Heating/Cooling units for residential houses
Heating/Cooling units for residential houses
(OP)
Dear all,
I would kindly ask for your assistance please.
I am supposed to select appropriate heating/cooling strategy for luxury residential houses (130 sqm TFA each) located in a sea resort.
I am thinking of using small fan coil units.
What do you think about combination of underfloor heating and ceiling cooling?
Based on your experience, what would you prefer taking into account cost, efficiency,maintenance and thermal comfort ?
Thank you muchly.
Best Sasa
I would kindly ask for your assistance please.
I am supposed to select appropriate heating/cooling strategy for luxury residential houses (130 sqm TFA each) located in a sea resort.
I am thinking of using small fan coil units.
What do you think about combination of underfloor heating and ceiling cooling?
Based on your experience, what would you prefer taking into account cost, efficiency,maintenance and thermal comfort ?
Thank you muchly.
Best Sasa





RE: Heating/Cooling units for residential houses
If you do this in a high humidity area (as in by the ocean) and don't treat the outside air before it enters the space, buy a ticket to Tierra Del Fuego. There will be lots of condensation and failure of building materials/finishes.
Radiant heating underfloor is a good system.
RE: Heating/Cooling units for residential houses
Radiant cooling is an accident waiting to happen, if ambient dewpoints are above say 18C
Take the "V" out of HVAC and you are left with a HAC(k) job.
RE: Heating/Cooling units for residential houses
Yes, I completely agree that one has to be careful about dehumidification in hot and humid climates, but I think that's been pretty well licked by now, eh?
Check out Stan Mumma's tests on radiant cooling panels where he ran them down to 14F below the ambient dewpoint, and how long it took before visible drops were seen on the panel surface:
http://doa
ht
http://doas-radiant.psu.edu/Journal2.pdf
Here is one link to the Bangkok Airport radiant cooling system:
http://www
A Google search on "radiant cooling" yields a ton of material, and it's a mainstream cooling system in many parts of the world, and is as common as VAV reheat systems in North America.
RE: Heating/Cooling units for residential houses
Thank you on your useful comments.
I quite agree with GMcD. Radiant heating/colling is quite popular on Europe.
I would say it is more expensive than other systems and problems with condensation might occur but almost ideal air temperature distribution in a zone is achieved resulting in improved thermal comfort.Moreover, set point temperature can be lower as enclosures (walls, floor, ceiling) are at higher temperature. Finally, problems associated with dust circulation could be avoided as heat is mostly transferred via radiation.
Thanks Sasa
RE: Heating/Cooling units for residential houses
RE: Heating/Cooling units for residential houses
Now chilled beams- those ARE, in many cases designed to be near the dewpoint and condensation regime, and do have condensation collection means in them.
Don't forget- no one here is advocating radiant cooling as the "sole" means of room cooling- you have to have all three legs of the human comfort stool: fresh air for ventilation, humidity control in humid climates, and radiant heat exchange control. ASHRAE-55 Standard.
RE: Heating/Cooling units for residential houses
The first step is to "climate adapt" the building design, and reduce the heating/cooling loads down as far as possible. Then look at active comfort systems.
RE: Heating/Cooling units for residential houses
In a dry climate like Europe, and in places where the ambient dewpoints do not hit 64F, like coastal British Columbia it would be a great system.
In places where the ambient dewpoint is 80F, it is a disaster waiting to happen. Might as well take the mentality that you do not have to insulate air conditioning ducts as long as they are run in the conditioned space.
You could not pay me enough to specify a system creating a 64F ceiling here. The underside of this decking was 78F when a couple tropical storms went by.
So you want to use radiant cooling in a humid environment, knock yourself out, it is like rebuilding the 9th ward and saying, we are good as long as the dykes do not fail.
Take the "V" out of HVAC and you are left with a HAC(k) job.
RE: Heating/Cooling units for residential houses
I can understand people being risk-averse, but isn't our jobs as engineers to design things to minimize that risk with known best practices? The North American HVAC industry has become a reactive bunch- let a crappy building envelope design get "fixed" by applying mechanical HVAC solutions to them, and the cheaper, the better. Since when did efficient = cheap?
