Need advice for radiant floor heat under carpet
| Posted in Energy, Heating & Insulation on
I’m in the process of building a two story 3400 sq.ft home up north. I want to install radiant floor heating throughout; however the concern is wall to wall carpeting on the second floor. With little kids I don’t like the idea a metal baseboard heat, I’ve seen a product advertised in Fine Homebuilding as a white painted baseboard that is heated. Has anyone have any experience with this product. Also, what is the best way to install A/C with radiant floor. I once saw an episode on This Old House where they installed what appeared to be a very few 6 inch circular ducts in the ceiling. No cold air returns. Also, what could someone expect to be a reasonable difference in cost of a gas forced air versus a gypsum-based radiant floor system?
Replies
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Flyman,
What I would recommend is radiant panels. Check out http://www.veha.com
Myson and Buderus are also manufacturers. You will find the pricing more reasonable than some of the more esoteric approaches.
Chris
*Flyman - RFH under carpeting works fine, just plan for it when sizing the tubing system. Or at least so everyone says... I'm putting in my first radiant RFH system now, so ask me next winter.The Veha radiators/panels seem like a step backwards to me... they command much more space (physically & visually) than baseboard. And for a well-insulated house, the smallest units are too big for smaller rooms.Speaking of well-insulated... depending on how far north "up north" is, a little planning for shading and such in conjunction with a tight house means it will take a couple of days to heat up, so you can escape the occasional hot day with no AC needed.Places like Radiantec promote an "open" RFH system, where domestic water flows through the floors on the way to the faucet, so in theory slightly cools the house during the summer. I'm not sure if this would make much difference... any out there actually doing this?Otherwise, the RF heating is one system; the AC is a completely separate system.
*RFH works very well under carpeting, as others have mentioned, the pad and carpet type imply have to be factored in when designing the layout.You can use a product such as Warmboard as your structural subfloor, the tubing snaps into the recesses milled in the warmboard, the pad and carpeting go directly on top of it. No need for another layer or underlayment. For AC, you can do standard forced air, but often times RFH will be coupled with a high-velocity AC setup like Unico or SpacePak. Those systems use small 2" supply duct with the small round outlets either in ceilings or floors.You will need an air return for your hi velocity AC, but often times one or two returns are used per floor instead of a return per room as with conventional AC.
*Mongo, Thanks for the info. Very helpful. Do you you know about cost? Say the difference of a gas 90+ efficient forced air verses RFH. Trying to factor all the costs...Thanks.....flyman011
*It's tough to specify prices, but some points to consider:You're going to need a gas unit for heat, as well as AC condensers to cool and air handlers to move both the hot and cold air. You could say, very generally, that these are your fixed costs.With a conventional forced air system, one set of ductwork will handle both the heating and cooling.If you step up to radiant heating and a hi-velocity air conditioning system, your costs will certainly increase. You're trading that single run of standard tin ducting for two separate methods...a hydronic pump/manifold/PEX setup for RFHeating, as well as a run of trunk duct and 2" supply lines for hi-velocity cooling.If you're in a cold-weather climate and you're building a house that you plan on living in for some time to come, I truly believe RFH is superior. It can be more costly, but the comfort, to me, is well worth it. Pure opinion there.Conventional AC vs Hi-velociy AC? Some go one way, some the other in new construction. In remodeling, Hi-v is far easier to retrofit. Hi-v claims better dehumidification and less temperature stratification due to better air mixing, as well as being visually less obtrusive due to smaller outlets. Hi-v is also easier to run, as 2" ducts are easier to hide in the framing than large tin ducts. Conventional claims it's quieter and more economical to install.Ballpark? I'd venture a combination of RFH and Hi-v AC would be about 30% more expensive than standard forced air heating and cooling in new construction. The differential could be less, it could be more...much depends on where you're building and who's doing the construction. Someone new to the technology, or someone who's familiar with it.What does "flyman" fly?
*Flyman-Also check out Radiantpanel. 1" thick by 5" tall aluminum. The look is to mimick trim baseboard. http://www.hydronicalternatives.comAlso the water temp can be reset like radiant floor systems.Hope this helpsDave H.
