A Do-It-Yourselfer retrofit heating system designed and supplied by NRT, combining baseboard, two types of joist-mounted radiant heat, an oil boiler and an NRT Control Board.

There is a Photo Gallery for this project.

Download a full size PDF of the Tomashek design drawings here.

Ed had done his homework. He researched radiant for a long time, and his neighbor and friend had recently been burned by a Vermont radiant supply company, so he knew he had to be careful. After having looked locally for a designer and/or installer, Ed's neighbor had found us, and we were already planning to help bail him out of his predicament. So, we decided to kill several birds with one stone, and Rob traveled to western New Hampshire to make some deliveries to other clients, and to check out Ed and his neighbor's systems.

Ed wanted to do a retrofit; he had been heating his home with a wood stove for 15 years, and was tired of back rooms being cold while they roasted in the great room and kitchen... and of hauling wood all winter! The first floor's joists were accessible from beneath, but the second floor only had a few chases we could use, so it was immediately determined that radiant could only be installed on the first floor. The basement had very modest heat demands, and was not deemed as critical as the first floor as well, so instead of undertaking a heck of a retrofit down there, it was settled that the basement and second floor would use baseboard heat, and the first floor would use joist-mounted radiant.

Well, upon looking at the house, immediately we were dubious we'd be able to do it with radiant alone in the main room. We had a two-story cathedral area, with large amounts of glass, a big chunk of floor space taken up by a large wood stove and hearth, and nearly no wall space available for supplemental. To top it off, Ed had wood floors in there, and we were in extreme northern New Hampshire, so it gets COLD! It looked like we weren't going to be able to get Ed to the dream of wood-less heating without wearing sweaters in the winter.

However, after we did the heat load calculations and took a hard look at the situation, we realized that we were at the limits of what the floor could handle, but the situation was doable. However, extruded aluminum heavy-gauge plates were absolutely required in the main room and master bathroom, or we just couldn't make it. That was fine, but the rest of the first floor rooms really didn't need that kind of output, and would have shut themselves down all the time since they needed much lower water temperatures to heat than the main areas. Since radiant is most comfortable when we can operate it as near to continuously as possible, that wasn't a great situation; we don't want noticeable "on-off" periods, we want the room to be continuously warm! Plus, extruded plates are expensive, so we'd hate to spend Ed's money on them just to have them shut off all the time because they were too strong for the lower-load areas. We could have counteracted that by adding another mixing station, and creating a two-temperature radiant system, but that would have added even more to the cost of the system, plus a lot of unnecessary complexity to the system plumbing and wiring, and more components that could eventually break down.

So, we took a hard look at the numbers. We found that if we did the low-load rooms with lightweight plates, that they would operate at the same water temperature ranges as the heavy plates in the high-load areas. We didn't need a second mixing control, and we could save money on the plates, and still achieve a more constant operation in the lower-loss rooms! Of course, with lightweight plates we have to think about the possibility of expansion noise, however we knew that we could make sure this was not a problem with our control strategy.

The actual tubing install wasn't the easiest either, since Ed had a ton of non-standard joist spaces in there. However with a few rounds of communication, we were able to create a tubing layout for him to address the worst of the issues. I bet Ed wishes we could have ground off all of his flooring nails for him too, but we haven't gotten that up on our Services page yet ;)

For controls, we knew we wanted to be able to use outdoor reset to run the boiler cooler when possible. This would increase cycle lengths for the baseboard areas, making them more comfortable, it would run the boiler more efficiently, and we needed boiler protection to make sure that radiant return water temperatures didn't shock the boiler. We needed to be able to give priority to domestic hot water demands as well, so the heating system didn't make it hard for his boiler to recharge his hot water storage tank during high domestic usage periods, like the morning showers. Finally, whenever we are using radiant with conventional boilers, we know we need to mix the radiant water temperature down, since the boiler kicks out a water temperature far too hot for the radiant floors!

There are many ways to mix, but the best way to do it is to vary the radiant water temperatures along with the outdoor temperature, and it's even better when we can read indoor temperatures too to provide "indoor feedback". Especially where lightweight plates are used in joists, this is very important. Without being able to drop the radiant water temperature, the only thing you can do is turn the system on or off. Especially when it's warmer out, this means the water the pipes can cool down for a long time, then get slammed with water far hotter than needed! This is not comfortable, it's not good for wood floors, and it's also a worst-case scenario for expansion; the bigger and faster your change in temperatures, the more dramatic the system expansion, and the more noise it will make.

So, we used a Tekmar 371 whole-house control to give Ed all the features his system should have. It handles all the boiler firing and protection needs, to fire the boiler optimally under all kinds of different situations. It varies both the boiler temperature and the radiant temperature, using Variable-speed injection, based on outdoor temperature, so when it's warmer out, the system runs cooler, and thus longer, smoother, more efficiently and more comfortably. As a nice bonus, it also gives us indoor feedback, so instead of relying only on outdoor temperature, the system can see what's going on inside, and further adjust its water temperatures to accommodate! This gives us the ultimate comfort system, the best protection for Ed's wood floors, the most efficient operation, and the best protection against expansion noise possible.

But who was going to install the controls? Well, Ed had seen an example of one of our control boards before, and he decided he wanted us to prefabricate his control panel for him, and we did so (pictures in the gallery). Basically this let Ed install his baseboard and floor tubing, saving a pile of money, and left just the boiler and storage tank install for Tony Tec.. nice and simple. Ed connected his manifolds to the board, and Tony connected his boiler and storage tank, a handful of wires were hooked up, and Ed was ready to fill and run his system!

The end result? As Ed says, "We have been in this house for 15 years, and last winter was the first time we were in total comfort. Would I do it again? My wife says Yes!" Poor Ed lost his old outdoor thermostat; he used to be able to tell how cold it was outside by how cold his bathroom floors were!