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How to choose a New Furnace for Your Home
Article originally posted by company founder: Marc Bluestone
The purchase of a new furnace is a major investment. Unfortunately, since many furnace replacements are done on an emergency basis, too many homeowners make quick decisions rather than smart and informed choices. I hope this article will provide you with information to help make the most of your investment.
There are several issues to consider in choosing a new furnace. While there is a tendency to simply choose a model equivalent to the one you are replacing, that ignores the major advances that have been made in energy efficiency and comfort technology during the 20 years that your system has been installed.
Choices to Be Made
Furnace Efficiency Options
The first decision you need to make is how efficient you want your furnace to be. You will have to choose between 80% AFUE furnaces and 90% Plus AFUE furnaces.
What does AFUE mean?
AFUE stands for Annual Fuel Utilization Efficiency. In layman’s terms, a furnace’s AFUE rating equals the % of energy consumed by the furnace that actually heats the house. The rest of the energy goes back outside through the chimney. So an 80% AFUE furnace uses 80 cents of every dollar of gas you’re paying for to heat your house. It wastes the other 20 cents while 95% AFUE furnaces use 95 cents out of every dollar of gas that you are paying for. If your existing furnace is 20 years old, chances are it is probably about 65% to 70% AFUE. 20+ year old furnaces can be as low as 60% AFUE or less.
Should I Choose an 80% AFUE or 90% Plus AFUE furnace?
The biggest difference between the 80% and 90% Plus AFUE furnaces is the amount of gas they waste. The 80% furnaces waste 20% of the gas you pay for. A 98% efficient furnace only wastes about 2% of the gas you pay for (this percentage depends on the make, model and brand of furnace you purchase).
Another difference between the 80% and 90% Plus furnaces is the way the exhaust leaves the house. 80% furnaces still use a traditional metal pipe for their exhaust. If your furnace is currently being vented into a brick chimney and you decide to purchase an 80% furnace, you will need to protect the chimney with an aluminum liner (if it does not already have one). The 90% Plus furnaces use a PVC pipe for their exhaust. This PVC pipe usually exits the home directly through the closest side wall.
If you plan to live in your home for five years or more, I wouldn’t recommend the 80% AFUE furnaces. You probably spend more money heating your home than you spend on all of your other appliances (including your air conditioner) put together. It makes great financial sense to get the most efficient furnace you can to cut down your gas bills. If you don’t plan on living in your home for a long period of time, the 80% furnaces will initially cost you less money (which could make the most financial sense for that situation). One thing to keep in mind: a prospective home buyer may hesitate on purchasing a home with an 80% furnace and if for some reason you end up staying longer than expected, you will be stuck with the higher gas bills. The price of energy has gone up and will continue to rise forever. You should also know that 80% efficient furnaces will no longer be available for sale in the St. Louis area beginning May 1, 2013. This is due to federal energy efficiency regulations. Thus, in many ways, purchasing a new 80% furnace (prior to May 1, 2013) is buying into an obsolete product.
What Size Furnace Do You Need?
I have found two things to be true…
For that reason, I would recommend that any furnace replacement be combined with a proper look at furnace sizing. Furnace sizing depends on obvious variables such as the size of the house. It also depends on less obvious variables like air leakage, insulation and duct condition.
Houses that are tightly sealed, have adequate insulation and well sealed duct systems can use smaller furnaces. That saves you money at time of purchase as well as on your gas bill every month.
Also, proper sealing, insulation and good ductwork improve comfort and cause house temperatures to be more stable.
Furnace sizing is determined using a ‘Manual J’ load calculation that considers all of these variables.
Additionally, expect your furnace size to be smaller if you move to a higher efficiency furnace (since less heat is wasted you don’t need to produce as much).
Single Stage, Two Stage or Modulating
Whether you choose an 80% AFUE furnace or a 90% Plus AFUE furnace, you will have to choose between the Single Stage, Two Stage or Modulating burners.
Single Stage is the traditional furnace design of the past and for many years was the only option available. When the thermostat calls for heat, the furnace comes on (full power) until the thermostat reaches the set temperature. Example: If you have a 100,000 BTU single stage furnace, it will come on and run at 100,000 BTU’s until the thermostat is satisfied. Having a single stage furnace is like having a stove with only two settings – OFF & HI HEAT.