*Mongo, Thanks again for the reply. I'm not exactly sure what you meant by still going to need a gas unit for heat. Are you referring to the mechanical unit needed(ex. boiler,water heater) to heat the water for RFH? What type of heat unit were you referring to? I realize that A/C condensers were needed but didn't factor any type of external heat unit. It seems Hi-v is the way to go... to me it sounds somewhat counter-productive to go to the expense of RFH to run conventional duct work for A/C. By the way, "flyman" flies passenger Boeing 767/757Thanks...
*Flyman, I pulled the "gas unit for heat" from your previous post, #3.1 above, you mentioned "...gas 90+ efficient...".Yes, a heating unit will be needed to heat water for domestic usage (showers, washing dishes, etc), as well as for your RFH. The same unit, properly sized, can be used for both applications. Whether it be electric, oil, or gas fired is often dependent upon your locale. Here in the northeast (I'm in CT), electric is $$$, oil is readily available and more affordable. Gas is available, thought mostly in urban areas.A high-efficiency gas fired water heater can be used to heat your DHW and your RFH. I recommend splitting the system (not co-mingling the water for both applications) with a plate heat exchanger or something similar. Or you can use an oil-fired boiler.The hot water heater or boiler will typically be located in a basement.The air conditioning condensers are completely separate and typically located outside of the house on a concrete slab.I prefer in-floor or under floor staple-up radiant over baseboard-type radiant panels for myriad reasons.How far "up north" are you building? The heating calcs, the quality of contruction, and the size and rambling nature of the house will dictate the number and size of heating units required. Usually one will suffice.
*I'm a novice at this whole thing, but we are building a log home and will put in radiant heat. Its your standard Colorado log home with cathedral ceilings and wall of glass in the greatroom (gotta get those views you know). Anyway, we were planning to do staple up with aluminum fins and have carpeting on top. The guy from the hydronic heat company came out and looked at it and said there was NO WAY we could heat our great room with its high ceilings, lots of glass with a staple up system and still have carpeting. We would either have to change our flooring (more expensive) or go with gypcrete (also more expensive). We decided we'd rather spend the extra money on upgrading our heating system rather than flooring so we are doing gypcrete. Gypcrete is coming in at about $1.50 sq ft installed. I figure upgrading the floor to wood would have cost about that much and we also save money by not having all those fins. Installation will be about 2 billion times easier :-) and we will end up with better soundproofing between the main floor and the basement. Anyway, I mention that just in case you have really high ceilings or a lot of glass. IF you do, you may wish to have someone figure out how to make sure your rooms are comfortable.One other thing, this guy mentioned that a lot of companies will install staple ups in the situation mentioned above, but they'll run the water through the pipes at a really high temperature which makes the floor almost too hot. Just something to watch out for. You only have to run 110 degree water through gypcrete which saves you money on your monthly bills. Hope I'm making sense.
*PDF, Thanks for the reply. I'm curious, you mentioned $1.50 sq ft installed for the gypcrete. Did that include everything (heating unit, tubing, manifolds, etc..) or was that just for the gypcrete/tubing? If not, how many square feet did you install and what did the entire RFH project cost? Thanks..
*I paid a little over $2 a ft for the gypcrete, and it was only gypcrete. No tube, manifolds, etc. The other stuff you mention is all other pricing. My HVAC contractor does rough estimates at $5 a ft for a RFH install.
*That was just gypcrete on a 1950 sq ft area. I thought that was pretty cheap myself. Still not sure what the whole system is going to cost. All I know is that by going with gypcrete and the tubes on top of the floor, we'll save ourselves a LOT of installation time.
