- Intro
- Reducing electricity consumption I: Lighting
- Reducing electricity consumption II: vampire/standby power
- Reducing electricity usage III: Major appliances
- Renewable energy for the home
- Cutting the cord
- Reducing heating and cooling costs
- Reducing water consumption
Over the last week, we've talked about myriad ways to save money and the environment by swapping out lighting, eliminating vampire power, cutting the cord, operating your major appliances more efficiently, and generating your own clean energy. Today, we're going to look at how to most efficiently heat and cool your home, because with just a little effort and relatively low investment, you can notch significant savings while lowering your carbon footprint. And as always, I make sure these efficiency upgrades fit within our modern first world lifestyle. Remember my rules:
1. I do what I do to save the world. That's my top priority, bu t...
2. Saving money is important! The upgrades have to make financial sense.
3. Don't sacrifice comfort.
I know some of you want to rail against rule #3, outraged that us decadent over-consuming Americans put too heavy a load on our environment. And sure, that is probably true. But people aren't going to change their lifestyles by bitching at them about it. I consider this approach much more productive: save money, live the lifestyle you want, and woah—bonus!—save the world while you're at it! Reality is, this stuff can be addictive. Once you go down the path of efficiency upgrades, you end up wanting to squeeze out new savings.
For example, one of my luxuries in life was scalding hot 20-minute showers. Now it wasn't my first efficiency upgrade, but once I calculated the cost of those showers? Woah. Screw that! They're now six minutes long. They could be shorter, sure, but that's still less than 20 minutes.
So here's my advice to you as you try and convince others to lower their carbon footprint: don't try to guilt them into changing their behavior, or berate them for it, or be angry about it. None of that will actually change anything. Instead, make it worth their while to live a more efficient lifestyle. Appeal to their pocketbook and make it easy for them to conserve, and that'll go much further.
And never forget the old adage about glass houses. Your efficiency record isn't perfect. For example, don't look down on someone for, say, using a dryer if you, say, still eat meat (an environmental nightmare of an industry). Be happy for the good choices that people do make. So anyway, off that soapbox onto the one I really want to be on today, let's go below the fold and talk about heating and cooling.
How many BTU’s?
- Stove top burner: 7,000/hour
- 10 minute Shower @ 5 GPM: 22,000
- 10 minute shower @ 1.5 GPM: 6,600
- Drying one laundry load: 11,000
- Heat 2000 sq ft home +40 degrees, average insulation: 62,720/hour
- One therm: 100,000
- One kWh: 3,412
The average US heating costs is $649 for natural gas, $938 for electricity, $1,992 for heating oil, and $1,500 for propane. I'm not an expert on heating systems, but wtf heating oil? Seriously, if you're still on that stuff, convert to something else already!
In any case, let's talk some basics, borrowing heavily from this excellent summary by Mr Money Mustache (really great site): You heat your home with BTUs. 100,000 BTUs of natural gas is a "therm", which here in California, costs me anywhere between $1.09 and $1.56 depending on the time of year and tier, but now averaging about $1.19 for me. If you've got electric heat, those 100,000 BTUs would equal about 29.3 kWh of juice, or a little over $5.50 at my rates ($0.19/kWh), demonstrating just how much cheaper natural gas is than electricity, at least in my neck of the woods.
Your house loses heat through thermal transmittance, as temperatures inside seek to equalize with those outside. You lose heat through leaks, walls, doors, windows, the roof, etc. Basically any external surface. Those surfaces have a "U" value, which indicates just how thermally leaky they are. So a single pane window is U-1, meaning it leaks one BTU of heat per hour for each degree Fahrenheit difference between your warmer indoor temp and the outside temperature.
So when you’re looking through a giant 10×10 foot window (100sqft), from a 70F room out into a 0F deadly-cold wintry blizzard, your window is leaking out 100 x 70 = 7,000 BTU per hour of heat into the night. That’s 7 cents per hour or $50.40 per month of heat from that single window.
Odds are your windows add up to far more than that throughout your entire house. I haven't done a full accounting of mine, but I probably have around 600 square feet of windows including my sliding glass patio door. Windows and insulating material have an "R" value, which is the inverse of the U factor. So an R value of "2" means a U value of 0.5, or the equivalent of two single-pane windows. You'll see people talk about insulating their attics to R50, which would be like stacking 50 single-pane windows.
With that knowledge, we can move up to understand the heat loss of an entire house. A 1000 square foot house probably has an outside surface area of about 2000 square feet including the roof. If it has standard R-13 wall insulation (and no windows for this example), and the temperature inside is 68F, it loses how much heat on a 32 degree day? 2000 square feet x 0.08 U-factor x 36 degree temperature difference = 5760 BTU per hour = $1.38 per day.
