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Cooling a house without forced air.

BlueGoose

I'm working on an expensive custom home that will be built in a high-end neighborhood located in a northwestern state -- meaning there really are only 2-3 warm months (at most) per year. The client intends to use a hydronic radiant in-floor heating system to warm the house during cold weather. But, now he's wanting to add a forced air system to support air conditioning in warmer weather.

Our client expects to live in this house with his family -- he's reasonably confortable with the passive cooling solutions we've proposed, thinking he and his family would be fine during the warmer months. But, he's increasingly concerned that not having a forced air system will negatively affect his resale value should he decide to sell this house down the road.

Anybody else encounted this issue before? Any good alternatives to a forced-air cooling system?

 
May 21, 08 2:21 pm
Antisthenes

you already had an air handler system for circulation yes?

natural venting, what is the orientation you can cause this effect with a passive solar method if you plan ahead.

May 21, 08 2:37 pm  · 
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quizzical

Antisthenes -- I'm trying to avoid installing either an air-handler or duct work. Currently relying on optimizing orientation, providing deep overhangs, fenestration screening, lots of natural ventilation, whole house fans, etc. Client's not sure that's going to be enough to protect resale value.

May 21, 08 2:43 pm  · 
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Philarch

Can you use Radiant floor/ceiling cooling? I know there is a condensation issue but coupled with a dehumidification system...

May 21, 08 2:52 pm  · 
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holz.box

some nice thick concrete/rammed earth walls would help...

May 21, 08 3:18 pm  · 
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StuntPilot

This Project uses a high-velocity duct system for supplemental purposes. The systems are traditionally used in adding A/C to older structures... it's still ductwork, but it might be small enough to consider.

May 21, 08 4:06 pm  · 
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strlt_typ

so quizzical is also Blue Goose?

May 21, 08 4:11 pm  · 
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quizzical

No ... BlueGoose works here at our firm ... we were discussing this issue this AM and thought we'd post an item here to see what others might have to say on the subject ... he volunteered to insert the post ... he then left on a trip, so I provided the follow-up comment ... sorry ... should have made that clear.

May 21, 08 4:18 pm  · 
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ff33º

Heat pumps , also cool when run backwards.....although, not common....custom radiators can act as a heat sink..this is obviously experimental and not common. For super geeky efficiency, you can also supplement the cooling with geothermal system ( its always 54 degrees down there right). ..and if it is a two story..strategically placed fans can draw cooling from crawlspace/basements..oh wait fans ARE forced air..I dunno..good problem though..

I am curious to see more ideas!

May 21, 08 5:08 pm  · 
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farwest1

From this website: (http://www.toolbase.org/Technology-Inventory/HVAC/hydronic-radiant-cooling)


Radiant Cooling - Hydronic
Keeping homes cool with chilled water rather than chilled air.


Radiant cooling systems rely on chilled water pipes to distribute cooling throughout a building rather than a conventional system that uses chilled air and ductwork. Radiant cooling systems rely mainly on the direct cooling of occupants by radiative heat transfer (heat transfer through space like the sun’s warming effect on an object in its direct path) because the pipes, which are commonly run through ceilings, maintain the surface at temperatures of about 65°F. Through radiative heat transfer, people in the room will emit heat that is absorbed by the radiant cooling surface. To manage indoor humidity levels and air quality, a separate ventilation system to supply fresh air is needed. Due to the ease of controlling water flow, independent control of areas of the home is relatively simple.

There are at least three methods of delivering chilled water in radiant cooling systems. The panel system is the most common of these. Aluminum panels that carry tubing can be surface mounted or embedded on floors, walls, or ceilings. Another, the capillary tube system, consists of a mat of small, closely spaced tubes that are embedded in plastic, gypsum, or plaster on walls and ceilings. Or, similar to hydronic heating systems, a concrete core with embedded tubes can provide the conduit and thermal storage capacity for a cooling system. In each of these systems, the water is mixed with glycol and cooled by an air-to-water heat pump, a cooling tower, a ground-source heat pump, or even well water. Because the radiative surface is typically a whole floor or ceiling surface, the water can be as warm as 65ºF and still provide comfort.

Energy Efficiency

Water movement via pressurized pipe uses less energy than blower fan delivery of air. Energy losses in ductwork are eliminated.

Ease of Implementation

Kind of difficult

With professionally configured and installed units, a radiant cooling system can be used in any climate. However, because of the risk of condensation in very humid areas, proper design and installation is critical. These systems are most economical in desert climates such as Arizona where the humidity is less low. A forced air system, such as an air handler or dedicated fresh air system, may need to be incorporated to remove humidity and pollen. Some systems have a relatively slow system response upon start-up. Once room surfaces reach a desired temperature, however, they tend to maintain that temperature with relatively little extra energy.

Initial Cost No comparable products

System cost will vary with climate conditions. In climates that require dehumidification, the controls and equipment necessary to effectively cool with hydronics will be more costly than a conventional central forced air system.

Operational Cost No comparable products

The preferred installation is ceiling mounted, as this reduces air stratification and facilitates collection of condensation. Radiant cooling should provide a comfortable indoor environment using less energy than conventional forced air systems.

