We are planning on using radiant floor heat in our new house. We love the idea of warm feet and the reduced circulation of dust. One of the disadvantages of choosing RFH is that we’ll need a seperate system for AC. That means seperate delivery systems (ducts and PEX) and seperate mechanical systems (a boiler and an AC unit).
I remember reading almost ten years ago about ground source heat pumps. I thought back then that it might be a slick way to go. That was before we moved to Maryland. Our first apartment here had a heat pump. It was freezing cold all winter, despite $120/month electric bills. Much of the winter here is (at least “was”!) too cold for standard heat pumps to function well. Since then, the idea of putting a heat pump in the Dream House was unthinkable. However, a ground source heat pump might work much better.
(Important point here: I don’t know anyone around here who uses a ground source system. There’s probably a good reason for that. Initial cost, maybe?!?)
Which brings me to my question: Can a heat pump (ground-source or otherwise) be used in conjunction with radiant floor heating? If so, I could use the same mechanicals for both heat and AC, which could offset the additional costs of installing the in-ground heat sinks.
Just curious if these technologies go together. I’d also love to hear any thoughts you might have about ground source heat pumps.
Replies
Do a search on "geothermal" or ground source. Lots of discussion in the past. I have one feeding RFH and a Unico AC system and love it. Plus, there are alternatives to ducts if you want to avoid ducts. In a house I have under design, we're feeding pex through the walls to supply a fan coil in each room needing AC. Some details on http://www.multiaqua.com/ . Plus, there are gas powered units that can make hot or cold water, and then tie in to RFH or fan coils.
Where are you in MD JJ? There are a lot of Geothermal systems around. You just need to ask the right people. I'm in Carroll County and could put you in touch with a guy that does radiant and HP both. (He installed my new heat pump this winter).
The primary mitigating factor around here for geothermal systems is cost. There is a lot of excavation involved in putting in a closed loop system. Hence $$$$$$$. My uncle lives on the Eastern Shore, endless supply (or seemingly so) of freshwater from a cheap to dig (in sand) well. His open loop system was much cheaper than a closed loop system on the western side of the mighty Chesapeake.
You might want to reconsider the Heat Pump. I suffered through 5 winters with an antique heat pump till it finally died this winter. had a new one installed. A 12 seer American Standard unit with variable speed air handler. I was down on heat pumps and hesitant to replace with the same. But I gotta tell you the difference between the new and old units is like night and day. My family is actually comfortable now. No more chilly mornings. Haven't lived through a summer with it yet, but I expect to be happy.
Just my 2 cents (as a homeowner)- but there are some good contractors around that can help you with what you are proposing.
Hey Frontier,
We currently live in Ellicott City and we're going to be building in western Howard County, near Mt Airy. We had a heck of a time finding land. The area is growing fast and both Howard and Carroll Co's are pretty aggressive in setting land aside in agriculural preserve. We were looking for 5 acres for X dollars and ended up with 3 acres for 1.5X dollars.
If you could recommend a good contractor or two, that would be a big help.
To All,
Thanks for your feedback. This sounds very promising. I plan on insulating the house very well, locating the house just north of a pair of tall oaks, and putting the master suite on the first floor. I'm hoping all of these things will reduce the required cooling. These wall units that are fed by PEX lines sound like a pretty slick solution.
I do have a couple of follow-up questions.
How noisey are these wall units? I'm a guy who places a premium on quiet.
Any ballpark info on cost per unit and sq ft capacity?
Are these units typically drained directly through the wall? And does that present an air infiltration problem? Or, are they typically drained to the main stack?
Also, and this is admittedly a crazy idea. I'll have a pair of long trenches dug for 1) untilities from the street and 2) the drainage run to the septic field. Can I bury my loops in those trenches? (I'm almost sure I just asked something stupid. But, if you don't know the answer, it's better to ASK something stupid than to DO something stupid.)
Thanks for all of your input!
Jon
>How noisey are these wall units?
With the compressor and such located elsewhere, they are as quiet as a whisper fan can be.
You most probably cannot share a trench. You can't even do that with phone and cable, for example. Neither co wants to ever have to dig down there and accidentally pop the other guy's line. Liability and all that, in addition to safety issues.
Good point!! They could never reopen those trenches if they were packed full of cooling loops.
"Are these units typically drained directly through the wall? And does that present an air infiltration problem? Or, are they typically drained to the main stack?"
I've seen them done both ways. I've also seen lots of problems draining it right out the wall in terms of insects setting up house in the outlet pipe, and in winter (forced air) the condensate building up icicles/freezing over and blocking drain, etc... If you're just cooling, you won't have the ice problem because no water will be running out in the winter.
running them inside isn't real expensive (cheap flexible tubing). I think you might need an indirect drain to the sanitary though.
Just installed the ground loop for a geo project I am doing. This system will be heating the home with radiant floor heat and the swimming pool thru a titanium heat exchanger up here we do not require air conditioning, of course some people still install it for the two or three weeks we will need it in a year. Clouds suggestion would be the easiest solution, but the fan coil units cost might add up quickly if you want to cool to many areas. In this case you might want to look at pricing out ducting. Another cost to remember when you are costing this out is the fancoils have condensate pans, so you will require your plumber to drain each pan. Here is a picture of the ground loops this is four of the 15 loops that went in the ground. This is the first time posting a pic since the change so lets see how it goes.
Edited 5/20/2002 7:42:13 PM ET by KC
Welllllllllllll.........
If at first you don't succeed.
Do you stand those slinkies upright before you backfill them? The only other one of those I've seen a pict of was done that way.
The fan coils we're using will have a condensate line run through the shotcrete wall of the concrete dome at the same time as the supply and return lines are run. That part'll be simple, though you're right that it must be done. And you're also right that the cost can add up. But at least it offers a non-ducting solution for those who want to avoid ducts.
Cloud
The slinkies were backfilled as you see them. They were backfilled with 6" of sand. There is a good amount of water running along the clay in the pic. so the sand will be saturated with new water (aka. heat) passing by the loops year round.
Now that I have the hang of it. Here is a pic. of the RFH