Question:
I’m interested in using a hydronic floor system, for cooling. Presumably there would be one or two central dehumidifiers used as well. The house is in central Virginia. I’m trying to avoid installing forced air A/C (which would only be used 10-20 days a year anyways) in a superinsulated (straw-bale), passive solar house. Comments welcome… a
Response:
> I’m interested in using a hydronic floor system, for cooling. Presumably > there would be one or two central dehumidifiers used as well.
… The main problem is that as you cool air there is a tendency for water to condense. If you cool the air with your floors then the water will condense on your floors and you’ll have cold, wet floors. Due to the fact that warm air rises, you’ll find that even with cold floors you may still have warm rooms. Anthony
Response:
> I’m interested in using a hydronic floor system, for cooling. Presumably > there would be one or two central dehumidifiers used as well. > … > The main problem is that as you cool air there is a tendency for water > to condense. If you cool the air with your floors then the water will > condense on your floors and you’ll have cold, wet floors. Due to the > fact that warm air rises, you’ll find that even with cold floors you > may still have warm rooms. > Anthony
I realize that the floor has to be kept above the dewpoint. Thus the use of whole house de-humidifiers. It is my understanding that such systems are in use in Europe. I’m trying to get more info and hopefully some case studies here in the US (and pref in the mid-atlantic region). a
Response:
> I’m interested in using a hydronic floor system, for cooling. Presumably > there would be one or two central dehumidifiers used as well. The house is > in central Virginia. I’m trying to avoid installing forced air A/C (which > would only be used 10-20 days a year anyways) in a superinsulated > (straw-bale), passive solar house. > Comments welcome… > a
It would be a wonderful way of heating the house. When I build my dream house the bathrooms are going to be heated like that. No more cold feet shock when I step out of the shower! Yay! I’d not bother using it for cooling. There is the condensation problem that the other fellow mentioned, and if you are putting in central dehumidifiers, you need to put in ductwork anyway. Have you considered putting in a whole house fan? Those are far more efficient and are also mighty handy when you burn something on the stove.. –Dale
Response:
- Hide quoted text — Show quoted text -> I’m interested in using a hydronic floor system, for cooling. Presumably > there would be one or two central dehumidifiers used as well. The house is > in central Virginia. I’m trying to avoid installing forced air A/C (which > would only be used 10-20 days a year anyways) in a superinsulated > (straw-bale), passive solar house. > Comments welcome… > a > It would be a wonderful way of heating the house. When I build my > dream house the bathrooms are going to be heated like that. No more > cold feet shock when I step out of the shower! Yay! > I’d not bother using it for cooling. There is the condensation problem > that the other fellow mentioned, and if you are putting in central > dehumidifiers, you need to put in ductwork anyway. > Have you considered putting in a whole house fan? Those are far > more efficient and are also mighty handy when you burn something on > the stove.. > –Dale
Yes. Will have whole-house fan. My strategy is as follows: hydronic heat (geothermal, with water-piped fireplace and solar h2o panels integrated) hydronic cooling (geothermal) two in-ceiling dehumidifiers (house is two main areas, and mostly ‘open’ space) whole house fan for evening cooling when appropriate. walls and ceiling expected to be R40 min. passive solar design, with deep overhangs, mass, appropriate glazing etc. Really the only ‘innovation’ is the hydronic cooling. If you google it, there’s a bunch of pretty good links, but little in the way of case studies. a
Response:
- Hide quoted text — Show quoted text -> > I’m interested in using a hydronic floor system, for cooling. > Presumably > > there would be one or two central dehumidifiers used as well. The house > is > > in central Virginia. I’m trying to avoid installing forced air A/C > (which > > would only be used 10-20 days a year anyways) in a superinsulated > > (straw-bale), passive solar house. > > Comments welcome… > > a > It would be a wonderful way of heating the house. When I build my > dream house the bathrooms are going to be heated like that. No more > cold feet shock when I step out of the shower! Yay! > I’d not bother using it for cooling. There is the condensation > problem > that the other fellow mentioned, and if you are putting in central > dehumidifiers, you need to put in ductwork anyway. > Have you considered putting in a whole house fan? Those are far > more efficient and are also mighty handy when you burn something on > the stove.. > –Dale > Yes. Will have whole-house fan. My strategy is as follows: > hydronic heat (geothermal, with water-piped fireplace and solar h2o panels > integrated) > hydronic cooling (geothermal) > two in-ceiling dehumidifiers (house is two main areas, and mostly ‘open’ > space) > whole house fan for evening cooling when appropriate. > walls and ceiling expected to be R40 min. > passive solar design, with deep overhangs, mass, appropriate glazing etc. > Really the only ‘innovation’ is the hydronic cooling. If you google it, > there’s a bunch of pretty good links, but little in the way of case studies. > a
