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  1. #14
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    The cadallac system deals with latent and sensible loads separately no matter what you do.
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  2. #15
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    Awesome in any case

    If I understand right, the sensible cooling portion is to be partly handled by a radiant cooling system of a type unfamiliar to most of us. Would you size it to handle the entire sensible cooling load? Or would there be a 2nd cooling system with the usual forced air?. Most or all of the job of latent cooling will be done by dehumidifier. Do I understand correctly?

    Would your radiant cooling system have provision for water removal if condensation occurs, or will you simply guarantee not to operate at the conditions to create condensate? Are you able to describe more fully how they implement this system in that Bankok airport? Surely there is an interesting paper published about that installation.

    I am highly impressed. It's fascinating to read about cutting edge designs like this. It would make great material for a technical paper to be published by somebody in the building science field. If you do build these systems in the home, I very much hope you get published and equally much hope that I get to read that paper!

    Best of luck -- Pstu

    [Edited by pstu on 02-27-2006 at 07:26 PM]

  3. #16
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    No would be screwed blue and tatooed if the indoor dewpoint got too high p-student.

    Need dehumidifiers and something to dry out the ventilation air to pressurize the terminal.
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  4. #17
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    To PStu

    These radiant cooling systems are operating NOW, HERE in North America and are becoming better understood. They are very popular systems in Europe, and are being applied in China now too. Just do a Google search to see what's out there. To answer your specific questions:

    Yes, in drier climates, where de-humidification isn't a concern, the entire sensible cooling load can be handled by the radiant cooling system depending on where the radiant surface is - floors aren't as good as ceilings. The design goal is to keep the total cooling loads low in the first place by a high performance envelope and window system, and the radiant cooling can then work best. In a dry climate, theoretically you could use very low radiant cooling surface tempertaures (say down to 57F) to get higher cooling capacities, but then depending on the radiant surface (floor vs ceiling) there are comfort issues. Cold floors=not comfortable, Cold ceilings= workable, but to a point where it's too cold on your head/shoulders. Normally the design rule of thumb is radiant cooling floors min, temp= 65F, radiant cooling ceilings min. temp = 62F

    The design goal is to do as much radiant cooling as you can, to the limits of ambient dewpoint and surface temperatures, and use the air side as a "second stage" as required, where cooling loads are higher than can be controlled by the radiant system. All of the de-humidification would be done at the air unit where the moisture is squeezed out in a cooling coil and drained away. basically a conventional air conditioner, but much smaller since it's sized only to handle the latent load (de-humidification load) and whatever supplemental cooling is desired.

    The radiant surfaces are NOT supposed to condense if the design is done properly, so no provisions for condensation control are needed at the radiant floors/walls/ceilings. In some humid climates where there is a risk of higher indoor dewpoints, a dewpoint/condensation sensor imbedded in the radiant surface can be used to reset the cooling water temperature up to prevent condensation, but then this is where you'll want the supplemental cooling from the air side. The aim of these systems is to reduce the air side to the absolute minimum to save energy, and try to do most of the room sensible temperature control from direct hydronic radiant systems.

    There are many papers and system descriptions for these radiant cooling systems on the 'net, just do a search, have a cup of coffee, and read till you're bored.

  5. #18
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    I don't see it as a second stage 'air side' air conditioner, it would be a dehumidification/reheat system. The panels would eat up most of the sensible load.

    Would be a real low SHR to deal with.
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  6. #19
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    I could see the radiant cooling being popular in Europe for a couple reasons.

    Traditionally there has not been much forced air heating in Europe and therefore limited duct work and the climate is fairly mild in the summers in Northern Europe.

    Ductless splits are quite popular in the UK, especially since it is hot water heat to begin with.

    Residentially I do not see much economy of scale in the savings of distribution. In a hot humid climate, especially year round cooling, it could be an accident waiting to happen.

    Biggest problem is a low SHR, and the ceiling panels just lower it even more. Characteristic of ventilation load in tropics would be SHR=0.2. Remove the sensible space load with panels and with internal latent gains, it gets even tougher to deal with.



