Archive for the ‘cooling’ Tag

Keeping Cool Without Breaking the Bank (Or Not)   1 comment

It’s been a hot summer here in Sacramento this year. I don’t know if it has actually been hotter than normal, but it seems like there have been more no-Delta-breeze nights with subsequent day temps near or above 100 degrees. Keeping cool has been a priority.

A few years ago I posted about some of my strategies of keeping a house cool (here and here). The first strategy is to block the sun from shining in/on the windows and exterior walls. Curtains will block sun from coming in the house but the windows and walls still heat up. Shade trees, awnings, or extended eaves keep the sun off the windows/wall so that they don’t heat up. We’ve got awnings over all of our east and west facing windows, and tall rosebushes in front of the south facing windows. The shade trees on the south side of the house aren’t yet big enough to offer shade.

The second strategy is to take advantage of breezes. At night, the breeze coming in through open windows may be able to cool the house down sufficiently to delay or prevent turning on the A/C the next day. (This strategy works great in Sacramento…when there’s a Delta breeze.) When there’s no breeze or it’s hot as blazes outside, though, fans can serve in some situations to help you cool off.

There’s a third strategy that I use but haven’t written about before and that’s to not heat the house. Sounds obvious, right? But as my husband has pointed out, most people don’t really think about it. Is it summer and the forecast says it’ll be around 100 degrees? Then don’t run the dishwasher, stove, oven, or vacuum during the day. It’ll just heat up the house and make the A/C turn on earlier. Even TVs, computers, and any other electronic appliance will generate heat. The TV on in our house for long enough for my husband to get in a game of Battlefront can raise the temperature by a couple degrees. A computer? I’ve worked from home and watched the temperature tick up as I sat in front of the thermostat (in the office) working on my laptop. Even when the A/C turns on, unless the room with the heated appliance is next to the thermostat and therefore controls the thermostat, it will still be warmer and less comfortable than the rest of the house.

We’ve managed to have a couple days early this summer when it reached 100 degrees outside and our A/C didn’t turn on because we were out of the house part of the day, didn’t turn on the TV or computers until later in the day, and moved the toaster outside for breakfast. (There are many more days when we’ve added plenty of heat load to the house, but small victories, right?) I should also mention that in summer our thermostat is programmed to 83 during the day, and my husband usually turns the cooler on manually at around 79 or 80 degrees.

One great thing about the strategy of reducing heat load is that it’s double $ savings. You’re saving money by not using electricity to power the heat-generating device(s) and saving money by reducing energy spent cooling the house. However, as we learned this year, casual applications of these strategies aren’t enough to “tunnel through the cost barrier” to borrow a phrase from Amory Lovins. I was sorely disappointed early this summer when our A/C died and had to be replaced. For a while I forgot about all the monthly savings these strategies have netted us as I stewed about having to spring for an expensive new A/C. As much as I would have loved to be able to live without heating and cooling, we’re not there yet and the new system has won me over with its super-efficiency and quiet operation.

Posted August 17, 2014 by mayakey in conscious living, energy use, frugal living, home, simple living

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Energy Vampires Beware! The Kill-A-Watt Meter Is Here!   Leave a comment

This week wraps up my personal energy audit and I have to say it has been eye opening. I’m in love with my Kill-a-Watt meter now (yes I am a nerd). I think I’ll probably keep using it to take some longer term measurements here and there, and I’ll make it available to any of my friends who want to borrow it as well. In a future post I’ll get into some of the surprising results that we got, but I’m still measuring my computer’s usage as I type this. What I have done is an analysis of what percentage of our home energy usage is heating, cooling, water heater, passive appliances, and active appliances. I did this through a combination of meter reading, bill analysis, and direct measurements. This is based on only one year, and I didn’t take into account heating degree days or cooling degree days, so the HVAC numbers have a rather high error rate.

I described in a previous post a simple method for estimating how much energy use use for heating and cooling. I forgot to mention that if you have both gas and electricity, you’ll need to convert therms into kWh. For the analysis at our old house I used the converter at convertme.com. For us: heating was 16% of the annual total and cooling was 20%.

