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    Hydronic radiant heating subtleties (19 Posts)

  • CA_Girl CA_Girl @ 3:25 PM
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    Hydronic radiant heating subtleties

    Hello folks,

    We are in the middle of a new home construction in the SF Bay Area in California - framing is complete. There are three levels, and the basement and main floor are planned for hydronic in-floor heating using pex in gypcrete (2.5" buildup for insulation and gypcrete). Exception is a home theater space in basement, which will mainly require cooling, so no in-floor system planned. Also, there is no in-floor system planned in the upper floor, which has three bedrooms and bathrooms. We got a quote for mini-split units to heat/cool the upstairs and the home theater, and I am not happy with the price/value ratio - I would prefer a non-forced air system if I am going to spend that much. It's not feasible to install a pex in gypcrete solution upstairs now because we don't have the 2.5" height or the structural strength in the upper floor. We could use aluminum spreaders and pex below floor boards ... However, although we don't expect to use cooling much, it would be nice to have in the bedrooms, so I am wondering about hydronic ceiling tubing to cover the entire upstairs and in the home theater ceiling. Any thoughts on this approach? Separately, does anyone have thoughts on the Daikin Altherma air source heat pump for supplying hot/cool water for this whole setup? Contacts who might be able to design this complex system in CA? Thank you!!
  • Snowmelt Snowmelt @ 4:28 PM
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    Not to sound negative

    I come across customers like you all the time. You want the best comfort that's reasonable with the highest energy savings.
    Well you have it, besides geothermal radiant floor is it. If done properly you will have 92-97% efficient system for heating. With cooling ductless is the better way to go. I don't understand why you wouldn't want the home theatre done with radiant floor. Or at least warm floor to keep toes warm.

    As far as cooling you have 3 choices
    1. Traditional
    2. Ductless
    3. High velocity

    Ductless is the way to go.

    You also said you preferred not to have forced air, then on the secound to last sentance you want a heat pump.

    That's why I like service calls and trouble shooting.
  • CA_Girl CA_Girl @ 5:32 PM
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    Thanks, Snowmelt ...

    Why "not to sound negative"? I don't think I understand.

    Besides traditional, ductless and high velocity, there is also radiant cooling.

    We definitely need cooling in the home theater - that cannot comfortably or realistically come from an in-floor system. Other cooling options (mini-split, radiant in-ceiling) usually have heating included for no cost. So why spend on an in-floor system? Besides, with the floor levels in the home theater, acoustic pad and thick carpet, don't think we will get warm toes anyway.

    Heat pump does not imply forced air. The Daikin Altherma is an air source heat pump, and it is typically used to provide warm water for hydronic radiant systems.

    What I'm really hoping for is advice from someone who knows about in-ceiling systems, and their comfort for heating bedrooms during mild winters. (I already know they will be super comfortable for cooling, but that's not our main use.)

  • Snowmelt Snowmelt @ 7:36 PM
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    I went to the websight you just mentioned, seemed like you stil need a water heater and you had units in the room that connects to the heat pump so in winter coil gets warm, in summer coil gets cold, you still have to have a box in the room for the coil with a fan. It can handle the radiant floor also. So it's really just combing a heating and cooling in one big unit.
    Did you get any prices yet?
  • hot rod hot rod @ 7:42 PM
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    a couple thoughts

    Zehnder is a manufacturer of ceiling heating and cooling panels. They build some really WOW stuff. Perhaps they have some design advice or contractor leads. They had an amazing display at the ISH Expo in Germany last year. I believe they manufacture in the Buffalo NY area now.

    Monterey Energy Group does a lot of radiant heating and cooling design. is an award winning contracting firm that designs and installs unique radiant systems. has some good ideas and advice on radiant cooling and a handful of engineers hang their with radiant design experience.
    This post was edited by an admin on March 30, 2014 7:44 PM.
  • Gordy Gordy @ 7:48 PM
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    Radiant ceilings

    Are wonderful, and would do well in sleeping areas.

