Hydronic Heat

IBC

The International Building Code - established by the International Code Council - see ICC

ICC

The International Code Council is the largest and most respected organization in charge of regulating the building industry. They are responsible for the International Building Code (IBC). Their evaluation service (ICC-ES) evaluates and certifies the safety and effectiveness of building materials.

Indirect Water Heating

The heating of water with a storage tank using an internal heat exchanger to separate the system water from the house supply water. An external heating source, such as a boiler, is required for this extremely efficient hot water heating system.

Insulation Rating

The number assigned to a form of insulation to denote its effectiveness.

Insulation, Reflective

A type of insulation material employing a surface that reflects heat. Aluminum foil, sheet metal, and paper products coated with a reflective oxide compound are some of the reflective materials used to back insulating surfaces.

Insulation, Thermal

Materials used to minimize the flow of heat in or out of objects, such as steam pipes, refrigeration units, or buildings. Heat transfer through an insulator occurs by conduction or radiation. Although no material can completely prevent this transfer, materials can be selected which give the best insulation for a specific application.

Joist

A horizontal structural member that supports the load of a floor or ceiling.

Jumper

A wire used between two points in an electrical circuit to make a connection and/or to temporarily bypass part of the circuit.

Kilowatt

1000 watts.

Kilowatt-hour

Measurement of electrical energy usage equal to one thousand watts in one hour. National average is about $.08.

Lag Period

The time between when the concrete slab (radiant panel) is warmed by the boiler water and heat is radiated into the living space.

License

A formal authorization granted by a legal agency to perform specific tasks in a project. An inspection or license may be required for the installation of a radiant heating system.

Lightweight Concrete

A concrete that weighs 90 to 110 pounds per cubic foot because of the use of lightweight aggregate. Regular concrete weighs approximately 150 pounds per cubic foot.

Linoleum

A tile or sheet floor covering of ground cork, wood filler and pigment, held together by linseed oil or other binders which solidify, and then backed with felt.

Loop or Loops - (see also circuit)

Hydronic radiant systems heat a home by circulating hot water through tubing placed in evenly spaced layouts under the finished floor of the home. There are limits to the length of a tube that water can be efficiently pumped through. It is accepted hydronic practice to limit the length of any single circuit of 1/2″ tubing to less than 350 feet. Each of these circuits is called a loop. Most homes will have their floor area heated by a varying number of these loops.

Low Mass

Low mass refers to a system where the weight of panel material is specifically reduced in order to speed up the reaction time between when heat is called for and when it is delivered. A low-mass, radiant floor heating system has performance qualities that include fast response time, easy to control room temperatures, and lower design water temperatures.

Manifold

A main header or run of piping from which auxiliary or branch piping is run to distribute liquids and gases to multiple locations. Headers are generally larger in diameter than branch piping. A junction at which various tubing loops meet. Made of brass, copper, or plastic, with a header and several ports to interface with PEX tubing. Designed to install in a closet wall, between the studs, with an access door.

Marble

Crystallized limestone valued in architecture and sculpture for its durability and beauty. Marble is brittle and must be carefully installed and well supported in any application. Radiant heat conducts very well under marble and is often used to remove the chill they are known to have.

MBH

Gas inputs are expressed in MBH, which is thousands of BTU/hour.

Membrane

A thin coating or sheet of material, usually water-resistant, such as the thin polyethylene sheets used to water-proof roof or floor surfaces. Membrane sheets can limit vapor release from concrete once it is heated with radiant heating tubing or electric radiant heating cables.

Mixing Valve

A device used to supply a consistent, lower, pre-regulated water temperature to a radiant system. Mixing valves are most often used in conjunction with high temperature boilers, many designed to heat water to temperatures in excess of 160 degrees. In radiant floor applications, mixing valves do not lower the boiler temperature. Instead, they are plumbed so that the water returning to the boiler from the heated floor branches off to the “cold” side of the mixing valve. In this way the “return” water, after losing much of its heat to the living space, is re-heated to the proper temperature by bleeding small amounts of super hot boiler water into the mixing valve.