*This is a great discussion on RFH. My situation is very similar to Flyman's... Mine is new construction in Central Oregon. Winters are cold with significant snowfall. Summers are hot, but very dry. The area is high desert.My house is about 5000 sq ft. I am sure that I want RFH for the first floor, but I am unsure about the 2nd floor. I do want central AC... so I think I have the choice of either type of heating upstairs.The lower level is about 2500 sq ft total, and includes a 1000 sq ft great room with cathedral ceilings, and also a 2 story foyer. The floors on the lower level are primarily hard surfaces (wood, tile, slate) with a small amount of carpeted areas (about 400 sq ft). I think this is a prefect area for RFH.The second floor is also about 2500 sq ft, is primarily carpeted with the exception of hard slate/tile flooring in the 4 bathrooms. About 1000 of the sq footage upstairs is directly over an unheated garage (if that matters).OK, here are my questions:1) Given that I want central AC (I think two units)... should I use the hot air ductwork for the upstairs since it is carpeted? I do know that that the RFH would be beneficial up there do to the hard bathrooms floors, but I do not know if I would lose too much efficiency due to the large percentage of carpeting2) The first floor heating system is over a crawlspace... so the risk of severe leakage damage is limited. Is there a significant risk of leaks on the second floor causing damage? Should I consider that when choosing forced hot air, or RFH?3) Regarding RFH... I noticed some manufactures also promote driveway snow/ice removal systems. My driveway is small (maybe 1000 sq ft). It is feasible to add RFH type of heating to a driveway? Would this be expensive, or can I reuse the same boiler used for RFH? I assume they use an anti-freeze solution for exterior use... does that mean I need a separate boiler? On a related question... can the same boiler also provide domestic hot water?4) Regarding the central AC... assuming that I go with RFH upstairs, would I be better off with conventional AC ductwork, or would it be better or more cost effective to go with the Hi-V AC systems?Thanks in advance.Jim Pappas
*PDF, where at in CO?And there are other alternatives to what you were given that may save you a bunch of money. Sometimes us Wet Heads get stuck thinking RFH is the ONLY way to heat a house. It is the best. But there are often very attractive ways to supplement it with non-RFH heating methods so you have the best of both worlds at a reasonable cost.E-mail me for more info if interested.BTW, the comment about the high floor temp was true and also wrong at the same time.
*re: #3Not that expensive to install. Megabucks to operate. If you gotta ask you usually can't afford it. It's that expensive. In CO it often adds $500 to $5,000 to the monthly bill.Yes you can use the same boiler. Use a heat exchanger to isolate the rest of the zones.And yes, you can get you DHW (domestic hot water) from the same boile. Just use a side arm water heater with a coil inside it. Ask your heating pro for more details or e-mail me.
*I cannot afford $5K/month to operate a snow removal zone. In the area where we are building, we get a several good snow storms each winter. I have no idea how much it will cost me to have my driveway plowed...but I would guess about $50 or so. I was figuring that it would not cost more than that on a per-storm basis to operate a snow melting zone under the driveway. It would not be running all of the time, just during the snow storms.
*No, it most likely won't cost you $5K in your situation. I was just giving you a range. Forewarned you are so if you still want it I say go for it.
*How much is warmboard vs gypcrete? Which is a better way to go? This is for new construction.It seems that Pex tubing is installed right after the warmboard is installed (prior to framing). Isn't the tubing subject to a lot of damage during the construction process? I plan to talk to my builder about options here, but would like some opinions first./Jim Pappas
*Jim,Here in the Chicago area I was quoted $4.50/sq.ft for Warmboard (Materail only)and $1.50/sq.ft for gypcrete (material and installation). Here is a web page that I found that may be useful for other alternatives. http://climatecadvanced.com/installation/retrofit/retrofit.html
*Ed - does that $1.50/ft2 include the sub-floor to hold up the gypcrete? Although still looks like a significant difference.
*Jim, It did not include the price of the sub floor. 3/4 T&G ply is about $1.60/Sq.ft(material only). I would have strongly considered the warmboard since I'm doing RFH in an existing house if not for the high price. My concern with Warmboard in new construction would be the added cost the framers will charge to put it down and the damage factor during construction. Keep in mind that the Gypcrete is aprox 15 lbs./sq.ft for an 1-1/2" pour so you may have some added cost beefing up the floor to support the weight. If I was building a new house I would go with the Gypcrete. Just my personal opinion.
