Image Credit: Carl Seville
Image Credit: Carl Seville The flex duct liner was strapped to the metal boot, but had no mastic applied. I really hate these site-built covers for 1-inch fiberglass filters. First, the filters don't do much of anything and they leak like crazy. The only way to seal them is to tape them up — and then no one ever changes the filter. The architect didn't leave any room for the ductwork in this house. I guess they just assumed that it would magically be taken care of.
Image Credit: Carl Seville
More Green Building Curmudgeon
In my business of certifying buildings, most of my work involves working with architects, contractors, and trade contractors who are trying to create green buildings. Unfortunately, they frequently miss the mark in some key areas.
Many of them are well intended but don’t have a broad enough view of their projects. Others only do the minimum required to meet a green building standard forced on them by someone else. And a few, thankfully, seem to get it and work hard to do the right things.
This post, the first in a series about problems I run across, will focus on HVAC.
Loads of problems with loads
All green certification programs require Manual J load calculations, and some also require Manual D duct designs. I review these reports to make sure that they meet program requirements and match the building, and in almost all cases they do neither.
In most cases I think the problems are due to ignorance or inexperience, although I have seen loads that I believe were intentionally altered to justify installing an oversized system that an HVAC contractor wanted to sell. One easy way to bump up a load is to add in excessive internal loads. I once saw a report that showed about 25 people living in a house; that made it look like the house needed about twice as much cooling capacity as it really did.
On several projects, once the loads were corrected, the contractor was able to reduce total system size significantly, ultimately saving money and improving efficiency and comfort.
Mastic, mastic everywhere, but not a leak is sealed
Once we get past the hurdle of properly sizing HVAC systems, there is still the challenge of proper installation. Proper duct installation and sealing is an ongoing problem.
I have seen installers who love to slap on the mastic — but unfortunately, they put most of it on the insulation, with little or none used to seal the actual duct connections. Once I manage to hack my way through the hardened mastic on the insulation to look at the collars and wyes, there is usually little if any mastic on the actual duct connections.
I always recommend that HVAC installers do not put any mastic on the insulation — or, if required by their inspectors, to do so only after the internal duct connections are inspected for proper sealing. I’m still waiting for someone to listen to me.
Giving me fits
Beyond problems with duct sealing, I see far too many flex ducts jammed into spaces where they don’t fit, installed between roof rafters and twisted into pretzel-like shapes.
For those projects that require a Manual D, many installers choose to ignore the design. Or in some cases the design won’t work with the structure, and they are required to redesign in the field.
One big issue when testing duct systems for total leakage is sealing of HVAC boots to walls and floors. Some programs require this sealing, but the work is too often forgotten.
And my least favorite installation, kick space registers in kitchens, are more often than not simply dumped into the cabinet base rather than being sealed to the toe kick, leading to significant duct leakage.
Location, location, location
The most consistent HVAC problem, particularly here in the South, is locating ducts in unconditioned attics. This is the responsibility of the architect or the builder.
This practice has been lamented on GBA and throughout the industry for many years, but there just hasn’t been that much progress, although some builders are moving to spray foam roof-lines to bring the HVAC into conditioned space. While this is a better solution, I just can’t get over the feeling that this is a late response to a poor design. Why not just plan to install ducts inside the building envelope and have a regular old unconditioned attic? It would cost less and work as well or better that the alternatives.
Dreaming of a job without problems…
Someday I would really like to get through an inspection and find nothing wrong, but I am not keeping my hopes up. Looking on the bright side, the constant need for inspections and corrections suggests good job security for the near future.
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6 Comments
Ductless Mini's To The Rescue
That is why I believe ductless mini's are the better solution, where applicable. Like the article mentioned, duct work always gets done incorrectly and it's all about fast and sloppy. The homeowner pays for these mistakes for the life of the home. With a ductless mini, there isn't much to get done incorrectly and with the elimination of duct work, 90% of the battle is won. Not to mention the higher SEER numbers and reduced labor costs that come with mini's.
passive and net-zero fantasies
Carl ... underlying your post is the hidden and oft avoided fact of the true cost of super-insulated airtight, passive and net-zero buildings. Doing it right is a labor of love and that love is not forthcoming from seasonal workers paid production rates.
It takes days to properly seal a building and careful attention to and the use of the right construction details that must be planned ahead of time and coordinated throughout the process. Workers have to be trained, closely supervised, instructed job-to-job, checked. and corrected. Site supervision costs are staggering. Specialty building materials are not only very costl, they are not readily available and take the time and coordination of special orders, delivery wait time, and delivery, special treatment and storage charges.
The claims of achieving high standards for <5% up to 10% are bogus. Look at the Canada Passive House Institute's ridiculous claims of relative costs followed by a couched admission of their failure to be competitive:
"For an apartment building the incremental cost for Passive House is around 3 – 5%, while for single detached houses in northern Europe the extra cost is typically higher, between 6 – 9%. In Canada building energy standards are lower than in many parts of Europe, and it is relatively difficult to source high quality components here, so the incremental cost of building a Passive House would typically be 10%, assuming that the builder has some experience and training in this type of construction. Are Passive Houses a good investment? Yes, absolutely – with an 80 – 90% reduction in annual heating/cooling fuel consumption the energy savings will cancel out much of the increased up-front investment cost of increased insulation, better-quality windows and ventilation systems.
