Radiant Ceiling Heating & Cooling

Canuck

I've got a real live wire here that I'm pricing. Residential - about 2000 sq ft with in floor heating in basement and ceiling heating/cooling (tubing in the ceiling finish) for the rest of the house. The entire system is (IMHO) ultra-leading edge application of hydronics. I've checked the website of the design engineers and am impressed with their projects to date. I'd like to hear from anyone who has experience in this application - not so much on the pitfalls of poor design, (Yikes, we've hit dew point on the tubing and the ceiling is now on the dining room table), more of the 'what works and what doesn't work' on installation, thermal barrier, vapour barrier, fastening methods, etc. I appreciate the help

GMcD

Engineering

Hopefully the designers have some practical experience in this application or they could be in for a steep and expensive learning curve. The first step, especially when dealing with radiant cooling, is to design the envelope and glass solar control properly. The key is to minimize/eliminate fast acting solar load transients at the glass/perimeter. Let the natural light in, but not the solar gain. This does two things- keeps the cooling load low enough that radiant cooling system hydronic temperatures are going to be above the indoor dewpoint, and two - keeps the energy use to a minimum for the cooling plant. Hopefully there is a heat recovery ventilator somewhere in the system, or you've only got half a comfort system.

I question the radiant heating in the slab and the radiant cooling in the ceiling - why two separate systems? I question the building design approach that would result in that type of arrangement. If the homeowner wants warm feet, and radiant cooling, you can do all that from the floor alone (not as efficiently, mind you...). Radiant cooling does not "need" to be done from the ceiling. Vice-versa- why not use the ceiling system as the heating/cooling emitter? If the homeowner wants the warm toes, fine. I'm not sure I unserstood your description properly - is the main floor being treated to combined radiant heat and cool from the ceiling only, and only the basement floor slab has a heating only system?

Having designed and commissioned radiant heating/cooling systems, and learned from the Europeans, so I think I can comment safely on these systems. The design effort is spent on designing the building envelope around the radiant system, NOT designing the radiant system to react to the building loads.

Bob Gagnon plumbing and heating

most important feature

of my radiant cooling system is the fan coil unit with a drip pan underneath, that removes humidity and lowers the dewpoint in the house. The fan coil also greatly increases the cooling capicity. Bob Gagnon

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Canuck

Clarity

Perhaps I should have been clearer; only the basement has floor radiant (heat only). The main and second floors have tubing in the ceiling only, and are combined heating and cooling.....and yes, there is an HRV in the system.

As for the engineers and design, they look like they've done their homework. I guess that I'm concerned about the installation process. I've got a lot of experience in radiant heating projects, but this will be my first attempt (if awarded) at radiant cooling. I'm usually assisting the engineers/designers of large radiant heating projects on the symantics of system application/installation, but I'm drawing a big goose-egg on this one as I have no experience to draw from. Anyway, thanks for your input. If things go ahead, I'll post job progress.

GMcD

Sounds good so far

What climate zone is this project in? Is there a need to de-humidify the incoming outdoor air in the summer? What type of radiant piping system is being used for the ceiling? If it's 1/2 PEX on some kind of staple up or warm-board system, it should be a pretty easy install. One of the engineering issues that hopefully someone has accounted for is what water temperature in the tube is required to get what surface temperature at the ceiling surface. I find that there is enough insulating quality of a drywall overlay on top of PEX tube that the water temps may have to be driven fairly cool to get the desired emitter surface temperature. This could result in condensing temperatures at the PEX tube and at the contact area if the house needs a higher cooling load than say 15 btuh/SF (requires a radiant cooling surface temp of about 66F)

That's why I'm a fan of the capillary tube system- imbed the tubes in a plaster surface - fabulous contact from tube to emitter transfer medium - and the tubes are closer to the surface of the emitter so that the water temp in the tubes only needs to be within a degree of the desired emitter surface temp.

Brent_2

source

what are they using for the cooling source? geothermal?

Canuck

Tubing

The project is in Toronto, Canada, and yes, there is definitely a need to dehumidify incoming air. Due to the proximity of Lake Ontario, we can typically get 90+ % non-condensing humidity. There are cooling coils in the HRV system.

The tubing installation/style is presently open-ended. They're talking about 1/2" PEX, and again, I don't have any radiant 'cooling' experience to direct them one way or another. I know that there's a product (Karo?) that uses capillary tubing. How it's terminated, the advantage/disadvantage aspects, availability in the great white north, etc. - I'm not sure of. Obviously I need to do more research, however I thought I'd start here first, seeing as this media is probably the best concentrated source of information.

GMcD

Karo in Canada

Is presently being marketted by Olympic International in North Vancouver. On the Karo website there is a listing for a rep in Quebec that I've not heard Boo about so I don't know how active they are in marketting the product.

Ceiling installed PEX is just a reverse application of staple up, just upside down. No big deal.