*Our builder told us he would charge more for installing warmboard. Given the prices, I think gypcrete makes the most sense. As I mentioned above, that is what we are planning to do. What temperature do you run the water when using warmboard? In other words, is it as efficient as gypcrete?Paula
*Ed W, After I posted my above message, I had to wonder about the $1.60/sq ft for 3/4" plywood. That number doesn't seem quite right. A 4x8 sheet of plywood is 32 sq ft. At $1.60/sq ft, that would make a sheet of plywood $51. I know its expensive, but not that much. Am I mixed up in my thinking? I am blonde, so I hope I'm not missing something obviousPaula
*Paula, my mistake, it's more like $.62/sq.ft. It's around $20 for a sheet of 3/4 T&G ply. For more information on Gypcrete you may want to contact Maxxon Corp. They are the manufactures and are very good about answering any engineering questions. What ever you do make sure you get a good qualified hydronic heating contractor. There is alot more engineering that goes into a hydronic system than forced air. Try to find someone that does nothing but hydronic heat. Best of Luck with your project. -Ed
*He did his division upside down... Hope he builds right side up!... Jusst kidding!1/1.60=.62!near the stream,aj
*Instead of using gypecrete, you might try using a Youker mix of lightweight concrete. It's heavier than gypcrete, but lighter than normal concrete, and a lot cheaper than gypecrete. The floor joists might need to be beefed up a bit to support the extra weight, but the cost of beefing up the joist's should be cheaper than using custom installed gypecrete. Also, your local concrete plant should be able to mix it up for you. Buy Dan Holohans book "Hydronic Radiant Heating for the non-engineer installer" $20, it has the recipe for the Youker mix as well as lots of info about radiant heating systems.
*Ed, we have hired a hydronic heat company to design the system and hook it up. (Anyone read Dan Holohan's book? The owner of this company is mentioned several times in that book.) We will be doing the grunt work, and they will be the brains of the operation. Also, Wet Head Warrior is not too far away from me if I get into too much trouble. :-)Anyone know what temperature you run the water through the tubes when using warmboard? Just curious, that's all. I'm sure it all depends on different situations, but I'm just wondering if the temp is hotter or about the same as gypcrete.
*Paula,I think a lot has to do with your finish floor covering. You may have to run hotter with carpet than say tile or stone. But most of this should be determined in your heat loss calcs. There should be specs on the BTU/sq.ft output of both products. There was a very knowledgable sales rep for warmboard on this site that maybe able to answer all your questions about warmboard. Do a search for warmboard on this site. -Ed
*Underfloor staple up runs 120-150 degrees with hardwood floor depending on outside temp. Warmboard would run lower I would think...Closer to 100 degrees... 120 max. Btus are not a problem when your home is insulated well.near the stream,aj
*Paula:Regarding your question about Warmboard's water temperatures, we find that Warmboard typically runs about 20 degrees or so lower than what Wirsbo's software calls for in a regular concrete slab. Gypsum-based lightweight concrete is more porous than regular 'crete so it takes hotter water than that to transmit through it.Alternatively, to run the water at the same temperature in either concrete or Warmboard, you would need to place the tubing at 8" OC in the concrete to equal Warmboard at 12" OC.Save hot water or save tubing.At 12" OC, the concrete will "stripe" upon heat-up to the tune of about 7-9 degrees, whereas Warmboard will stripe a maximum of 3 degrees for a very short period of time. Very quickly, Warmboard evens out to 0-1 degrees.If you provided me with a sample heat loss number and the floor covering for that area, I could look up the necessary water temp and BTU output for you. Or I could sent the brochure that has the table on it. Write to me at my e-mail address for more info.Barry E. [email protected]
*Warmboard water temp examples: One-hundred degrees = 20 BTU/ft2/hr with a floor covering R-value of 1.0.Eight more degrees = 25 BTU/ft2/hr with same floor.Maximum floor surface temperature of 85 degrees (some hardwood folks might say 83 degrees is max) produces 35 BTUs of heat with 125 degree water (same floor).Hope this helps.Barry E. LaDukewww.Warmboard.com
Just want to give another option for a heat exchanger:
http://www.brazetek.com/products
You can also find a plenty of products for assembling a radiant floor heating system here:
http://www.pexuniverse.com
You're pretty close to getting yourself into DHW.
Might be a little late for the OP since his post was 8 years ago!!