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Radiant Heating System Forced Air System Hydronic Baseboard System Advantages & Disadvantages of Heating Sources Underfloor Ventilation System
Radiant Heating System

Efficient and Clean
	Radiant heating warms the occupants in a room rather than warming just a room itself, resulting in the need for lower temperature settings — and this means lower fuel costs. Fuel consumption with radiant heat is considerably lower, and consequently, so are the gas or oil bills. Radiant heating also offers health and safety benefits. It does not dehumidify the air, so in winter, room humidity is more ideal. Unlike forced hot air, radiant heat will not dry out breathing passages or furniture, and with no fans or blowers, radiant is dust-free.
Virus particles, bacteria and pet dander fall to the floor instead of circulating constantly in the air. Slab foundations and high ceilings lend themselves to this form of heating (and cooling) for obvious reasons. First, the slab is a tremendous thermal mass to hold heat. The heat also stays at floor level where the people are, not up at the ceiling or flowing out the seams of the siding. Superior comfort and efficiency, together with the benefits of a safer, quieter and more environmentally friendly system, have made this technology the fastest growing heating method. Since the systems are easy enough to install, contractors can have their own crews install the system and avoid the additional costs of hiring an HVAC subcontractor. Operating cost savings of 30 to 50 percent are also quite attractive to building owners and tenants .
The Concept	Back to the top
	The basic concept of radiant heating and cooling is simple. Heating tubes are laid down before the floor is poured. Once embedded in the slab, the tubing contains circulating hot water (or cold water for cooling) heated by a boiler, hot water heater or solar collectors.
The result is an even, comfortable heat with no blasts of hot air to stir up dust or dirt. The absence of unsightly ductwork and radiators provides added space and flexibility in floorplan design. Businesses using these systems confirm what some folks have known all along -— when your feet are warm, you feel warmer all over! Because the heating system is installed within the floor, the air temperature is always highest at floor level and decreases steadily toward the ceiling. Unlike hot air heat, the moisture content of the room is more stable for climate sensitive facilities. Because no blowers or fans are required, the systems are quiet and dust free. “First of all, it’s out of the way – there are no big heaters, radiators, fans or ductwork to work around on the shop floor,” boasts Allard. “My employees love it because their feet are warm and the entire work area stays warm. In fact, the slab holds the heat so well, I can shut the system down on weekends and it stays warm until Monday.
Simple Yet Elegant	Back to the top
	Proportional reset describes a situation in which a hydronic subsystem with a manually set mixing valve will automatically vary its supply water temperature (e.g. reset) as the hot water source supplying it is reset. Figure 1 shows this relationship. Notice how the water temperature in the mixed subsystem (shown as the pink line) decreases "proportionally" to the decrease in boiler water temperature (shown as the red line). Boiler inlet temperature protection is a must when connecting any conventional boiler to a low temperature distribution system.
If omitted the boiler can operate at temperatures low enough to cause sustained condensation of water vapor and other compounds in the exhaust stream. The resulting corrosion will be swift and in many cases severe. Condensing flue gases can eat through a standard 26 gauge galvanized vent connector in a matter of months. Finally, the ability to work with a large temperature difference between the supply and return sides of any hydronic system is an opportunity that should not be missed. Doubling the temperature drop of the distribution system cuts the flow rate requirement in half. This reduces pipe size, circulator size, and even more importantly, lowers the operating cost of the circulator over a long system life. In short, high DeltaT is the holy grail of hydronic heating design.
	Hot water from the boiler loop is supplied to the 1-inch PEX-AL-PEX "building loop" at 180 degrees F under design load conditions. The building loop is set up as a two-pipe reverse return system with several crossover bridges made of 1/2-inch PEX-AL-PEX tubing. The two-pipe reverse return layout of the building loop is self-balancing, with each crossover bridge operating at a constant flow rate of 0.8 gallons per minute. Each crossover bridge has a pair of closely spaced tees that lead off to the radiant floor subsystem in a given apartment. Hot water is drawn into the radiant subsystem from the upstream tee and mixed with cooler water from the return manifold.
The mix proportions are controlled by two manually set globe valves. Once set, these valves do not modulate (as do thermostatic and motorized mixing valves). Back to the top At design load conditions the water temperature on the supply side of the building loop is 180 degrees F. The water temperature supplied to the floor circuits is approximately 140 degrees F with a 20-degree F temperature drop between the supply and return manifolds. The water temperature on the return side of the building loop is 120 degrees F. The temperature drop of the building loop under these conditions is 60 degrees F. Each gallon per minute of flow in the building loop carries 30,000 Btu/hour along for the ride. The total building loop flow rate of 6.4 gpm is easily handled by a 1-inch pipe, yet conveys 192,000 Btu/hour from the mechanical room to the building. That's the magic of a high DeltaT. As outside temperatures rise, the building loop temperature is reduced from a design value of 180 degree F., down to about 120 degrees F using a boiler reset control. Since the mix proportions remain unchanged, the water supplied to the floor circuits automatically reduces to about 102 degrees F when the outside temperature is about 34 degrees F. Back to the top At higher outside temperature, or during periods of internal heat gain, the thermostat in each apartment interrupts operation of the floor circulator as necessary to prevent overheating. To minimize short cycling, the reset control automatically widens the operating differential of the boiler as the outdoor temperature increases. Resetting the boiler water temperature also improves seasonal efficiency and hence decreases fuel use. The boiler loop contains a three-way thermostatic mixing valve set to protect the boiler from unacceptably low inlet temperatures (about 110 to 120 degrees F for the boiler used). Following a cold start, this valve reroutes water from the boiler outlet back to the inlet. The boiler quickly warms above the dewpoint of its exhaust gases. After the boiler has warmed up, the valve allows hot water to flow to the closely spaced tees where the building loop connects to the boiler loop. Heat that initially circulated in a holding pattern between the boiler and three-way valve is now released to the waiting loads. The process is comparable to making sure your truck's engine has revved up before you start letting out the clutch. This valve also protects the boiler from low inlet temperatures in the event several apartments are simultaneously recovering from cool slab conditions.
Forced Air System	Back to top

