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Should I Setback My Thermostat at Night?

Yes! Well, mostly yes. Well, it depends. About 99 percent of the time, setting back your thermostat at night will save you a substantial amount of money. The other one percent of the time is a much more complicated discussion, but worth looking into with these sub-zero temperatures we’ve been experiencing recently. This article is going to dive into the nuts and bolts of the matter to not only help you make informed decisions but also give you a solid foundation of how forced air furnaces work. So what do you need to know?

This article is for forced-air, natural gas or propane gas burning furnaces only. Some of this won’t directly apply to your house if you have electric radiant heat, a heat pump, geothermal, oil, or any other type of heating system in your home. Fortunately, most heating systems in Kalamazoo are forced-air gas systems. Not sure what type of heating system you have? Keep an eye on our workshop schedule for our next Heating Systems class!

I also want to point out that this article focuses on concepts and generalizations so that the average homeowner will understand what is going on with their heating system. If you are an expert in this area, please do not pick apart the article with things like latent versus sensible heat, how energy converts, density ratios, specific heat, thermal inertia, altitude, U values, etc. That being said, I am happy to write more articles in the future on specific aspects of these if anyone would like to know more. Feel free to post questions on our Facebook page.

The Basics of Heat

Before we can answer the thermostat question, we must understand what heat acts like, how heating systems are designed, and how homes are heated. The most important thing to remember right now is that heat moves from warm to cold, and the greater the difference in temperature between a warm area and a cold area, the faster the heat moves. The cold weather from outside does NOT come in to your home. The heat that is IN your home moves to the OUTSIDE.  When the heat leaves your home, the temperature drops inside.  There is actually no such thing as “cold.” Cold is simply a concept to describe the absence of heat.  Cold does not move – only heat moves.

Heat moves in three basic ways; convection, conduction, and radiation. We aren’t going to get into the differences between them right now although your furnace does use all three to move heat in your house, and heat leaves your house in all three ways.

Heat does not care which way is up. We often think and say that “heat rises.” Heat does not rise, but rather, warm air rises because warm air is lighter than cold air. This is an important concept to keep in mind because heat actually escapes your home into the cold outside from all sides, including through your basement. About a third of the heat lost in a typical old home is through the basement, while only about 10 percent is through the attic.

The way we keep heat from escaping from your house is with air sealing and insulation. One of the best insulators we know of is actually air itself. Different types of insulation – fiberglass, cellulose, spray foam, or foam board – do nothing more than trap air pockets inside it. It’s the air that is doing the insulating, not the insulation itself. BUT, and this is a big but, air that is moving is also one of the best ways to move heat. This is why air sealing is so important. Air moving through any type of insulation will move the heat out of your house at a very fast rate and make your insulation worthless.

Heat is a type of energy, much like electricity, light, or motion. Heat energy is measured in British Thermal Units (BTUs). The amount of heat energy stored in one cubic foot of natural gas is 1000 BTUs.  When you burn one cubic foot of natural gas, you release 1000 BTUs of heat energy, which heats up your furnace and is transferred into your home by the blower fan. Furnaces are sized according to BTUs; they most commonly range anywhere from 40,000 BTU to 120,000 BTU. When you get your bill from the utility company, they charge per MCF of gas used.  One MCF is equal to 1000 cubic feet, or 1,000,000 BTUs worth of heat. back to top

The Basics of Heat Loss and the Right Size Furnace

Now that we have a basic understanding of heat and how heat moves, let’s look at how we decide what size furnace to install in your home. If you install a furnace that is too small, it won’t be able to heat your home adequately in the winter. If you install one that is too big, it costs more money to run and your home becomes uncomfortable from drastic temperature swings (more on this in a little bit).

To “right-size” a furnace, we calculate the amount of heat that will move through every part of a house that is connected to the outside. This includes exterior walls, ceilings, doors, windows, basement walls, basement floors, crawlspaces, and any other place that has the outside on one side and the inside on the other. In addition, we calculate the amount of “air infiltration” that moves in and out of your home between the inside and outside.

This is done using the amount of surface area of a house component and the “R value” of the material to figure out how much heat moves through it.  We figure out air infiltration either by running diagnostic tests with a blower door, using a computer simulation model, or making an estimate from a chart based on how the home was constructed.  We put all of this information into a very large spreadsheet and calculate the total heat loss.

Now you are probably thinking “But wait! What if I build the exact same house in Florida as the one I have in Kalamazoo? You can’t say that the house in Florida needs the same size furnace!”

