# Warmboard Radiant Heat



## Bodger (Oct 23, 2008)

I posted this in the HVAC section but only got one response. Sorry for any redundancy:
Has anyone ever used a product called Warmboard? It's a 1 1/8" plywood sub-floor with grooves routed into it and has a top layer of thin sheet metal that is embossed into the grooves. 1/2" PEX is then snapped in and the hot water flows through.

What I don't like about it, apart from the dificulty of installing it as sub-floor and the expense of $175 per sheet, is that the PEX has to be placed right after subfloor goes down (so PEX is in and under interior wall sole plates) and then endure the remaining months of construction, some of which is done by buffoons who can't see an orange pipe to save their arses and drill through it anyway. Not to mention debris in the channels and so forth.

Just wondering if anyone else has ever worked with this product.


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## Aframe (Mar 24, 2008)

I looked into it for a second floor addition, but decided against it for many of the same reasons. Never got to pricing it out so that was not a factor. 


I think a good place for it would be for a large open rooms where you don't run the risk of it being damaged with walls going up. As long as you could get into the floor from below.


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## Bodger (Oct 23, 2008)

Aframe said:


> I looked into it for a second floor addition, but decided against it for many of the same reasons. Never got to pricing it out so that was not a factor.
> 
> 
> I think a good place for it would be for a large open rooms where you don't run the risk of it being damaged with walls going up. As long as you could get into the floor from below.


 It could be accessed from below, but you'd have to isolate a leak area and then cut through the bottom of the plywood. The tubing channels are marked underneath, I'm assuming for that reason and also so you'll knpw where the tubes are from below to avoid damage in the first place.
I think I'll stick with the more conventional radiant heat floor methods in the future. AFTER the framing is done, and everything else that can be.


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## JenRan (Jun 20, 2007)

Watched warmboard going in on a house next door to one I was building. Looked time consuming as you have to follow the predetermined layout. I also don't like the fact that tubes are there for the duration. I envision the drywall screw making its way next to a tube and puncturing the tube.

Found this product on the internet, never had a chance to use it but it looks like a good alternative:

http://www.gcsradiantheat.com/


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## genecarp (Mar 16, 2008)

Did a similar system some years ago, it was only about 5/8'', not a subfloor, we used it as a second layer. it was the best product choice for our application, we installed braz walnut over the radiant. A bit hairy nailing the floor, but a nice system overall.


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## wyoming 1 (May 7, 2008)

You donot have to run warm board under your walls you can have it set up room by room so you can have different zones. With Warm board they recomend using alpex or kitec it has the aluminum in the tube.I believe they also make a router tip so you can cut the radius in the end of the run so you do not have to run it under the walls. We usallly do an under the floor install using aluminum plates but I just went and looked at a solar heat job the other day and they had used warm board. I have a friend that sells radiant heat systems I will call him and get some more info and post back


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## Bodger (Oct 23, 2008)

wyoming 1 said:


> You donot have to run warm board under your walls you can have it set up room by room so you can have different zones. With Warm board they recomend using alpex or kitec it has the aluminum in the tube.I believe they also make a router tip so you can cut the radius in the end of the run so you do not have to run it under the walls. We usallly do an under the floor install using aluminum plates but I just went and looked at a solar heat job the other day and they had used warm board. I have a friend that sells radiant heat systems I will call him and get some more info and post back


Thanks. I had problems with the Warmboard company itself as well. They were sent project floor plans from which to formulate their layout plan. Very necessary because the routed grooves for the tubing are supposed to be kept away from the sole plates by about 6 inches. 

Warmboard's CAD did not match the plans, their material take-off was incorrect and I got shorted on sheets so I had to wait for a shipment from Sacramento which set back my sub-floor install by ten days. Even if the plan is correct, there is some custom routing that has to be done and they send a template and router bit with a follower bearing. 

Of course there were design changes which meant I had to set sole plates right over the tubing, and then the tile contractor's crew set DensShield and blew a few coarse thread screws right through the tubing.
I just got the system up and running and I'm keeping it on to insure there are no leaks prior to installing the engineered flooring.
All in all, I would avoid this product for use throughout an entire house. Too fragile for the construction going on, and too difficult for morons to avoid with their screw guns and auger bits.