That's obviously an oversimplified example to make a point: your house is losing heat from all its external surfaces. This calculator will give you a rough estimate of the heating needs of your home. So for my well-insulated 2,000 square foot home, to increase my internal temperature 28 degrees (68 inside, 40 outside), I'd need 26,342 BTUs per hour. Key to that calculation is the difference between inside and outside temperatures. In other words, the smaller the difference, the smaller the heating load. So obviously, the lower the inside the temperature, the lower the heating bills. And lowering it even part of the time (like at night or when you're out during the day) saves money, even if your heating system has to work later to raise the temp back up. This is an apparently controversial assertion with some, but it's true: you don't expend extra energy lowering and raising your indoor temperature. You save it.
Lesson: Running your house at 67F during the day and 60F at night will save you about 20% on your gas bill compared to a house that runs at 72F around the clock.
HOME ENERGY AUDITS Lots of people will talk about the benefits of a home energy audit. Given my experiences, I'm not one of them. One was done by the people who put in our radiant floor heater, and the other by Solar City as part of their solar panel installation process. Both did door blower tests, used to determine how much air the house loses to air leakage. Our first audit found that the house was overly tight, and that the lack of fresh air could be dangerous, failing to remove dangerous gases emitted by things like furniture and plastics, radon, unhealthy buildups of CO2, and the like. A lack of air circulation in energy retrofitted buildings has led to what's known as "sick building syndrome".
As a solution, the contractor installed a bathroom fan and installed a vent (similar to these) on the other side of the house to allow for greater air circulation. (This was an "energy efficiency" audit, and the guy installed a Panasonic bathroom fan that sucks 17 continuous watts, when for $40 more Panasonic has a model that sucks just six. And yes, that's still pissing me off.)
Then Solar City came a year later, with their test, and found that the house was leaking TOO MUCH air, the equivalent of a 17" hole. Their test found that the home's "air changes per hour" was 0.82, when they recommended 0.35. So yeah, one test said I was moving significantly less than the recommended amount of air, while the other said I was leaking far above it. And in the meantime, the only thing that had changed was a 2" vent and the fan. I would like to say that Solar City's audit was of higher quality than the one done by the small contractor, but Solar City's was an absolute disaster, misidentifying the appliances I owned, making multiple math mistakes, recommending I replace my double-pane windows with ... double-pane windows, recommending I replace my three-year-old water heater with a tankless system, even though at the time my house had a one-year-old tankless heater, etc. And you should've seen their estimates for my lighting load, since they didn't even bother to see what kind of lights I had (LEDs, as you know from earlier this series). So I came out of the experience very unhappy with the idea of home energy audits. But it was worse than that. I got some heat leakage measurements done with an infrared gun. Stuff like this:
That's pretty helpful stuff, and reminds me that I need to double-check some of those areas out (like the lack of insulation around my hallway light fixture). However, both audits missed two of the biggest heat drains in my house: the old vents left over after I converted to radiant floor heating and my two fireplaces. I found those with my dinky $30 thermal leak detector. If the auditors could hunt down leakage around my wall sockets, you'd think they'd find the biggest culprits.
So in any case, I'm sure there are good and helpful home energy auditors out there. My experience was extremely negative, a waste of money, and nothing I couldn't have worked out on my own. Hunt down your own leaks using that cheap thermal leak detector (or heck, repurpose an iPhone 5 and create your own FLIR infrared camera for $350 if you've really got the cash to burn). Because really, I have little reason to recommend one of those guys. Maybe some of you can convince me otherwise in the comments.
Actually, there is one place where it would make sense to get an audit—if you've tightened your envelope and want to properly size your heating unit. Knowing how much BTUs you are bleeding to the outside would allow you to source a unit that isn't too big (more expensive and less efficient for smaller spaces) or too small (cold!). Otherwise, you don't need someone to find the leaks for you and tell you to plug the holes.
Finally, another way to improve indoor air quality? Plants! These plants, in particular, have been proven to remove dangerous substances from the air, and some continue to churn out oxygen even at night.
HEAT
Electrical waste heat
Before we get into the real sources of home heat, let's talk a bit about ambient sources of heat. Basically, for every watt you use of electricity inside your house, you are generating about 3.4 BTUs of heat. Heat, after all, is a byproduct of electricity usage. That's why your refrigerator compressor is warm, and power bricks and computers and light bulbs (even LEDs) and TVs and radios all get warm.
That heat gets kicked back into your house. So in my case, this month I'll average about 400 kWh of continuous electrical usage inside my home's envelope (excluding things like my radiant floor heating pumps and dryer exhaust, which is vented outside), that means an extra 1,400 BTUs per hour.
We saw above that my house needs an estimated 26,342 BTUs to heat the house during the coldest Berkeley weather, which means that waste heat covers about 5 percent of my needs, more when it's not as cold outside. Cool! I just need to shave another 95 percent of that heating requirement and I've got a self-heating house!
