Hydronic Radiant Floor Heating Design Considerations
Heated floors are the most cost-effective and energy-efficient type of heating since they are clean, quiet, and stylish. They provide more design flexibility (no bulky appliances taking up room), need less upkeep, and are trustworthy and safe.
As with any effective hydronic design, all necessary considerations should be taken into account. Instead of trying to make corrections afterward, it's far simpler to do it right the first time.
Additionally, with radiant floor heating, the aftermath can be a nightmare. Correcting loop lengths, kinks, and leaks typically requires some form of deconstruction because tubing is rarely readily accessible.
The above radiant heating diagram is an example of a multiple-zone radiant floor heating installation. A hot water heater that is already in place is utilized in this hydronic system. ¹
Floor Types
The type of floor construction determined is an important aspect of the radiant floor heating design and process.
Screed Floors
Most screeded floors are created by applying a 65-75mm thick layer of sand/cement mix over insulation. To allow for heat movement in the screed throughout the year, edge insulation should be installed all around the room's perimeter before the screed is poured.
In order to fit the heating pipe inside the screed's thickness, the heating pipe is fastened to the top of the insulation right before the screed is poured.
There are 3 different ways of securing the pipe to the top of the insulation:
● Staples: Staples will offer a reliable fix for the pipe if the insulation you buy is hard, such as extruded polystyrene like Polyfoam or Styrofoam or polyurethane like Celotex.
● Screw Clips: Staples won't grasp the pipe securely enough if the insulation is soft, such as standard density or high density expanded polystyrene like Jablite or mineral wool like Rockwool. Screw Clips should be utilized in this instance.
● System Plates: These plastic panels with molded pipe grippers are vacuum-formed and fitted on top of the insulation. System Plates hold the pipe firmly and uniformly spaced apart.
Fully Floating Timber Floors
These are floors where tongue and groove chipboard or plywood panels are often created to support a wooden floor deck that is supported by panels of insulation. The only thing keeping the floor deck in place is its own weight.
Heat Loss Calculation
Due to the rarity of uniform flooring throughout, block loads often don't function well with radiant floor designs. The completed floor may mean that two equal rooms with identical heat losses may require different supply water temperatures. A room with dense carpeting and heavy cushioning will need hotter water than one with tile or stone.
Determine Tube Spacing
Depending on the kind of space, the BTU/hr requirements, and the installation technique, the majority of residential applications will be 6 inches, 8 inches, 9 inches, or 12 inches. Extruded plates are invariably 8 inches, and basements typically have 12 inches on center. Depending on the room heat loss and how cold you want the supply water temperatures to be, concrete overpours range from 6 inches to 12 inches.
Water Temperature
The temperature of the water returning to the boiler from the tubing circuits must be high enough to avoid the condensing of the boiler flue gas, which will accelerate corrosion of the boiler's piping and internal components and drastically reduce its lifespan. Water returning to a traditional boiler has to be at least 140F to be secure. You should raise the water's temperature significantly before it re-enters the boiler because radiant floor circuits need to supply water at much lower temperatures—typically between 100 and 130F—and because the water will return from the circuits 15 to 25F cooler after transferring heat to the room floors.
Radiant floor heating requires high-quality design and engineering expertise, so if you are considering a hydronic radiant floor design, contact our specialist team to discuss your project.
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