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## wyoming 1 (May 7, 2008)

Thats what I was going to check on I thought they made a router and template but was not positive. Its biggest benefit is it is suppose to warm the house quicker


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## Bodger (Oct 23, 2008)

wyoming 1 said:


> Thats what I was going to check on I thought they made a router and template but was not positive. Its biggest benefit is it is suppose to warm the house quicker


 The faster warm-up is one of their selling points for sure, apparently they tout the sheet metal top layer as the reason why their product is better. I've installed this into a house 1 1/2 miles from the beach, and their is no other HVAC involved, just the radiant heat floors. No AC and no air exchange capabilities as you would have with an FAU. 
I pointed out to the architect and HO early on that anything that heats faster due to a metal top layer will probably cool slower as well. I can see this being a problem in LA where it can be 60 degrees in the morning and then 80 degrees pretty quick. And windows always open to provide ventilation, sounds l;ike a lot of smog dust to clean to me.
Whatever, I'm just a grunt and what do I know. I'm covered in any case, let them go with form over function. I hope they are constantly pleased with not seeing any ducts or mechanical soffits as they clean dust and walk on a hot floor when they should be enjying A/C


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## Aframe (Mar 24, 2008)

"I_t could be accessed from below, but you'd have to isolate a leak area and then cut through the bottom of the plywood. The tubing channels are marked underneath, I'm assuming for that reason and also so you'll knpw where the tubes are from below to avoid damage in the first place._"

I was thinking of access into the joist bays for insulation/wiring etc. had not even thought of trying to patch from below, that would really bite.

"_I pointed out to the architect and HO early on that anything that heats faster due to a metal top layer will probably cool slower as well_."

The layer of aluminum would heat up quickly, but would also loose it quickly too. the main purpose is to spread the heat out so you don't have hot stripes running the length of the room
The mass of the plywood would retain the heat between cycles,

Like you said radiant is def not for "quick" heat


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## wyoming 1 (May 7, 2008)

Here in WY I like the staple up or warm board better than conc or gypcrete incased because it might be 20deg. one day so you turn the heat on well it takes a day to heat up a 4 inch slab the next day it is 65 and you have all the windows open trying to cool this slab down that is just radiant heat. No doubt the conc. install is more efficent in the dead of winter but fall and spring it is tuff to get regulated. We have put in infloor systems with optional base board registers for quicker heat (spring and fall ) but cost goes straight up. Me personally my next house will have radiant floor heat I like it and you can set the tstat at 65 and be warm and toasty.


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## Bodger (Oct 23, 2008)

Aframe said:


> "I_t could be accessed from below, but you'd have to isolate a leak area and then cut through the bottom of the plywood. The tubing channels are marked underneath, I'm assuming for that reason and also so you'll knpw where the tubes are from below to avoid damage in the first place._"
> 
> I was thinking of access into the joist bays for insulation/wiring etc. had not even thought of trying to patch from below, that would really bite.
> 
> ...


Makes sense. I think I'm somewhat against it because of where we live, it just doesn't get that cold out here. I've had winters in LA when I never ran my heat at all. Fireplace in the living room, dogs and woman in the bed at night, never felt like a needed a warm floor to wake up to. But I grew up in southern Ohio, cold means cold back east.


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## wyoming 1 (May 7, 2008)

Yeah if you have to put in all the duct and cold air returns for forced air it doesn't make sence to drop anothe 20 to 30 for radiant southern ohio I grew up in northern Ky


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## Harvey Ramer (Mar 8, 2009)

*Forget about warm board!*

Warm board offers a host of problems in a radiant system. Let me start off by a little bit about Radiant Heating. 1st. step is to determine the heatloss of each room. Then you figure the BTU/h of each sq' of floor surface. Having those calculations you can now determine the tube spacing, tube sizing, water temp and gpm needed to heat the room. Warm board takes the heat out of water very quickly meaning you have to be very carefull about water temps so as not to overheat and damage the floors. HARDWOOD FLOORING MAX TEMP 78 DEGREES!!! A different water temp for every room will ad thousands to the cost. Also warmboard dissapates the heat so quickly that it results in uneven heating. Example. A typical Radiant loop is calculated at a 10 degree water temp drop between supply and return. With warmboard this jumps to a 20 degree drop. So with a 300' loop coming into a room and weaving back and forth till the other side and then exiting guess what happens. The floor tends to be warmer on the one side of the room. The only time I would use this type of application is in a retrofit where it is impractical to do it any other way. It is just to expensive and offers a host of problems most of which we haven't even discussed. It is apparent to me that Warmboard knows very little about Radiant heating but is merely in the business of selling grooved boards. 