Natural Gas

Methane, a gas formed in the earth in oil-bearing areas, that is used to fuel furnaces, water heaters, and radiant heating boilers.

NEC

National Electrical Code.

Net Floor Area

The floor area not covered by partitions, stairs, and other construction features; usable floor area.

Ohm

A unit of electrical resistance.

Ohm’s Law

A series of formulas describing the relationship between current, voltage, and resistance. Current (I) equals voltage (E) divided by resistance ®, or I=E/R. This relationship can be used to solve for any one of these three values if the other two are known. Ohm’s law applies to all electrical circuits, and is therefore valuable in sizing circuit components and wiring.

Ohmmeter

A device for measuring electrical resistance.

On Center (OC) - also OCI where “i” stands for inches

The distance between items as measured from the centerline of one item to the centerline of the next. For example, floor joists that are placed 24″ on center, measure 24″ from the centerline of one joist to the centerline of the next. This measurement is used to determine which size of our RetroHeat product you need.

Open Circuit

An electrical circuit that has a break, or is “open,” so that the current cannot flow through.

Open System

A radiant system integrated into the home’s plumbing system. In other words, the same water that ends up in your hot shower has passed through the floor first. Open systems use one heat source to heat both the floor and the domestic water. It’s an efficient system because one properly sized water heater doing two jobs eliminates the “standby loss” of a second unit.

Perimeter Heat Loss

Heat loss through the perimeter, or outside surfaces, of a building which are exposed to the exterior elements. Effective wall insulation, double-pane windows, and insulated doors can be used to help control this heat loss.

Permeability

A measure of the ability of water to flow through a material, such as concrete.

PEX Tubing

PEX is an acronym for cross linked polyethylene. PE refers to polyethylene, and the X refers to the cross linking across its molecular chains. This type of tubing is used for domestic plumbing and radiant floor heating. Used since 1973, with many billions of feet installed, it is proven to be the most durable and reliable tubing in the world.

Polarity

The direction of electric current flow through a circuit indicating the positive or negative charge of the current. In direct current, there are two poles, one positive and one negative. Current flow is from negative to positive.

Pole

The number of hot wires that are connected to an electrical circuit breaker. For example, a single-pole switch has one hot wire and a double-pole switch has two hot wires.

Pole, Single Pole and Double Pole

The number of hot wires that are connected to an electrical circuit breaker. For example, a single-pole switch has one hot wire, and a double-pole switch has two hot wires.

Pounds per Square Inch (PSI)

Pounds per square inch is a measure of pressure, a load applied by one commodity on another. Fluid pressure, which includes both liquid and gas, is measured in terms of either pounds per square inch absolute or pounds per square inch gauge. This measurement should be considered for insulation under concrete for snow melting systems or radiant heating in new pour construction.

Pressure Reducing Valve

A safety device which supplies the boiler with reduced water pressure from the city supply. The normal pressure setting is 12 PSI. It also maintains the boiler water level should a loss of water occur in the panel.

Pressure Relief Valve

A safety device which releases boiler and system pressure should it exceed a preset level. The normal pressure setting of these devices for the low pressure boiler is 30-45 PSI. The preset level should never exceed the operating pressure of the boiler.

Pressure Switch

An adjustable safety device which prevents boiler operation when the system pressure falls below the preset level, usually 5 PSI. It helps prevent boiler coil and heat exchanger damage by preventing the boiler from firing during an unsafe low water pressure condition.

Pressure Test

A hydrostatic (water) test of the concealed radiant panel used to determine the “tightness” and “leak-free” condition of the tubing. The test should always result in “no loss” of the pressure and be performed in accordance with Code-approved procedures. The introduction of helium, nitrogen, oxygen, or other type of air to pressurize the system for testing is not an acceptable test and will likely result in inaccurate conclusions.

