There I discussed mainly the design, building envelopeExterior components of a house that provide protection from colder (and warmer) outdoor temperatures and precipitation; includes the house foundation, framed exterior walls, roof or ceiling, and insulation, and air sealing materials., and heating and cooling systems. Here I'll take it further and look at water (management, conservation, and heating), performance, verification of the builder’s work, commissioningProcess of testing a home after a construction or renovation project to ensure that all of the home's systems are operating correctly and at maximum efficiency. , and homeowner education.
To continue with our discussion of the essentials, let's take a look at some of the other main areas of building a Pretty Good House.
The Pretty Good House needs to get the details right for three aspects of water.
Management. This is a given right? Getting the flashing details correct, installing an effective drainage planePath that water would take over the building envelope. Concealed drainage-plane materials, such as building paper or housewrap, are designed to shed water that penetrates the building’s cladding. Drainage planes are installed to overlap in shingle fashion (weatherlap) so that water flows downward and away from the building envelope., and keeping water away from the foundation is something that should happen on every house. Some problems are best avoided with good design (like not putting a window where water pours off of a roof, as shown in the photo below). Some need careful attention during construction (like installing the kickout flashing above that window that IS installed under a roof).
Conservation. We use a lot of water in the U.S. According to Data360, we're #1 in the world in per capita water consumption. Since 1992, we've done a lot better at putting in water-conserving fixtures in homes, but there's still room for improvement. The two biggest opportunities I see for most homes are hot water distribution and landscaping. For the former, we need better design and perhaps demand-type recirculating systems. Rainwater catchment and using drought-tolerant plants and less lawn are the way to go to reduce landscaping water.
Heating. The choice of a water heater is a complex issue. Sometimes a standard water heater is fine. Sometimes an expensive but more efficient heat-pump water heater makes sense, especially when powered by photovoltaics. In fact, that combination could be better than a solar thermal water heater. Whatever water heater you choose, just make sure it's safe and the fuel makes sense in your area.
There's plenty of opportunity even without discussing how we heat the water, however. We waste a lot of the energy of heated water by stranding it in uninsulated pipes in distribution systems that are too big and spread out in many homes. The solutions:
- Design to have a centrally-located water heater or smaller distribution system.
- Insulate all hot water pipes.
- Use a water heater with heat traps (to prevent thermosyphoning).
- Install a demand-type recirculating pump (not continuous).
A Pretty Good House should be a high-performance home, keeping the occupants comfortable and healthy, their energy bills low, and the house intact. When the building envelope and mechanical systems are done right, when the design minimizes future problems, and when understand how to operate it, a Pretty Good House is a pretty good place to live.
Do we need to quantify the performance and set thresholds? I think so. Looking at the HERS Index is a good place to start when modeling the house, but I like energy intensity as well. To throw out an arbitrary number — Hey, that's what everyone does! — let's say a Pretty Good House should have a HERS Index of 70 or lower. I've looked at a lot of rating files from different builders, and I think this won't stretch them past their elastic limit, especially given where the energy codes are taking us. (See Martin Holladay's overview of the 2012 IECC.)
Using energy intensity, I'd say we should aim for 5 kilowatt-hours per square foot of conditioned floor area or lower. For those of you in cold climates with lots of heating degree days, you can normalize to that factor as well, but I don't have a good feel for what the numbers should be there.
In addition to setting targets, though, I think we need to have some followup to see how well the house actually performs. Does the house actually perform over the first year as well as the model predicted? Were the occupants comfortable? See below for more.
A Pretty Good House can't be pretty good just because the builder says it is. It might turn out to be pretty good, but one of the best things about the Energy StarLabeling system sponsored by the Environmental Protection Agency and the US Department of Energy for labeling the most energy-efficient products on the market; applies to a wide range of products, from computers and office equipment to refrigerators and air conditioners. new homes program is that it requires third-party verification. A home energy rater gets the plans and specs in advance and completes the projected rating. Then they go out and do the pre-drywall inspection. At the end, they do the final inspection and update the HERS rating file.
That's a pretty good way to ensure that the house gets built right.
Commissioning and followup
One thing that doesn't happen much with residential construction is commissioning and followup. Once the house is complete but before it's occupied, it should go through a complete commissioning process. This is common for commercial buildings, and is a pretty good idea for residential, too. I wrote a little about commissioning a new home last year but would like to see a more robust procedure. The idea here is to check out all the systems and make sure they're performing as they should be.
Followup should be part of the process, too. When the home is a year old, let's get out the energy bills and interview the occupants. Let's look at the envelope and the HVAC systems. What's working well? What's not working as it should?
Finally, occupant behavior turns out to be a pretty big factor. Sometimes things don't work well simply because the occupants don't know how to operate the house properly. A good, detailed homeowner's manual can help solve some of the problems, but how about an orientation session, too? Give the new owners some hands-on training in how to live in their new home.
And how about the idea that Sam Rashkin promotes — the 60 year home warranty, as offered by Toyota Homes in Japan? Read more about this and his other ideas in his book, Retooling the US Housing Industry.
This has been a great exercise in thinking about how we can improve homes. Those of us who work in the field need to keep rethinking how we do things and striving for continual improvement. The energy efficiency and green building programs have taken us a long way, but the reason we're having this discussion now is that there's a lot of frustration with where many of them are headed now.
So, let's keep asking questions. Here are a few more for you:
I look forward to your comments.
Allison Bailes of Decatur, Georgia, is a RESNET-accredited energy consultant, trainer, and the author of the Energy Vanguard blog.