RE: Heating/Cooling units for residential houses
The analogy of New Orleans is perfect. It's built below sea level, and will be perfectly safe as long as the levees hold and the pumps do not fail. But they have failed, and will fail again.
Take the "V" out of HVAC and you are left with a HAC(k) job.
RE: Heating/Cooling units for residential houses
RE: Heating/Cooling units for residential houses
http:
http://www.plasticmagen.com/16/
http://www.bekausa.com/
RE: Heating/Cooling units for residential houses
Take the "V" out of HVAC and you are left with a HAC(k) job.
RE: Heating/Cooling units for residential houses
RE: Heating/Cooling units for residential houses
You should read Joe's number one dumb thing to do in the South, you are personifying it.
Radiant cooling has no place down in the tropics, will work great in low dewpoint places like BC, Europe, but is, and will remain to be, a big accident waiting to happen in a humid environment.
How do you avoid dykes failing and filling the 9th ward like a goldfish bowl, you bring in 5 trillion yards of fill to elevate it. Or build new dykes good until the next big one.
How do you avoid a catastrophic condensation problem? By not maintaining ceilings 15 degrees below the ambinet dewpoint.
Go read the Florida Solar centre a bit, one of their biggest comments is to tell home owners to not set the thermostat below 78F. The minor reason is it saves money on operating costs, but the major reason is, it is not below the ambient dewpoint.
Traditional homes here, without air condtioning never had mold because there were no surfaces colder than the ambient dewpoint.
Air condition a framed home here and now you are maintaining a space a FEW degrees below the dewpoint. Constant infiltration can then become problematic.
Now you want to promote a radiant ceiling a good 15 degrees below the ambinet dewpoint in a home, that is IDIOTIC. A house is going to have all the pressurization and safeguards that an airport terminal pressurized to keep jet fumes out will? I don't think so. Joe homeowner is going to add "condensation detectors" on his ceiling, or have safety controls to shut your cooling off if RH rises? Why have the POS system in an application it has no business in, in the first place.
Use it in dry Europe, coastal BC, a hospital in Canada where it belongs.
Take the "V" out of HVAC and you are left with a HAC(k) job.
RE: Heating/Cooling units for residential houses
Whoa, whoa whoa. You and I don't disagree- I am NOT "promoting" radiant cooling in an application where there are significant risks- risk number one being the expertise of the building design team and the installers in a hot and humid climate. All I am promoting is that radiant cooling has a place in the low energy building systems toolkit, and it has to be applied correctly, and that there are common, reasonable "good practice" safeguards to reduce the risk to be no different that a correctly designed and installed "all-air" system. I am not saying it should be a mainstream application in the Bahamas or Costa Rica - one can design a low energy building comfort system there quite easily without radiant cooling.
I used the Bangkok Airport and Winnipeg Building as examples of radiant cooling in a hot and humid climate just to illustrate that it can be made to work in an extreme climate. There has been no information yet from Bipvguy about his specific location of where he is designing these McMansions, so he may, in fact be in a location where ambient dewpoint excursions don't go to high levels like they would in the SE US zones.
What I AM promoting is climate adapted design, and to design the building to conform to the local climate and lower the cooling and heating loads as far as possible by relying on passive building design, THEN apply suitable mechanical systems that ARE APPROPRIATE FOR THE LOCAL CLIMATE.
I take issue with folks who dismiss radiant cooling right away due to the extreme blanket comments that get made like the ones above. Radiant cooling doesn't have to be set at 63F to 65F to "work". All you need is large surface areas to be kept a a few degrees below what you want for comfort - in a hot and humid climate, a radiant surface kept at 74F-75F can provide comfort if the ambient room "operative temperature" for comfort only needs to be in the 77F to 78F range. Large surface areas at small delta T's to the room can provide significant cooling effect. When you consider that the average surface temperature of the average human is 85F, any surrounding surface cooler than that will provide "radiant cooling" anyway.
What are the average floor surface temps inside the tropical houses at mid-day where they are slab on grade and "ground-coupled" - ie- no insulation under them?
