Insist on professional HVAC calculations instead of guesswork. The biggest problem with sizing your furnace and air conditioner is that so few people know how to do it accurately. Even many contractors rely on a simplified rule of thumb (which is, incidentally, illegal) that translates square footage into a one-size-fits-all answer. The result is usually oversized units that cost more, use more energy and fail to maintain the temperature you desire inside your home. Professional calculation factors in many of your home's unique characteristics to obtain the correct HVAC sizing. Online calculators can often get you close. So will calculating some of these measurements yourself. It may not be as precise as an engineer's, but it will ensure you can spot any gross inaccuracies. Find your home's total square footage if you will be heating and cooling the entire area. Multiply the length by the width to obtain the figure if you don't have the exact amount from the house plans or sales contract.

Include home additions and multiple stories in the square footage. Exclude areas of your home that will not be heated nor cooled. Calculate the British thermal units required to heat and cool your house, based on square footage alone. Multiply the square feet by 25. The result is the base BTUs needed. Adjust the base BTUs if you have unusually high ceilings (more thab 8 feet). Multiply the BTUs by 25 percent. Add the result to the base BTUs. Factor in the people who are usually in the house as each will affect the heat generated inside the home. Multiply the normal number of occupants by 400 and add that result to the base BTU calculation. Alternatively, for high levels of activity, boost the BTUs per person to 600, if desired. Divide the total BTUs by 12,000 to calculate the equivalent air conditioning tonnage. Alternatively, use the BTUs to size the furnace required. With heating, the BTUs multiplied by the efficiency rating equals the output BTUs, which is the number your estimates require.

For example, if you need 30,000 BTUs and the furnace is 85-percent efficient, you need a furnace with 36,000 BTUs to match an output of 30,000 BTUs. Things You Will Need Measuring tape Calculator Tip References Ask Weldin: How Much Cooling Do I Need?how much to replace inside and outside ac unit: BTU Calculator Photo Credits Jupiterimages/liquidlibrary/Getty Images Suggest a Correctionac split unit dimensionsThis is one of the most common questions we hear, and the best answer is, "it depends." window ac units in winterBecause there are so many variables involved in sizing an industrial HVAC and/or pressurization system, we need to get some information to assist you in your selection. Fill out the form below and fax it to us, or scan it and email it to us.

From there, we can begin to better understand the individual needs of your application and find the perfect system for you. HVAC Load Study Request Form Unit size will vary based on not just the size of the interior space. In fact, in most industrial applications, the heat load is generated by the electrical equipment housed in the building. The second factor is generally location of the building. Finally, lighting and personnel can add to the heat load. Specific Systems has over four decades of experience helping our customers find solutions to their HVAC needs, and we look forward to helping you as well. At Specific Systems, we take your safety seriously. That's why we go through the painstaking process of third-party certifications on our systems. If you aren't seeing these logos from your HVAC vendor, are you certain that the system you are buying is safe? Looking for our ISO 9001 Certificate? What does "Explosion Proof" mean? What size HVAC unit do I need?

Do I need purge and pressurization? Which refrigerant do I need? Do you build fully custom HVAC? At Specific Systems, we manufacture HVAC specifically designed for the modular building industry. Our industrial systems can be used on any of the building/enclosure types below, and fit just as well on static structures as they do on modular buildings. Let us help you get the correct HVAC system for application.When it comes to your heating and air conditioning system, bigger isn't always better, and smaller isn't always more economical. THE WRONG SYSTEM SIZE COULD COST YOU A system that is too large will cool or heat your house quickly, but you still may not feel comfortable. That's because it will satisfy the temperature setting on your thermostat before it can adequately remove sufficient moisture from the air—which is what makes you feel so sticky and uncomfortable in summer. What's more, the stress of short cycling (too many starts and stops) will shorten the life of your

equipment and increase your heating and air conditioning bills. A system that is too small just cannot get the job done. The  will run constantly in the summer and the  will do the same in winter, which may overtax your system and increase your energy consumption. In most homes across the country, systems are in fact too large. an oversized system not only makes it more difficult to control your comfort levels, it costs you money, because you're essentially paying to heat or cool space that isn't even there. That's why a properly completed load calculation is so important. dealer can determine the correct system type and size for your home by doing a room-by-room load calculation. This heat loss/heat gain analysis is the best indicator of the correct system size and takes into consideration such critical factors as: Climate Number of windows and type of window treatments Insulation and ductwork Building materials and roof construction Skylights and