Five Percent: Conserve Energy

Climate Change Is Important: Energy Conservation is the First Step


January 18, 2009

Home Energy Projects for 2009: Request for Comments

Category: Conservation,Energy Audit,Household,Sustainability,Take Actions – Tom Harrison – 6:52 pm

I have several household energy reduction projects in mind and am hoping to get some advice about which one I should take on first. I am considering:

  • Tankless (on-demand) Hot Water Heater
  • Foam Spray Insulation combined with Energy Audit
  • Geothermal Heat Pump
  • Solar (PV or Water Heat Assisted)

I have a lot of questions about which ones make sense, how to tell which one is best, how much they’ll cost, and how to measure all of it.

Tankless Hot Water Heater

We currently have a 40-gallon, gas-fired water heater in our un-insulated basement. It is not an efficient model. My family of four uses hot water at about this daily rate:

  • A low-flow shower-head that uses less than 1.5 GPM, used to take about 15 minutes of showers per day, all hot water: 22 Gallons
  • Dishwasher, run about once per day, estimated 4 Gallons
  • Various other uses, e.g. hand washing, pot washing, estimated 3 Gallons
  • No hot water for laundry — always cold

Total: 29 Gallons per day.

From this, I can then be sure that I am heating at least 11 gallons of hot water all the time for no purpose whatsoever (the tank holds 40 gallons). Worse, since the tank can heat water as you use it, it can deliver 56 gallons of heater water. We could certainly get by with a 20 gallon tank heater, although I believe the building code stipulates a certain required size based on average usage patterns. Grumble.

There are several other factors to consider here:

  • The heater is in the cold basement, and while well-insulated, the heat it does emit is wasted
  • It can take a while to get hot water up to the faucet; that amount in the pipes is pretty much wasted. I wash my hands and face with cold water on most days — not my preference in winter weather.
  • My wife and I, and sometimes my son, tend to shower in the morning before work and school, so the actual time during which we need hot water is probably and hour in the morning and after dinner at night for dishes. Doesn’t this mean we’re basically keeping water hot for 22 hours just so it can be ready for several short bursts in the other times?

The real cost of heating water would be simple to figure out: how long does the gas burner run, and at what rate, on the water heater. But we don’t have a meter for the water heater. And it’s not fair to count summer usage (when the heat, also gas, is off). Perhaps I can rig up some electronic timer or something.

Bottom line: water heating is remarkably inefficient, delivers a poor quality result (long wait for hot water at the tap), and the damnable things break unexpectedly, except are guaranteed to break during double-time, and when there is no choice of which heater to install.

On demand systems seem like a much better solution to the problem. Gas is apparently better for whole-house applications, but I wonder if a small electric unit under the counter in our kitchen could provide for the dishwasher, sink and bathroom sink close by? And if we installed an on-demand unit, must it be located so far from the main source it supplies (the shower, on the second floor)?

Foam Spray Insulation and Energy Audit

We had our 1920’s era house walls insulated with blown-in cellulose about 8 years ago. They certainly missed a lot of spots — back in 1920 they used diagonal braces at the corners of each story of the house, and fire blocks, and all sorts of other things that get in the way. We have insulated the attic floor with fiberglass and some of the basement, as well. We have modern double-glazed windows all around, and have done a pretty good job caulking. But it’s pretty clear that we could be doing a lot better. We live in Boston, which is cold in the winter and hot in the summer.

I am looking for a service that will identify where there are leaks, and missed areas and fill them in. I have to think the expanding foam would be a great option, since I would believe that it’s possible to get the stuff in fairly surgically — the blown-in cellulose require removal of clapboard siding, and that required a subsequent repainting of our house due to the chipping and so on. I have seen infra-red photos of houses, and also tests in which a big suction fan is mounted on a door so that the sources of air infiltration (drafts) can be found and resolved easily.

I have not had a lot of success finding a local service that would do such a task. I don’t have a sense of what the cost is, nor do I have a sense of how much I could reduce my heating bill.

It’s also the case that we keep the house pretty cool after 8pm and until around 7am, and then again during the days, using our programmable thermostat. But my sense is that any heat kept in (or out in the summer) is a good thing.

