Currently I am working on three projects that all have radiant floors in some of the rooms. That might not sound that unusual but I do live in Texas and we are going through one of the hottest summers on record – and yet people are asking for radiant floors … that’s because radiant floors are wonderful. I still wonder if I would put them in my house … I am not a barefoot person inside, not sure why but I like to wear slippers. My wife on the other hand hates having anything on her feet and constantly walks around barefoot. I know she would love to have nice warm floors in the colder months so that she could forego socks or slippers – sort of a big deal since our house has concrete floors.
Since I tend to get “wordy”, I thought I would have some G-Man from the Department of Energy describe the different types of radiant floor heat – it won’t be as interesting but you’ll have a firm grasp of what you have to work with.
Air-Heated Radiant Floors
Because air cannot hold large amounts of heat, radiant air floors are not cost-effective in residential applications, and are seldom installed. Although they can be combined with solar air heating systems, those systems suffer from the obvious drawback of only being available in the daytime, when heating loads are generally lower. Because of the inefficiency of trying to heat a home with a conventional furnace by pumping air through the floors, the benefits of using solar heat during the day are outweighed by the disadvantages of using the conventional system at night.
Electric Radiant Floors
Electric radiant floors typically consist of electric cables built into the floor. Systems that feature mats of electrically conductive plastic are also available, and are mounted onto the subfloor below a floor covering such as tile. Because of the relatively high cost of electricity, electric radiant floors are usually only cost-effective if they include a significant thermal mass, such as a thick concrete floor, and your electric utility company offers time-of-use rates.
Hydronic Radiant Floors
Hydronic (liquid) systems are the most popular and cost-effective radiant heating systems for heating-dominated climates. Hydronic radiant floor systems pump heated water from a boiler through tubing laid in a pattern underneath the floor. In some systems, the temperature in each room is controlled by regulating the flow of hot water through each tubing loop.
Out of these three systems, we only use the electric radiant systems. I can’t imagine using the air-heated ones – it seems like something Dennis Hopper would have come up with and wildly inefficient. The DOE tells me that hydronic systems are very energy-efficient but we don’t use boilers in Dallas and I think the DOE is full of baloney. Since we only are looking for “spot heating” (warming just the bathroom or kitchen) instead of “sole source heating” (heating your entire house), we are in a turn-on & turn-off situation … and the cost of running these small areas just a few hours (at most) a day is vastly more cost-effective.
There is also product and installation cost difference; in a typical bathroom we might spend $800 on the electric system where a similarly sized hydronic system might cost $4,000. Despite what G-Man Bill tells me, electric radiant heating systems are the only type we ever use. There are several different brands we specify – Nuheat, Infloor, Suntouch, etc. and they are all good products although I’m not a huge fan of using the mat systems. As far as the degree of difficulty for the different types of installation, I suspect the contractors have their preference as well.
This is a view looking down at a typical electric wire layout (Nuheat and Infloor offer these types of systems). There is a strap (shown below as a gray bar) that you adhere to the sub-floor and then weave the wire back and forth to create your area of coverage. The heat will not extend more than about 2″ from the wire so that is a consideration for the spacing and general layout pattern. The good part about this system is that you can control the exact areas of coverage and the installation procedure doesn’t change for irregular areas.
Another variant on the electric cable and strap system is the electric wire preset into a mat mesh. If you have a really simple layout than this system work fine. Some of our bathrooms run a little (cough, cough) larger and these mats only come in predetermine widths. For example, I have a 7 foot wide area to be covered and my mats will only accommodate 6′ so the solution is to widen the gaps between the mats (boooo). I am over-simplifying things but you get my point.
Another reason I don’t love the mats system is that the area represented in the above drawing just in front of the shower. For this irregular area, you are supposed to cut away the mat mesh to expose the heating wire, and then set the wire in place using … hot glue. What?! The only time you should be using hot glue is for building architectural models or trying to attach your hair piece (I think… might be wrong about the hair piece).
Both system come with a sensor that you connect to the heating wire during installation – it’s called a ‘Loud Mouth” – I’m pretty sure it just blares a tone rather than talking endlessly about the semi-semi-pro baseball league team he plays on and how they got screwed out of making the playoffs for the 4th year in a row and how his batting average is crap but it’s not his fault because Coach has him batting 8th in the lineup and…..
All this thing does is monitor the electrical current in the heating wire during installation. That way, if something goes wrong and the installer accidentally cuts a line, you’ll know it immediately and they will know where to fix the damage. This is a lot better solution than trying to find the problem after the wires have been covered up with the finish floor material.
So there you go – an actual informative post written on an actual architectural product – wasn’t it fascinating and entertaining? Yeah, I know, boring stuff … but I need to know all about these things because clients want them and so far every person who has them in their house is in love with them. I’ll try to make these more interesting in the future.