Posts Tagged ‘right-sizing’

Cooling with Mini-Split A/C

July 25, 2011

With the monster heat wave we’ve been having, a question that has come up several times this week—how can I add central air if I have a hot water heating system (and thus don’t have ducts to move the air)?

Mitsubishi Minisplit A/C

Minisplit air-conditioning is recognizable by it's slimmer--and quieter--outdoor condensing unit.

The good news is that there is a great answer—ductless minisplits. And mini-splits have some big advantages going for them.

    • Mini-splits are some of the most efficient systems available, and you know we’re a fan of efficiency.
    • Mini-splits come in smaller sizes, better matching cooling “loads” in the house.  And as you’ve heard me say, when it comes to A/C, bigger is NOT better.
    • Not only do they come in smaller sized, but they can also modulate the amount of heating or cooling by varying the refrigerant flow to dial is the amount of cooler you need now, not just what you need on the worst day (see bigger is not better, above).
    • With no ducts, there is no duct leakage.
    • They are really quiet!
Mitisubishi Mr. Slim Indoor A/C Unit

The indoor units, while different than a simple grill, can usually be unobtrusively tucked away, like in this hallway, for instance.

    Mini-split systems have a different design aesthetic, and some people don’t look the way the look.  However, it’s often possible to tuck them in an unobtrusive location where they’re barely noticed.  And there are options like a “ceiling cassette” with is mounted above the ceiling with just a grill visible.  Ducted mini-splits are another option.  The allow you to hide the unit, in a soffit for example, and use short ducts for the return and supply air.  With the ducted systems, you can allow feed multiple rooms from a hallway, for example.

A mini-split system is often more expensive than bolting on A/C to an existing warm air furnace and duct system.  But it is usually less expensive than adding A/C and ductwork if you have a hot water system already.  And because of the smaller sizes available, mini-splits are often a better choice for a more efficient home—one where we’ve air-sealed, insulated, swapped out lighting and appliances for more efficient models, and upgraded windows.

So, if you’ve got hot water heating, whether it’s baseboard, radiators, and in-floor radiant, don’t sweat it.  Ask us if a mini-split might be a great cooling solution for you.


With Air-Conditioning, Bigger isn’t Better

July 13, 2010
While a huge size may be important when it comes to city-crushing monsters, bigger isn't always better for air-conditioning

While a huge size may be important when it comes to city-crushing monsters, bigger isn't always better for air-conditioning

East Coasters melted in the heat and high humidity last week. Some people are probably wondering if their air-conditioners are big enough.

All too commonly, we see comfort issues caused by air-conditioning systems that are TOO BIG. Too big? A lot of people are concerned about systems that are too small. And many contractors will size up “just in case” and to avoid call back complaints that the air-conditioner isn’t keeping the house cool. Sometimes they’ll replace existing systems with bigger systems. Generally that’s not the right answer.

An A/C that is too big pretty much ensures that you won’t be as comfortable as you should be most of the time. Systems that are too big can cool you house down quickly. But if you live in a humid climate, it’s more often the humidity that really makes us uncomfortable. To reduce the humidity, you need a smaller system that runs longer and pulls a lot more humidity from the air. The smaller system uses less energy per minute, so having it run longer doesn’t mean you’ll be using more electricity. Longer run times also mean that your system hit peak operating efficiency, something that it can’t do if it’s running only for very short periods of time.

There’s an additional problem caused by sticking a larger air-conditioner onto your existing duct system. Often the ductwork cannot handle the increased capacity and air-flow required. And again, this means your system won’t be operating efficiently.

If your system is older, you should consider replacing it with a system that is “right-sized” and more efficient. In terms of efficiency, look for Energy Star as a minimum—and a higher efficiency in warmer climates. And ask your contractor to size properly using “Manual J”—ask for the report. Multistage and variable speed equipment can help, too. If your current system doesn’t seem to be keeping you and your home cool enough, there may be other things that make a lot more sense than a bigger A/C. Good insulation, tight ductwork, and controlling heat gain are all important strategies to make you more comfortable and save money.

Learn more about your cooling and heating system.


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