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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.

“The work Community Homeworks has done for us? We never could afford it.”

Paul and Sharon returned to Kalamazoo five years ago to be closer to family. Since then, they’ve been adjusting to the challenge many older homeowners face – figuring out how to deal with home maintenance and repair issues on a fixed income.

FullSizeRender (2)Their small home on Kalamazoo’s Eastside was built in 1915 and like all older homes, when it needs repair or maintenance, it can be a challenge. Paul and Sharon first contacted Community Homeworks in the summer of 2014 with some plumbing and electrical issues. What they didn’t expect was the care and attention that they experienced from both our office staff and the field techs and subcontractors who visited their home.

“Eric, Denny, and Jason from Budget Drain were so kind and compassionate, and they provided unbelievable skill and patience in solving our problems. Robin is amazing – she’s so easy to work with and what a coordinator. Everyone is so dedicated there.” 

Our techs are always looking for other issues homeowners might not be aware of, and also keep an eye out for homes that could really benefit from weatherization improvements. Some simple repairs and air sealing around their front door made a big difference as cold weather set in, and when we launched our special Furnace Program last fall, Paul and Sharon applied and qualified. Their new high efficiency furnace was installed in November of 2014, and the savings were immediate. “Our high bill went from $285 to $139!” according to Sharon. They are now enrolled in our whole-house weatherization program and will have the additional air-sealing and insulation completed this fall, sure to produce even more savings.

It was through the Furnace Program that Paul and Sharon first found their way to our Education workshops. Everyone who received a new furnace agreed to attend 6 education workshops as part of their participation. What have they liked about the workshops? Everything. The topics are interesting, the instructors are helpful –

“The workshops are great. Even if we can’t do the work ourselves, we know what needs to be done. It makes us more informed and confident when we have to hire someone.”

We love partnering with families to help them keep their homes safe, affordable and sustainable, and we look forward to continuing to work with Paul and Sharon!

Cool Collaborations: Weatherization in Vine

Have you ever wondered what the steps are to weatherize a home? You may have noticed a draft around a window or door, but do you know how much heat is actually escaping your home and from where? And do you know how to improve the air sealing in your home enough to make a difference? Community Homeworks has just completed a pilot project with the Vine Neighborhood Association to work with a group of homeowners, tenants and landlords to weatherize eleven homes and apartments. The project was designed to bring Community Homeworks’ technical expertise and supervision together with the residents own efforts to produce real energy savings.

The first step in a weatherization project is to do an audit to determine how much air loss is happening. Have you ever heard the term “blower door test“?

Blower Door Test

Infographic by Sarah Gerrity, Energy Department.

Each home and apartment in the project had an initial blower door test performed. All the participating residents were trained by Community Homeworks on how to do the necessary air sealing of their homes using caulk and insulation. The goal was to achieve a 20-30% reduction in air infiltration in the second blower door test. Once that goal was achieved, Community Homeworks installed high-efficiency furnaces in each residence (and several new water heaters where needed). More than $70,000 in improvements were made in the 11 homes – residents can anticipate 25% or more in energy savings going forward. We are looking forward to evaluating the results of this pilot and continuing to develop innovative ways to bring the benefits of energy savings to the community.

Group Volunteer Project with Local Nurses

2014 bronson nurses volunteer day 033On June 18, 2014, a group of four nurses from Bronson Hospital’s Ortho-Surgical Unit and their family members came out to Community Homeworks’ office on Bryant St. to help beautify our block by weeding, landscaping and building a bench to go with our brand new Book Box. The volunteer event was initiated by Tina, who contacted Community Homeworks several weeks ago about group volunteering. Materials for the bench were contributed by the Edison Neighborhood Association’s Go Green Edison project.2014 bronson nurses volunteer day 012

Although the damp weather made extensive outdoor work difficult, the group was able to do some weeding and mulching in our outdoor beds. The big project was constructing the new handmade bench – using reclaimed lumber, the team got to work cutting, planing, and sanding the lumber, assembling, and applying the first coat of varnish.2014 bronson nurses volunteer day 019

Thanks to Tina for her leadership in making this event happen, to Tammy for volunteering her time and construction skills, and to Teresa, Carrie, Tasha, Casey and Megan for your hard work! If you would like to volunteer individually or as part of a group please contact Emily at education@communityhomeworks.org, or call 269.998.3275 (ext. 204). If you want to build your own bench, the plans can be found here; for information on reclaimed lumber and other deconstructed home materials, please contact Tammy Wilson at the Edison Neighborhood Association.