Pressure/Temperature Gauge

A device which monitors water pressure and temperature of the heating system.

Primary Heat

Primary heating systems are intended to be used as the sole source of heating or at least the main source of heating. Ambient Thermostats are generally used for primary radiant heating opposed to a floor sensor that thermostatically controls a system based on floor temperature.

PSI

Pounds per square inch.

Pump

1) A device used to circulate water throughout the boiler and distribution tubing. The unit can be water or oil lubricated. Proper pump sizing is essential to provide adequate heat for the home; 2) A device that raises, moves, or compresses fluids by pressure or suction. Electric pumps are required on all radiant hydronic systems.

Quarter Sawn

Wood that has been cut from a log quartered lengthwise and at an angle of at least 45 degrees between the board face and the annular growth rings. This method of cutting lessens the warpage and shrinkage of the lumber. Radiant heating systems under hardwood should use a quarter sawn selection or a species of hardwood that is resistant to warping and cupping. Plain sawn is the other common cut of hardwood used for flooring yet is not as resistant to warping like a quarter sawn variety.

R-Value

A unit of measure of thermal resistance. The higher the value, the better the heat-insulating capabilities of the material. For example, an 8” lightweight concrete block has an R-Value of 2.00 and a 1/2” sheet of plywood has an R-Value of .63. The concrete block has far better heat-insulating properties than the plywood. This unit is used to find the ‘heat-loss calculation’ for a home so that preparations can be made to properly heat a home. radiant heating systems need low R-Values for carpet pads to allow the heat to pass through it and high R-Values are encouraged everywhere else.

Radiant Barrier

Generally a paper thin, pure aluminum material used to reflect 97% of the infrared heat spectrum back up to the heated floor.

Radiant Baseboard

A heat distribution device containing hot water inside a cast-iron or copper-finned radiator that runs along a wall’s baseboard.

Radiant Heat

A type of heating that warms objects instead of air, the floor being the largest object, to heat a home. The air in the room is warmed when it comes into contact with the warmed objects. Heat loss is reduced and the radiant heat remains in the lower part of the room, warmer near feet level and slightly less so at head level, creating the perfect climate for comfort.

Radiant Operating Temperature

The floor temperature should never exceed 85°F.

Radiant Panel

The mass of concrete or other material which, when heated, stores and releases radiant heat energy into the living space. All objects, people, furniture, walls, etc., are warmed by absorbing and transferring the radiated energy. All areas within the living space are evenly heated.

Radiation

The transfer of heat by direct rays from your body to cooler objects around you.

Radiator

A cast iron heat distribution device containing hot water or steam that can be a free-standing unit or recessed into a wall.

Recovery Rate

Basically, how fast a water heater or boiler can heat water. Recovery rates are generally measured by how many gallons of water can be raised 90º in one hour. If a water heater, for example, stores 50 gallons of water, a recovery rate suitable for radiant heating would be the ability to heat 1 1/2 times its storage amount within one hour. In other words, it could heat 75 gallons each hour. The best water heaters on the market can heat almost three times their capacity.

(Recovery rate is important in radiant systems because the water in the radiant tubing cools down to room temperature between heat cycles. Depending on the size of the zone, this could be as much as 20 or 30 gallons of water. So, when the system kicks on, this 70º water enters the water heater and “dilutes” the temperature. A water heater with a good recovery rate will heat the water back up quickly and return the radiant system to its desired operating temperature (125º). Gas and oil fired water heaters offer the quickest recovery rates, electric water heaters the slowest.)

Reflective Insulation

A type of insulation employing a surface that reflects heat, such as foil backing. Used in wall insulation or with various radiant heating projects to direct heat. Snow melting systems do not require using insulation due to the fact that it can actually prevent the Earths warmth contribute to heating a driveway or walkway thus forcing the radiant heating system to work longer.

