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?