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Musings of an Energy Nerd

Simplicity versus Complexity

Complicated equipment has a downside

Many homeowners would be hard pressed to identify all of the equipment in a typical residential mechanical room.
Image Credit: Andy Shapiro

Designers of energy-efficient homes — especially homes aiming for net-zero energy use — must inevitably grapple with the question of simplicity versus complexity.

Residential designers can choose from an array of sophisticated appliances that improve comfort and help homeowners reduce energy use. Examples include heat-recovery ventilators (HRVs), condensing boilers, ground-source heat pumps, solar hot water systems, on-demand water heaters, heat-pump water heaters, photovoltaic modules, and co-generation systems.

Most of these devices perform well. However, designers who specify sophisticated appliances need to consider the trade-offs that accompany such hardware:

  • Higher upfront costs;
  • The need for proper commissioning; and
  • The need for proper maintenance.

Commissioning? What’s commissioning?

Builders often underestimate the importance of commissioning all HVAC equipment after installation. (“Commissioning” simply means making final adjustments and tuning up equipment to verify that it functions properly.)

Unfortunately, most new homes are imperfectly commissioned, leading to one or more of the following errors:

  • The air conditioner has the wrong refrigerant charge.
  • The airflow over the cooling coils has not been verified.
  • Duct systems haven’t been checked for leaks.
  • The airflow through forced-air registers hasn’t been adjusted to meet specifications.
  • Pressure imbalances between bedrooms with closed doors and adjacent hallways have not been remedied.
  • Exhaust fan airflow hasn’t been tested.
  • Heat-recovery ventilators have not been balanced.
  • Atmospherically vented appliances haven’t been checked for backdrafting during exhaust fan operation.
  • The temperature set-points on the solar hot water system controller are improperly set.

HVAC commissioning errors almost always result in needless increases in energy costs. Many HVAC specialists can share horror stories about commissioning errors, running the gamut from irritating to outrageous (for example, air-source heat pumps with electric resistance elements that operate for most of the winter).

You mean I have to change the filters?

For four years in the 1990s, I provided capital needs assessments — glorified home inspections — for multi-family residential projects in Vermont. During that time, I inspected hundreds of residential buildings maintained by professional management companies.

Almost all of the buildings showed signs of neglected maintenance. Among the problems I saw:

  • Crawl space pipes that had been leaking unnoticed for years.
  • Fifteen-year-old HRVs with filters that had never been changed.
  • Fresh air intake vents for HRVs that were clogged with leaves, cobwebs, and animal hairs.
  • An exhaust vent blocked by a bird’s nest.
  • Disconnected attic ducts.
  • A disconnected furnace flue.
  • Emergency lighting with dead batteries.

There’s no reason to believe that American homeowners are any better at maintenance than the average residential property management company; in fact, they may well be worse. That’s why anyone involved with home inspections can share stories similar to mine.

The more complicated equipment, the greater the maintenance headaches

Many of today’s harried homeowners don’t even know where all of their mechanical equipment is located, much less the equipments’ maintenance requirements.

Even well intentioned homeowners sometimes decide that it makes economic sense to neglect equipment maintenance. The classic example: after a few years of operation, many active solar water heaters develop problems — for example, a broken control, a burned-out pump, or a leaking tank. Faced with a repair bill of hundreds of dollars, many homeowners decide to disable rather than repair the solar equipment.

Maintenance costs eat into energy savings

Let’s say you’ve calculated that your new $7,000 solar hot water system will save you $124 a year (the average savings shown in a 2006 study by Steven Winter Associates). Since the equipment helps lower your carbon footprint, you’re willing to accept the fact that your solar water heater has a long payback period. However, the payback period may be even longer than you realize.

After saving $124 per year for five years, you’ve saved $620. But if a failed pump requires a $300 repair, you’ve just seen half your savings evaporate.

Another example: thousands of homeowners have decided to upgrade from a conventional water heater to a Polaris condensing water heater — a sophisticated appliance that is both highly efficient and frighteningly expensive. Unfortunately, many of these homeowners have seen all of their energy savings disappear; the money has been passed to the local plumber who stops by regularly to replace another failed Polaris igniter.

Moral: K.I.S.S.

Considering the potential drawbacks of overcomplicated equipment, it’s good for designers and builders to follow these principles:

  • Always favor envelope improvements (thicker insulation, better windows) over equipment upgrades.
  • When specifying equipment, keep it simple.
  • Include realistic maintenance costs in all cost-effectiveness calculations.
  • If possible, locate most of a home’s mechanical equipment in one centrally located (and spacious) room.
  • Insist that your HVAC contractor show evidence that installed equipment has been properly commissioned.
  • Provide homeowners with a three-ring binder that describes the home’s equipment and lists maintenance requirements.

As advocates for the Passivhaus standards remind us, it’s far better to have simple, inefficient heating equipment in a house with thick insulation and triple-glazed windows than it is to have sophisticated HVAC equipment in a house with code-minimum insulation.