As to your concerns about overheating a room with a slab application this can be overcome with a neat little device called an OUTDOOR RESET. This consists of a electronic mixing device with an outdoor tempature sensor. As the air temp rises outside it atomatically lowers the Radiant water temp. This not only cures the fall/spring problem but also makes your system 5% to 30% more efficient.

Don't turn your Radiant system into a nightmare. A common sense and practical approach is always the best. I have found that attaching tubing to the under side of the subfloor with heat emission plates works quite well and is very cost effective.


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## Luke (Nov 8, 2006)

*Warmboard*

We used it one time about five years ago and I'm not looking forward to the next application - if there is one. In addition to the problems others have noted in their responses to the original post, carpet tack strip installation is a scary proposition. Our project consisted of a large master bathroom and a master closet that measured over 16' x 24'. The closet had tons of built-in cabinets, shoe storage units, hanging clothing units, etc, that all had to be installed after the warmboard was installed and it was a nightmare. It seems like a great idea but in actuality, there are other systems that work just as well if not better and are substantially easier and more cost effective to install.


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## Terry Alsberg (Sep 9, 2009)

*Warmboard info*

Forgive the length of this reply but this thread raised so many issues, especially by Harvey Ramer, that I thought I would try to address them all in this reply.

Thermodynamically, the job of a radiant panel is very simple. It conducts heat from the water in a tube to the surface of your floor ... period ... end of sentence. This why in the radiant industry, conductivity is king. Aluminum is obviously an excellent conductor and wood is obviously a poor conductor which explains why frying pans are made of aluminum to spread heat evenly and efficiently but often have wood handles to stop the heat from reaching your hand. The staple up systems that Ramer seems to think are the best are in fact the worst performing systems precisely because installing tubing under a horrible conductor such as wood subfloor is a bad idea. Yes you can drive limited amounts of heat through wood which is why staple up systems can work to some degree. But they do not work nearly as well as a radiant system could or should. 

It is a fact of thermodynamics that as conductivity goes down, water temperatures must go up. Don’t take my word for it, check out the performance charts on page 234 of the Uponor/Wirsbo design manual 5th edition 2004. In order to get 20 btuh/sf (a common heat loss in the US) out of a bare hardwood floor at a 10 degree delta T you will require 142 degree water to achieve a 65 degree inside temperature. And if half of those floors are covered with area rugs which is not uncommon, the required supply water temperature goes up to 175 degrees which is 10 degrees above what Wirsbo recommends for their tubing. If you like your home to be 70 degrees inside, you will need 180 degree water! Warmboard would require 95 degree water for bare wood floors and 130 degree water with 50% of the floors covered with area rugs. And you save 1% of the fuel cost to heat water for every three degrees that you lower the water temperature. Which means that Warmboard will save about 15% on your heating bills year after year, decade after decade. This explains why the top engineers at the top universities such as MIT and many others choose Warmboard for their Solar Decathlon homes. The Solar Decathlon is the US Department of Energy’s proving ground for the best in efficient building technologies.

Ramer claims that Warmboard sucks too much heat out of the tube early on in a loop which he mistakenly believes necessitates a high Delta T (20 degrees) down the length of the tube. This might be true if we ran the same water temperature as a terribly inefficient staple up job. The beauty of Warmboard is that it does not require such extremely high water temperatures. Once you lower the supply water temperature about 45 degrees, the rate of flow of heat from tube to panel matches the staple up system. Most Warmboard systems have 10 Delta T’s or lower. My personal home operates at about an 8 degree Delta T.

