Geothermal, in floor radiant and ?

foolingreensMarch 4, 2005

In our new house we will use DX Geothermal and I would like to use in floor radiant for heating. Question is what to use for cooling.

House will be passive solar with plenty of insulation.

Would rather not use ducts as allergies are a problem with my wife and would like to eliminate blowing dust around.



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If you have a well-sealed home, you will NEED fresh air circulation to avoid suffering from "sick building syndrome", which is very bad for health even if you don't have allergies. I have allergies, too, and was plagued by pollen, dust, etc. in our old homes. For our new home we have a geothermal system using forced air for heating and cooling. We included a HRV in the system, and we filter the air with an Aprilaire 2200 pleated media filter. We change the air in our home every 2.5 hours. This ensures there is no build-up of off-gas contaminants from furniture, finishes, building materials, etc.

If you don't have a well-sealed home, and it is new, you got ripped off. Homes built to modern codes and standards allow very little air infiltration -- nowhere near as much as you need to avoid sick building syndrome. You need air changes for health.

You will need to move cooled air with air ducts. There's no other way. Since we needed ducts to distribute cooled air, we decided to go with forced air heating as well, at the suggestion of our builder. We were skeptical it would be comfortable and nearly dust-free, but the builder and the HVAC supplier did a great job of designing and installing a well-designed system. The only change I would make is to install a split system with separate controls in the basement, and I would use radiant heat in the basement. Our basement is completely below grade, and the characteristics of our home (heat loss, heat gain) mean that the basement heating and cooling needs are very different from the rest of the house. Our main and upper floors are great -- even with forced air, the temperatures throughout our main and second floor remain within 2F, no matter what time of the day or year, and no matter how sunny or cold it is outside. This is a revelation for us -- we couldn't believe that forced air and a 2 story foyer could give us that kind of temperature uniformity with some south facing rooms on the second floor getting direct sun for ~ 8 hours per day, and some north facing rooms on the main floor getting no sun at any time. It shows what good design can achieve.

Relief from allergies requires a lot more than stopping dust circulation. "Living" creates dust, and it will circulate whenever you move. We tried to remove the sources of dust, so we have no fabric window coverings, have carpet only in our home theatre, and use hardwood and tile in all other rooms. (We have a few area rugs for decoration). This combination has worked very well for us.

    Bookmark   March 5, 2005 at 5:22PM
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You can't use radiant "heating" to accomplish cooling. You'll need the ductwork etc for some type of air conditioning if you need to have that.

I'll ditto the need for fresh air in ANY newly built home. Using an ERV does NOT mean sucking in all the pollen etc that causes problems for some people. It mean bringing in fresh oxygen and exhausting CO2 AND moisture in the air from breathing, cooking, showering etc. If you DON'T do this; you are in essence living inside a balloon if it's a tight house.

I spent my first winter in this house with NO ERV, and found out the hard way what it's like to live in a house that's too tight for it's own ( inhabitants ) good. "Stuffy" is one word for it . . . . every time we'd open a door in the winter; there'd be a cloud of "fog" forming . ... the moisture level was so high cuz the place is so tight. Had mold grow in closet corners etc. Being radiant heat with "no" air movement made it worse as the air was stagnant as well as stale. Within hours of installing and turning on the HRV the change was miraculous . . . . it rapidly became obvious that the air in here until then was horrible.

Do NOT go without an ERV of some type; the right one for your place / system; will indeed go a long ways to HELP those things you are trying to avoid . . as well as simply give you much better air to breathe ANY time the windows are shut; heating OR cooling . .. .


    Bookmark   March 6, 2005 at 9:55AM
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thanks for the replies and the comments on the ERV. I had seen cooling panels. These appear to be panels that are built in the ceiling thru which cool/cold water is pumped thru some sort of heat exchanger to cool a room. They are expensive but then you don't need ductwork. Anyone used or seen these?

    Bookmark   March 6, 2005 at 10:32AM
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I've never heard of cooling panels, but that only tells you I don't get out much. :-)

Such panels would have to be very effective at removing the moisture that will undoubtedly condense on their cool surface. Since it is highly advisable to have fresh, filtered and conditioned air brought in through an ERV and circulated through your home, why not use it for your AC?

    Bookmark   March 7, 2005 at 2:15PM
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Obviously someone has not been paying attention to the recent EPA studies on allergins and asthma.

Aa a result of ever increasing uses of synthetic materials in both construction and furnishing, plus our insistance on nearly air tight homes, into which we pour hundreds of gallons of chemicals in the form of cleaners, scented this and polished that, the interior of most homes in America is now 30 to 50 times more poluted than the worst urban enviroments outdoor air quality.

Our local TV station reported that the EPA had done a 60 day study on 500 randomly selected homes in New York, Atlanta, Colubus, Ohio, Kansas City, Mo, San Francisco, Calif and Seattle, Wash.

After 60 days it was concluded that based upon indoor air quality standards the EPA would have issued enviromental health hazard warnings and if they had been industrial workplaces over 40% would have required respirators for prolonged exposure.

    Bookmark   April 14, 2005 at 8:53PM
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Is an ERV generally added to any new HVAC system being installed these days?

How much does that sort of thing cost and is it totally independant of the ground source heat pump.

    Bookmark   April 26, 2005 at 7:01PM
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An ERV is called for, for one simple reason: fresh air exchange with at least a good part of the "waste" heat ( or "cool" ) being recovered in the process. It has NOTHING to do with your source of heat; except that they must play well together; and in fact may be combined in some installations.

It is not related to any new system being installed necessarily; but is a real good idea in any NEW construction . . that is a "tight" place. Some area codes require them, some could care less. But if you've got a tight place, you need one that is properly sized / installed for health reasons.

If you're replacing an HVAC system in an older place; probably not a need for it. In a new, tight place I would not consider NOT having one installed.

They can be integrated with an HVAC system; or can be stand-alone . . . mine ended up being a stand-alone as I have radiant in-floor heat and therefore NO air circulation means. The ERV does the circulating for me; due to placement of incoming and outgoing air ducts.

In a tight place; you need to ensure adequate combustion air for any / all fuel burning appliances. They must have an adequate source of enough volume of freash air to burn their fuel. This is INDEPENDENT of an ERV; which takes air OUT of the living "envelope"; and replaces it with an equal volume of pre-conditioned air. While they both bring in fresh air from outdoors; they are SEPARATE paths . . . and both must be provided for . . .

I happened to buy a Renewaire brand ERV; it fit my needs / layout very well. There are lots of others out there too to choose amongst to fit your particular layout / heating / cooling system . . . .


    Bookmark   April 27, 2005 at 6:37PM
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With a good filter system and the right size and type equipment you can keep the dust down and still have duct work. You will need duct work to exhange the air.

You must start by getting accurate load calculations done on the structure for proper equipment selection and application.

    Bookmark   April 29, 2005 at 11:35PM
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