The next task was a bit more challenging, and that was determining the passive electric load. The first step is really easy: read the meter. For a couple of weeks, every night right before I went to bed I grabbed a flashlight, pad, and pen and walked out to the electric meter to record the kWh display. And the next day my husband did the same as soon as he got home from work in the afternoon. During that time we had (almost) no active electricity use. I figure that the garage door, toaster, etc. are minor enough compared to 15 hours of passive usage that it didn’t significantly affect the readings. After dividing the difference between the two readings by the elapsed time, you get kWh/hr. Ours came to just over 5 kWh per day. That is our passive load, aka energy vampires, and includes things like the water heater, cable box, refrigerator, microwave and stove clocks, cell phone chargers, etc.

The second step was the step that I found so exciting this year, and that was measuring the contributions to the passive load from all of the applicable appliances with plugs. For several weeks I’ve been using my Kill-a-Watt meter to measure the daily electric usage for many of our appliances, including everything that is plugged in all the time. By subtracting out this measured total from the passive usage I calculated from the meter, I was able to estimate how much electricity the water heater uses and the non-water heater passive usage. For us: water heater uses 18% of the annual total and passive appliance use 13% (which means active appliance use is 33% of the total).

It is really nice to know that heating and cooling use less electricity than our appliances. Unfortunately it is probably easier to reduce energy used for heating and cooling (shade, insulation, sweaters, etc.) than appliances (turn of the TV and computer?). I did take a closer look at our passive load and I think we can reduce it by 15% by moving a few more things to power strips that get turned off at night. We found some surprising energy hogs that I’ll save for a later post.

Note that I didn’t bother using my electric rate to calculate $ spent on heating/cooling/water heating/passive/active appliances once I had the kWh, but for a lot of people that would be the desired end number.

Posted September 28, 2011 by mayakey in energy use, home

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Calculating Baseline Energy Use   1 comment

The easiest task in a personal home energy audit is to analyze electric and gas bills to observe patterns. If there’s a time of year, like spring or fall, when for an entire billing cycle neither cooling nor heating is needed than it’s pretty easy to determine an average typical non-HVAC daily and annual energy use. Then it is pretty easy to subtract and  determine how much cooling and heating increase energy demand during the appropriate season. It’s a rough calculation, since there may be seasonal fluctuations to the “typical” energy demand like more lights on during winter, but it’s a good start. I calculate that we typically use 10-11 kWh per day non-HVAC, which comes to 3,840 non-HVAC kWh over the course of a year (65% of total). Heating required approximately 990 kWh for the year (15% of total), and cooling required approximately 1,200 kWh for the year (20% of total).

The next task is to break down that “typical” energy use a bit, but this requires a bit more effort since you have to read the meters. Reading the meters isn’t challenging, especially now that digital smart meters are being rolled out. I hear that some utilities are already using the smart meters to provide customers with real-time tracking ability from their computers, but walking into the back yard and reading the meter really isn’t much work. There are a few different strategies for meter reading schedules. You can read it once per day to get a feel for your real “typical” energy use and the fluctuations, you can read it twice per day to differentiation baseline and active use, or you can read it many times per day to track specific appliances.  The latter is what I did last time I did a home energy audit, and it is a BIG PAIN! So this time I have a Kill-a-Watt to do the measuring for me, and we did twice per day readings. For a couple of weeks I read the meter immediately before going to bed, and Mike read the meter as soon as he got home. During that time there was very little active use of electricity: a toaster or blender for breakfast, a brief light on in the pre-dawn, and the garage door. I consider those to most likely be negligible over the 15 or so hours of baseline energy use. What I mean by baseline is the stuff that is always on: refrigerator, cable box, thermostat, etc. It’s the baseline because even if you eliminate all active energy demand the house will still draw this baseline amount. It’s relatively constant, with minor fluctuations like water heater working harder in winter and fridge in summer. So now I know that our baseline home energy use is approximately 4.8 kWh per day, which is almost half of our typical daily energy usage.

