (but not all).

  8. #23
    General Engineering Contractor ballvalve's Avatar
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    Check my link to passive radiant systems, there is a lot on the web. But it automatically puts cold water in the floor during the summer, extracting some heat and tempering the incoming water to the heater. Only a few valves for you to adjust a few times a year.

    I like the Polaris, its improved they say, and it has ports already installed just for the passive system, although you don't really need them. They have a fantastic recovery rate, and unless you are snowed in all winter, one is enough. The longer one unit runs, the higher the efficiency anyway.

    When you use hot water, the water entering the heater is floor temperature, so if in winter, you have a huge storage mass of warm water to extend the recovery rate - I dont have the math to calc it, buts it self evident. In summer you leave all your zone valves open, and you can pick up some btu's from that sunny slab for free. Its all about 1 top quality check valve and some simple routing of plumbing.

    If you get your hands dirty and use small screeds for the mortar upstairs, the pipe is about 30 cents a foot, ready mix mortar a few bucks a bag, and the screeds perhaps 100 bucks. Just about any kid can level out [very dry mix] mortar between sticks a foot or so apart. Thats probably $1000 dollars. And you can tile over it. The gyp crete guy was "created" to do fireproofing between floors of motels/ hotels. He's way out of work now and wants to pay his mortage on his pump with your job.

    My system works fine with the water at about 130 degrees and less. It just means cranking the hot water handle more than the cold one.

    Yes, you still need all the mechanicals to be done.

    Gyp is just basically sheet rock mud, and not very hard. Perhaps there are newer products. But I'll never part with 6 grand for it.

    I never used it. I suppose you could stain it and use a good catalyzed finish on it, but dont dance in high heels or let the German Shepherd chase the kid up there.

    As to the "code" submit the plan for the combined system. I never saw one questioned in any manner. And I see no merit to the objections at all. The "code" should be out checking meat and lettuce in the stores for listeria and bacteria, where they might actually save a life.
    Last edited by ballvalve; 09-26-2011 at 12:54 PM.

  9. #24
    In the trades Dana's Avatar
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    I don't write the code, but I'm bound by it. Open systems are allowed in combis in MA provided it's controlled with minimum circulation times per hour when not in heating mode etc. It gets to be a bit messy when it's more than a single-zone. Buying the heat exchanger and another pump, or using something with the heat exchanger built into the unit makes life with the inspector simpler.

  10. #25
    General Engineering Contractor ballvalve's Avatar
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    How about those monster homes with 300 feet of pipe dead ending in the guest bath?

    Ma. should MAKE you circulate that if they want to justify their minimum circ times.

    In any case, I don't drink a whole lot of hot tap water, and the passive system automatically circulates all zones all the time when cold water is being used, as long as the valves are partially open.

    I read about a lot of dead people that ate a melon or a sprout, but never from their radiant heat system.

  11. #26
    DIY Junior Member Steve29's Avatar
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    Here's a breakdown for the amount of glass we have planned: of the entire exterior (vertical) surface of our house, 65% is insulated walls, 28% is insulated-glass windows and 7% is butted-glass windows. So it's 35% glass right now.

    Yes, I entered into Taco real glass U values of .355 (Cardinal low-E 366, as an example). (The ACH is .5/hr.) I have not tried changing the amount of glass yet, but I will - it will be interesting to see what it takes, even though we won't be able to lop much glass off when it gets right down to it. But I did try a few things: 1) increasing the walls from the current R18 to R24 reduced the load only ~2K, 2) decreasing the glass U value from .355 to .27 saves 3K cooling and 6K heating, 3) dropping the U to Taco's lowest allowable of .24 drops another 1K cooling and 1K heating. So that last effort takes us from the original numbers of 115K cooling/109K heating down to 109K cooling/100K heating - not very compelling.

    I'm pasting a jpeg of the Taco result page below, but since I'm not sure it will display I'll say a couple things about two big numbers that are biting us, one for cooling and the other for heating:

    You probably are used to looking at their results table, but I'm not. a) The window solar contribution to the cooling load is 40K, but as far as I can tell Taco isn't taking everything into account (for instance, we have a lot of ENE glass, but we'll have exterior shades for summer mornings - I accounted for that in Taco by putting in huge overhangs but saw no change in this number. Also, our south glass has proper overhangs to mitigate solar gain in summer. West glass area is minimal.). b) The ventilation contribution to the heating load is 40K, a really big number, but I don't understand what it is - there's already an infiltration number of 9K. (Ventilation adds 8K to the cooling load.)

    Name:  Taco base case_R18 walls U35 glass_100%.jpg
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    Last edited by Steve29; 09-27-2011 at 02:56 PM. Reason: poor image first time

  12. #27
    General Engineering Contractor ballvalve's Avatar
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    Do a passive and adjust the valves and temp of the water to the REALITY of the built house.

    I would'nt get tied up in programs details very deeply. You have already identified many flaws.

    Do a whole house fan at night, and you might never use your air cooler. I have one 100$ window AC to cool my 3rd floor bedroom, and a ton of mass inside. Never even used the AC this year, with some 100' days.

    If I want to really cool off, I tunnelled a wine cave in the mountain about 100' and it holds around 50-60' F.
    Last edited by ballvalve; 09-28-2011 at 12:24 PM.

  13. #28
    DIY Junior Member Steve29's Avatar
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    I love the wine cave! We live in a passive solar house of our design, also with tons of mass (including a small earth-coupled wine room) so, like you, we appreciate mass and nighttime cooling. And yes, for this new house in Sedona we are planning for a whole-house fan. We just don't have much mass in the design other than the downstairs slab. Hence my interest in gypcrete and tile with radiant, but as you pointed out that's not cheap mass by any means. We'll do 5/8" drywall everywhere, but are told a double layer would cost too much. Not sure how else to get mass.

    Re messing with the program, I wanted to get a handle on the cooling load, too. Our (somewhat conventional) architect immediately spec'd three big AC units on the drawings. We've never lived in a house with cooling so that made us nervous.

    Not sure what you mean by doing "a passive". I had no luck with googling it.

  14. #29
    General Engineering Contractor ballvalve's Avatar
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    Thats the type of system shown by 'radiantech' or such on line. I believe I left a link somewhere above.

  15. #30
    DIY Junior Member brennl's Avatar
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    Quote Originally Posted by Steve29 View Post
    Excellent summary of singles vs a multi - thanks! I didn't realize the 3" lines were carrying refrigerant. I'll look into wall vs ceiling mounts and continue on the Taco expedition (am a little nervous of what it'll tell us....)
    me too i did not expect it that the singles vs a multi - tanks ..this is awsome

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