HVAC in tight spaces

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When undertaking a major addition or remodeling job that involves upgrading the HVAC system, one of the major hurdles is how to integrate the new space into the existing house.

October 01, 2001

When undertaking a major addition or remodeling job that involves upgrading the HVAC system, one of the major hurdles is how to integrate the new space into the existing house. Often the problem centers on how to distribute the space conditioning in areas where there is no room for ductwork.

The good news is that several new options address the space problem and might provide the right solution for your next project.

High-velocity heating and cooling

SpacePak designs its systems to be matched with hydronic coils and a central air-conditioning system. The compact system provides for easy installation in applications where saving space matters. Two-inch ducts are easily weaved throughout a structure, avoiding bulkheads normally associated with conventional ductwork. The ductwork is considerably smaller because a SpacePak system typically uses only half the air volume to provide heat.

Benefits of high-velocity systems

 

 

 

 

 

 

 

  •  They can be used to centrally cool structures where wet heat (steam or hydronic) or electric systems are installed, for cooling, or where the installation of sheet-metal ducts would be expensive or difficult.
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  •  Distribution of air is through flexible, pre-insulated, 2-inch (inside diameter) tubing installed through wall structures and around obstructions.
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  •  The system uses half the volume of air used by conventional systems. Beyond 2 to 3 feet, the air is draft-free.
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  •  The air-conditioning coil can remove up to 25% more moisture from the air.
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  •  Each duct run has special sound-attenuation materials that absorb airborne and regenerated noise to provide a quiet air-distribution system.
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  •  The system is the least noticeable installation of any system. The only visible part of the system inside the finished home is a small, 2-inch terminator (one-seventh as large as the usual 8-inch ceiling diffuser).

    How the system works

    Energy Saving Products describes a typical installation: Air is circulated in the house by a blower unit. The air is filtered and runs through one of two coils in the air handler. When the thermostat calls for the air to be heated or cooled, one of the coils is activated. The blower squeezes the air under pressure into a 10-inch metal supply trunk. After a short run of 2 to 3 feet, the main trunk splits into two trunks, one for each floor.

    The first-floor trunk crosses the center of the basement ceiling with two branch trunks splitting to reach outer walls. The basement trunk is an 8-inch metal duct, and the branch trunks can be as small as 4 inches. The 2-inch flexible hoses connect from the trunk to the floor vents.

    Multiple heating zones are fed by one central boiler, allowing home buyers to heat their homes efficiently and economically.

    The second-floor trunk can be reduced to a 7-inch metal duct and run from the basement through holes cut into the floors and ceilings up to the attic, where it will run along the walls. The 2-inch flexible hoses connect the trunk in the attic to vents cut into the ceiling or the top of the walls. All of the 2-inch flexible duct is 10 feet long to absorb the air noise, making the vents quiet. Where the vents are close to the trunk, the hoses are looped or coiled in the joist bays to reduce sound transmission.

    All of the room air is stirred by the stream of air from the vents, making the temperature at the ceiling very close to the temperature near the floor. The air stream from the vents will be felt for the first 2-3 feet, which calls for locating the vents in the corners of the rooms blowing up from the floor or down from the ceiling.

    The air is drawn into two large return vents — one in the ceiling of the second floor and one in the floor near the first-floor entrance. Bottoms of bedroom and bathroom doors need to be cut to give a 5/8-inch gap to allow airflow when the doors are closed. The return-air duct from the second floor will run parallel to the 7-inch supply trunk back to the air handler. The air handler balances the pressure with an outside air pipe, virtually eliminating drafts. The blower unit has speed controls that allow it to run continuously using only 150 watts, the equivalent of two standard light bulbs.

    Radiant hot-water systems

    Another heating solution is radiant hot-water systems. Running 3/4-inch copper is a lot easier than finding room for new ductwork. Grundfos has provided the pumps for both radiant baseboard and floor radiant heating systems for more than 50 years.

    Clay Thornton, president of Thornton Plumbing & Heating, says, “In our market in Salt Lake City, radiant heating systems are what our customers want. We buy Grundfos pumps by the hundreds.” For example, he says, “We are doing a job on an 11,000-square-foot, 100-year-old mansion in Holladay, Utah. The area is in high demand and full of historic buildings. Our client wanted to bring the mechanical, electrical and plumbing systems up to code but retain the historic character of the exterior. The general contractor suggested leveling the house and building a new one. We suggested another option for heating the house.”

    His designers suggested radiant floor heating. They designed 10 heating zones for the house, each with a separate pump. They used electromechanical operators to control the pumps — one pump per zone. They also specified a hot-water recirculating pump.

    “Radiant floor heating is better heat than baseboard heat, but in retrofit situations baseboard is easier,” Thornton says. “With a radiant-heated floor, you have to add 11/2-inch gypcrete to the floors. Underfloor heating (attaching hot-water pipe under the subfloor) has its place where gypcrete is too expensive or difficult.

    We use software that looks at how floor coverings affect heat transfer. When stapling heating pipe up to the subfloor, we use an aluminum heat-emission plate. It has a circular notch that fits around the pipe and distributes heat more evenly across the floor. We then put foil-backed insulation under the floor to keep the heat where we want it.”

    Hans Kircher, HVAC director for Grundfos pumps, says, “The real issue is sizing pumps. Most engineers think the worst thing you can do is undersize a pump. The real issue turns out to be that oversizing pumps is more of a problem.” With the new Grundfos three-speed pump, flow rate can be adjusted to meet the performance requirements.”

    There are many ways to be creative with retrofit heating and cooling. Often what looks impossible or too costly just requires a new way to skin the cat. Running pipes rather than ducts might be a way to save a job that might have otherwise gotten away.

    Also See:

    Product Economics Chart

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