You would be absolutely correct. If you remember from the beginning of the article, the larger the difference in temperature between the inside of your home and the outside world, the faster heat will move to the outside. To account for this, we use what is called a “design condition.” Design condition is what mechanical contractors are required to use by the State of Michigan to properly size a heating system.

As a side note, if you ever replace your heating system in your home, be sure to ask the contractor for the “Manual J” calculations before hiring them. Manual J is the standard they are required to use to size your furnace. If they don’t have one or tell you that one isn’t needed, don’t hire them. Your existing furnace is NOT a good indicator of what size your new furnace should be. Rule of thumb, experience, or any other method they may mention is almost always wrong as well.

Design condition simply means keeping your home at 70 degrees when it is about as cold as it will get outside in your location. This is based on the 99th percentile of cold temperatures where your house is located. In Kalamazoo, this temperature is five degrees outside. Why did we pick five degrees for Kalamazoo when it’s below zero right now? This number is calculated based on the actual winter temperatures over the last 10 years. Ninety nine percent of the time, the winter temperature was above five degrees, and one percent of the time, the temperature was below five degrees.

We add all of this information to the big Manual J spreadsheet and we calculate the total heat loss of the home when it is 70 degrees inside and five degrees outside. This is given in the number of BTUs per hour the house will lose during that time. We then match that total potential heat loss of the home to the correct size furnace to have a “right-sized” heating system. This means when it is five degrees outside, the furnace will run nonstop to keep the home at 70 degrees inside. back to top

Why Not Just Put in a Super-sized Furnace?

By now, you are probably thinking that we could skip all of this stuff and just put in a great big furnace that will keep the house warm even when we have arctic temperatures outside. This is how it used to be done years ago and we find many very old furnaces in homes that are two or three times the size they should be. Oversized furnaces not only cost more to keep your house warm regardless of the outside temperature, they make you uncomfortable as well.

First, let’s tackle the comfort issue. A good analogy would be to imagine standing in front of a bonfire on a very cold night. When you face the fire, your front gets very warm and it feels nice but your backside is still freezing. You find yourself turning around over and over again in order to keep both sides of your body warm but you are never truly comfortable because you are too hot on one side and too cold on the other. Oversized furnaces work the same way. When they turn on, they send out a lot of heat all at once and immediately make the air warm in most areas of your home. They turn off very quickly and wait for the house to cool down before turning on again.

The sudden inrush of heat from the big furnace heats the air but not the furniture, walls, and other stuff in your home. Thermostats detect air temperature. This means that the furnace will turn off but the “stuff” in your house will still be cold. The heat from the air will move into the cold stuff in your home to warm it up causing the air to cool down quickly. This means the thermostat will then turn the furnace back on to heat up the air in your house again. This results in the furnace “cycling” on and off many times per hour, creating an up/down/up/down temperature swing and making the house feel drafty inside. The industry term for this is called “short cycling.”

The second reason not to oversize a furnace is that a furnace becomes more energy efficient the longer it runs. When a furnace first turns on, all of its parts are cold and the ductwork that delivers the air to your room is cold. The burning gas in the furnace must first be used to heat up all of this metal before it can move the heat to the air in your home. This usually takes about two to five minutes to happen. A furnace which is oversized might only run for five minutes before turning off again. This means that you are spending a larger amount of your gas bill just heating up the mechanical system in your basement and not in heating your living space.

So why did the industry decide to use a design temperature that only covers the heat load of a house 99 percent of the time? Remember that the furnace needs to be sized to handle really cold days, but not be too large for the warmer 30 degree days. The magic number to produce energy efficiency, indoor comfort for you, and make sure you are safe in case a polar vortex comes to town is 99, resulting in a furnace that is slightly smaller but more than up to the task. If it is below five degrees outside only one percent of the time, the outside temperature will not go too much below this for very long in most cases.  Even with the bone-chilling cold of negative 10 degrees in Kalamazoo over the last few years, it generally only happens at night and the temperature rises back up during the day. This means that the furnace will be undersized for only a few hours at a time and the inside temperatures will stay warm enough because of thermal inertia. back to top

Answer the Thermostat Questions Already!

Now we have almost all of the information we need to answer the question about setting back a thermostat at night. The simple answer to the question is yes, 99 percent of the time you should set back your thermostat at night to save money. In Kalamazoo, if it is more than five degrees outside, your properly sized heating system will have no problem bringing your home back up to temperature in a reasonable amount of time.