A Two Stage furnace has a couple of nice benefits. It has two different heat outputs (Half Power Heat and Full Power Heat), depending on what the thermostat tells the furnace it needs. The thermostat will base that decision on the temperature of the house. Example: If you have a 100,000 BTU two stage furnace then the first stage will come on (50,000 BTU’s) first. On mild days it will heat your home on first stage without a problem. If it cannot satisfy the thermostat, the thermostat will tell the furnace to activate the second stage (100,000 BTU’s). For a very large portion of the year a two stage furnace will heat your home without ever needing to ramp up to second stage. When it’s running in first stage it’s using about half the gas. As a result, the Two Stage furnace will run for a longer period of time than the Single Stage furnace – which is good because the longer a furnace runs the more evenly it will mix the air in the home. If you experience uneven temperatures (hot and cold rooms) in your home during the heating season, the Two Stage furnace should help or even eliminate this problem.
Modulating furnaces take all the benefits of two-stage furnaces and go even further. Where a two stage can run at 50% or 100% power, a modulating furnace can continuously vary its output in 1% increments. This allows the system to tailor its performance to your home’s conditions and to maximize run-time, which provides better comfort, more consistent temperatures and maximum efficiency.
Both two stage and modulating furnaces come equipped with Variable Speed blowers and are regarded as an upgraded choice because of the comfort they deliver. The thing that makes the Variable Speed furnace so much better than the others is the blower motor. The blower motor is what forces air through your ductwork. It runs during the heating mode, it runs during the cooling mode, and if you run the thermostat fan switch in the on position – your fan is running 24/7/365. Needless to say, the fan is one of the most important parts of the furnace to consider.
Single Stage furnaces have one set fan speed for heating and one set fan speed for cooling. Whether that setting is too high or too low for your duct system, that’s what that furnace will put out. The blower motor on a variable speed furnace has no set speeds. It adjusts itself to your duct system. It constantly measures the pressure in your duct system and adjusts itself so that you always have the correct amount of airflow. This motor runs off a different voltage (DC voltage). Because of the technology, it costs MUCH less to operate than all other motors. Variable Speed furnaces are the quietest furnaces you can buy, they’re the most efficient furnaces you can buy, they offer better comfort than any other furnace you can buy, and most air conditioners are rated about 1 SEER more efficient when paired with the Variable Speed furnace.
Exhaust for High Efficiency Furnaces
As described above, High Efficiency (90% Plus) furnaces exhaust their combustion gases through a plastic pipe through the sidewall of your house rather than up a chimney or flue. They also have a second pipe that allows the furnace to draw its combustion air from outside the house. This is a nice benefit that you can’t get with an 80% furnace. Without a second pipe, furnaces draw their combustion air (the air needed for the flame to burn) from inside the home. The whole time these furnaces run they are blowing your indoor air right out the exhaust pipe. When you exhaust out indoor air, you put your home under a negative pressure. Your house wants to replace all of the air that it blows out. It replaces that air by pulling in air from every place that it can find (windows, doors, cracks etc.). This is what makes your home feel drafty. It also hurts energy efficiency because it discards air you have paid to heat and replaces it with outdoor air.
With a two pipe furnace you are bringing in air through one pipe, burning it and sending it right out the exhaust pipe. With a two pipe furnace, you are not throwing away heated air or putting your home under a negative pressure every time it runs.
Which furnace makes the most sense?
When selecting which furnace to invest in, I highly recommend balancing your decision with the amount of time you plan on living in the home. If you are staying for 5 or more years, I would HIGHLY recommend a 90 Plus Variable Speed furnace. It is what I have in my own home and a large percentage of our customers have installed this furnace and consistently report improved comfort and lower utility costs. If you have limited funds and you can’t afford the best furnace and the best air conditioner money can buy, I would recommend spending the extra money on the higher efficiency, variable speed furnace. The furnace will pay you back faster and will offer benefits during the heating and cooling season.
