Staying Frosty Through A Texas Summer

Nexus4-HighTemperature.pngSome time ago I characterized a high quality coffee machine as essential equipment for home office dweller. That remains true, but given the last four weeks straight of 90+ degree days, culminating in a daytime high of 107 F (!) last weekend, I’m revising my stance to nominate the air conditioner as technological king of this hill.

When my wife and I bought this property some dozen years ago we were specifically looking for a home with a garage apartment that I could adapt into a home office. The one bedroom, ground floor, garage apartment here seemed the perfect candidate.

In general, my home office has served me well. In fact, I’m truly blessed to have such a space. Even so, over time I’ve made some changes to enhance my productivity, including replacing the air conditioner…twice!

The path by which I can to have the current air conditioner was not simple. Along the way I have learned a few lessons. Since the major purpose of this site is to share such experience I thought it about time that I addressed the matter of keeping my cool.

The office originally had an elderly through-the-wall air conditioner that I called simply “The Beast.” It was not unlike something that might have been found in an older budget motel. Think “Bates Motel” style.

The-original-office-air-conditioner-aka-The-BeastThe Beast was rated for 18,000 BTU and it cooled the space well enough. It also had heating capability, which was handy for a few weeks of the year. It was big enough that it required 220 VAC.

My major complaint about The Beast was that it was a loud as a locomotive.

The image to the right is the only one I could find of The Beast. It was taken as my wife was documenting the contents of the property for insurance purposes. That was just as Hurricane Rita approached the city in the fall of 2005.

When The Beast eventually broke down a costly repair seemed simply pointless. However, I was short of funds at the time so I took a bit of an adventurous path. I bought a 12,000 BTU split-ductless air conditioner on E-bay.

Then I hired our regular local air conditioning company to install it. They were the company that had installed the new and more traditional American Standard system into the house. They didn’t have much experience with mini-splits, but were happy to follow the manufacturers directions if we paid for their time.

At the time split-ductless (aka mini-splits) A/C units were relatively rare in North America. I had seen them used in the UK and been impressed both with their efficiency and quite operation.


At that time the only brand name that had a significant presence in the US was Mitsubishi’s Mr. Slim, but they carried a hefty price. I took a leap of faith and purchased a Soleus Ductless Mini Split system from AJ Madison. The system cost $750 including shipping. Add another $200 for installation.

The transaction was conducted over E-bay, but I actually spoke with the reseller about the product in making my selection. To be specific, I asked them for guidance on sizing. Given the size of my space I wasn’t sure whether I required 12K BTU (1 ton) or 18K BTU (1.5 ton).

They advised that for my 400 square foot office a 1 Ton system was sufficient. I confirmed their recommendation using one of the many online calculators that are available.

They were both wrong.

The guidance that they offered was based upon certain assumptions about your building and climate. Even though my office is reasonably new construction, Houston is hotter than most places in the US. Additionally, at the time I had a lot of equipment in the space. That gear puts out heat, meaning that I needed more cooling capacity than they recommended.

The upshot of this unfortunate fact was that in the peak heat of the Texas summer my office was uncomfortably warm. On the very hottest days I would take a laptop into the house and work there instead. It was bothersome, but manageable.

My leap of faith in opting for the mini-split system was rewarded in that, with the demise of The Beast, the office was blissfully quiet. Also, the office electrical usage plummeted. Mini-split systems can be energy efficient, often with very good SEER ratings.

The story doesn’t end there. The small Soleus air conditioner stayed in place for three years, but it eventually suffered a fault. Since it was too small in the first place, I opted to replace it with a larger unit from a respectable manufacturer. I wanted local support as well so contacted several HVAC companies and requested quotes.

In the end I selected Air Tech Of Houston who were offering a 2 Ton Fujitsu Halcyon system for a price that I could manage. Air Tech had the major advantage of having a lot of experience with mini-split systems. One of their technicians was recently returned from military service in Iraq where he had been involved in their use to cool critical mobile IT infrastructure.

Since Air Tech had come out to my office in preparing their bid they were confident that 24 K BTU was adequate. Also, they’re local so they had better context for understanding normal sizing for the area.


It was still spring time when I accepted their bid. Six weeks passed without word from the company. As the days were getting warmer I was starting to lose my patience.

When pressed they reported that the 24K BTU hardware was not available from the distributor. In order to actually do the installation they offered me a 30K BTU system for the same price. Since it was starting to get genuinely hot I agreed to this accommodation.

In hindsight, I shouldn’t have been so agreeable.

The fact is the 30K BTU was too much cooling capacity for my space. Normally too much capacity isn’t necessarily a bad thing. In air conditioning it can be.

This situation was exacerbated when I changed jobs. In my former line of work I had a lot of computer hardware running much of the time, spewing out several kilowatts of heat. More recently I have no such server hardware around.

An oversized air conditioner will cool a space down very, very quickly. This leads to what the technicians call “short cycling” where the unit runs in short bursts, turning off and on automatically, very frequently.

When the gear runs in this manner it doesn’t run constantly enough to be effective at taking the humidity from the space. The upshot is that you can be cool but also clammy. There’s just too much moisture remaining in the air.

This situation can also lead to mold creation, both inside the air conditioner itself and elsewhere in the room. Faced with this potential I eventually purchased a freestanding dehumidifier to ensure that humidity is well controlled.

While the Fujitsu air conditioner is wonderfully quiet, the dehumidifier is not. Even so, the pair are an acceptable solution on all fronts.

There are a number of lessons here for anyone who has a home office with HVAC independent of the rest of the home. Split-ductless air conditioners are a great option, especially where energy efficiency and ambient noise are concerns. Whatever the type of gear you choose make certain that it’s correctly sized for both the space and the amount of heat generating load in the space. Remember that control of humidity is just as important as control of temperature.

As an aside, Not long ago I was walking through a Lowe’s store. As I walked past a row of air conditioners I saw that the boxes were labeled with both the BTU capacity of the device and guidance about the size of space it would address. That guidance was based upon the same 500 sq ft/ton rule of thumb that I feel I have disproved, at least for here in Houston.

Of course, a manufacturer is going to create product packaging to be used all across the country. The guidance that might be adequate for Michigan may be wholly incorrect for Texas or Arizona. Do your homework. Don’t just trust in the label on the box.

  • mjgraves

    This suggestion came via email;

    “Right now my husband and I are looking to replace our old unit for something that is far more efficient.

    One thing that I really appreciated about your post was that you linked to a convenient BTU calculator in it. It really helped me figure out the right sized unit. One problem that I noticed however, was that the calculator only measured BTUs for my room, not the entire house. I did some digging and came across a calculator that does both:

    I just wanted to pass it on to you in case other people visiting your post come across the same issue. It might be a good idea to link to the other calculator instead.

    Keep up the awesome content! I really appreciated it.