One of the most important appliances in any office building, and by far the costliest one, is the central heating/cooling system. If you are faced with repairing or replacing a central unit in a building you own, you probably already know that it is quite an investment and has to be approached in a most deliberate, and deliberative, manner. HVAC (heating, ventilation, air conditioning) work is not cheap, and requires trained, certified personnel to install and set it up correctly.

On the other hand, you may just have an office or suite that you rent or lease, and are concerned with buying a portable or window-fitted air conditioner to supplement your older building's weak performance come summer. Despite a difference in cost estimates in the thousands of dollars, the solution to either of these dilemmas is found the same way - planning, research, budgeting and then "just doing it."

The "load calculation"

Whether you will roll in a portable a/c unit, mount one in the window or hire a contractor to install one in the basement as a central unit, you still need what the HVAC industry calls a "load calculation." This is just a slightly arcane way of quantifying how hard an air conditioner or heater has to work to cool or heat the volume of space in your office. No reputable HVAC contractor will talk makes, models or specifications until this calculation has been done. It can be done with computer software and/or with "Manual J" from the Air Conditioning Contractors of America.

It should take a professional no more than about an hour to measure the room dimensions and the layout of the walls, floors, windows, ceilings and doors, and then assessing the office's insulation to determine the "R" value. When the calculation is finally made, you will know what the equipment requirement is, which is essential for efficient operation. Oversized units will cost too much to operate for the amount of work they are doing, while undersized ones will fail to provide sufficient, continuous comfort and will run longer, meaning both larger energy bills and smaller life spans.

Efficiency and green power

An air conditioner's efficiency is a crucial consideration, and investing in a more efficient system will result in cost savings over the life of the installation. The greater the unit's efficiency, the greater the up front cost, but your return on investment (ROI) will be gauged by the savings you will accrue over time. An air conditioner's efficiency is denoted by the Seasonal Energy Efficiency Rating (SEER), which indicates the amount of cooling you receive per "unit of electricity." Therefore, a higher number means you are getting more for your money.

Again, regardless of the installation type - window, portable, central unit - you need to get an air conditioner that will do the job you require. Either way, to beat the summer heat without overpaying for energy, you should consider using a programmable thermostat so you can set a higher temperature (or turn it off) for when you are out of the office, and then schedule the unit to return to a comfortable level perhaps 30 minutes before the first employee arrives in the morning.

A few "central" issues

If it is a central unit you are dealing with, there are some things that come into play that do not matter in the consideration of a portable or window a/c unit. In a "business grade" air conditioner, the compressor - the motor or pump device that does the lion's share of the work - can be quite expensive to repair or replace. Of the two kinds of compressors used in modern equipment, the "scroll" compressors are the most efficient and the quietest, too, which makes them more expensive, at least initially. The "reciprocating" compressors are not as efficient, are much noisier and typically have a shorter warranty.

When you are getting a central unit installed, it should go without saying (although nothing does any more) that choosing a knowledgeable, reputable contractor is critically important. You may even need the help of a contractor to make an informed decision in the first place, so finding a good one is essential. Get referrals from friends and colleagues, check references, ask about insurance and bonds, put everything in writing and get at least three or four estimates.

Whether you get a window unit to chill down one particularly hot spot in your small office, or a new central HVAC unit for your office building, you need to know at least the basics even to discuss the matter intelligently with contractors or sales people. You need to know how much volume (three-dimensional space) you need to cool, so that you can determine what kind of equipment is best. Don't forget to aim for efficiency and long-term duty cycles over low initial cost, as higher quality equipment provides better ROI and requires less remedial maintenance. Central a/c or a portable wheeled unit will both cool the air, while making the right choice of either will end up being a cool move on your part.