You can now invest in “Smart Vents” for your home. Here are nine reasons why you should not.
What’s a Smart Vent?
Keen Home, Inc. has introduced a product called the “Smart Vent”. The company claims the product will help you “increase comfort and reduce energy costs by regulating your home’s temperature room-by-room”. The vents communicate with each other and your smartphone wirelessly “to regulate airflow in rooms too hot, too cold or not in use most of the day.”
If that sounds great, check out the video above to see how easy it is to replace an existing vent with a Smart Vent. You’ll get a look at the product in the video.
Keen Home, Inc. has presented a handsome website and an offer for you to order their Smart Vent product. Since the Smart Vent product seems to fundamentally misunderstand how the central heating|cooling systems in our homes work, please give some thought to the following reasons why you should avoid products like the Smart Vent.
The Air Conditioning Contractors Association publishes manuals that set the standards for the design, installation and maintenance of heating|cooling systems in homes. One of those manuals (Manual D) describes how to design supply and return ductwork systems.
The supply duct system carries conditioned air from your central heating|cooling system to the rooms in your home. The return duct system brings air back to the central heating|cooling system so it can be conditioned again. The constant air flow through the system should keep the temperature steady so you don’t notice periods of hot and cold.
The supply and return ductwork systems are designed to flow a certain amount of conditioned air to|from each room. The size of the duct serving each room is determined based on the air flow needed to condition that room. The amount of air flow is determined based on room function, room size, insulation, number of windows, etc.
If you close vents in rooms with the expectation that you’ll send more air to the rooms with open vents, you’re trying to flow more air than the ducts to those rooms were designed to deliver. Increasing the air flow above the system design can result in excess noise in ducts and at vents.
You may notice, the face of the Smart Vent is the same size as commonly installed vents but the controller makes the open area of the vent behind the grille much smaller than a typical vent. The vents are part of the duct design for a heating|cooling system. If you replace the vents that were installed with the system with smaller vents like those of the Smart Vent, you can choke your system and experience increased noise even when the vents are open.
It’s common for home owners to select wood grilles for supply vents cut into wood floors. The problem is these grilles often flow significantly less air than the system was designed to flow at that grille. This chokes the system and can result in comfort + humidity issues. If you want the wood grilles, just design the system to account for them. That probably means you’ll get extra vents to flow the needed amount of air and you still get the look you want.
Central air conditioning typically uses a coil in an air handler to cool the air. The coil in your air handler is cooled through refrigeration. The air in your rooms flows through the return ductwork system to be cooled as it moves across the very cold coil before it’s blown back into your rooms through the supply ductwork system.
If you reduce the air flow across that coil by closing vents in your home, you can freeze the coil. That happens when the humidity in the air literally freezes into ice as it encounters the coil. You wind up with a block of ice. Freezing your coil can cause significant damage to your coil (indoor equipment) and your compressor (outdoor equipment).
When you’re heating your home, your furnace expects to have a certain amount of air flow so the heat it produces is moved out of the furnace and into your rooms. When you restrict the air flow by closing vents, that heat can build up in the furnace and damage the equipment.
Gas furnaces typically use heat exchangers to warm the air that’s flowing from your rooms through the furnace. Reducing the air flow in a gas furnace by closing vents subjects the metal heat exchanger to much hotter temperatures. When the metal heat exchanger in a gas furnace cracks from constantly warming up and cooling down, it can allow lethal flue gases like carbon monoxide into your home through your heating system.
Many new central heating|cooling systems use variable-speed equipment. Instead two speeds (off and on), variable-speed air handlers can blow air through the ducts at multiple speeds. They can sense how much air they’re flowing and adjust the fan speed based on your heating|cooling needs.
If you close the vents on a variable-speed heating|cooling system, it will realize that it’s not flowing the volume of air needed to meet the thermostat’s call for heating or cooling. When that happens, the unit ramps the fan up to 100% capacity. That’s a great way to erase the energy efficiency of a variable-speed system (you’ve made it a two-speed system) and burn out the blower motor much faster than you would if you didn’t close the vents.
Air flow through a central heating|cooling system allows the system to filter the air. If you’re paying attention during the design (when you choose a new system), you can opt for a higher-end filter to address allergies and other issues.
If you’re using a system like Smart Vent that only considers temperature, you’re not addressing the other issues your heating|cooling system should be designed to address. If you close the vents to rooms in your house, you reduce the amount of filtered air in those rooms.
Supply and return ductwork systems should be balanced. The system should be returning as much air from the house as it supplies to the house. When you close the vents on the supply side, the system won’t flow enough air to fill the return side.
The result is the central heating|cooling system pulls air from unintended places. That air comes through the path of least resistance. If you have a leak in your return ductwork, your heating|cooling system is going to pull more air through that leak. That means the system is pulling in air from the attic or crawlspace. That can create health issues… among other problems.