There’s very little that I can do to reduce that baseline energy usage. I’m not getting rid of the fridge or the alarm, and while I would love to turn off the cable box I can’t without breaking it. What I want to know is how much of that baseline goes to the water heater. By using the Kill-a-Watt I’m measuring as many of these baseline contributors as I can and then I’ll be able to calculate an estimate of how much hot water contributes to our energy usage. My guess is that it is most of the baseline.

Posted September 2, 2011 by mayakey in energy use, home

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Awning Time   3 comments

Summer’s here, and with it comes our canvas awnings. Well, they’re not needed this week since the forecast high temperatures are the same or lower than our programmed A/C setting. But a couple of weeks ago, and fourth of July weekend, getting those awnings up quickly was imperative in the face of hundred degree temperatures with no evening Delta breeze.

We have the awnings from our old house, but unfortunately discovered that they don’t quite work here. We have larger windows and an open back patio that means we get no relief from afternoon and evening sun. The old four foot long awnings don’t manage to shade the entire window and sash, especially if there is a breeze. So we got longer six foot canvases at the hardware store. This is the only cotton item that I can think of where I voluntarily purchase a non-organic fabric. The painters drop cloths at the hardware store are perfect in that they have a tight weave that doesn’t let any sun through, but are thin enough that they let the light through. I tried canvas from the fabric store one year and it was eternal twilight in the house. Since we can, this year we bought strong metal screw-in hooks to hang the awnings from the eaves. Now there is no more need to go outside after a windy day and re-glue/replace fallen/broken plastic hooks. Up until the last minute we hadn’t decided if we wanted to continue using our “cheap” canvas awning strategy or do something a little nicer since we own the house now, but it really stands out as the best option. If/when we decide to do something else, the hooks on the eaves can be used for something else like hanging plants or windchimes.

Just a refresher, the awnings are part of my primary strategy for climate control in the house during the summer: keep the sun off. If the sun doesn’t shine on the walls, it won’t heat them up as much, which in turn doesn’t heat the inside as much or as fast; and if the sun doesn’t shine in the windows the interior of the house doesn’t heat up nearly as fast. This is vital for walls/windows that face east, and even more so for walls/windows that face west. For the last two weeks I experienced the difference first hand since our office is in the one room that doesn’t have an eave so we haven’t figured out how to hang an awning. (Disclosure: we also haven’t figured out how to shade the bay window in the living room since canvas hanging from the eaves isn’t really attractive, but those windows face south and are still fully shaded by the eaves.) During the last two weeks I worked from home to avoid the offgassing of the new carpeting at my work office, and even with a curtain completely shading that window from the inside all morning long that room was significantly hotter than the rest of the house. I’d be sweating in the office (with the door closed so as to not heat up the rest of the office), but the rest of the house stayed cool well into the afternoon. In fact, even at 8 or 9 in the morning there is a noticeable difference between the unshaded office and the master bedroom, even though they are right next to each other and the bedroom is occupied while the office is empty.

In addition to buying new canvas to fully shade the windows, we are also shading part of our back patio this summer. Mike had bought one of those collapsable canopies last year and for fourth of July we put it up in the patio and hung another awning (actually our tent ground cloth) on the west side so that part of the patio is in shade all day long. This also helps to keep the house cool because then at night there’s less radiant heat coming off the concrete. For that reason we plan on keeping the canopy up for most of the summer. It’s amazing that there’s still a difference in the temperature of the concrete at 10pm under the canopy versus the exposed areas. I look forward to getting rid of much of that concrete and reducing the thermal mass around the house.

Posted July 12, 2011 by mayakey in energy use, home

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Breezing In   2 comments

Ugh, it’s hot. So… here’s part two in the series on strategies that I have used to keep my house cool (see Awnings Up for part one) without over-reliance on air conditioning.