It is worth a try, the big thing is the management of the system to keep the floor from becoming a condensing surface. If you are still in construction, see if you can add some water loops on vertical wall surfaces, with a drip pan underneath them to catch the condensation, so even if floor cooling doesn’t work out, you still can use the cool water effectively. I thought maybe water loops in the ceiling would be good, but that is where the air is going to be hottest, and if that starts condensing, then you have created an indoor rainstorm. Which would be a bad thing. If you can direct the incoming air to the house through some sort of pre-treatment area, that would be a great place for these water loops to be placed in the summer. even if they do condense, they dehumidify the incoming air and cool it off. Have you looked into those buried pipe systems that pipe in outside air and run it through a long buried pipe and then into the house with a small fan to suck that air into the house? This gives you geo-ambiant air for makeup into the house, allowing you to make the house more airtight elsewhere. –Dale
Response:
remember, that if you don’t want condensation on the floor, you have to dehumidify the air. however if the watervapor should condense in the dehumidifier and not on the floor, this also means your dehumidifier is doing most of the cooling job!! (based on the assumption, that the dehumidifier is one of the (most-common) types based on cooling)
– Hide quoted text — Show quoted text -> I’m interested in using a hydronic floor system, for cooling. Presumably > there would be one or two central dehumidifiers used as well. The house is > in central Virginia. I’m trying to avoid installing forced air A/C (which > would only be used 10-20 days a year anyways) in a superinsulated > (straw-bale), passive solar house. > Comments welcome… > a
Response:
<snip> > the incoming air and cool it off. Have you looked into those buried pipe > systems that pipe in outside air and run it through a long buried pipe and > then into the house with a small fan to suck that air into the house? This > gives you geo-ambiant air for makeup into the house, allowing you to make > the house more airtight elsewhere. > –Dale
Have not… but sounds like and interesting idea – sort of like e cheap geothermal forced air (!). thanks a
Response:
> remember, that if you don’t want condensation on the floor, you have to > dehumidify the air. > however if the watervapor should condense in the dehumidifier and not on the > floor, this also means your dehumidifier is doing most of the cooling job!! > (based on the assumption, that the dehumidifier is one of the (most-common) > types based on cooling)
Good point. I’m having a mech eng do some consulting/number crunching. It will be interesting to ask about this. a
Response:
I saw this tried in a solar underground home in central Missouri a number of years ago. The pipes were there for heating and there was a 65*F spring on the property so 2 +2 added up to the inevitable 5. The floors were wet and ruined a bunch of carpeting. They ended up doing, somewhat, as someone else has suggested by running the water through (believe it or not) a pair of truck radiators with several small solar fans to push the air around. The radiators put off several gallons of condensate a day (I think) but it was no problem because it was all happening in the utility space where it was easily controlled. Last I heard the home has remained ultra low grid power use for all these years. Also, they HAD to circulate the air inside and had a centralized de-humidifier that ran almost year ’round. Primary heat was about 2 cords of wood/year if memory serves—for almost 2400 Sq. ft. !
– Hide quoted text — Show quoted text -> I’m interested in using a hydronic floor system, for cooling. Presumably > there would be one or two central dehumidifiers used as well. The house is > in central Virginia. I’m trying to avoid installing forced air A/C (which > would only be used 10-20 days a year anyways) in a superinsulated > (straw-bale), passive solar house. > Comments welcome… > a
Response:
This is kind of what I wanted to do. Place one tank under ground with hoses to a pump unit. Place a batch solar collector to my hot water line and to the pump unit. The batch water heater will have three sections so it can be set so that during summer it can make just enough hot water for DHW use. During winter it can be set to provide both DHW and hot water to the pump. The pump sends the hot or cold water to an automotive radiator inside an old window air conditioner. The fan draws air over the radiator and either heats or cools it. The advantage I see is that the condensation would be outside. The case would have to be insulated. Any ideas on doing it this way?
– Hide quoted text — Show quoted text -> I saw this tried in a solar underground home in central Missouri a number of > years ago. The pipes were there for heating and there was a 65*F spring on > the property so 2 +2 added up to the inevitable 5. The floors were wet and > ruined a bunch of carpeting. They ended up doing, somewhat, as someone else > has suggested by running the water through (believe it or not) a pair of > truck radiators with several small solar fans to push the air around. The > radiators put off several gallons of condensate a day (I think) but it was > no problem because it was all happening in the utility space where it was > easily controlled. Last I heard the home has remained ultra low grid power > use for all these years. > Also, they HAD to circulate the air inside and had a centralized > de-humidifier that ran almost year ’round. > Primary heat was about 2 cords of wood/year if memory serves—for almost > 2400 Sq. ft. ! > I’m interested in using a hydronic floor system, for cooling. Presumably > there would be one or two central dehumidifiers used as well. The house > is > in central Virginia. I’m trying to avoid installing forced air A/C (which > would only be used 10-20 days a year anyways) in a superinsulated > (straw-bale), passive solar house. > Comments welcome… > a
Response:
> I’m interested in using a hydronic floor system, for cooling.
Sounds doable. >Presumably there would be one or two central dehumidifiers used as well.
Dumping the latent heat outdoors… >I realize that the floor has to be kept above the dewpoint…
Sure. Ceiling fans and thermal mass and night ventilation can help. You might try some numbers… Nick
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