Geothermal Heat Pump

Geothermal certainly makes sense in some places and some houses. I think it does here in the Boston area, but I wonder what the best kind of solution is for us. A hole is drilled for pipes that go deep into the ground, and a loop is created. Water (or special fluid) is circulated through the ground loop until it reaches the ambient temperature, which is around 50° F throughout the year. In the winter, this is warmer than the air outside: it contains heat that can be extracted and used to warm the house. Likewise, in the summer, that water is cooler than the air temperature and can be used to cool the house.

The thing about heat pumps is that the “extraction” part requires an electric motor, both to pump the fluid through the pipe loop as well as to get something (air, forced water) to a higher temperature so that the house gets heated. I think most heat pumps are designed to use electricity to add additional heat to the water when it’s really cold, and that sounds inefficient. Could we use our existing gas burner in conjunction with a geothermal loop?

I would guess that cooling is simpler, especially in a house with central air ducts. We have forced water for heat — I wonder if it is possible just to pump cold water through the same radiators that we pump hot water through in the winter?

Solar for Electricity (PV), or to Augment our Water Heating

Our house’s roof ridge runs almost exactly North-South, which is the worst orientation for solar. We’re also in a failrly cold part of the world. All indications are that solar is not a good fit for us. Before I rule it out, I wonder if others have thoughts.

What about wind? Our location is also surrounded by a lot of trees, and the houses are close together. I doubt this would be feasible.

And What About Life-Cycle Assessment, Sustainability, Government Credits, and Cost

I am looking at our energy savings mostly from a “reduce my overall footprint” standpoint. In many cases, I have found that I end up saving money in my investment, but I think seeing a return-on-investment is a bad way of looking at things. It’s very realistic, but it’s bad, since the amount of energy I use does not account for the costs to society of producing a lot of CO2 — perhaps sometime soon we’ll have this kind of cost built-in to the costs of the fuels we burn.

My water heater also probably has another 3 or 4 years in it; they are pretty much designed to break just after their warranty expires. No, seriously. At what point does it make sense to replace it? (I don’t think we can know until I get an accurate measurement of how much energy it actually uses).

Are there any tax credits, now or coming that would make a difference to me? What are the limitations of such credits?

10 Comments

  1. I’d go hot water heater!

    Comment by Mr Green Gear — January 18, 2009 @ 11:50 pm

  2. I’d take a pure guess that the water heater is the better bet in terms of overall gain and ease of implementation, but I’d be interested to know what you conclude on solar power, in whatever form. For people living in rented accommodation, some of the options you discuss are not available, but use of solar power might still be possible. I’m thinking about a solar oven myself.

    Comment by Tony Wildish — January 19, 2009 @ 4:43 am

  3. Wind is probably not a good option. It depends on average sustained wind speed, the size of the swept area and the height of the tower. The fact that the houses are close together probably makes wind a bad choice.

    Have you considered solar hot water? This depends on the amount of sunlight you receive but solar hot water may be a better investment to consider than solar electric.

    Given your four choices, I think hot water is the best choice.

    Comment by Paul Lambert — January 19, 2009 @ 1:54 pm

  4. As much as I like PV solar because it’s really neat, most of the US (and New England in particular) isn’t a wonderful place to install, because of the exposure (lack of) and weather

    I would second Paul’s suggestion – look at passive solar assist for hot water heating. This can also be used with closed loop floor heating system. The in-line flash water heaters also work well (but not for heating the whole house).

    Along these lines, I was at a talk at PARC a couple of weeks ago by a solar industry analyst and his short guidance was basically “paint the house white and put a black water heater on the roof” to maximize your personal “greenness”…

    Comment by Ho John Lee — January 26, 2009 @ 12:19 am

  5. I too have a 40 gallon hot water heater that’s pushing 15 years old. I started looking at a company called Pulsar in 2006 that was going to put out a microwave-based hot water heater. Turns out the math was all wrong (1), but I still remained interested in the tankless hot water heaters.

    There are both electric and gas/propane powered models, and they work on flow capacity and temperature differential. There are units that do 2.3gpm and 45 degrees F delta, and others that do 7.5gpm and 65 degrees F delta. For me, I prefer a higher delta and flow because I like to take really long really hot showers. Sometimes energy saving be damned because the quality of my life improves after such a shower!