And yeah, those exists. In ultra-tight homes, like those built to passivhous standards, ambient electrical and human heat (and solar gain, described below) are all that's needed for heat, even in cold climates like Scandinavia. That's my long-term dream, to have a house that doesn't need any supplemental heating. Human heat, you ask? Yup. Humans generate about another 330 BTUs of heat per hour. So for my household of five, that's another 1,500 BTUs per hour. Woo! I'm now 10 percent of the way there to a self-heating house! Then again, I'm still shaving watts, so ... I just better find other ways to heat my home.
Solar gain
Direct sunlight delivers about 90 watts per square foot (1,000 watts per square meter), or about 1,500 BTUs. Most of that hits the south side of your house, so if you have any south-facing windows, guess what? That's free heat streaming into your house. Not all the heat enters your house. It all depends on the solar heat gain coefficient of your windows. They make them for warm climes (they block the heat) and cold ones (they let more heat in). But assuming windows that allow 30 percent of heat in, you've still got a serious source of heat coming into your house.
Rule of Thumb: Each 3×5 window facing South gives you about $2 per month of free heat (in a moderately sunny climate).
I linked to John Saves Energy before, and his detailed write up on passive solar heating is also worth a look. In summary, his house in Utah heats up to 76 degrees in the winter, even with outdoor temps in the 40s. Two quick tips of his:
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Remove window screens from south-facing windows in winter. John found around a 40 percent gain in heat by removing those window bug screens.
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Wash those south-facing windows. In his experiment, a dirt window reduced solar heat gain by 10 percent.
With clean windows, John calculated the actual heat production of the sun:
At my latitude, on December 21, the sun angle is ~27° degrees. With reference to vertical windows, the sun hits them at an angle of 63° on December 21, and 33° degrees on June 21. So in the case of our 0.70 windows and an average solar illumination of 1000 watts per square meter, the actual solar heating power entering through the south-facing windows varies from 1000 x 0.70 x 0.891 = 623 watts/meter^2 (58.2 watts/ft^2) on Dec 21st, 520 watts/meter^2 (48.6 watts/ft^2) in the spring/fall and 381 watts/meter^2 (35.7 watts/ft^2) on June 21. On December 21st, the winter solstice, if it were a perfectly clear, sunny day and all of the shades on the south-facing windows (275 sqft worth) were open, the equivalent of 16,000 watts of heat would enter the home. That's like 10 electric space heaters all running simultaneously, For FREE!!!
This is one of those places where the low winter sun actually works to our advantage. That was the reason eaves were invented—to block the higher summer sun while allowing in more winter sun. Then homebuilders stopped using them. Good efficient homebuilding takes those solar angles into consideration to build homes that can be extensively heated by the sun. And while winter cloud cover obviously hinders some of this heating ability, even a cloudy day passes 20 percent of the sun's potential through your windows. So maybe not 10 space heaters, but two of them is still free heat.
Note that solar heat gain is really relegated to south-facing windows. The rest of your home's windows are sucking out the heat pulled in by those southern facing windows. So good modern efficient home design stacks its windows on the south-facing side of the house, while minimizing windows on the other sides because even the most efficient windows will have R values far lower than a well-insulated wall.
Also, materials such as tile, marble, or concrete retain more of that solar heat gain than wood or carpet. Again, smart home design takes advantage of that. Most of us with existing homes, absent a major renovation, have to make do with what we have. More on thermal mass here.
Thermostat settings
We used to run the heat at 71 in our house all day and it was glorious. And wasteful. Keeping rule #3 in mind, we've still been able to reduce those temps with minimal impact. We now keep the house at 69 during the day. This almost never matters because we have heavy window coverage on our south side, so solar gain warms up the house to at least 71 degrees on the coldest days (which in the Bay Area, are in the low to mid-50s). At night, we lower temps to 66. We can't go colder because of our two aquariums.
Our planted tank has no heater, and the plants and fish can't go much lower than the high 60s (heat from the filter warms the water an extra two degrees past ambient). Our reef tank needs even higher temps, high 70s. If the ambient temperature drops too much, the tank's electric heater runs longer and at 200 watts, erases any efficiency gains I might otherwise enjoyed (remember, gas heat is much cheaper for me than electrical heat). Once the aquariums are gone I'll revisit those nighttime temps.
To be clear, it is almost always better to lower your home temps when possible (while away or at night) than to keep a steady temp through the entire day. You don't use more energy cranking up your furnace to get back up to a desired temp. (Just as you don't save gasoline by idling a car engine for more than 15 seconds rather than turning it off.) The only exception is if you have geothermal heat. Otherwise, create a schedule.