RE: Heating/Cooling units for residential houses
Take the "V" out of HVAC and you are left with a HAC(k) job.
RE: Heating/Cooling units for residential houses
RE: Heating/Cooling units for residential houses
tap water is about 81 or so this time of year, the pipes are underground
Take the "V" out of HVAC and you are left with a HAC(k) job.
RE: Heating/Cooling units for residential houses
As soon as I can drive a few ground rods I will have my own weather station up and running and will log solar radiatin as well.
Take the "V" out of HVAC and you are left with a HAC(k) job.
RE: Heating/Cooling units for residential houses
You seemed to take my comments about radiant cooling as if they were applied directly to your local climate. I hope I've been clear that my comments about radiant cooling were "in general", and that there are climates where radiant cooling isn't going to be a useful toolbox item for many applications.
What happens in your climate where active mechanical air conditioning is used which keeps room surfaces (walls, ceilings, floors) at within a degree or two of the air temperature on "normal days", and you get one of your humid events blowing through? Is there enough condensation formed for a long enough period to cause problems in the air conditioned buildings?
RE: Heating/Cooling units for residential houses
In a climate where a humid day is maybe 60F dewpoint, it is almost imopossible to oversize air conditioning to the point of driving up RH to an unacceptable level, as the latent load is just not there.Good example gorund source heat pump sized for a NW Ontario heat load, could be 100% oversized for space cooling but will not drive up RH to an unacceptable level as the mositure is not there in the ambient air.I would doubt an ambient dewpoint on Van Island gets much above 60.
I am presently working out an intermittent ventilation system to keep tropical homes with decent IAQ and low RH. So far I can get a home to hold under 40% RH at the cost of averaging 1200 PPM CO2.
I can make a home hold 800 PPM CO2 at the cost of 68% RH.
Shooting for 45% and 1000 PPM.
I normally keep my own place warmer, was just proving the air tightness which is rivalling R2000 with a sealed attic, and wanted to see how RH held against worst case conditions which I had courtesy of Dean and Felix.
Take the "V" out of HVAC and you are left with a HAC(k) job.
RE: Heating/Cooling units for residential houses
As I stated before, any surfaces that can be maintained below the average human skin surface temperature are potential radiant cooling surfaces- so in hotter climates, where the average accepted comfort temperature is usually in the 76F to 79F range (PMV Values from ASHRAE-55 and other studies), some minor sensible cooling can be realized from radiant cooling surfaces held at 72F to 74F ranges, or lower depending on the local climate and how often the ambient humidity has excursions beyond that. In climates where the average ambient humidity is always going to be above a 73F wet bulb, well, then radiant cooling isn't a good option, and a lot more reliance on air convection for operative temperature control is best.
RE: Heating/Cooling units for residential houses
In the north it is easy to apply vapour barriers at the ceiling plane, on the under side of the trusses, the traditional 'warm side of the insualtion'. Although it is supposed to stop water vapour, it also blocks air.
To apply a ceiling vapour barrier here is prettty much impossible, given that the warm side of the insulation is on top of the insulation in an attic. The trusses do not want to make it easy for you.
Having a cool ceiling with no-practical way of keeping the attic air from contacting this ceiling is NOT WISE.
The way around this is then to seal the attic, not vent it, and then have your insulation above the roof deck. I have done this myself, built four apartments in this manner and I am making quite a study out of it.
The next best thing to do is seal the attic and apply icynene on the underside of the deck.
Combine this with concrete walls and you can be as air tight as R2000, very easy to pressurize, very resistant to infiltration.
Framed walls with fibreglass insulation are just filtered fresh air intakes.
Those acclimatized to the tropics would get a far better return on their money if they installed and ran ceiling fans to cool them by convection. The ceiling plane is the most prone place for air to infiltrate in and is therefore the absolute dumbest place to have a cool surface.
So if you want to use it in a place and get some kind of benefit having a wet dripping ceiling and a predicted mean vote of +3 , knock yourself out.
Take the "V" out of HVAC and you are left with a HAC(k) job.