The first principle to reduce your cooling load is to block the sun. The second principle is to take advantage of breezes (both outdoor and fan-made) and cool night temperatures.

Taking advantage of natural breezes is especially easy in this part of California since we get the Delta breeze every night (except tonight which explains why it is 11 pm and the house is still at 84 degrees). As soon as the temperature is the same outside as inside, we open up the doors and windows and let nature finish the cooling, for free. When it’s really hot, we leave some windows open overnight so that the house is nicely chilled by morning. Likewise in the morning we keep the doors and windows open until the breeze coming in is the approximate temperature that we want the house to be. If a house is warm in the morning in the summer, it will be even worse later in the day, so do whatever you can to take advantage of night cooling. Even a slightly warm breeze can actually make a room feel cooler by reducing the stuffiness.

To really take advantage of breezes and indoor vs outdoor temperatures, you have to understand not only your overall climate, but the microclimates around your house and the ventilation patterns inside your house. Vegetation, hardscape, and shade elements make a big difference outside; while knowing what path the air will take through the house helps optimize the natural cooling inside. Our driveway is shaded on the west side starting in mid afternoon, so in the evening the air in the front (south) side of the house is comfortably cool long before the temperature has dropped on the west side of the house. We can open the front door and windows relatively early, and likewise we can keep the side door (west) open until early afternoon because it is still shaded and cool there. But our bedroom is a dead zone and we have no option except the air conditioner in there.

The other aspect of breezes is of course the use of fans. They don’t cool the room (in fact they technically heat it up a little bit), but when sitting in front of a fan it is possible to be comfortable at a much higher ambient temperature than otherwise. Fans in windows and doors can help the cool night breezes reach the entire house. Not all fans move air from one side to the other, though, and there is such a thing as overkill. Using a network of four fans in an attempt to force the breeze into the dead zone that is our bedroom really showed up on our electric bill, without helping cool our bedroom much. Unfortunately, while there are EnergyStar ratings for ceiling fans, there are no efficiency standards for floor fans. The last couple of times that I shopped for a floor fan I tried unsuccessfully to find out the energy usage to make sure I bought something that would be efficient. I don’t trust marketing: “efficient cooling and ventilation!”; I want numbers.

Posted June 28, 2010 by mayakey in energy use, frugal living, home

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Awnings Up   7 comments

After a long cool spring, summer appears to be here. Last weekend we had to hang our awnings in an attempt to keep the inside temperature from getting too hot, but we still had to turn on the air conditioner briefly.

As renters, we have been limited in what we could do to make our home comfortable in the summer (especially when our landlady decided to cut down all of the trees on the west side of the house right before summer started one year). But we have figured out a few strategies that I will share.

The first principle to reducing your cooling load is to block the sun off/out of the house. If the sun doesn’t shine in the windows, then it won’t heat up the inside of the house. Better yet, if the sun doesn’t shine on the window or wall at all, it won’t heat the window or wall above ambient temperature, which will then radiate into the house. And even better, if the sun doesn’t shine on the ground near the house the amount of heat reflected back up at the walls is reduced as well. If you own your house you can plant a tree or large shrub, or construct an awning or other shading structure; but most renters are limited to just closing the blinds.

During my second summer in Sacramento I challenged myself to a no-AC summer, which meant figuring out other ways to keep the house cool. I decided to create cheap and non-permanent awnings for the west facing windows by hanging canvas drop cloths from the gutters using glued-on hooks. As I mentioned above, not too long after I moved in here our former landlady cut down the trees and turned the side yard from a mossy and shady lane into a hot dry oven. I was thrilled, I tell you, and in response we bought the longest drop cloth we could find and stretched it all the way along the west wall. Because of the proximity of our neighbor’s house that three feet of awning keeps the sun off of the entire height of the wall for most of the afternoon and evening. At one point we tried canvas from the fabric store, but discovered that the nice thing about canvas drop cloths is that they are thin enough that they don’t block all of the light, just the sun.

canvas awnings

Posted June 11, 2010 by mayakey in energy use, frugal living, home

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