    Maybe supplement the bath with over the top electric radiant floors would be an elegant touch.

    As for the cooling aspect you would still need a means of dehumidification (ductwork) with any radiant cooling method unless you live in a arid region of the country. San Francisco would not be so. All though the duct sizing would not be as large as a conventional FA system.

    Sounds like you are headed down the right path for what you want. Question is would a radiant design be more or less cost effect ice than your mini split quote.
    This post was edited by an admin on March 30, 2014 7:49 PM.
  • Mark Eatherton Mark Eatherton @ 9:03 AM
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    Love my radiant ceilings...

    I actually like them MORE than my radiant floors. Oh sure, floors are great, but ceilings and walls are the two most overlooked potentials. There are numerous manufacturers with radiant cooling information in their installation manuals. Check Uponor and Watts for sure, and I am certain more will be out soon.

    Radiant cooling is no longer "conceptual" but rather is a proven method of delivering high quality comfort. It's going to take a while for people to get their brains wrapped around it, but it works exactly like radiant heating, except on the other end of the comfort scale.

    The best example I can give of that is the feel you get in an un-airconditioned home when you walk down into the basement. Feels like you are walking into a sea of coolth, doesn't it? Welcome to the world of radiant cooling.

    The great thing about doing radiant ceilings is that you don't have to cover every square foot of the ceiling unless you are dealing with a lower temperature heat source. In your case, you are kinda half way in between a low temp alternative energy (solar) and a high temp source (gas fired boiler) so you will have to do more surface area to compensate for the lower heating value (115 F), but it is still worthwhile, and will deliver excellent radiant "comfort". Floors have their applications, but ceilings and walls are WAY overlooked.

    Good (panel rads and baseboard), better (radiant walls), best (radiant ceilings) and FANTASTIC (radiant floors throughout)… or a mixture of all three.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • CA_Girl CA_Girl @ 1:00 AM
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    Great info so far ...

    Snowmelt, we don't precisely know the size of Daikin Altherma we need, but have an estimate of $9000 for a 54K BTU/hr system, to supply both domestic and radiant hot water. This does not include solar preheat, or the fees for engineering the system to include cooling, which is the trickiest part. There aren't a lot of qualified professionals here on the west coast.

    hot rod, thanks for the links! Zehnder panels look cool, but I'm fairly certain their pricing will be out of reach for us. And I'll study the other sites; very interesting info at first glance.

    Gordy, great to hear you think radiant ceiling would be comfortable for bedrooms. Also, great idea to do radiant electric in bathrooms - they are small, so it won't be large $, but would be awesome to have warm feet even on summer/fall mornings, which tend to be chilly here. We were planning an HRV; sounds like we need an ERV instead to do radiant cooling. The mini-splits require soffits and some ducting to the exterior, so their costs add up quickly ... hope we can squeeze in radiant ceilings with associated engineering, and an HRV->ERV upgrade (which by itself doesn't seem to be more $$) in the same budget.

    One issue - the home theater will require cooling even when the bedrooms are in heating mode, in winter. I wonder how we can make that work ...

    Let me know if any other ideas! Thank you all.
  • SWEI SWEI @ 8:40 AM
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    Simultaneous heat and cool

    would require two terminal heat pumps -- something the Daikin VRV line does, but not the Altherma.

    We do not discuss price here, but the tax credits should make the solar kit roughly zero additional cost.
  • Sal Santamaura Sal Santamaura @ 12:00 PM
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  • CA_Girl CA_Girl @ 4:56 PM
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    Thanks again, and another question

    Thanks, Mark, for the lovely response on ceiling radiant - makes me feel infinitely better about failing to provision for in-floor radiant in the bedrooms.

    SWEI, will look into the Daikin VRV and solar tax credits.

    Sal, will get in touch with Alan.