Reinforced Concrete

Concrete to which reinforcement has been added in the form of steel rods, bars or mesh to increase its strength and resistance to cracking.

Reinforcing Bar - Also Rebar

Steel bar designed to be placed in concrete for reinforcement. Concrete has compression strength; reinforcing bar adds resistance to breaking when other types of forces are applied. The bars have a patterned, or textured exterior, which allows them to bond or interlock with the concrete mix. They come in a variety of sizes, starting at ¼ inch diameter and increasing in size in increments of 1/8 inch. Also called rebar.

Relay-Transformer

The control system for the boiler which provides electrical power to the pump and gas valve when the thermostat calls for heat.

Repair Coupling

A brass fitting used to repair a damaged section of radiant tubing, generally in a slab application. The coupling is double clamped with stainless steel hose clamps and sheathed in a piece of clear vinyl tubing to prevent the concrete from corroding the metal fitting.

Retrofit

The act of installing something after the primary area has already been constructed.

Roughing In…

Is the installation of part of a radiant heating system. Heating cables, wires, or PEX tubing can often be ‘roughed-in’ to concrete or under any floor covering and then electrical controls or boilers can be hooked up at a later time for convenience or for budgeting reasons.

RPA

The “Radiant Panel Association” has been created to facilitate communication and cooperation among those interested in the advancement of the radiant panel heating and cooling industry, primarily in North America.

Sleepers

Strapping placed on an existing floor to create “sleeper bays” in which to run radiant tubing. Most often, 2X4’s laying flat, 16″ on center, act as the best sleepers. They raise the floor 1 1/2″ and allow adequate room for even the largest tubing. Sand or concrete is generally placed over the tubing, between the sleepers, and the sleepers are then used 1) to screed across in the case of a concrete floor, or 2) for nailing down the finished floor.

Splice

To join two pieces together.

Staple-up System

Tubing stapled to the underside of the subfloor.

Stratification

A term referring to the uneven heat distribution of most forced air systems. Hot air is blown around your living space creating pockets of warm, then colder, air. Hot air also tends to collect near the ceiling where it is needed the least.

Subcontractor

A contractor performing work for another contractor.

Subfloor

The layer of flooring that is fastened directly to the floor joists, and to which the finish flooring is applied. It is constructed of plywood sheathing or 2 x 6 planks, and may be a single or double layer.

Suspended Slab

A radiant floor system installed on top of an existing floor.

Tankless Water Heater

Powered by gas or electrical power, these small units give you the benefit of on-demand hot water by bringing in cold water and then passing it through a heat exchanger. These systems are electronically controlled to the inflow of water and maximize efficiency. Since a holding tank is not required and water is ‘flash’ heated, the heater can provide an endless supply of hot water.

Therm

The mesasurement of a unit of heat equal to 100,000 Btu.

Thermal Coefficient of expansion

A factor designating the amount of contraction or expansion that takes place in a material as the result of temperature changes. It provides a means for the designer to determine the amount of change that will occur in something. Concrete, for example, uses expansion joints to compensate for shifting slabs during times of hot and cold temperatures.

Thermal Conductor

A solid or fluid, such as a metal or water, that allows heat to flow through it.

Thermal Insulator

A material that resists the transfer or passage of heat. Carpet or carpet pad is a thermal insulator to radiant heat and needs to be carefully specified before installing.

Thermal Mass

In the context of radiant heat, materials capable of absorbing and storing heat energy. Concrete, sand, slate, and tile possess a greater thermal mass than wood. The greater the mass, the longer stored heat will remain in the floor.

Thermostat

A device which senses “air or floor” temperature, controls operation of the heating source, and maintains the room temperature within the living space. Because of the effects of the heating system, the settings with hydronic radiant panels are 3-5°F lower than with forced warm air for the same comfort level.

Tile

Flat square shaped sheets or slabs of material used as a surface covering. Common tile materials are clay, metal, various types of stone, asphalt and plastic. Tile is optimal for incorporating a radiant heating system.