    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  7. #20
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    I looked at doing a mansion down here and for about US 20K dectron would build a 100% outside air unit that could pressurize the house with about 700 CFM of dried out outside air, that would basically take care of all the latent load by displacing air with a higher dewpoint than it was supplying.

    The home also has a large swimming pool so included in Dectrons big price tag, was a pool water heater. Pay to heat pool and dehumidify your house for free.

    Worst scenario here is when a tropical system approaches, its pouring rain, still 81F out, and no sun shining through all the glass the rich want to see there multi-million dollar views of the Caribbean. So being able to pressurize the place with dry air with a mid 60 dry bulb, would handle all the cooling in that situation.

    Smaller 100% outside air units are available for this kind of climate and be about US $6000 for 200 CFM.

    This system was scrapped so the split systems serving the manison were all upgraded.

    Then there is the salt corrosion factor and you are doing well to get 5 years out of the equipment. So you could keep replacing condenser coils on the custom built OAUs, or replace standard residential condensing units.

    Radiant cooling down here would require some specialized systems to handle the ventilation air. I am a pro HRV and ERV guy, but with p-students two year quest I have finally come to realize the limited effectiveness of an ERV on a residential basis as you still have infiltration. The resi ERV will not be able to provide much of a ventilation unbalance to significantly reduce infiltration. Commercially I feel the ERV is quite viable.

    The other problem here is RO water and copper piping does not stand up well.

    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  8. #21
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    Envelope and climate

    Carnak: you are speaking of extreme conditions, while the majority of North America has climates not unlike most of Europe. Another myth: "Europe has a mild climate so you can do radiant cooling there". BS. These systems are installed from Sweden to Turkey and they work. Why? better building envelopes in the last 20 years. Check out the climate data for most of Europe and compare that to similar climate zones in North America- a lot of commonality.

    You say yourself that the ERV/HRV and Dectron (another techno-solution) couldn't handle the infiltration in your climate. Well, isn't the infiltration and better building envelope (climate adapted) the problem to be solved first? The building envelope is an integral part of the indoor comfort system and that's where the HVAC system starts.

  9. #22
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    Who to respect

    Gmcd, here is another question for you to ignore. Do you respect ASHRAE 6.2 recommendations? Because that suggests a minimum outside air exchange of approximatly 0.35 ACH in homes. My point is you cannot obey ASHRAE and say all your problems can be solved by tightening up the house. Whether you have ERV, HRV, or ventilating dehumidifier, there is a serious amount of load from infiltration in any case.

    I have relatives in Italy and Poland and neither is very close to the climate I experience in S.Texas. Lots of old buildings, not that many new ones. I can say that on none of my trips there, have I ever seen a radiant cooling system. Not to say they don't exist, but I would have noticed if they are widespread.

    I do have a ton of respect for the knowledge Carnak has shown on this board. He is trying to show us facts and science rather than indulging in a pipe dream.

    Regards -- Pstu

    [Edited by pstu on 02-28-2006 at 11:27 AM]

  10. #23
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    Re: Envelope and climate

    Originally posted by gmcd
    Carnak: you are speaking of extreme conditions, while the majority of North America has climates not unlike most of Europe. Another myth: "Europe has a mild climate so you can do radiant cooling there". BS. These systems are installed from Sweden to Turkey and they work. Why? better building envelopes in the last 20 years. Check out the climate data for most of Europe and compare that to similar climate zones in North America- a lot of commonality.

    You say yourself that the ERV/HRV and Dectron (another techno-solution) couldn't handle the infiltration in your climate. Well, isn't the infiltration and better building envelope (climate adapted) the problem to be solved first? The building envelope is an integral part of the indoor comfort system and that's where the HVAC system starts.
    I can see you are passionate for radiant cooling and there is nothing wrong with that. You were demonstrating how well it will work in a hot humid environemnent and I am just pointing out it is potentially an accident waiting to happen.

    A lot of places in Europe will have climates similar to Vancouver and they are not challenging climates. Turkey looks pretty dry, the majority of places have worst case humidity designs of less than 100 grains. Easy climates.

    Typical european will not have air conditioning. They finally got some warm temps last summer and it damn near killed them.