U.S.Code Acceptance

A new and seldom-used cooling method, hydronic radiant cooling is not prescribed in the codes like radiant heating.

Field Evaluations

Not Applicable

Installation

The most efficient installation will be ceiling mounted. The piping network is tied into a heat source such as a heat pump. Coordination among mechanical and finish trades is more complex for a radiant cooling installation than with forced air cooling. Panel and capillary systems can be compromised by trades people or homeowners penetrating the hydronic supply with fasteners.

Warranty

Not Applicable

Benefits/Costs

Due to water’s superior ability to store and transport energy, thermal energy can be transported in water through pipes with little pump power, saving approximately 70 to 80% of the energy used by fans to deliver conditioned air in a building. This alone can reduce the peak-power usage of the air conditioning system by 30 to 45%. Cooling can be more comfortable and zoned cooling is relatively simple with hydronic systems.

In many climates, dehumidification is an important aspect of air conditioning. Radiant cooling systems require exacting design and, possibly, added equipment and controls to assure that indoor environments are comfortable and free from excess moisture that can result in surface condensation.

May 21, 08 5:22 pm  · 
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ff33º


This image shows radiator we made for our 2008 Solar Decathlon House..it is made form reclaimed copper piping and flanks the kitchen sink. I know it is not a "high end " application ..but it works as ..as a cooling heat sink ....the heat pump takes fluid partially heated by the sun..and runs it through the hydronic system in winter..then in summer..the heat pump runs backwards in the summer..cooling the space . For humid clients a drip tray is installed.


...and pardon the bright orange ..that is a reclaimed shipping container we built our house out of...and those people are the tourists in DC.

May 21, 08 5:22 pm  · 
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ff33º

oh crap....can you guys resize that please...dang..I forgot it was huge..

here is another view:





dont look at me I didn;t pick that lamp shade!

May 21, 08 5:24 pm  · 
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holz.box

chilled beams!

...says our mech.

May 21, 08 5:24 pm  · 
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ff33º
Antisthenes

if you have no air circulation system how do you cycle air and pass code?

May 21, 08 5:28 pm  · 
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quizzical

Meta: not to be negative, but while these techniques actually may work in terms of reducing the air temperature in a room, I would be concerned about a few things:

a) any solution that causes moisture to collect on any internal surfaces would seem problematic ... aside from being uncomfortable to walk on (especially in bare feet) damp concrete seemingly would do bad things to carpet and furniture legs over time. Plus, even in a somewhat arid climate, it would seem that mold and mildew could become difficult to avoid or control.

b) if the objective were to avoid installing ductwork, then a dehumidification solution would require, what ... a standalone dehumidifier inside each room ... seemingly requiring lots of energy and producing a fair amount of noise ... plus, there would need to be a way to remove the collected condensate.

May 21, 08 5:28 pm  · 
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xtbl
May 21, 08 5:37 pm  · 
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Philarct

ff33
when did that take place?
i couldve went

May 21, 08 5:44 pm  · 
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Doug Johnston

you could install a geothermal system with a water-to-water heat pump, and fan coils in every conditioned room. if you have higher-power fan coils (like 3ton) running at very low speeds you can heat each space with little or no ductwork and using much less energy. not a cheap system, though.

In hot/humid climates this type of system will also dehumidify at the same time due to increased condensation on the fan coils (collected in drain pans and condensate lines - both standard options on fan coils).

use 2-pipe fan coils with direct drive motors, drain pans, and condensate lines.

Call Mac Word at thermalflow.net and ask him about this type of system - he can custom-build all your units at competitive costs but with higher efficiency. Its a system developed by Myron Katz, and Mac built Myron's system and has since improved upon it. Shipping of the units from texas could be expensive, though.

May 21, 08 6:44 pm  · 
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ff33º

Philarct

...back in oct 07..we set up the house on the Mall....the thing that is so cool is that..one of our engineers came up with this hair brained scheme to use large storage tanks to store all the heat and all the "cold" generated by the heat pump..they are like thermal batteries...when it is too hot, the house use the cool tank..when it is to cold ...it uses the warm tank...the sole distribution is the radiator...it radiates heat or sucks heat out o f the space depending on the season..also we have a thermal collection system under teh array...a simple idea, that not so many ppl think of..



meta... desiccant systems are the holy grail for inventive mechanical engineers ..if you can make it work , you'll be rich.

May 21, 08 6:47 pm  · 
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Doug Johnston

also - if you install a desuperheater on the heat pump you get free hot water during part of the year.

You could also look into solar thermal panels to create hot water for the radiant floors. This might not be cost effective if its not a sunny area.

sorry - just re-read your post and somehow I got mixed up - you're looking for cooling. definitely look into the system i described above - its heating, cooling, and dehumidification all in one. The problem is that its a lot of equipment if you're only using it for cooling a few months of the year.

May 21, 08 6:53 pm  · 
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ff33º

..also, i recommend running the pex through the freezer and wrapping it around the bag of peas in the fridge...

May 21, 08 6:57 pm  · 
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snook_dude

Passive Chimney Vents Should Do the Job if you have enough mass in your building. Cool air sinks Warm air rises. I did work on a house
using this method in Tucson Arizona many many years ago.

May 21, 08 7:09 pm  · 
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