Towel Warmers

Towel Warmers are a fashionable way to augment heating in any bathroom. These towel racks are comprised of metal tubing that traditionally uses a glycol water mixture and is either hard wired to 110V or is plugged into a socket. The fluid is heated and warms the entire rack and then radiates heat throughout the bathroom.

Transformer

An electrical device having a primary and a secondary coil, each with a specific and often different number of turns of wire composing the coil. A voltage is generated in the secondary coil by alternating current passing through the primary coil because the magnetic field from the alternating current is moving in relation to the conductor. The voltage generated in the secondary coil is proportional to the voltage in the primary coil with relation to the number of primary and secondary coil windings. Transformers are used to drop the high voltage in overhead power lines to lower voltages that are safe for use in residences and other buildings.

Tubing Materials

The following are common examples of materials which have been and are currently used for the distribution piping: Copper, Type “L”; Armco Plastic Coated Steel; Cold Rolled or Extruded Steel; Non-Barrier Polybutylene; PEX Non-Barrier Polyethylene; PEX Cross-Linked Barrier Polyethylene; Rubber.

Tubing Sizes

For most practical applications, two tubing sizes are best. 7/8″ Poly and 1/2″ PEX offer the greatest flexibility. The 7/8″ Poly provides the highest heat output (50 BTUs per ft.) and can be spaced 16″ on center. But a compromise is made when it comes to bending diameter. However, in a wide open slab environment, bending diameter is not as much of a problem. In floor joists, spacing of 16″ on center or greater is the most practical use for the 7/8″ size. The 1/2″ PEX (25 BTUs per ft.) can also be used in virtually any application, but it should be spaced 8″ on center. It will heat the same as the 7/8″ Poly tubing, but you have to use twice as much of it. It can raise the cost of a radiant system a little bit. However, 1/2″ PEX has thicker walls, hence, a greater pressure and temperature rating. In high temperature applications it’s the best way to go. Its great durability is also ideal for snowmelt situations.

U-Value

A unit of measure of heat transfer through a material of known thickness determined by the number of Btu lost per square foot per hour, assuming a 1 degree F difference between the sides of the material. The lower the U-value, the greater the insulating value of the material.

Underwriter’s Laboratories (UL)

An independent testing agency which can be hired to test and assess the operation and safety of almost any item or product. Once the item has been tested and approved by Underwriter’s Laboratories, the manufacturer can put a UL sticker or tag on the item to show that it has been tested.

Uniform Mechanical Code (94)

A system of procedures designed to provide consumers with complete requirements for the installation and maintenance of heating, ventilating, cooling, and refrigeration systems and used throughout the United States by local jurisdictions.

Universal Plumbing Code (94)

A system of procedures designed to provide consumers with safe and sanitary plumbing systems and used throughout the United States by local jurisdictions.

Vapor Barrier

A water-resistant material used on a surface or structure to stop or retard the movement of moisture through the surface. Commonly used in walls under drywall, between concrete and wood flooring and under concrete slabs.

Watt (W)

The common measurement unit for electric power, named for Sir James Watt (1736-1819) who suggested that the unit of power be the rate at which a horse performs work. A watt is equal to volts multiplied by amps in a DC circuit and in an AC circuit with a purely resistive load. One watt is the equivalent of 3.41 Btu per hour.

Zone Manifold

Most often a factory built manifold that contains the circulator pumps, ball valves, check valves, in-line thermometers, pump flanges, drain valves, and all the plumbing hardware necessary to effectively distribute heated fluid to multiple heating zones.

Zones

A zone generally refers to a given area controlled by a thermostat. Radiant heat allows you to have variable control of each zone unlike a forced air system. Any room or area in a radiant heat home can be zoned by using a separate tubing loop and manifold to control the heat of the individual room or area. This is convenient for rooms that have different floor coverings or are not used as often as other rooms.

Zoning

The ability to individually select and control the area in the home to be heated.