    Anyway, I personally am most interested in your take and experience with a tankless hot water heater. I use natural gas right now, and at today’s prices, it’s tempting to stick with it with a tankless. But electricity may soon become more and more sourced and created at home, which makes the electric models also interesting.

    I’d be interested to find out:
    * Do they result in a significant cost savings? It’s hard to separate the natural gas usage from my hot water heater vs my gas stove and oven (my wife is a chef, so it might be 50%/50%), so if you have natural gas only heating your water, you have better numbers.
    * Do they really heat the water the stated delta at the rated flow? E.g. when two showers and the dishwasher or clothes washer are going, are you disappointed with the temperature coming from the tap?
    * Do they have any unexpected cons, such as noise, installation costs, or other maintenance issues?

    Your posts are well written and balanced, with full disclosure of your testing methods. I would definitely benefit from you going tankless.

    [1] http://www.hodgeslab.org/2006/04/tankless_microwave_water_heate.html

    Comment by ooglek — April 20, 2009 @ 11:13 pm

  6. Very interesting blog. I also live in the north shore of massachusetts and I have an older house (1910) and i have an energy audit in August. Hopefully the 75% is still valid as per Bob the Energy guy. My house is not the most evergy efficient house. My heating bill was about $400/month. I have oil heating with 1 zone for most of the house (steam). My den has a gas heater. My windows are split with 50% new windows (approx 3-4 years old) and 50% older (12 + years).

    My question is for the insulation, how did you pay the contractor? Did you give them only the 25% of the total costs? Or did you have to give them the full 100% and then National Grid sends you a check for the 75%?

    I’m also looking at a tankless unit gas powered. My water heater is about 10 years old in my cold basement. It’s a 40 gallon tank. So I’m sure in the winter time my basement temperature reaches around 40 degrees or even less. My basement is made of big rocks jsut like any old house basement. So my heater has to constantly keep 40 gallons heated at about 120 degrees F. On a regualr day we use about 20-25 gallons. SO having a heater than has to maintain the water temperature is a waste. A tankless water heater I term it as ‘pay per use’ or ‘heat as you go’. You only use the gas when you need the water. In the summer the basement is still cool so the heater still has to maintain the water temp at 120 at any given time (24 hours a day, 7 days a week, 365 days a year). Now imagine I use only 2 hours of hot water a day, the savingd would be considerable. Tankless units are more expensive but even the short run benefit is great. I predict a 30%-50% reduction in gas consumption from the water heater itself.

    Solar panels in Massachusetts doesnt make sense. It’s still not cheap to buy and install and we are not favor in terms of sunshine. We might have 20-30 days of good sun in the summer?

    Energy costs are rising and a well insulated house is what will save you most of the $$ in the short run. Bob the energy auditor told me that my heating cost could be reduced by up to 50% just from having proper insulation both for the outside walls and the windows (LoE windows) and outside doors. Does it make a big difference to get the energy credit windows compared to the regular LoE? For $15 extra per window (as per Home Depot)? probably not. Just make sure that you have R-38 insulation in your attic since a lot of companies will give you only R-30. New England houses need a full 12 inches in the attic and generally R-13 or R-19 for the walls. I’m not sure for floors. Making sure you also insulate inside walls is important.

    Comment by Tree Hugger — July 21, 2009 @ 10:45 am

  7. Hi Tree Hugger —

    We payed the contractor 100%, National Grid sent us a check for the 75% rebate. This is/was a deal for work completed by 7/31/09 by contractors approved by National Grid, although our guy said he expects National Grid to extend the offer.

    Tom

    Comment by Tom Harrison — July 21, 2009 @ 7:35 pm

  8. Hi Tom,

    How long did it take NG to send you the check?

    Comment by Tree Hugger — July 23, 2009 @ 3:43 pm

  9. About 3 weeks.

    Comment by Tom Harrison — July 23, 2009 @ 10:30 pm

  10. I just had my energy audit done and he said that I will only pay the contractor 25% of the whole cost not the whole amount.

    They send their contractor and the contractor bills them for the 75%. So my total is going to be about $2000 and I will only pay $500. Thats great news. Just my attic will be $1600 for R-30 insulation.

    Comment by Tree Hugger — August 6, 2009 @ 2:05 pm

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