Thus, programmable thermostats are a must. I'm particularly fond of one my more recent gizmos: the Nest thermostat. At $250, the device seems ridiculously expensive. But the little sucker has already saved me serious money. Let me explain how and why.
It's a "learning" device, which means it learns your schedule and adjusts your home's temperatures accordingly. If you always come home at 6 pm, it knows to turn off during the day, but kick up the furnace in time for you to come home to your desired temp. It even learns how long it takes your furnace to heat up, so it knows the exact precise time needed to get to the ideal temp by the time you walk in the door. It also tracks outside temps via the internet, so if it's particularly cold, it knows to kick in earlier.
The learning feature is actually wasted on my family, since my wife works from home and I come and go at irregular hours (though it can sense when we're all gone and lower the temps as a result). But it's absolutely brilliant with my radiant floor heating. Radiant floor heating can take hours to move the temperature up a degree. The Nest learns how long it takes to do so. For example, I let my home's temps get down to 66 degrees at night, but I want the house at 70 degrees when we get up at 7 am. So, depending on how cold it is outside, the radiant floor will kick in between 2-4 am. But better yet, radiant heat continues warming the house even after the heater shuts off. That's the whole point of radiant—it heats the floor material, which heats furniture and walls and everything, and it is the radiated heat from your home's mass that ends up heating the air. So even after the radiant floor heat systems shut off, the air temperature continues to rise for a while before it start to fall. The Nest Thermostat knows this, so it'll kick off before the home reaches the desired set point. In other words, if it's heating toward 70 degrees, it'll kick off at 69.
The fact that it's web and mobile controllable means you can massage your settings when you're away. You can keep it low until you're ready to come home, then crank up the heat. You can plug it into your home automation if you've got that sort of thing. And all that controllability actually makes a difference. Compare my natural gas usage the past two years:
Embedded Content
Guess when I got my Nest thermostat? Mid-June of 2014. I was already notching significant savings year-over-year—the difference between having a seven-person household and a five-person one, as well as dropping our daytime temp from 71 degrees to 69 (though like I said, the latter doesn't mean much given our typical daytime solar gain). But as nice as that first-half was, the Nest-powered second half of 2014 was downright dramatic. January through May, my household averaged savings of about 20 percent over 2013. July though December, after I got the Nest, those savings are nearly 60 percent. The difference in raw therms is 270. So let's say that I would've gotten 20 percent savings regardless, that means I can attribute 178 therms of savings to the new thermostat. At $1.19 per therm, that comes out to savings of $212. In six months. It will pay for itself in about another month and a half, making for a fantastic return on investment. The December 2014 number is particularly dramatic not just compared to December 2013 (wasteful houseguest and colder temps), but November 2014, which was a warmer month. The difference there? New insulation strategies, which I'll discuss below, and shorter showers, which I'll talk more about that when I get to the "water" installment of this series.
Radiant floor
Radiant floor heating systems pump hot water through pipes in your floor to heat from the bottom up. Unlike forced air systems, radiant gradually warms the floor, the furniture, the walls, etc. You know how if you sit near a window in winter you can feel that cold draft radiating from the window? Well, this is the reverse, and it feels glorious.
Now people think that radiant floor heating means you can walk barefoot on toasty warm floors. That's not how it works. Generally speaking, the water in the pipes is about 10 degrees warmer than the target room temperature. So if you are aiming for 70 degrees, the floor will be around 80 degrees. Given that body temp is between 98-99 degrees, the floor will feel cool.
Still, the difference between an 80-degree floor and one in the 60s is dramatic and I'd never go back. Furthermore, without dust blowing around, my allergies and those of my son were huge alleviated (he no longer needed nasal spray to breathe at night). And while the heating system's water pumps were stupidly placed in the crawlspace directly underneath my bed, the sound (more of a hum) is still way quieter than that of a traditional furnace. While radiant floor proponents once pushed the notion of energy savings, the idea being that people can be comfortable at lower thermostat settings, you see less and less of those claims today. Now, it's only about comfort, and that's about right. My house never saw any energy savings from radiant. Part of that was that we went from a furnace set to 68, to radiant set to 71. It was fun being nice and toasty, and while I don't have the data to prove one way or another, energy costs appeared to be about to same or slightly higher. So don't go radiant if energy savings are your only motivation. But for comfort, it's unbeatable. If you're a handy do-it-yourself kind of person, Mr Money Mustache actually installed radiant on his own, and of course documented the process.
Air-Source Heat Pumps
I live in a two-story home. The first has radiant. The second? Nothing. Well, not nothing. I have electric heaters, but they never run. Way too expensive to do so. If my mother is visiting? She gets electric heat. My son and niece who live in the two bedrooms upstairs? They get thick blankets and, for extra cold nights, electric mattress pads (it's always cheaper to heat your body than a whole room).