The complicated answer to the question is that one percent of the time you should not set back your thermostat at night, even though it would still save you money. Remember that if the temperature is five degrees outside, your properly sized furnace will run continuously to keep the inside at 70 degrees until the outside temperature rises again. If the temperature is four degrees outside, your furnace will run continuously and will keep the inside at 69 degrees. When it is 0 degrees outside, your furnace will run continuously and will keep the inside at 65 degrees. Of course, we know that the outside temperature doesn’t stay constant – the temperature typically drops at night and rises again during the day most of the time. If you go to bed at 10pm with your thermostat set at 70 degrees when it is five degrees outside, your furnace will continue to chug along to keep the temperature constant in your house.  However, if the temperature drops to -5 by 2am, the house will not instantly become 60 degrees. It will most likely be around 69 degrees inside at 2am. This is because the temperature outside doesn’t drop instantly and the inside of the house is already at 70 to start with. Because of thermal inertia, it takes time to lose the heat already in your house. As the night goes on, it may drop to negative 10 degrees for an hour right at sunrise and your house will most likely be about 67 degrees. Once the sun is up and the day warms, the temperature outside increases back to five degrees or more, and the furnace will be able to gain ground and bring the house back up to 70 degrees and turn off.

The thermal inertia in the house is why the temperature inside the home doesn’t drop as fast as the temperature outside of the home. This means that the temperature swings inside your house are substantially leveled out and most of the time you probably won’t even notice. back to top

So what happens when I set back the thermostat when it’s 0 degrees at night?

If you take the above scenario except that you set your thermostat to 60 degrees when you go to bed at 10pm, your furnace will turn off until the temperature inside drops to 60 degrees. The furnace is able to keep up with the 60 degree temperature all night, but you will have lost all of the thermal inertia in the home between the 60 and 70 degree marks when the furnace turned off at 10pm.  This means when you turn the temperature back up to 70 in the morning when it is negative 10 degrees outside, your furnace may not be able to get the temperature above 60 degrees until the outside temperature rises.  Once the temperature outside starts to rise, the furnace will slowly gain ground to get the house back up to 70 degrees.  This can take hours on a very cold day, and in some very cold stretches lasting several days, you may never get your house back up to 70 degrees until it is consistently above five degrees outside.  Your furnace ends up fighting a ten degree temperature rise instead of a three degree temperature rise had you not set the thermostat back at all.

This is all assuming that the furnace in your home is correctly sized.  If your furnace is oversized right now, then the five degree temperature may be much lower before it can’t keep up. If your furnace is undersized, then you may be in trouble when it is 10 degrees or warmer outside.  The only way to know the exact temperature at which you should not set back your thermostat is to either run a heat load calculation on your house or to experiment every time it gets very cold and track your results.

Go back to the beginning.

Seeking Technicians for our Repairs Programs

New job opportunities! (updated January 5, 2018)

We are seeking a qualified technicians to support our programs.

The full job description and application details are here for an HVAC Field Technician and for a Construction Trades Technician.

If you are passionate about serving others, working in a supportive team environment, and want to share your talents, we want to hear from you!

Three Ways to Share Our News

Would you be an ambassador and help us get the word out?

Here are three ways that we are promoting this giving season.

Please choose one, and we will provide the supplies.

So that we can provide the promotional materials you choose, call our office at 269-998-3275, or email Todd at tholm@communityhomeworks.org.

Thank you for being an ambassador of Community Homeworks!

We appreciate your support. This offer is good through December 20, 2017.

 

Yard sign: Place in your front yard or in front of your business. We will drop off and pick up.

Tabletop Brochure: This handy display will hold brochures that your customers can take with them.

Poster: Do you have a bulletin board at work? Your place of business? Here is a poster for you.

You can download the poster here.

For the yard sign, please note: per city ordinance, such signage “shall not be placed in and shall not project into the public right-of-way”.

 

Shop AmazonSmile – They Donate to CHW

Holiday shopping is easy with Amazon’s Holiday Gift Guides. Shop at smile.amazon.com, and Amazon donates to Community Homeworks. Find great gifts for everyone on your list!

AmazonSmile is a simple and automatic way for you to support Community Homeworks every time you shop, at no cost to you. You’ll find the exact same low prices, vast selection and convenient shopping experience as Amazon.com, with the bonus that Amazon will donate a portion of the purchase price to Community Homeworks.

You shop. Amazon gives.

Public Notice – Seeking Licensed Contractors

Community Homeworks is seeking licensed and insured electricians, plumbers HVAC, roofer and general subcontractors who are interested in contract work in bidding on home rehabilitation and repair projects for up to 80 homes during the 2017 calendar year.

