Does Shutting Furnace Vents Improve Energy Efficiency?

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Katherine Velsvaag

Subject: Boiler

Is this also true for hot water heat? We have baseboard heat and by the time it reaches the farthest upstairs room there seems to be little heat. It's always 2-3 degrees cooler in the farthest bedroom and the closer bedroom is much hotter.

mt

Subject: Low heat in zone

Your problem could be in the piping of the system. Sounds like the baseboard loop length is too long. Get a contractor in ivolved.

Steve Odem

Subject: Rarely

"Why closing vents actually wastes energy

Because the rooms in your home have cold-air returns as well as heating vents, shutting the vents doesn't prevent air movement. "

Rarely is this true.

Having extensive experience as responsible for building permitting and inspection, only a very tiny percentage of single family homes, condos or apartments have more than one cold-air return. The exceptions are large and expensive homes and they may have multiple HVAC units.

Given that, the whole premise of this report is almost inapplicable to the vast majority of homes.

Diane

Subject: Cool bedrooms

What is the best way to have a cool bedroom during the winter When the furnace is running?

Ryan

Subject: 1 Return Upstairs-1 Return Downstairs

I have a new furnace & air conditioner that was installed at the end of the summer 2015. I had only 1 return in my living room for a kitchen, living room, 2 beds & a bath. 1 return collectively for those rooms.

I then blew out my chimney for a duct chase into my attic to supply my upstairs with central air (2 beds, full bath) & get rid of the electric heat & windows air conditioners. One furnace & 1 air conditioner to supply the whole house but only have 1 return in the center of my upstairs along with the 1 return downstairs. They are separate systems, so they need seperate returns, but 1 return for each system.

Bottom line, I'm wondering if I can shut 2 registers downstairs & leave the doors shut to the rooms and not cause a negative airflow or whatever & screw up the equipment? I will have the living room, kitchen & bathroom registers open with the main return all open for the downstairs system. Wouldn't that stop air going out the registers I close & send more out of the registers left open? Heating the main level of the house faster & shutting the system down quicker?

I just want to make sure I won't destroy my new equipment. I'm going to call American Standard, the manufacturer, and find out what they have to say. I also need to know if a MERV 8 would be alright for my system. I'm currently using an fpr 4 from Home Depot & I've read FPR is just a bs marketing ploy by Home Depot. I want to use something that has been legitimately tested to benefit my family & my system.

Any knowledgable information people in the field can offer, I'd appreciate.
Ryan from Central CT

Kathryn Bond

Subject: Closing vents on second floor

Since first floor is colder than 2nd in winter, if I close 3 ceiling vents on 2nd floor, won't that force warmer air back to first floor or keep it from rising to 2nd floor rooms?

Chris Nyman Weller

Subject: Heat Rises

The primary article was updated to address this... and the good news is: YES, you can close (or they recommend "partially close") the upstairs vents in order to funnel more of the heat downstairs. However, on the 2nd part of your question, you just can't beat physics. Heat will always rise. :-]

Scott

Subject: Variable speed furnace is the key

With a variable speed furnace and 2 stage AC unit in a zoned system, variations in the pressure and demand are adjusted for so these won't be issues. These are issues inherent to a single stage HVAC system.

Paul

Subject: Even without a return in each

Even without a return in each room, the efficiency of heat transfer (both in heating and cooling mode) across the heat exchanger is decreased if the airflow rate is significantly impeded. If you have an appropriately sized unit, no more than 10% of the registers should be closed. The loss due to inefficient heat exchange per unit of fuel will actually outrace heat loss from unheated rooms if the furnace is not operating in its nominal air flow range. For a 2100 Sq Ft home, closing up one or two vents probably won't have a great effect, but closing off four or more probably will. Also interior walls are generally less well insulated than exterior walls, so the heat will ultimately flow to the unheated areas anyway. When in doubt, leave registers in unused rooms slightly open to allow for proper airflow.

Brett

Subject: What are you talking about

I have never lived in a home with return air vents in each room. Every home I have ever lived in has only a single return air vent (where the filter is) in a central location, which cannot be closed off (ie. a hall or stair landing). Closing off vents in unused rooms only closes off air being fed into that room. Granted it will cause excess pressure in the ducts, but that air is forced out of the vents that are open. I don't see anyway that closing two vents out of 14 will damage anything or cause any problems.

Chris Nyman Weller

Subject: Return air in EVERY room. Seriously?

I also wondered what the guy meant when he said he has a return air vent in every room. I've lived in mostly older homes in Western Washington, Southern California, and Central New Mexico... and I also administer repairs and maintenance at a property management company... and I've yet to see a home with return air ducts in every room. Is this a real thing? Seriously?

Geoff

Subject: What are you talking about?

I have never lived in a home that did not have return air in every room that has fresh air vents. Of course, I live in MN, not in a Southern state. We have a variable speed, high efficiency furnace. A few vents are partially closed in unoccupied bedrooms and we have a clock thermostat. We are comfortable and have a reasonable budget.

Adam

Subject: The cold air return they are

The cold air return they are talking about is not the big one attached to your furnace. They are talking about the returns from each room. Usually the larger looking ones lcoated near the top of the wall or on the wall, not in the floor.

