Idea for safe room: ductless heating and cooling

[Guest guest]

For those of you who were thinking of rebuilding, a new (?) ductless

heating and cooling system a builder told me about. Here are a

couple of links. My neighbor put a room addition on and has it and

likes it.

A specific brand by Mitsubishi:

http://www.mrslim.com/Products/Category.asp?ProductCategoryID=7

GENERAL INFO:

http://www.eere.energy.gov/consumer/your_home/space_heating_cooling/i

ndex.cfm/mytopic=12630

U.S. Department of Energy - Energy Efficiency and Renewable Energy

A Consumer's Guide to Energy Efficiency and Renewable Energy

Ductless, Mini-Split Heat Pumps

Ductless, mini-split-system heat pumps (mini splits) make good

retrofit add-ons to houses with " non-ducted " heating systems, such

as hydronic (hot water heat), radiant panels, and space heaters

(wood, kerosene, propane). They can also be a good choice for room

additions, where extending or installing distribution ductwork is

not feasible.

Like standard air-source heat pumps, mini splits have two main

components: an outdoor compressor/condenser, and an indoor air-

handling unit. A conduit, which houses the power cable, refrigerant

tubing, suction tubing, and a condensate drain, links the outdoor

and indoor units.

Advantages

The main advantages of mini splits are their small size and

flexibility for zoning or heating and cooling individual rooms. Many

models can have as many as four indoor air handling units (for four

zones or rooms) connected to one outdoor unit. The number depends on

how much heating or cooling is required for the building or each

zone (which in turn is affected by how well the building is

insulated). Since each of the zones will have its own thermostat,

you only need to condition that place when someone is there. This

will save energy and money.

Ductless mini-split systems are also often easier to install than

other types of space conditioning systems. For example, the hook-up

between the outdoor and indoor units generally requires only a three-

inch hole through a wall for the conduit. Also, most manufacturers

of this type of system can provide a variety of lengths of

connecting conduits. If necessary, you can locate the outdoor unit

as far away as 50 feet from the indoor evaporator. This makes it

possible to cool rooms on the front side of a building house with

the compressor in a more advantageous or inconspicuous place on the

outside of the building.

Since mini splits have no ducts, they avoid the energy losses

associated with ductwork of central forced air systems. Duct losses

can account for more than 30% of energy consumption for space

conditioning, especially if the ducts are in an unconditioned space

such as an attic.

In comparison to other add-on systems, mini splits offer more

flexibility in interior design options. The indoor air handlers can

be suspended from a ceiling, mounted flush into a drop ceiling, or

hung on a wall. Floor-standing models are also available. Most

indoor units have profiles of about seven inches deep and usually

come with sleek, high tech-looking jackets. Many also offer a remote

control to make it easier to turn the system on and off when it's

positioned high on a wall or suspended from a ceiling.

Split-systems can also help to keep your home safer since there is

only a small hole in the wall. Through-the-wall and window mounted

room air-conditioners can provide an easy entrance for intruders.

Disadvantages

The primary disadvantage of mini splits is their cost. Such systems

cost about $1,500–$2,000 per ton (12,000 Btu per hour) of cooling

capacity. This is about 30% more than central systems (not including

ductwork) and may cost twice as much as window units of similar

capacity.

The installer must also correctly size each indoor unit and judge

the best location for its installation. Oversized or incorrectly

located air-handlers often result in short-cycling, which wastes

energy and does not provide proper temperature or humidity control.

Too large a system is also more expensive to buy and operate.

Some people may not like the appearance of the indoor part of the

system. While less obtrusive than a window room air conditioner,

they seldom have the built-in look of a central system. There must

also be a place to drain condensate water near the outdoor unit.

Qualified installers and service people for mini splits may not be

easy to find. In addition, most conventional heating and cooling

contractors have large investments in tools and training for sheet

metal duct systems. They need to use (and charge for) these to earn

a return on their investment, so they may not recommend ductless

systems except where a ducted system would be difficult for them to

install.

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