Posts Tagged ‘A/C’

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.

Cheers,
Mike

Staying cool and saving during the monster heat wave

July 21, 2011

The incredible heat wave continues across the Midwest and the East Coast.  To temperatures pushing—or passing—100 degrees, add stifling humidity the bump the heat index over 120 in some places.  In this case, it’s the heat AND the humidity.

While our friends down in Houston are used to this, and they’ve got the air-conditioning to deal with it.  This is beyond what many people and homes and buildings in the East and Midwest are prepared for.  And the heat can be deadly. So it’s worth taking a few minutes to talk about what you can do.

We often providing cooling tips, and they’re worth revisiting.  But let’s hit a couple of important reminders for you and your home to help get through this.

Keeping your person cool

  • Drink more fluids (nonalcoholic, and without caffeine), regardless of your activity level. Don’t wait until you get thirsty to drink. Warning:  if your doctor has you limiting fluids or reducing water, check in with her to find your specific recommendation.  Remember, if you’re sweating a lot, you need to replace electrolytes, too.  I like a diluted sports drink (otherwise they can be too sweet).
  • If possible, stay indoors in an air-conditioned space.  If you don’t have air conditioning, go to the shopping mall or public library–or the time-honored tradition of going to a movie theater.  Might be a good reason to go so Harry Potter again!  Some locals might have heat-relief shelters.  Check with your local health department.
  • Go swimming in a cool pool.  Take a cold shower or a cold bath.  (Not a hot shower or hot bath!)  Cooler water can be an excellent way to cool down your body temperature.
  • Wear lightweight, light-colored, loose-fitting clothing.
  • If you’re going to be outside, try to do it early in the day or late in the evening when it’s generally cooler.  Try to avoid heavy exercise in the heat.

The Centers for Disease Control has a helpful Extreme Heat guide the offers additional details and advice.

Keeping your home cool

  • According to CDC, air-conditioning is the number one protective factor against heat-related illness and death.  Room air-conditioners can help.  And installing a central AC unit is usually done in a day.
  • Keep the heat out!  During the day, if it’s cooler inside than outside, keep windows shut.  And keep window shades down to block out direct sunlight.  Open the windows at night if it’s cooler outside than in. 
  • Fans to the outside—blowing in either direction—can help if it is cooler outside than inside.  But they’re counterproductive if it’s hotter outside.  Ceiling fans (and other fans) help you stay comfortable—but only while you’re in the room.  The fan motors actually generate heat, so turn them off when you’re not there.

Finally, children, the elderly, and the sick, are especially susceptible to heat.  Keep a close eye on them. 

Of course, contact us if you’d like more permanent, energy-efficient solutions.  But in the meantime, be safe, and stay cool.

Mike

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.

Thanks,
Mike

A/C: Bigger is NOT Better

July 15, 2009

Part of the continuing myth-busting series.

Energy Myth:  For Air-conditioning, a larger unit is better.

Reality:  Bigger simply is NOT better.  In fact, too big is much worse than the “right size”, and often worse than a little bit too small would be.

Unfortunately, because it allows them to take short cuts on determining the right size, and not worry about duct leakage or poor insulation, many contractors fudge it, and install a ton or more of extra capacity.   Don’t fall into this trap.  The benefits of a properly sized air conditioner are huge. 

A sad thing is that an oversized A/C costs you on the front end and throughout its life.  A bigger unit costs more.  And thus you lose right out of the gate.

Oversized units “short-cycle”.  That is they turn off quickly.  Air conditioners don’t gain their full efficiency for several minutes after start up.  If you’re A/C shuts off before that, it’s not operating at peak efficiency, and you can pay up to 10-20% more.

But it’s worse than that.  Air-conditioners remove less humidity from the air at the beginning of their cycle.  And longer run times help pull more moisture from the air.  So an oversized unit, which runs less, will leave a house feeling clammy even as the air temperature is dropped.

Bigger capacity also means a bigger fan (assuming the contractor even looked at air-flow).  And all else equal, a high air-flow means more noise—really high air-flow can create downright annoying noise issues.  And the short run times don’t allow the air time to mix—you get blasts of cold air.

In short…

A too-big A/C costs more up front, costs more to run, won’t remove humidity as well, can be noisier, and less comfortable.

A right-sized A/C costs less than an oversized unit, is less expensive to run, does a better job removing humidity, can be quieter, and with longer run times does a better job mixing the air and delivering consistent comfort.

Don’t let your contractor talk you into something bigger than you need!  And ask to see the sizing calculations, generally the “Manual J” sizing.  [Even better, ask how you can tighten ducts, increase insulation, and reduce heat gains, to get an even smaller unit.]

Stay cool,
Mike

Energy Myths: Cooling

July 10, 2009

A recent conversation at the grocery store gave me an idea for a new thread—debunking some energy and energy-efficiency myths.  Despite the Spring-like conditions in the Northeast, it really is summer, and I’ll start off with a few cooling myths.

MYTH:  Using a programmable thermostat—or adjusting manually—and ratcheting back your heating or cooling where no one is home doesn’t really save energy.  Quite simply, yes it does!   The longer your house stays at a higher temperature when in cooling mode (or at a lower temperature when heating), the more energy and money you will save. This is because heating and cooling cost depends mostly on the difference between indoor and outdoor temperature—the closer the temperatures indoors and out, the less energy you use.  Depending on usage, on how far you change the setting while you’re gone, and how efficient your home is, you could expect to save 5 to15%.  A programmable thermostat can adjust temperatures automatically for you.   (Caveat:  in areas with variable rates—peak summer rates are often late afternoon.  You’ll use less energy back turning off the A/C while you’re gone—but you may pay more.  The answer here is to make your house as efficient as possible to get the cool air in and keep the heat out!)

MYTH:  Turning off the A/C, but leaving the fan on to mix the air saves energy.  Nope.  First, you’re actually using energy—and creating heat—with the fan.  Second, most duct systems leak air to the outside—keeping the fan on actually increases this leakage, so you may lose the cool air even faster. 

MYTH: The lower you set your thermostat, the faster you’re A/C will cool your house.
False.  You should set the thermostat at the temperature you want–it will reach that point just as quickly as if you set it lower.  Setting it lower means you’re likely to forget or to “catch” it at the right time, making the room colder and wasting energy.

A lot more home energy misconceptions out there—and I’ll try to hit some them in the coming months.

Thanks,
Mike


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