Image Credit: Andy Shapiro
More Musings of an Energy Nerd
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…
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9 Comments
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.
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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....)
No more turbo V-8s in cars with flat tires!
Martin
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.
I know what you mean
Michael,
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.
Canadian Passive House Presentation
[Edited.]
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 http://www.acrechelsea.qc.ca/eng/events.html 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 http://www.theblacksheepinn.com/ 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 http://www.acrechelsea.qc.ca/eng/events.html 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.
Cheers,
Andrew
Thanks
Andrew,
Thanks for the invitation.
My e-mail address is [email protected] .
Martin Holladay
This is timely for me as I consider what to do with my heating system. I currently have oil-fired hydronic heating. I love the radiant heat given off by the cast iron radiators, but I can't in good conscience stay on oil for the long term. I hate burning FF, I worry about the risk of an oil leak, I'd love to take the chimney down, and the oil is expensive.
I'll be replacing my furnace with heat pumps in the next few years. Part of me would love to try a fancy air-to-water system and keep the radiant heat. But they're very rare here (and it seems most of Canada for now), and much more complicated than the mini-splits that everyone here has now. Will I be able to get parts? Will any of the installers here have experience, or am I paying for someone's education process? Will the system make sense to the next homeowner, or even to my family? The more I think about it the more I'm pretty sure I should K.I.S.S.. I know I've already made that decision when thinking about replacing my oil-fire domestic hot water heater. It will be a dead-simple electric resistance water heater rather than a heat pump water heater system. More expensive to run, but very little to have go wrong.
Ian,
I agree with your logic. Good luck!
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