There are two basic ways of heating a home; radiant heat room by room, or a central heating system. Radiant in each room can be electric, wood stove, gas heater, kerosene, coal, a fireplace, etc. Central systems can be hydronic, steam or forced warm air. Hydronic and steam. A forced warm air system uses ductwork to distribute heated air from a source (furnace or air handler) to each room. The furnace can produce heat from any number of fuels; gas, oil, electricity, wood, or coal, or a combination of any fuels. An air handler will use a hot water coil to produce heat. Unless fresh air is piped in from outside of the home, the system will re-circulate 100% of the air it supplies. This means it must obtain air from the home by way of a return air duct or ducts. Properly installed, a warm air system becomes a loop by which air is drawn from the living space through return ducts to the furnace, heated, and sent back to the same space through supply ducts. The advantages to this type of heating system are numerous. The air can be heated, cleaned, sterilized, humidified, or cooled (central air conditioning). If return air ducts are strategically located, the will reduce heat loss by recycling the warmest air back in to the system that collects at upper areas of the house. Supply ducts located around the outside walls of the rooms will temper the cold air as it infiltrates the home and reduce any discomfort from the air flow to a minimum. The disadvantage is that ductwork takes up space. When installed by an experienced contractor, the ductwork will take up minimal or no extra space, and literally disappear into the framing of a house.
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Advantages & Disadvantages of Heating Sources