If you’ve closed the supply in a room that has a return, the system draws air from the path of least resistance. That can be leaky exterior doors, windows, light fixtures, electrical outlets, fireplaces or other common air leaks. Closing the supply vents changes the volume of supply air without changing the volume of return air. That draws even more air and humidity through existing leaks.
This has the EXACT OPPOSITE effect suggested by the Smart Vent. When you draw more air through leaks in the summer, you draw hot and humid summer air into your home rather than making it more comfortable. When you draw air through air leaks in the winter, you draw cold air into your home rather than making it more comfortable.
As the temperature of air increases, so does its ability to hold water vapor. A ninety degree day with ninety percent relative humidity (RH) has about four times as much water vapor in the air as a seventy degree day at fifty percent relatively humidity. (Seventy degrees at about 50% RH is a typical indoor condition.) That’s why it feels dramatically cooler when you step into air conditioning from a hot, muggy summer day.
Central heating|cooling systems (even in older homes) should be designed to address two loads: sensible (temperature) and latent (humidity). In new homes with tighter building enclosures (fewer air leaks), there’s also a need for ventilation. There must be some way to introduce fresh air and deal with the humidity in that air, even if it’s through a stand-alone system in the home.
Central cooling (air conditioning) systems remove humidity from the indoor air when that air comes into contact with coil in the air handler. The humidity in the air condenses onto the coil, drips into a pan and drains out of your home. It’s like the humidity in the air of your home condensing onto a cold drink but your air conditioning system is designed to collect the water and drain it away.
Your house has leaks. Even the tightest homes have leaks. It’s just that tight homes leak dramatically less than many older homes. If your home (and your heating|cooling system) is old and leaky, you’re probably having comfort problems in your home. They’re the sort of comfort problems that would cause you to shell out hundreds of dollars for Smart Vents.
If you use those Smart Vents to restrict the air flow in your home, you’re not delivering lower-humidity (conditioned) air to each room. You’re creating indoor humidity problems by trying to direct the cool air to certain rooms.
Humidity spreads out to reach a uniform level. If you close the supply vents in some rooms, you’re not effectively addressing the humidity in those areas. The humidity spreads to other parts of your home.
Every one of these Smart Vents takes 4 AA batteries. This looks suspiciously like a product designed by a battery company so they can sell more products, regardless of what they do. Surely, exposing the batteries to the very warm air delivered by your heating system in the summer and the very cold air delivered by your cooling system in the summer is not going to help those batteries last any significant length of time. Four batteries per vent means even more really expensive batteries to replace rather than just using a manual vent as we have for generations.
Your central heating|cooling system probably already has these features installed. Many vents have adjustable louvers in them so you can control the air flow. Many supply duct systems have dampers in them to adjust the air distribution between different parts of the ductwork system.
Like most technology solutions, the manufacturer is selling you control. Do you really need that control? What’s the point of having Smart Vents and being able to control them unless you’re going to be in and out of those rooms constantly? The reality is you probably won’t be and any existing comfort issues can be solved much more effectively through other means.
Your central heating|cooling system should be tested an balanced. Earlier, in “Reason One”, you learned about the design of ductwork systems. The system should have been designed so the installer knows how much air should be flowing through each vent. You can have the air flow at each vent checked to be sure the system is performing as it should. Installed systems often don’t perform as they were designed without testing and balancing to get the air flow to each room correct. That process is often called “commissioning”.
Why the Smart Vent Is NOT Like the NEST Thermostat
One of the other extraordinarily irritating things about the Smart Vent is that the manufacturer insinuates that the Smart Vent is similar to the Nest thermostat. The Nest thermostat is a learning thermostat that monitors your habits of adjusting the temperature and builds a schedule for you. In that sense, it’s like a programmable thermostat that’s more user friendly.
The Nest thermostat shouldn’t cause the problems listed above that the Smart Vent is likely to cause. The Nest thermostat has been relatively successful so it’s disappointing to see suggestions a dissimilar product like the Smart Vent could have the same effect.
If you have health, comfort and efficiency problems in your home, they’re probably related to your heating|cooling system. Rather than wasting your resources on Smart Vents, you should get control of your indoor environment by solving your air leakage problems. You can invest in air sealing and insulation (relatively cheap, passive systems) as a first step.
Once you have control of your indoor environment, you’re ready for a properly designed, installed and commissioned central heating|cooling system. That will be a much more effective way to address your health, comfort and efficiency problems than the Smart Vent. Addressing those issues will also increase the value of your home.
Architectural Digest published “A New Vent Cover Keeps the Temperature Just Right” in its technology section on November 1, 2015. It’s not clear if the article is paid placement for the Smart Vent or if the folks at AD just didn’t consider the challenges of changing the air flow of a central heating|cooling system.
Anyone who understands central heating|cooling systems should be able to come up with a list of problems with closing vents in a moment. That’s not a good sign for the Smart Vent yet Keen Home, Inc. will still take your money.
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