But that hasn't stopped me from looking for alternate options so that upstairs doesn't get overly cold at night (especially when we have guests). The answer has become clear: air-source heat pumps.
Remember how geothermal ground-source heat pumps can be 500-600 percent efficient, using a small electrical draw to pump heat stored in the ground? Air-source heat pumps pull heat from the air, pulling in 1.5-3 times the energy used to power them. So basically, they are about half as efficient as geothermal at a fraction of the cost. And like geo, they can switch between heating and cooling. Either they're extracting heat from outside, or they're extracting heat from inside.
Their big problem is that they draw heat from the air, even cold air. But not too cold. Once temperatures drop below 40 degrees, their ability to heat is compromised and their efficiency rating falls, so they work best in either temperate climates like my own, or with supplemental heating for when the mercury dips low. Still, the technology is improving and several manufacturers now make models rated down to the single digits.
Another issue is that when pairing them with a ductless mini-split (which I would do for simplicity's sake), they emit a loud wooshing sound—a problem for me since I've gotten so used to silent heating. First world problems, I know. And really, it's not me sleeping upstairs anyway. I haven't gotten quotes just yet, but the installation of a air-source heat pump with ductless mini-split supposedly runs around $3-5,000. This is a good recap of one homeowner's experience installing an air-source heat pump with mini-split. Here's one from a homeowner in chilly Massachusetts. You can also get these things ducted, thus avoiding the mini-split eyesore.
Spot heating
It's always cheaper to heat yourself than to heat an entire room. I'm actually smitten by this heated mattress pad. I've put them on all the beds in the house. What I've found is that people turn them on to warm up the bed before going to bed, and then turn them off once they are toasty warm. The energy use has been negligible—about 60 watts when first firing, for about 20 minutes, and then only about 4 watts to maintain (at setting "2", anything higher gets too hot). And giving my home's occupants that option has made it easier to sell to the family on lowering the temps to 66 at night (and 62 upstairs). Remember the importance of Rule #3: if the family complains about something too much (with cause), they win. So this has helped ease the transition to cooler nighttime temps.
And when the aquariums find a new home and I experiment with even lower nighttime temps, having the ability to heat ourselves in bed will make that a much easier sell. Spot heating also applies to heating rooms you actually spend time in. So if you have forced air heating, close the vents on that unused guest room. No need to waste money and energy heating (or cooling) spaces that aren't being used by anyone. As for forcing people to wear sweaters and hats inside their homes? Not my thing. Rule #3!
COOLING
See above re: air-source heat pump. Why cool the air with expensive air conditioning when you can more efficiently remove the heat in your home with an air-source heat pump? Not really my area of expertise, though. [Edit: air-source heat pumps, when in cooling mode, operate exactly like air conditioners. The difference is that they can also operate in heat mode.] I live in Berkeley. We see 80 degrees or higher maybe five days out of the year. Our hottest month, September, averages a high of just 75 degrees (with nightly lows of 53 to purge any residual heat).
Also, consider a whole-house fan in the attic, especially a solar-powered one. Purging hot air from the attic can mean a five-degree difference in your home's temperature on the hottest days. Even if it's not enough to make your home comfortable, it can take a huge load of your cooling system. But yeah, this isn't an area in which I have any particular expertise. I moved to the Bay Area specifically to escape hot weather. I'm glad it's not something I have to worry about at home. If you want more, John Saves Energy has some tips. Update: This is helpful from the comments:
Progress on AC efficiency has been dramatic. Pre-1980 most A/C had a SEER below 6. Current standards typically require a minimum of 14. Units are available with SEER as high as 30.5, and SEER >20 is available in many models. SEER is based on standardized tests (assuming at 'typical' variation in indoor/outdoor temperature delta over the course of a cooling season), so the highest SEER is not necessarily the most efficient unit for a specific given application, but it's a good rule of thumb for the layman. SEER=3.412*COP COP*100 = "% efficiency" in the sense used in your table for heating appliances. Hence, 14 SEER is ">400% efficient" in that sense. Real-life performance is all about actual operating regime and system maintenance. Your location is likely to overperform ratings.
Again, I don't know much about (or have reason to worry about) cooling, but that tells me that if you're running an old AC unit, you could see huge gains with newer models. Get a heat-pump, and you have a single highly efficient unit handling most of your conditioning needs.
WATER
Today's edition has already gotten so long (over 8,000 words it looks like) that I've decided to move anything related to water to the final water chapter, including heating options. Expect that chapter after the new year.
ERV and HRV
Heat Recovery Ventilators and Energy Recovery Ventilators allow for greater air circulation in tightly insulated homes with a twist: rather than suck in cold air in the winter from a vent like the one in my house (or hot air in the summer), you use the heat from the expelled air to warm up the incoming air.