Fuel	Advantages	Disadvantages
Oil	Market competition usually moderates prices Slightly more efficient than gas Less expensive than gas when used to heat large buildings Can be easily supplied in areas not served by gas	Requires delivery Requires regular maintenance Occasional price fluctuations Older equipment can be noisy, dirty, and difficult to maintain Risk of an oil leak and environmental contamination Occasional odors Risk of puffbacks Electricity to run oil burner adds to cost of operation
Gas	Plentiful supply is assured by the local gas supplier Price is regulated, limiting price fluctuations Equipment is quiet Requires slightly less service than oil equipment Has no electricity-consuming oil burner Service is often included in the price of gas, so there are few additional expenses	Limited choice of suppliers Even if you can choose a different supplier, the gas will be only delivered by one company, reducing price competition May not be available in your area
Electricity	Plentiful supply is assured by local electricity supplier Requires minimal routine maintenance Does not require the ventilation needed to burn a fuel	Very high expense, especially in the greater New York area
Solar Energy	No ongoing fuel cost	High initial cost of installation Potentially high ongoing maintenance cost Not enough sun in the greater New York area during winter months to make this practical The supplemental heating that must be supplied is often expensive electric heat

Hydronic Baseboard System	Back to the top
Hydronic baseboard heat has been around since the 1940’s. It evolved from the heavy cast iron radiators that were popular in previous decades. Baseboards had a few advantages over heavy cast iron radiators. They are light, easy to install and able to deliver heat faster. Cast iron radiators radiate heat whereas baseboard heaters were designed to radiate and convect heat.

	The convection process works like this: The baseboards draw the cooler air through the bottom of the baseboard past the fins and out the top.
Advantages But is Hydronic baseboard heating practical today? The answer is: "Sometimes yes and sometimes no". When deciding if baseboard heating is practical you must compare it to the predominant heating system in the U.S.; forced air. Hydronic baseboard heat has many advantages. Hydronic heat doesn’t dry the air like a forced air system, and it doesn’t spread dust particles. This is important for those who suffer from allergies or dry skin conditions. It is more compact system… no huge ducts overhead or in the basement cutting into headroom. It is easily separated into separate zones, which lowers heat bills and improves comfort. One of the biggest advantages is that it is an easy system for the do-it-yourselfer to design and install. Disadvantages But what about the disadvantages? Many people don’t like the fact that the baseboards themselves take up room on the wall. Hydronic baseboards also take longer to raise the room temperature than a forced air system. The biggest disadvantage is the cost of the system. When comparing the baseboard system to a forced air heating, they are quite comparable in cost. However, when you add air conditioning into the equation it's a different story. To get air conditioning with a baseboard system you need a separate forced air system. With most forced air systems a condensing unit and an evaporator coil is added to the system. When and Where If you suffer from allergies or skin irritation, installing a baseboard system is probably worthwhile, even with the added cost of an extra system for A/C. If you live in a mild climate and don’t need A/C, a baseboard system is an excellent choice. In dry climates, you could opt for hydronic baseboard heat and an evaporative cooler for the summer months. This is probably the healthiest heating and air conditioning option available. How it works How does the hydronic baseboard system work? Well for starters a boiler is used instead of a furnace. Water is heated in the boiler and then circulated to the baseboards with a pump. Typically, the water is heated to 170°-180°. The system is a closed system meaning that once the system is full, no water is added, the boiler just heats the same water over and over (see fig. above). Copper or PEX (plastic pipe) pipe is used to carry the water from the boiler to the baseboards and back again.
Zones One major advantage of a hydronic heat system is that it can be easily separated into zones. For example, each bedroom can be controlled by a separate thermostat. To save money, the thermostat can be lowered or turned off in an unoccupied area. To create a zoned system, generally two pipes are run. One pipe sends hot water to the baseboards and the other returns the water to the boiler to be reheated. A Thermostat controlled valve opens to let water to a zone (see fig. below). When the room reaches the desired temperature the valve closes.


Conclusion Hydronic baseboards are a time-tested system that have many advantages over other systems. They produce an efficient even heat, and are easy for the do-it-yourselfer. Whether baseboards are right for your particular situation is a matter of climate, budget and health considerations

Building Systems