Ramer also misstates that Warmboard requires numerous different water temperatures from room to room. This is simply untrue. Warmboard has been available since 1998. With over 20,000,000 square feet of Warmboard in service, which represents over 10,000 installations, including two installations in Antarctica, and hundreds in Alaska and Canada, I don’t know of a single house that required more than one water temperature to run its Warmboard. You simply set the water temperature to meet the needs of the highest heat load room and then let the thermostat and zone controls automatically cycle the water flow on and off as required in the lesser demanding rooms to match their heat load. And no, the floor does not go from being suddenly hot to suddenly cold. Cycling the water flow on and off is normal in most radiant systems and it merely causes the surface temperature to nudge up and down by a few degrees over perhaps about fifteen minutes as needed to adjust output to meet changing demand. Because of its fast response Warmboard is able to provide more accurate temperature control. In fact, besides the requirement of energy efficiency which is just one component of the Solar Decathlon, accurately controlling interior temperature for ideal comfort is another important judging category in the competition. Again, the best engineers at the best universities choose Warmboard for its ease of control and ability to provide constant comfort.

Regarding the 78 degree limit Ramer alleges for hardwood, I am not aware of any such limit. Some but not all hardwood manufacturers do not like to see their hardwood go above 80 degrees, but the Hardwood Flooring Council limit is 85 degrees. Let’s apply a little common sense. Air conditioning has been common for only about 50 years while hardwood has been used for floors for well over a thousand. In most parts of the US it gets to 90 degrees or above for extended periods in the summer which means that the floors in a home without air conditioning routinely get to 90 degrees or above. And if the floors are under a sunny window they routinely get to about 110 degrees for at least a few hours every day. For those of you with infrared temperature guns, check this out for yourselves. How did all the hardwood floors survive these temperatures for thousands of years? Quite nicely in most cases. Fortunately most radiant systems have surface temperatures in the 75-80 degree range. A 20 btuh/sf load (common for most well insulated modern homes in the US) requires an 80 degree surface temperature to reach a 70 degree interior temperature regardless of radiant panel type that is under the floor. Warmboard works particularly well with hardwood for a variety of reasons. Our installation manual lists over 30 manufacturers of hardwood, including some of the premier supplier such as Carlisle, Launstein, Junckers, etc. that are happy to warrant their hardwood to 85 degrees when installed over Warmboard.

Regarding job site workability, all radiant systems have their advantages and disadvantages. Personally, the thought of crawling around in the dirt in an 18” crawl space while stapling up tubing and emission plates seems like a royal pain in the butt. And even if there is 8’ of head room to work in, the prospect of climbing up and down ladders hauling heavy tools, while working overhead and lacing 300 feet of tubing back a forth in joist bays and through holes in joists doesn’t seem much like much more fun. 

Warmboard has different challenges. Yes the carpenters have to follow our plans, but isn’t that what carpenters have to do all day long with virtually every part of a construction project? Paying attention to plans as you nail down Warmboard may add a couple of man-hours to the entire subfloor installation process, but that couple of hours is much less than the labor for virtually any other radiant panel system. To Luke, who found it scary to nail carpet tack strips and cabinets to Warmboard, the 5/8” o.d. tubes are 12” on center which leaves 11-3/8” between the clearly visible tubes to nail anything you need to Warmboard. Thousands of tradespeople have managed to miss the tubing. In fact, most other systems, especially staple up, have the tubing hidden thereby increasing the risk of damage. And yes, if you have careless workers you can damage a tube, but most don’t. If you do manage to put a nail in a tube despite the clear visibility of the tubes, well the repair takes about fifteen minutes and no it is not done by cutting out the subfloor from below. It is easily done form above by cutting the tubing at the damage, prying the tubing out of the groove, installing a coupler and putting the repaired length of tubing back in the groove. To Bodger who worried about ventilation, no hydronic system (which includes all radiant floors, wall radiators and baseboard heaters) provides ventilation. In areas where it is not appropriate to crack a window, heat recovery ventilators are routinely used

At the end of the day, we believe that 20,000,000 square feet in service is a powerful statement that most contractors find it easy enough to use and prefer the challenges that Warmboard presents to those that other systems present. We have numerous contractors who have done more than a dozen Warmboard jobs and would use nothing else in part because they are familiar and comfortable with its installation. But most importantly, the comfort and efficiency keeps their clients happy which means Warmboard helps them build their reputation for quality which helps them get that next job. Warmboard is not perfect, nor is any other building product you can use, but when it comes to comfortably and efficiently heating a home we stand atop our industry.


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