ERVs remove humidity as well, while HRVs just exchange air. In both cases, you are retaining about 70 percent of the heat (or chill) of the expelled air, lowering heating and cooling costs while insuring your house gets fresh clean air. I looked into them, but 1) they require vents, and I am busy ripping mine out, and 2) they are powered by a fan, sucking more wattage than I'd prefer. Still, I admit that I chafe at having tightened my house so well that I need a 3" hole on the side of the house in order to pull in fresh (and cold) air. If I had a bigger home, I'd certainly be looking at one of these to circulate fresh air throughout the whole house.
LEAKS
First step, seal all leaks. You can make an older home far more comfortable with some expanding spray foam and a caulking gun. Because even before you get to convection heat loss, your leaks are the equivalent of having an entire window open in your home. Some good suggestions:
- Replace old leaky windows with new one that have an air infiltration rate of < .1%
- Pull the casing off of your windows and doors, pull out any fiberglass between your windows/doors and the rough openings (it just filters the air for you. how nice) and shoot expanding foam in there.
- 3. If you have an unfinished basement, seal up the rim joists. You can do this with spray in foam, or rigid foam board surrounded with expanding foam.
- 4. Go around the outside of your house and find any penetrations where cables, pipes, whatever, goes into your house. Caulk around them.
- 5. Have a blower door test done. If you don't want to pay to have one done, rig up your own blower door setup. There are youtube videos on how to do this. Take a stick of incense and walk around the house while the blower door is running to find the air leaks and seal them up, one way or another.
- 6. At this point you've probably sealed up your house tight enough that you need to start looking at mechanical ventilation. This will take away some from your energy savings, but you will be breathing clean air that hasn't come in through your dirty walls, and attic.
Here's what I did: I got one of these cheap $30 thermal leak detectors:
You set the desired temp, then as you point it at walls, outlets, doors, windows, etc, it gives you a digital readout of the surface temperature. And it shines a light on the area it is measuring, changing colors depending on temperature: green (target temp), red (hotter), and blue (colder). So it's easy to wave around walls and corners and whatnot just looking at the light color, and when it changes to blue—ta da!—a weak point has been discovered. Then it's easy to determine whether it's poor insulation or an actual leak at play. So for example, here are some readings I took one early morning (2 am) in November as I scanned my house, all temps in fahrenheit:
Indoor air temp: 68
Outside temp: 58
Front door, top: 66
Front door, bottom: 64.4
Door crack, bottom: 63.1
Mail slot in door: 60.8
Windows: 62.7
Patio sliding glass door: 61.8
Living room skylight: 62.4
Ventilation hole: 59.3
External wall power outlets: 63
Foyer floor 67.4
Foyer throw rug: 68
Foyer interior wall 68
Foyer exterior wall 67.2
This told me that I was loosing heat to convection through the door, windows and walls, but even more heat to leaks in the mail slot in the door, through the crack at the bottom of the door, and even the electrical outlets (both light swtiches and power outlets. So last month, I attacked those. For the mail slot, I got an insulated one. Now, instead of 60.8 degrees (near parity with outside temp), it consistently measures around 66-67 degrees, regardless of outside temp. I could get a mailbox outside, but rule #3. Having the mail deposited inside my house is pretty sweet. And more secure as well. For the power sockets, I got these foam wall plate gaskets:
I installed them on all outside facing outlets in the house. When I tested outlets side-by-side, one with the gasket, the other without, the outlets with the gaskets measured a consistent 3-4 degrees warmer than those without. I also took the opportunity to spray in some foam into gaps around the wall and the electrical box. Almost all of my outlets had gaps. [Tip: wear gloves when using spray foam insulation. The stuff is insanely and obnoxiously sticky.]
The crack below the door surprised me as it seemed well covered with a little rubber skirt. Didn't matter, cold air was still seeping in. So I bought a door snake from Etsy (lots of beautiful ones available, and plenty of you are handy enough to make your own). Every night I block that under-door leakage. A lot less cold seeps in from down there.
But the two biggest leak offenders I found where the ones I already spoke about above: the old and obsolete heating vents and the fireplace. Both measured in the low 60s, and when I examined closer, both had noticeable drafts. Suddenly, the Solar City leakage test seemed far more plausible to me, a direct stream of hot air escaping to the outdoors, with cold air streaming in to replace it.
For the vents, I stuffed them full of bubble wrap (don't laugh, a great insulator), then spray foamed them shut, also taking care to spray-foam the shit out of the space around the metal vent and the wood flooring. While that seems to have killed most leakage, the vents are still colder than the ambient room temperature, so at some point I'll go under the house to completely finish sealing those off. Or I'll hire someone to completely rip them out and seal the gaps. Or I'll try to do it myself, then hire someone to clean up the mess I make. We'll see. But at least for now I don't have any more noticeable drafts anymore.