“I realized I love to learn.”

“I had lost all my pride in this house before Community Homeworks came along and did the things that they did. The classes they had me attend gave me all the pride back into this house…it’s like I just moved into this house!”

IMG_1211Barbara’s home in the Edison Neighborhood is nearly 100 years old. Struggling to keep up with the costs of maintaining an old and inefficient house, Barbara found her way to Community Homeworks and became part of a unique pilot program launched by Community Homeworks and Kalamazoo Valley Habitat for Humanity. In addition to receiving help with much-needed repairs and whole-house weatherization, Barbara was required to enroll in 12 education workshops.

How has her life changed? Reducing energy costs and repair expenses frees up limited resources for other essentials like food, education, and medical costs. It also makes it possible to dream bigger. The knowledge and skills Barbara acquired through the workshops at CHW gave her the confidence to take on the big project of refinishing her hardwood floors all by herself. And it doesn’t end there. Barbara’s experience of translating what she learned in our workshops into real-life accomplishment made her realize she has the capacity to do even more. “I realized that I love to learn,” she says, and is beginning to work towards a degree in Business Administration at Kalamazoo Valley Community College. We can’t wait to hear more from Barbara!

Painting Workshop at Van Tuinen Painting

On Saturday, March 29, a group of 9 low-income homeowners gathered at Van Tuinen Painting in Portage for a hands-on painting workshop, part of Community Homeworks’ “Renovations and Repairs” series. Materials for the class were donated by the Edison Neighborhood Association and Van Tuinen Painting. Participants learned about materials and techniques for painting interior and exterior spaces safely and effectively.

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Jim Van Tuinen, owner of Van Tuinen Painting, began the class with an overview of painting techniques and materials. Topics included the type of paint to use, different kinds of brushes and rollers, and ladder safety while painting outdoors. Jim then demonstrated the techniques for painting with rollers and brushes on various surfaces, including doors and window frames donated by the Edison Neighborhood Association. Participants had the opportunity to practice painting and receive feedback from Jim.

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The class was part of Community Homeworks’ education program, which teaches low-income homeowners the skills they need to save money and improve their homes. For more information and a calendar of upcoming workshops, visit the Education Program page.

“Community Homeworks saved my life.”

When Brandi contacted Community Homeworks in the fall of 2012, she was looking for help with some ongoing plumbing issues in her basement. Brandi had purchased the nearly 100-year-old home earlier that summer. Because the house was old and had been neglected for many years, Brandi expected there to be problems she would have to address. And when she ran into trouble getting the plumbing work she needed done right, she found her way to Community Homeworks through the city information line 211.

BrandiWhen the technician from Community Homeworks arrived at Brandi’s house to take a look at the plumbing, he found a more complicated situation. Brandi had  been feeling sick for several days, too sick to even get out of bed to answer the door. Fortunately, her friend was able to come and let our technician in. He noticed a strange smell in the house that was even stronger in the basement and decided to investigate, starting with testing for carbon monoxide in the air.

Testing revealed carbon monoxide levels above 150 parts per million in the basement and 75 parts per million on the first floor of the house. At those levels of exposure, death can occur within 24 hours.

So where was the carbon monoxide coming from? Most often, the source is malfunctioning gas-burning appliances like furnaces and hot water heaters that aren’t properly vented. So the first step in Brandi’s house was to disable the furnace and hot water heater to stop the CO levels from rising. The next step was to figure out if anything else might be trapping the gas in the house – one possible cause that most homeowners don’t think about is a blocked chimney flue. And sure enough, our technician discovered that the chimney was completely blocked by a large bird nest as well as sand that broken off from the mortar joints.

Brandi had turned on the furnace for the first time earlier that week with the first cold snap of the season, but her illness seemed like just a coincidence. Once the furnace was off, she began to feel better almost immediately and was back to her normal self within a day or two. And Community Homeworks was able to repair the chimney, install a new chimney liner, and bring her furnace and water heater safely back into service, as well as make the plumbing repairs that brought Brandi to us.

“I’m so grateful that Community Homeworks is here in our community. There are so many people here that need this kind of help. And you can count on them to do all the work they promise and to do it right.”

You can be a part of this story for countless more families in Kalamazoo – connect with our mission, donate to our work, or volunteer in our programming.