Heating/Cooling units for residential houses 2

[BIPVguy]

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

 

[AbbyNormal]

I got temp, rh , CO2 , ambient conditions logged for quite some time.

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.

 

[GMcD]

AbbyNormal: well you are obviously in a hot climate (like I didn't guess from your previous comments). How do the 75F wall and floor temps act when a humid event occurs? (wet bulbs over 77F-78F as per your photo above? How deep are the water pipes buried?

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?

 

[AbbyNormal]

My comments on radiant cooling were they belong in the right climate and that is one where the ambient dewpoints are not much up beyond 64F. If you have them successfully installed in climaytes like that let's talk about what you did, not how the King of Siam is avoiding a disaster waiting to happen.

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.

 

[GMcD]

Why should radiant cooling be only kept in climates where the ambient wet bulb wil be below 64F? If you found out more about the Bangkok Airport you'd see that the radiant cooling temperatures there are maintained between 72F and 74F with resets for humid period excursions.

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.

 

[AbbyNormal]

Again, good luck to them in Bangkok. The airport terminal will be well pressurized to keep out jet fumes. I do not see the method to their madness to want to employ a design that is just asking for it.

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.