The chimneys were particularly bad offenders. We have two in our house, but unlike most people, I hate them. One is blocked off by my piano, the other one is in a den that we've converted into a kid's bedroom, and is blocked off by doll houses. They are menaces in case of serious earthquakes (the chimneys WILL collapse and cause damage to my neighbor's house), and I certainly have no interest in burning anything in them. Not only is burning wood unnecessarily horrid for health and the environment, but it actually makes the house colder. (It does!) What's worse, few chimneys can have an airtight damper (it warps from heat), so you essentially have a big hole in your roof allowing warm air to rise and escape.
But the problem isn't just air rising and falling, but the "Stack Effect", which forms a funnel of air trying to equalize the difference in temperatures between inside and outside the home. I used this stack effect calculator to figure out how much I was losing out my chimneys. One is about 30 feet high, the other about 15. They have 8" flues. I set the indoor temp to 66, and the outdoor temp to 50. Between the two fireplaces, I was losing about 677 BTUs each hour, or 16,248 per day. A more precise estimate is tough, dependent on the indoor and outside temperatures for every hour of every day of the year. I'm not about to crunch those numbers. But for the winter months, I roughly estimated a loss of five therms per month, or 8-9 percent of my natural gas usage in November. If you live in colder climes, your chimney is likely murdering your heating efforts.
I got a chimney sweeper to cap both of my fireplaces, rendering them unusable but killing the stack effect. There was still the matter of hot air rising inside the chimney, cooling at the top, and dropping back down again—still a loss of heat. But these chimney balloons took care of that. If you use your fireplace frequently, this chimney umbrella looks pretty awesome, but is available for sale only in the United Kingdom. They promised me a US distributer in 2015 though, and were willing to take an order over the phone. I don't do phones though, so that was that. As you can see above, my December therms were lower than November even though December has been a far colder month. While installing foam gaskets around my electrical outlets no doubt helped, as did the door snake, I'm convinced the biggest difference was sealing off the ducts and the chimney.
INSULATION
My house was renovated before I purchased it, and the previous owners did a good enough job of insulation the outer walls. So I don't have much knowledge to offer in this department. It hasn't been a personal need. I think these days, it's all about blown-in closed-cell polyurethane insulation, and then only if you're remodeling. The payback periods for beefing up your wall's substandard insulation is too long to generally satisfy my rule #2. But if you must do it, pay extra for the spray stuff. It forms a moisture barrier, is bug proof, and has great R-value. The Solar City audit claims my wall insulation is R9. Not sure I believe it since they got so much other things wrong, but even taken at face value, pushing it up to today's R13 standard would only (according to Solar City) give me a 4 percent savings in energy. Given the cost of such an upgrade, this would never pay for itself. The attic is a big source of energy loss. Mine isn't too bad. Overall, the R value of the insulation in my attic is R25, essentially just rolls of fiberglass insulation piled on top of each other. R50 is possible, but I'm not sure it'd make sense for me. Mr Money Mustache gives us a chart of potential savings per 1000 square feet of surface area:
So my attic is roughly 1,000 square feet of surface area. It currently has R25. Going to R50 would cost about $500 (in materials, and I'd probably have to hire someone to install). That would save me about $50 per year in heating costs. If I did the work myself, that's a 10 year payoff, so okay, justifiable. It's on my bucket list of things to do. If you want more details on attic insulation, Mr Money Mustache's write up is superb. That leaves windows. And as we've seen, windows are the biggest source of heat loss in a house. If you have old single-pane windows, that R value of "1" is killing your heating bills. According to the Department of Energy:
“Windows in the U.S. account for 30% loss of building heating and cooling energy, representing an annual impact of 4.1 quadrillion Btu (quads) of primary energy. Windows have an even larger impact on peak energy demand and on occupant comfort.”
While a typical single-pane window has an R value of 1, a double pane window has an R value of about 3. Why isn't that number 2? Because the air in between the two panes offers valuable insulation. Triple-pane windows boost that number to around 5, with fancier and more efficient (and presumably more expensive) windows available.
Again, the previous owners retrofitted my house with nice double-pane windows, but as you can see from my heat measurements above, they are still a big source of energy loss. The patio doors are particular offenders given that they are single pane. Window upgrades are crazy expensive, lucky for you and me, there are options to improve their efficiencies.
First, look into window inserts. These guys have pretty affordable inserts. I had them quote out some of my windows and skylights, and for example, a 4x4 skylight was quoted at $70. Remember, the key here isn't the material of the "glass" they use (it's vinyl, actually), but the insulating air trapped between your window and the insert.