Air Quality, Humidifiers & Thermostats
Replacing your furnace also creates the opportunity to consider options that can enhance air quality, comfort & efficiency.
Air Quality: There are a variety of choices that can make the air in your house more clean. If you have asthma, allergies or excessive dust in your home, consider adding a high-efficiency air filter. These filters replace the standard 1” thick filter that you might be used to and does a great job of removing particulate matter from your air without reducing air flow. Air purification lights actively kill bacteria and virus’s and make your home’s air cleaner to breath.
Humidifiers: Indoor air tends to get very dry in the winter. Humidifiers can make your home feel warmer and be more comfortable and healthy. Added humidity also reduces static electricity.
Thermostats: We recommend that high efficiency systems be paired with programmable thermostats that automatically set-back the t emperature of your house when you are at work or sleeping. Even just a few degrees variantion can improve your efficiency dramatically and provide dramatic utility savings.
At the high-end, communicating thermostats work interactively with your furnace to discover the heating and cooling programs that are most efficient and then replicate it.
We also install thermostats that can be accessed through WiFi by your SmartPhone.
Good Advice (and a pitch for SmartHouse)
If you live in the St. Louis, Missouri area and you are considering a furnace replacement, SmartHouse would really appreciate the chance to earn your business!
At SmartHouse, the first step, done before any installation begins, is to perform an evaluation and estimate process. A technician will come to your home and start by asking a few questions. These questions will help us figure out what systems to recommend to you, and what changes we may need to make during the installation to fix some of the existing problems you may have in your current system including comfort problems like uneven temperatures, rooms that don’t heat or cool and drafts. After a thorough evaluation, he or she can sit down with you and explain what we have seen, make logical recommendations for your individual needs, and leave you with a few options and exact pricing on systems that will fit your needs.
It is important to note that SmartHouse technicians do not earn a commission on selling repairs or systems because we believe it is important that you be comfortable in trusting their recommendations. Their only goal is your satisfaction!
High Efficiency Systems
We install high efficiency comfort systems designed to be the most cost-effective on the market. I know it may be hard to believe, but technology has created systems that (for some customers) offer as much or more than a 50% reduction in energy bills. Whether you own a condo or a 10,000 square ft. home, we have a cutting edge system that can help you achieve the savings and comfort you deserve. Ask us about all the options we have to fulfill your particular high efficiency needs.
When we give you a bid for a new system, we make sure that the quoted price includes everything we need to complete the job. We also list everything included on a printed proposal. Rest assured that the price we give you is the exact price you will pay for the work that we propose. There are no hidden charges or fees, and taxes and permits (when needed) are already included in the price.
A Broader Look
SmartHouse includes a free evaluation of your home’s air tightness, insulation and duct system with every furnace replacement. It is a foundational principle for us that furnaces don’t work alone to make your house comfortable. They need help from the ducts, and your home’s shell (insulation & air sealing) to make it all work right.
Sure, it’s possible to oversize the furnace to make up for shell or duct problems – but the long-term cost of covering for the problem is greater than just fixing it.
Every York Affinity furnace & air conditioner complete system we install comes with our industry leading 10 year parts & labor warranty. For 10 years you won’t have to pay a single penny for any repairs. Problems caused by an act of God, equipment neglect or misuse are the only issues that may not be fully covered by our warranty. All 80% AFUE furnaces come with a 20 year heat exchanger parts warranty, and all 90% (or higher) AFUE furnaces come with a lifetime heat exchanger parts warranty. To keep these warranties valid, you must have each unit cleaned and checked by us once a year. This warranty is transferable to any new homeowner.
The Installation Process
When we come to your home to install a new system, our installation team will begin by introducing themselves to you. They will put covers over their boots, and cover the walking path (with painter’s tarps) between the door they will be entering from and the work area (so the working path will be protected). Then they will walk through the install process with you. They will explain all the steps involved and will discuss the placement of each unit (to make sure everyone is on the same page). When the installation is complete, they will review a checklist to make sure everything is complete and fine tuned to manufacturers specifications. Finally they will do a thorough walk-thru to explain how your new system works and how to operate the controls and settings.