"Even at current Canadian energy prices the total monthly cost of owning a Passive House will be very similar to the total monthly cost of owning a conventional house. However the Passive House owner will also enjoy higher indoor air quality and comfort, and will have security against rising fuel prices in the future."
This is an industry promoting itself. There is typically a 25% to 30% premium cost to building "green" and ample studies showing the savings are not realized in the life of the mortgage.
The same is true for solar, wind, geothermal and ducted HRV-ventilation systems. The math shows that the only way to afford to go green is to either be independently capitalized or rely on compound interest based mortgages. The number don't show a life cycle payback when the mortgage loans are factored in. In fact green is not really green at all, its high tech and it’s a luxury or the wealthy countries.
The only perpetual motion machine is the buyer going to the bank to pay the mortage.
Mini splits and high performance construction
Peter - I agree on using mini splits - I have them in my own house, but many people are reluctant to use them, fearing that they won't get even enough air distribution throughout their house. This can happen when doors are closed, although with a high performance building envelope, the temperature differences probably won't be much worse (and might be better) than what we see with most standard ducted systems.
To Flitch Plate: While I agree that meeting Passive House and other extremely high performance building standards likely cost more than most advocates claim, I do believe that entry level "green" building doesn't have to cost much, if any more than most standard construction. This assumes, of course, that buildings meet energy codes, building codes, manufacturer's recommended instructions (Grade 1 insulation anyone?) and there is a reasonably high quality of installation and supervision. The problem we face is that the entry level in residential construction is pretty incompetent, and often doesn't meet codes or product instructions. It would be nice if there was a bit more enforcement of codes and manufacturers were able to make sure that their products were installed correctly. In the meantime, there is still lots of work for me out there.
Green does not have to cost more than code minimums
Passive and net-zero fantasies? It is true that plenty of poorly engineered, poorly constructed or overpriced homes or systems cannot be cost-justified. But claiming that all solar, wind, and any green building can not save money is illogical, dishonest and insulting to professionals who do a good job in green building. You present no data to support your dumb universal claim. Please edit or remove your comment. I designed and built a passive solar home that cost approximately the same as typical construction and had extremely low winter heating and hot water bills. There's one example that contradicts your broad claim that all green is high tech or luxury and not going to pay for itself. I've designed super-insulated (not quite Passivhaus) homes that eliminate the need for a central heating system so cost little more than typical construction, yet would eliminate most of the substantial winter heating costs, and pay off the incremental cost of insulation quickly. There are plenty of examples of PV systems that pay for themselves via mortgaging the cost. Get real.
Certification Programs
Great article Carl, I let you guys chew on this then I have some more detail questions for Carl…..
Complaints, ability to “game the system” or “play the numbers” (IE: Minisplits w/distribution issues that are “exempt’ on the Energy Star HVAC raters check list) that crafts designs that optimize point accumulation (green energy efficiency) rather than system integration or any other goals. For example, a LEED certified home can be built that is only marginally better, in some categories, than conventional built as seen in post-build commissioning. Energy Star’s IAQ plus, fails to control toxic chemical level of materials at the build and manufacturer and they do not list it in the MSDS, there is no post build test to get the certification, no established limits (VOC parts per billion, etc) in ASHRAH 62.2 ventilation requirements either. These programs work under the ‘doing less harm” concept vs. ‘creating positive change” for a more sustainable building future. This tendency builds in the potential for complacency in thinking that if certain materials and design details are incorporated, the we have done “good enough” in “going green”, which keeps us from achieving more holistic changes to how our built environment affects it’s inhabitants and surroundings, nor encourages change in the way we design, build, use our building’s.
Passivhaus House: > .6 ACH @ 50 Pascals, no more than 4.75 kBTU of heat/sq-ft, no more than 38.1 kBTU of total energy/sq-ft/yr. Problem: penalizes smaller building’s, whose volume-to-shell is much lower than that of large building’s. The theory is the ventilation system alone can heat, or a small space heater. No scaling of the standard with respect to climate, penalizing cold climates building’s that must overcome harsher environmental conditions to meet the same standard.
Living Building Challenge (LBC) , developed in 2006 part of Living Building Institute by the Cascadia Green Building Council (a charter chapter of the USGBC). The goal is similar to LEED in developing key areas of evaluation (energy, materials, water, IAQ, and beauty) the fundamental difference is that the categories are not point-valued---they are all mandatory. There is a ‘red-list’ of excluded materials such as PVC and halogenated flame retardants. If they have to be avoided documentation of written contact with the manufacturer requesting development of products without use of the excluded materials is required for exemption. Another “fantasy” for now.
Intrinsic vs extrinsic incentive, competitive disadvantage.
Carl I feel you pain on quality, but it doesn't baffle me why it doesn't exist.
Quality costs more. Where it is not measured or rewarded it is competitive DISadvantage. You may have people with intrinsic desire to deliver greater quality, but in a "race to the bottom on cost" competitive environment, that is recipe for business failure.
In the 70's JD Powers turned quality from an esoteric to quantifiable competitive metric for the auto industry. We need transparency of results and recognition and reward for quality in Home Performance if we want it to exist and flourish.
Everything is in place, we simply need to overcome those who like current structures that allow them to avoid accountability. Excellence can't evolve without accountability.
Anybody wanting to learn more, and possibly stand with us, start here: http://bit.ly/ESHPOhioOneKnob
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