Unfortunately, they couldn't handle some trapezoid-shaped single-pane windows I have in an older part of the house untouched by the previous owner's big remodel. Probably because getting double-pane windows for such an irregularly shaped window was prohibitively expensive. Therefore, I have a bid out from these guys, Indow. While far more expensive (about $350 for an average window, per reports), they do irregular shapes and offer professional measurements and installation. I'd rather do it myself since I can measure stuff, and the nserts are designed to pop in and out whenever necessary. But whatever, even $350 would beat the hell out of getting new windows. And they don't get in the way of architectural details for those of you with old homes wanting to preserve your original windows. In fact, Indows claims that their inserts and a single-pane window have an R value of 1.87, just shy of the R-2 value of a regular double-pane window. So you'd get most of the energy savings at a fraction of the cost.
In addition to inserts, also consider window treatments. Honeycomb shades are extremely efficient insulators, as they trap air in between each cell.
Picking a random shade manufacturer, here's their R-value chart (very similar to that of others)
In other words, honeycomb shades can be as efficient insulators as upgrading to triple-pane windows. Heck, you can upgrade to triple panes, add honeycomb shades, and you are building a mighty fortress against heat loss. I got shades (at another place) without side tracks, and I kind of regret that. While the windows clearly transmit less cold with the shades down, you can still feel the cold seeping in from the edges. It's much reduced from an open window, but still chafes a bit. Several manufacturers offer side rails, and while I decided against them for aesthetic reasons, I might reconsider if I had to do it all over again.
I just installed my new shades in all the regularly sized windows in my house two weeks ago (so not including the trapezoidal windows), so it's too early to gauge energy savings. I'm not even sure the investment will pay for itself (I installed these things in 28 windows plus the sliding glass patio doors. It got expensive, fast). But it's definitely more comfortable sitting near windows, and getting blackout shades in my room, I've found that I'm getting better sleep now (bonus!). So I'm overall pleased with my decision.
Heavy drapes also work well as insulators, but note that they create their own stack effect and tend to accumulate condensation on the windows. That may or may not be an issue given your home's circumstances (if it's dry, when you open the drapes during the day that moisture would presumably evaporate quickly). Heavy drapes can have R values up to SEVEN. And you can get thermal liners that install behind your existing curtains, so you get some insulating benefits even with your existing window treatments.
Even with single pane windows (R-1), if you add window inserts (now a combined R-2), honeycomb shades (up to R-6), and heavy drapes (clocking in at R-13), your windows suddenly would be on part with your WALLS in insulating capacity. Remember, my walls are supposedly R-9, and R-13 is considered well insulated.
For my windows, drapes don't work aesthetically, so I have honeycomb shades. My fancy double-pane windows have an R-value of 3.6, and my shades add another 3.5, putting them (at night, when I close them) at R-7.1. Interior shutters also work brilliantly, since again, they are trapping an extra layer of insulating air. They have an R value of around 3.
But even if you don't have a lot of money to spend, you can still improve on your window's efficiency with bubble wrap. Yes, bubble wrap! Remember, air is a fantastic insulator, and bubble wrap is ALL about air, adding another +1 to your window's R values. I've actually installed bubble wrap in several non-public windows in the house, like one in our closet, and in our skylights and it seems to work great. It doesn't even look bad. Kinda artsy, actually. I'll be adding it to more windows, particularly those in the north-facing side of the house. And of course, there's the old window film you can tape to windows in winter, and blowdry them tight. I tried to install those this winter and it was such a hassle I quickly gave up. Rule #3 got in the way, though I may give it another try just because I already spent the money on that damn film, and my thriftiness is butting heads with my laziness.
Update: The National Trust for Historic Preservation and several green building organizations evaluated the performance of various window retrofits, and the data is pretty clear: installing new windows makes very little sense unless you have money to burn. The report has a bunch of great info, but you can summarize everything in these two charts:
Here you can see that yes, new windows will yield the best energy savings. But interior window inserts, storm windows, cellular shades, or a combination of those gets you pretty close to the performance of new windows at a fraction of the cost. This next chart, actually, compares these options by cost and rate of return on your investment:
Cellular shades are by far the best return, while new windows is better only than new weatherstripping (which does almost nothing to save energy and money). The best one-two punch, though not included in this report's calculations, would clearly be cellular shades and interior window inserts. And also note, spending a few thousand on the shades is a far easier lift than spending tens of thousands on new windows (in this study, the difference between roughly $4,000 and $34,000).
CONCLUSION
Phew! I've just spent two days of my "vacation" cranking this thing out, but I hope it was worth it by giving you guys a good place to start in reducing your heating and cooling costs. It's quite possible to notch significant savings without really compromising your lifestyle. And while the extra money in your pocket is nice, it's double awesome when you think of the environmental benefits of building a more efficient house. I've got one more installment in this series, on water. I'll work on that one the weekend after New Years, and hopefully have it ready to go early next week. Until then, have a great New Years!