Jeff

Subject: Most homes do not have return

Most homes do not have return air ducts in each room, thus flawing your logic in saying that cold air will be sucked in through the cracks. Freezing in the ducts that are closed? Come on!

Joe

Subject: Where do you live? In

Where do you live? In Minnesota all houses have return ducts in every room. Absolutely critical to proper heating.

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what should you pay.  You pay what you can afford.  1100sqft unit requires a min. of a two ton unit.  prices range from 2100-2900 depending upon the seers of the system.  13 seer is the min. the law requires  and for your situation with 1100 sqft.  do not worry about the seers as long as it is to code.  the bigger the house the more seers for economy.  1100 sqft is at the border line for a two ton system.  It is more important to have your new system balance, there is where you get the economy on your electric bill and gas.  Bryant, lenox, ruud and carrier are the brands you should stay with.All have the same basic factory warrantee and will last you longer than you expect as long as you maintain it with regular check ups twice a year once in the spring and then in the fall.

raymond gonzalez
koolray heating and air
 clarksville,tn
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APRStore.com offers a nice sizing chart for HVAC capacitors and furnace capacitors. Most of the capacitors I've looked at are $5 to $15 dollars, so a little less than Home Depot and Lowes.

 

Replacement is really easy, but be sure to watch a youtube video on how to replace it like this one: https://www.youtube.com/watch?v=_IpydZIsOJg

 

Stay safe and hire a professional if you feel unsure about doing it yourself!

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The only thing of importance, is the hvac professional you choose to use. Alot of manufacturer's pieces are built relatively the same, and will last about the same amount of time. The thing that matters most is what you can not compare between companies, and that is the installation. Purchasing a system is not like purchasing a car, where no matter where you buy it, they are all the same. Each installation is different, and usually what you are paying for is the level of expertise, and quality of the installation, the company who will actual give you the warranty, and the comfort that you will receive. Manufacturers warranties disappear every day. They always have a loophole where they can get out of paying, but your local dealer wants to keep you happy for future work, and to protect his reputation in the communiy. Look up 4 year old Nordyne and Goodman warranty problems. Choose the HVAC professional first. It will cost you the least in the long run. I have had to totally redo plenty of installations that were just performed because of an uncomfortable customer, and a system that keeps breaking down. The equipment is only as good as it's installation, and over 70% are not installed correctly.
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I think maybe you are confusing SEER, which is an efficiency-related rating (higher SEER means more effective use of the electric power used to compress the gas), and TONS rating, which is a measure of the total cooling power of the system. (Tons used to mean how many tons per hour of ice was used in evaporative cooling building systems - a Refrigeration or Cooling Ton equals 12,000 Btu/Hour of energy exchange. A BTU, which is another antique measure but still used, is the energy needed to change the temperature of a pound of water one degree fahrenheit. Unfortunately, because of varying humidity and evaporation, this is not readily related to house air heating or cooling without a lot of assumptions and some computations. Relating this to today's world - the Manuals BayAreaAc referred to account for all these energy conversions and determine an estimated cooling (or heating) requirement for your specific house. The type of construction, solar exposure, general climatic conditions such as average temperatures, humidity, and hottest and coldest normal ambient temperatures and desired inside temperture are all taken into account in the more sophisticated versions of the analysis, so there is no "standard", though a rough old rule of thumb was about 1 ton of cooling per 500SF of house. Obviously, this was a WAG only because it did not account for insulation, type of roofing, whether you live in Alaska or Miami, etc. The ACCA manuals do a very simplified form of evaluation to arrive at a "design", which generally will be adequate. OF course, highly precise calculations are not really needed because A/C units generally come in even ton ratings - so if you are at say 2.6 ton requirement you will be getting a 3-ton unit anyway. SEER ratings are not a direct measure of efficiency, but the relative difference between ratings gives you good idea of the unit's relative efficency in using electricity - so a 16 SEER should be about 19% more efficient (so roughly comparable lower electricity bill) than a comparably sized 13 SEER unit. 13 SEER is the lowest efficiency currently allowed to be built for general use, 19 SEER is about the highest efficiency made by pretty much all manufacturers, and about 25 SEER is the highest rated though very pricey shelf-item units, though special construction custom units can reach about 30 SEER. Note however, like any government sponsored rating, much of it is hooey when you get down to it - for instance, SEER ratings are figured based on 80 degree inside air temp and 82 degrees outside, when that is far from the normal case of mid to low seventies inside and high eighties or above outdoors. This makes the absolute SEER rating meaningless, but relative numbers still have meaning in comparing units. Note these efficiency ratings are for conventional air conditoners and heat pumps working in ambient air conditions. Ground sourced Geothermal or lake/river exchange cooling units, though initially more expensive in most cases, can greatly exceed the air-exchange unit efficiencies because they are exchanging heat with cold natural water rather than with a high-temperature outside air, and instead of continually compressing a gas are just circulating cold water. I worked on one geothermal cooling project which had almost infinite efficiency, which of course makes no sense - but the only power was for sensors and a control valve as the water flow was single-pass under gravity flow, so no power was used to circulate the water.