Interested companies should contact us to be vetted and placed on our Approved Contractors list. Approved Contractors MUST also attend a one hour Pre-Construction Training at the City of Kalamazoo on 1/09/17 or 1/11/17 to be eligible to receive contracts. If interested, please contact Shaun Wright. Deadline: submissions will be accepted through 1/6/17. Community Homeworks is a HUD Sec 3, EO organization. Minority owned and small businesses are encouraged to submit.

 

2016 Summer Newsletter & Annual Report

Click here for this issue of news and financials.

COMMUNITY HOMEWORKS ANNOUNCES FREE SALE

Offering free home repair & garden supplies to income-qualified residents!

Friday, July 15, 9 a.m. to 3 p.m., At Community Homeworks, 810 Bryant St, Kalamazoo

Community Homeworks will host a Home Repair Free Sale Flyer& Garden Supplies Free Sale for low-income residents of Kalamazoo County.

Families will have the opportunity to choose items from a wide selection of free home repair and garden supplies:

hardware     planters     ceramic tile     flooring     light fixtures

building materials     holiday items    much more

Those who come to the Free Sale will be asked to sign a self-certification waiver stating that their household meets the intent of Community Homeworks’ mission and vision, and that the materials will be used for that purpose.

Although everything is completely free, attendees will need to go through a “check-out” to ensure inventory records can be updated. CHW also reserves the right to limit per-person quantities of merchandise in order to have the greatest impact within the community.

CHW receives generous donations of merchandise from its corporate partners, Education Manager Kevin Dodd explains.

“We planned the Free Sale in response to a surplus of in-kind donations,” Dodd says. “We often receive more supplies than we can use in our programs, and sharing these material resources is another way to empower families in addition to our usual services.”

Come find YOUR free home items!

 

 

Save the Date! Furnace Fest 2016

Furnace Fest 2016 is Friday, September 23.

Save this link to check for updates.

DIY Home Maintenance for February

On Groundhog Day, Punxsutawney Phil, a rodent of unusual celebrity, predicted six more weeks of winter.  This means there could be extended opportunity to remain cooped up at home and continue with our household organization projects that we started in January.  If you refer to last month’s article DIY Home Maintenance for January, you can revisit those organizational tips and check your progress.

House Interior

 

This month’s article focuses on what you can do to document your belongings once you know what you have and where it is.  Compiling a home inventory or updating one you already have can help you in cases of theft, fire, or natural disaster.  While nobody likes to think about the potential for these unpleasant events to occur, a little preparation can go a long way to making the process of dealing with your insurance company easier should there be a loss.

 

Check out February’s Homeowner’s Insurance workshop at Community Homeworks to find out about the types of coverage and how home maintenance can affect your rates.   Learn about theft and fire prevention in our Home Safety and Security workshop scheduled for March.

This is a project you can do one room or area at a time so you don’t get overwhelmed by the process.  Schedule a weekend or several to get it all done. A little bit of work will provide substantial peace of mind. The following list of steps was taken from Todayshomeowner.com. They say that to prepare a home inventory you’ll need a computer spreadsheet or paper notebook, camera and/or camcorder, and a tape measure.  Ready, set, go!

  1. Outside: Take a video of all sides of the outside of your home, including patios, landscaping, hardscaping, and sheds. Follow this up with photos from each angle. Take close-up photos of specific items, such as rockwork, outdoor kitchens, water features, and lighting to show detail. Record measurements, model and serial numbers, purchase price, and any other information that could help you determine the replacement value of the object.
  2. Rooms: Next, move through your house room by room with a camcorder to video the interior. Slowly pan the room, starting at the upper left area from where you’re standing and moving toward the right, then down and back to the left across the lower half of the room. Repeat the process by taking wide-angle still photos of the room from each corner.
  3. Individual Items: Now focus your camera on individual items of value. TVs, stereos, furnishings and rugs, equipment and tools, anything that would be important to replace in the event of loss. As you take photos, record on your spreadsheet each item’s name and image file number, along with as much information as possible. Record brands, model and serial numbers, measurements, and descriptive features.
  4. Document Ownership: Finally, you’ll need to compile information to prove your ownership of each item. Record purchase dates and sources on your spreadsheet, and attach receipts and any appraisal statements to the inventory. Or, you can scan relevant document and attach them digitally to your inventory spreadsheet.
  5. Secure File: If you compiled the inventory on paper, organize all documents neatly in a three-ring binder. If your inventory is in digital format, organize the digital files and copy them to flash drive, CD, or DVD. Make three copies of your inventory: one to keep at home, one to keep in your safety deposit box, and one to store in a remote location, such as with your insurance agent or a family member.
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