Canuck

Heat/cool source

There is a 3T, ground source heat pump as the source of heat/cool. They have designed the system for three seasons: summer cooling, winter heating and 'shoulder' heat/cool (the in-between times). Sensors, controls and modulating valves are in place to adjust as the seasons change. There is a large mass stone column in the centre of the home for passive assistance. The heat pump also provides a primary heat source for the DHW, which has an electric water heater back-up. Grey water waste is separate from the rest of the drains and is diverted through a heat exchanger tied into DCW supply to the water heater. The nitty-gritty on all of the aspects of the project goes on for 15-20 pages.

GMcD

Geo-exchange

Check to see if there is a bypass designed around the heat pump unit so that direct geo-exchange water can be used for the cooling requirement rather than running a techno-device. Use a small plate HEX to the in-ground loops with a control valve setup so you can harvest the ground water temperature for the radiant cooling, and only turn on the HP during peak cooling loads (or as required for the ventilation air treatment). Pretty well anywhere in Canada, the ground temps will be less than the radiant cooling temps you need, so a simple modulating mixing valve off the HEX to the radiant system will perform very energy efficient cooling, and if the ground temps are cool enough, you can likely take care of the ventilation cooling during the shoulder seasons as well.

Canuck

Done, Done and..................

Done

GMcD

Beauty

Not too much else to add....Where is the project located, generally speaking - east? west? There are very few folks that can do a design like that and make sure it works properly.

Domdi

Using copper pipe for radiant heat

I have a small area to heat ~ 30 square feet [3 x 10]. It would be very convenient to use 3/4" copper pipe instead of PEX, is there any coating to prevent corrosion. Any suggestions will be appreaciated

Canuck

Location

The project is right in the heart of the city (Metro Toronto). My first issue is going to be the logistics of bringing in a well driller for the (3) x 200' deep sink wells. That's if we get the project.

Unknown

hey Geoff, what do you favor for a dehumidification solution, typically?

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GMcD

Dehumidification

Depends on the size/capacity required. I am fortunate to live in a climate where dehumdification is not needed in the summer. Typically it could take a few forms:

-small packaged stand-alone console dehumidification unit
-small DX split with reheat on the HRV ventilation unit
-small dessicant heat wheel HRV unit (Greenheck)

Most of my experience and current design effort is on large commercial/institutional projects where it's a lot easier to incorporate these systems in an integrated way. It is tougher on very small House systems, but should not be a big cost/maintenance hit if the HRV unit is properly selected with the right options. If the House is in a humid climate, then that is one of the basic needs for the total comfort system anyway, so should not be considered an "extra" add-on item to the whole system.

Weezbo

funny thing how that is i was in Toronto about 15 years ...

ago....i asked if there was anyone into radiant heating and cooling...visited some sites and asked if they had thought of using radiant for cooling..*~/:) it wasnt to be found on any of the new homes or buildings that i searched out...radiant heat little bit here and there....hydronic space conditioning...? not even on the fancy new commercial buildings or wharehouses ...and nothing down town anywhere...so you might have to search out the countryside by internet to find some quality experiential control stradgiest .... there definitely some minor technicalities with the control of space conditioning...over powering things doesnt seem like the truly viable stradgey,amelioration of the environment seems an easier place to start...for the most part each and every day is a new day maybe some day we will have more accurate information than we have now and someone who observes from another viewpoint will make a suggestion or two that will open the ability of all of us to see what is obviously been in clear sight all along. some old timers here in alaska use pond water thru a slab it is cold as heck outside yet, as the doctrine of manysidedness of the Jains suggests it is Relative truth to the observer. (cannot get that point over to engineery minds at times..) thing is ,moving water doesnt freeze if it is 60 below and you have running water thru the slab it will be warmer ,relatively speaking to what one is experiencing,that is like "MAn its Hot in here "! comming from someone who just walked 3 miles in the severe cold.."I am Freezing !"comming from the person in the 58 degree room...space conditioning is like that. it has a certain personal relative truth wrapped into it.. we are considered genius when we fluidly adapt to our environment. Thats the hydronic Way *~/;) peace

GMcD

Early radiant cooling

That's true- there has been a ton of radiant heating installations for a long time - perimeter suspended radiant ceiling panels mostly, and a few early perimeter radiant cooling attempts. There is an early attempt example in Oakland ( http://www.tga-feustel.de/ies/kaiser.html ) that had issues responding to the high solar loads and poor humidity control during the peak cooling season. See this weblink: http://doas-radiant.psu.edu/Linford_letter.pdf -it kind of outlines the common resistance among even modern HVAC engineers to the thought of "radiant cooling". Give them big honkin' warm and cold air systems and everything will be all right (except for the energy guzzling all-air system parasitic loads, and that fact that hot and cold air only addresses half of the human comfort factors).

The key to applying radiant cooling is in designing the building envelope to suit the limitations of the radiant cooling. The engineer now has to design solar control, look at interior zone load control, and combined with the needed ventilation system for short transient load control, design the "whole building" system using as much passive climate control systems as possible - no more "reactive" design of HVAC systems. The biggest energy and comfort gains come from proper building envelope design, and using passive means to achieve comfort control first, then apply a little bit of mechanical HVAC to trim. A clear understanding of mean radiant temperature, and radiant temperature asymmetry are required if it's going to work properly.

Ken_8

What corrosion?

From what source would there be corrosion?

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