Older homes frequently aren't very energy efficient because power used to be extremely cheap and building codes varied widely. In mild climates, that tended to happen even more. Our home in Oakland was built in 1948 and was far from energy efficient when we bought it: single-pane windows and doors, some of which didn't close well; original floor furnace; no insulation in the ceiling or walls; drafty fireplace.
I've done work on the house (and built a small addition), with a lot of it geared towards making the house more comfortable and energy efficient. I added glass fireplace doors shortly after we bought the house, and I've added insulation in the walls whenever I have a wall opened up for a project. But a lot of my efforts have been educated guesses at best.
These days in California, buildings (including my addition) have to be built to meet or exceed Title 24. It's not as energy efficient as GreenPoint rated or LEED rated, but it's a big step up from no efficiency requirements at all. Those rating systems are geared towards new buildings and remodels; for an older home, it's hard to tell how energy efficient it is, and, more importantly, how to make it more efficient and more comfortable in the most cost-effective way.
One way to do that is with an energy audit, and there are a couple of ways to do one. Sometimes your local utility will offer them for free or a low cost, but the results I've heard about locally are mixed.
Another way is to use the Home Energy Yardstick listed on the Energy Star website. For this you enter the size of your house, your power bills for the year, and your zip code, and it gives you a score relative to other homes and suggestions about reducing your energy usage.
Our house scored a 9.4 out of 10, which is pretty good. That's 3 MtCO2eq of greenhouse gas emissions — the equivalent of 0.51 cars. Reducing our energy usage 25% would get us to a 9.9, reduce the greenhouse gas emissions by 0.7 MtCO2eq, and save us about $197 a year in utility bills. I'm not sure we could reduce it that much without a big investment, but every bit helps, and the website's suggestions start off pretty good (with some useful guides for DIYers):
- seal air leaks in your home – DIY guide [PDF]
- seal the leaks in your ductwork (10% leakage or less) – DIY guide [PDF]
- add more insulation to your home (R-30 in the attic, R-13 in the walls)
But how much air is leaking? How much are the ducts leaking? How much will more insulation help? I've got R-19 or more in the attic and R-13 in the walls that I've had open for different projects, but how much will increasing that help? The DOE's Energy Savers site gives tips on how to find out where the air is leaking, but doesn't let you know the rate.
The suggestions then move on to some other possibilities, but given the small amount of information in the form, they're pretty generic:
- consider replacing your heating and cooling (HVAC) equipment
- consider installing an Energy Star qualified water heating system
- consider Energy Star qualified windows when replacing
- replace your lights with Energy Star qualified lighting
- install a programmable thermostat
- look for Energy Star qualified products
A lot of that doesn't apply to our house. For example, we've got an on-demand water heater that's only a couple years old; we already have CFLs and fluorescent lights everywhere possible; and we've had a programmable thermostat since we bought the house. And, of course, Energy Star ratings for appliances have to be taken with a grain of salt these days because of the GAO's recent findings about fraud. Fortunately steps are being taken to make it harder to get Energy Star ratings so hopefully they'll be more reliable soon.
Then about a month ago, I attended a local fair called Greening Oakland Homes that was put on by a community action group. One of the presentations at that was by Building Solutions, a Bay Area company specializing in home energy efficiency. I decided to have them check my house.
Building Solutions measures the house directly, so I was expecting a lot of information and wasn't disappointed. Before they arrived, I sent them gas and electric bills for the past year and answered some basic questions about the house. Once they arrived, they measured each room of the house, as well as the size and type of window on each wall. Their software performs a room-by-room analysis, similar to the energy usage calculations done for Title 24. They noted the make and model of the appliances, and inspected the attic and basement / crawl space for insulation and to examine the furnace and ducts.
They tested the air flow of each furnace vent, then sealed them all off with masking tape and pressurized the duct system with a blower to test for leaks. After that, they made sure all the doors and windows were closed and set up a blower door. That put a negative pressure in the house to test it for leaks. Based on how hard the blower has to work and the size of the house, they can calculate the size of the leaks. While the blower is running, you can also get an idea of where some of the leaks are by feeling for drafts. There was less of a draft around the original single-pane windows in the living room than I thought there would be, and a surprising amount in the fireplace even though the damper is closed and we have glass fireplace doors.
The next week, Building Solutions came out and delivered the report. I knew there was a fair amount of air leakage because the house was built in 1948 for a Northern California climate, but I was a bit surprised at just how much. Testing showed 1.28 air changes per hour — the equivalent of having a hole 11.91 inches in diameter in the house. There has to be some exchange of air to get fresh air into the house, but it should be closer to 0.5 air changes per hour. So first on the list of things to do is to seal the house better.
A pleasant surprise was that the duct system tested well, only 6.3% leakage. That's not zero, but below the 10% level suggested by Energy Star. The duct and furnace testing also provided other interesting results. The furnace is considerably oversized for our house. Building Solutions explained that HVAC contractors don't have much motivation to properly size a furnace. Their goal is no callbacks because of a house not getting warm enough or warm fast enough. An oversized furnace helps make sure that doesn't happen, but it's not as efficient as it could be, sort of like driving a sports car in stop and go traffic. A better choice when we have to replace it would be a multi-stage furnace that can adjust the amount of heat it produces.
Testing also showed that the dining room and living room get a lot more air flow than they need to be comfortable, whereas the master bedroom (which was added later when I built the addition) doesn't get enough. We don't find any of the rooms uncomfortable, but it does suggest the vents could be better balanced. And doing some additional sealing of the ducts to get closer to 0% leakage is worthwhile.
Not surprisingly, there was no savings to be had from switching to fluorescent lighting, since we've already got CFLs and fluorescent lights throughout the house. Similarly, the dishwasher is new (the bottom of the old one was rusting) with the kitchen remodel and so replacing it with the very latest and greatest would only save $5 a year. A new, efficient refrigerator, on the other hand, could save up to $97 a year.
Finally, replacing the remaining original single-pane windows with new, dual-pane ones would help a little with energy usage, but not enough to pay for them. It would help with comfort, and when the wall was open to replace them would be a great time to insulate the walls of the living room. Unlike new windows, that would pay for itself fairly quickly.
You'll notice that solar photovoltaic panels weren't in their report. Not that we wouldn't love to have an array, but our electricity usage is low enough and there's currently enough shading from trees in the neighbor's yard that it would take a long time to pay for itself. Before PV, it makes more sense to consider solar hot water, which isn't as adversely affected by shading, but first is sealing and insulating.
For less than $300, I found the audit well worth it for the additional information. For people who aren't the DIY type, Building Solutions is a contractor, too, and can be hired to implement any of the suggested items, from sealing the house better to solar hot water. (If you hire a company to work on your home, be sure they're licensed in your area.) For me, the audit let me know I've been on the right track with my DIY efforts, but also lets me know I need to concentrate more on sealing the structure.
This article was kindly contributed by Gene Anderson who blogs about various home improvement projects on the site DIY Insanity. He's currently tinkering with Google PowerMeter, so check his site out.