    Now, an additional question: We have a covered patio adjoining our kitchen - the master bedroom overhangs this area. It's open to the North and East, sheltered by the house on the West and South. Our evenings get chilly even in summers, so we'll need some form of heat to be able to sit out here for long. Since the concrete patio is not poured, and the ceiling above is not finished, I could add in-floor or ceiling radiant here on a separate zone. Could run the ceiling at higher temps than the floor ... Or add some other form of electric or gas heaters? What would you recommend? We have a slightly oversized PV array, so evening use would mean very cheap, almost free off-peak electricity.
  • SWEI SWEI @ 5:53 PM
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    VRV is big

    commercial stuff, and I don't believe they have a radiant indoor unit for it.  I think the smallest outdoor unit is 6 tons.

    For that patio, radiant would be by far the best option.  If you did the ceiling, you'd need to be absolutely certain the zone would never freeze, and I'd suggest something like a mechanical wall switch timer wired to the zone valve so it couldn't get left on.  Or you could just install a natural gas radiant garage-type heater out there.
  • Gordy Gordy @ 9:41 PM
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    Patio sandwich

    I would do both floor, and ceiling. Concrete with out tubing is a missed opportunity. Especially if bare feet are engaged. How high is the ceiling?
  • CA_Girl CA_Girl @ 11:28 PM
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    Heating the patio ...

    Thanks, SWEI and Gordy. While warm radiant floors would be wonderful on the patio, I think it would cost too much to embed tubing in that concrete and supersize our heat pump to handle the additional load. Plus, this is not an area that can remain heated continuously, and tubes in concrete would take hours of preheat to get comfortable, correct?

    We really need a fast response system for the times we're sitting outside. I looked at - they supply an electric radiant system designed for patios and driveways, but it's super expensive at about $10/sf plus installation costs. Maybe a gas or electric ceiling mount radiant heater would make more sense?

    BTW, the patio is going to be tiled. For barefoot comfort, should I consider adding insulation over the concrete slab and then tiling over? If so, I should have them pour a correspondingly lower concrete surface, since I want the finished tile to be the same level as the adjoining kitchen.

    The patio ceiling is 9'-9" high.
  • Gordy Gordy @ 12:05 AM
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    Thermal mass

    Yes you are correct about the slab taking some preheat time. Even if you did an over the top electric it would still take time. If usage patterns are not predictable then the gas heater would be the most responsive choice.
  • CA_Girl CA_Girl @ 10:20 AM
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    Patio comfort

    Any thoughts about rigid insulation either under or over the concrete slab - for improving barefoot comfort?

    Anyone know about systems like this for heating patios:

  • SWEI SWEI @ 10:31 AM
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    Radiant gas

    Yes, those are in the right family.  There are lots of options, in all sizes
  • Mark Eatherton Mark Eatherton @ 3:03 PM
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    I agree with SWEI...

    I wouldn't attempt to use hydronic radiant for a porch. If yours system is set up correctly with ODR, it would take the panels FOREVER to respond due to lower water temperatures on the shoulder seasons.

    I'd still recommend a twist timer AND a line voltage thermostat for the gas fired radiant heater. Mine makes me TOO hot, so I have to do the rotisarie method of temperature control (turn….. turn…. turn…).

    Make sure you install it per the manufacturer as it pertains to clearances, etc.

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • CA_Girl CA_Girl @ 10:48 PM
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    Daikin Altherma & Messana Air Ray

    Thanks for the input on patio heating, SWEI and Mark.

    I visited the Messana showroom today, and I'm very impressed with their ability to integrate a Daikin Altherma heat pump with their Ray Magic Ceiling panels. For condensation control, Messana has their own ERV which would replace the Zehnder HRV we were considering. And their integrated system would control their ceiling panels as well as our main floor and basement's in-floor radiant (pex in gypcrete) so that we have one solution for the whole house. Very excited. Will report back how this plays out.
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