    Did a restaurant here, owner is from San Francisco, has a chain up there as well and he could not understand why he could not use evaporative cooling here, becuase he uses it at home.

    You get in the American South and points south, then all the rules are opposite to how they work in the North.

    Tighest homes in the world, I would be a little biased and say Canada and what really helps is sealed vapour barriers. Put a vpaour barrier on an inside wall in a hot humid environment it is a disaster. So fine, apply 'put the vapour barrier on the warm side of the insulation'. Easy in Canada, especially for the ceiling. Sealed poly on the under side of the trusses. Try doing that when the attic is the 'warm side of the insulation'.

    So maybe not venting attics, and foaming the pitch is one solution, or vapour barrier/insulation beneath the attic is another solution.

    No winter stack effect to worry about but a lot of wind driven infiltration and prolonged exhausts can be dangerous too.

    So you can tighten up to an extent but if you want to stop infiltration you have to pressurize with dry air. Stops infiltration and provides your ventialtion. You run an ERV in balance then you still have to deal with infiltration.

    The dectron was not a techno gimmick, it killed two birds with one stone and it actually was a workable scheme to reduce the space cooling load as it took the latent out of the picture.

    Radiant cooling here would only make it more difficult to control humidity, and just has the potential of really going south.

    In Canada the typical home with forced air heat has uninsulated galvanized duct work running in their basements. Later they get central AC and there is typically not a problem with the ducts sweating.

    If I had metal ducts in conditioned space here, they would not sweat either if everything was perfect. Would I spec uninsulated metal ducts, no way. My theme song is not "Rain Drops Keep Falling on My Head"


    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  11. #24
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    "But it worked great in Arizona"
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  12. #25
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    Actually the majority of Canada compares to Siberia for climate
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  13. #26
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    Some responses

    From PStu:

    "Gmcd, here is another question for you to ignore. Do you respect ASHRAE 6.2 recommendations? Because that suggests a minimum outside air exchange of approximatly 0.35 ACH in homes. My point is you cannot obey ASHRAE and say all your problems can be solved by tightening up the house. Whether you have ERV, HRV, or ventilating dehumidifier, there is a serious amount of load from infiltration in any case."

    Actually no, I don't "respect" ASHRAE 62-1 recommendations because they are not good enough in my opinion. And I never claimed that "all the problems will be solved by a tight envelope". A house is a "system" right from the envelope down to the last nut and bolt. A tight house will require an HRV/ERV to provide healthy conditions and control indoor generated humidity and to control outdoor air coming into the house. I generally start at a minimum of 0.5 ACH and work up depending on what the local climate conditions are, and what supplemental heating/cooling is needed from the air side of the system. Remember, the Code is a "minimum standard" and it's OK to go above it, in fact encouraged, to rise above a level of mediocrity.

    Carnak: I understand the opinion that radiant cooling is just another "accident waiting to happen". However, it is a useful toolkit item to have in the right hands. You keep deferring to my location for radiant cooling applications, yet there are many radiant cooling systems in more severe climates, and they DO work. The point I'm trying to make is that it is a useful system for comfort and low energy when applied properly, and by "properly" I mean in a "properly" designed and built building that has a climate adapted envelope to allow radiant cooling to function with no risk. Based on your example photo, even conventional systems are regularly screwed up and cause enormous problems in hot'n'humid climates. I love reading the Wall'o'Shame on this board because it shows just how bad even conventional systems can be treated. In my opinion, an improperly installed air conditioning duct system is an accident waiting to happen, too.

    So, no, given the general quality of construction in many areas, I would not promote radiant cooling in the SE US. That was never my intent and I agree with your concerns for that particular climate. However, there ARE a lot of North American climate zones where it CAN work and it can save a heck of a lot of energy. Of course, the primary energy conservation system in a building is the envelope in the first place. The types of mechanical systems that can be applied are a secondary energy efficiency system.

    So, yeah, a radiant cooling system isn't a silver bullet and I never said it was. If we look at the original lead-off post- the guy was considering a house in Cincinnati, Ohio, not Florida/South East Texas and that is certainly a climate, combined with a geo-exchnage system, that might be a good aplication for a radiant cooling system, in a properly designed and built house.

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