For more information on why envelope upgrades make more sense than equipment upgrades, see Equipment Versus Envelope.

Last week’s blog: “The EPA’s Indoor AirPlus Program.”


  1. User avater
    Carl Seville | | #1

    Amen brother!
    I am right there with you Martin. I am very concerned that we have become enamored with technology at the expense of common sense. Check out this article in Fast Company, the 2009 Green Gadget Buyers Guide . It includes the Wall Mounted Efficiency Toggle (light switch), and the Onpipe Rehydration Service to replace bottled water (faucet). Makes sense to me.

  2. Dave Brach | | #2

    you hit the nail on the head
    These are extremely important points. As Americans, we really love buying gadgets and toys. This is why 90% of the conversations on energy always seems to dwell on active renewable energy systems instead of conservation, because conservation requires planning and can't be achieved with a cool and sexy off-the shelf product.

    It's quite ironic, and it has taken me a while to figure this out, but the most radical and cutting edge building products on the market today are the lowest tech: insulation, windows, caulk, air barriers, concrete (for thermal mass), window shades, etc. and the brains to choose and install them properly. These are the very things that will almost never break or wear out (well, except for the brains....)

  3. User avater
    Michael Chandler | | #3

    No more turbo V-8s in cars with flat tires!

    this is timely as I just today visited a house that has been performing well for years but saw it's energy bill double this winter. The owner is on sabbatical and has a house sitter in for the year. They heard that propane was expensive so they turned off the radiant floor and further tried to economize by shutting down the backup heat pump every night when they went to bed and turning it back on in the morning.

    Many of the complicated homes we build only work with an educated and involved homeowner. As time goes by the homeowner part of the equation shifts and the systems start to break down. The curious thing (on a couple of my older homes) is that the decision to provide a back-up system behind the complicated but efficient primary system can result in the energy saver being off line for several months before my phone starts to ring.

    I have a couple of customers out there who live with these extremely complicated systems I built in years past who are going to be in a bind for service if I ever get hit by a truck.

    Our company has really taken this whole thing to heart (esp. with our ten year succession plan, I don't want to leave this legacy to the next generation) but my own urge to play with tweaking the efficiency, and the customers enthusiasm for the latest thing provide fertile soil for over complication.

    In the end it's always about the envelope and controlling humidity. Dial those in and the rest is just icing on the cake.

  4. User avater GBA Editor
    Martin Holladay | | #4

    I know what you mean
    I know what you mean. As a builder and tinkerer and curious reporter, I have given in to temptation and added a few complicated bells and whistles to my own house. I figure that since I installed it, it's going to be easy to maintain. That's true, but the house will outlive me; then what?

    Even simple things like a few ball valves can add complexity. When I added a solar thermal system to my roof, I followed the advice of Tom Lane (the solar thermal expert from Florida) and added a bypass loop around the check valve in the collector fluid line; the bypass loop is controlled by a ball valve. When open, the ball valve activates "summer vacation mode." The idea is to shed heat from the water tank when no one is home by allowing nighttime thermosyphoning — in other words, to deliberately cool the water by shedding heat to the sky at night. This avoids overheating. But it's one more little complication that would need to be explained if I ever had a house sitter.

  5. Andrew Henry | | #5

    Canadian Passive House Presentation

  6. Andrew Henry | | #6

    Canadian Passive House Presentation (edited)
    Hi Martin,

    (edited the links AH)

    I enjoyed the posting.

    Don't know of a direct or indirect way of emailing you, so I'll do it by comment.

    I am organizing a free encore presentation of Malcolm Isaac's "Passive House Revolution" presentation. It's on Tuesday May 5th, not the 6th as presently posted as we had to change days so as not to compete with a band, at the Black Sheep Inn in Wakefield, QC.

    Malcolm's an acquaintance of Katrin Klingenberg, there's a link from the e-colab web site to Malcolm's house. I thought you might be interested in writng about a Canadian Passive House as the winter low temperatures would be among the most challenging for a North American Passive House to deal with. This past winter Wakefield had a number of below minus thirty nights. Additionally the lot Malcolm's Passive House is on is North facing, so it misses out on any Passive Solar benefit.

    There are one or two B&Bs and the Wakefield Mill is also a pretty comfortable place to stay for anyone coming from afar to the presentation; and Wakefield has a lot of great places to eat too.

    Malcolm is presently doing some contract work at the Passive House Institute, so he'll have some fresh insight on what's happening in Germany and the EU with respect to Passive House.

    Hope folks can make it to the presentation. There is an email address on this page that you can use for more info.

    Martin, I'd be happy to put you in touch with Malcolm if you are interested in his Passive House.



  7. User avater GBA Editor
    Martin Holladay | | #7

    Thanks for the invitation.
    My e-mail address is [email protected] .
    Martin Holladay

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