The only blue collar EA.
I have a background in carpentry and HVAC. Co-own an exotic lumber store & furniture shop with a mill and kiln. I do building diagnostics and the technical aspects of design. My company has performed ~2k energy retrofits.
JesseSmith
Karma: 264
I think to some extent the skepticism is warranted due to a mix of reduced airflow via restriction and the unknown q of bypassed airflow. Measuring airflow in a few locations with an inexpensive anemometer would be sufficient to allay these concerns, but using particulate as a proxy doesn’t seem quite as strong
Increasing pressure drop across a filter is probably the best proxy for whether a filter needs replacement. In the field, a new, high MERV filter will often have a measured pressure drop between .15 and .3 inches of water column. An increase of ~.5iwc is probably sufficient to indicate replacement. Where high merv filters are used, it’s not uncommon to have very fine particulate be the primary source of clogging which won’t be visible so visible dirt isn’t entirely reliable. It’s not uncommon for sophisticated control systems to automate this. It’s also fairly accessible as a diy tech.
Very similar to systems in the US! My sense is that many people have an ugh field wrt embracing basic trade knowledge, which is a significant impediment to even intermediate level projects. Glad you enjoyed the podcast!
Like you, I’m also somewhat surprised there hasn’t been more innovation here. I’m also disappointed by the current market for HEPA filters, and the widespread perception of HEPA supremacy. To some extent, part of the reason why we see low innovation may be connected to the problem of low HVAC competence, which I’ve written about previously
In my view there’s a point somewhere around a corsi box and possibly before where we’re probably better off embracing the HVAC trade and all of the tools and materials this encompasses. This probably means replacing tape with tin snips, and cardboard with sheet metal. These tools and materials exist for the express purpose of reducing time and expense, while delivering effective, aesthetically pleasing results. This should be done in a way that advances diy projects, but opens up an entirely new world of fans, ducts and filters of myriad stock sizes, each as separate components that can be placed together in a variety of configurations and installed virtually anywhere in a building.
As an example, vevor has a 6″, 400 cfm fan for ~$50. This is compact enough to be installed near the ceiling of a closet, which would greatly reduce motor noise in drawing air from/supplying to the adjacent room. Adding a sidewall filter grill and filter will run another $115, and we’d probably need some ductwork and a supply register. But at this point we probably have a permanent, quiet, discreet system for delivering >350 cfm cadr for <$250 in materials.
Interesting post! Is it possible that a partial explanation could be increases in cases via early or improved detection in some way?
My libertarian-ish/yimby sensibilities don’t love it. It also seems to already be a feature of many US states—eg I hold a NJ master HVAC license—and I don’t see it as have much benefit thus far.
Thanks!
Thanks!
Re 1) This is probably a factor, but I’d guess it would have low tractability and even if completely corrected would have limited impact. This was the basis for CheckMe that I mention in the post, and since then there are many technological innovations that make crosschecking really simple but have limited impact. For instance, if properly implemented, digital instruments integrated into platforms like measure quick would fix a ton of problems, but I don’t see much happening irl with this.
2) Exactly! Not sure on test, but operating within parameters doesn’t seem like a crazy ask.
3) Yes, that’s definitely on of the points I was trying to make. If we’re choosing between systems that have the theoretical capacity to work in a highly optimized way but are failure-prone and opaque vs systems that work sub-optimally but are readily verified and less failure-prone then I think we should choose the latter.
Thanks! Tbh I was pretty close to cutting that part due to superfluity so I’m happy to hear you found it insightful.
I agree that there are potential areas where drawing from a wide range of backgrounds could be better than the current structure. Tbc, I don’t want to overrate this and it’s likely highly domain specific. Long before this I started a piece on the widespread conflation of physical skills vs knowledge that characterizes much of the collapse recovery focus. This also also seems like a potential white collar silo phenomenon.
Seems right! I think some of the biggest opportunities are improvements to technology that anticipate and correct for downstream failure. To some extent sophisticated manufacturers already do this—eg constant airflow fans installed in restrictive duct systems tend to fail prematurely. Many of Mitsubishi’s air handlers now limit external static pressure to .8 inches of water column, I suspect in response to these high failure rates.
ctrl f “external static pressure”
Thanks so much for doing that!
Florida is a challenging environment. Right-sizing (manual J) of cooling equipment is especially important in humid climates. In over-sized systems, short run times tend to satisfy the thermostat but not properly dehumidify, because this takes much longer. In addition, Florida has many duct systems in unconditioned attics, and duct leakage draws humid air and contaminants from outdoors. If you have a system in an unconditioned attic this should be at minimum fastidiously sealed. Many people in building geek circles feel that conditioned attics are warranted, but my experience suggests that these aren’t often cost-effective retrofits: https://buildingscience.com/documents/building-science-insights-newsletters/bsi-119-conditioned-unconditioned
The final 2 considerations are 1) turning the AC fan to the lowest possible speed that can be sustained without freezing the indoor coil. This is generally ~325 cubic feet/minute per nominal ton of cooling. And 2) adding supplemental dehumidification. Target <55% relative humidity at ~75F. This can be a simple standalone dehumidifier piped directly to a sump or condensate pump.
For filtration, recommendations largely in line with pandemic seem fine for small particulate too—i.e. MERV 13 filters in centralized systems. IAQ monitors can be great tools as well!
Reach out directly if you need anything!
Thanks! I’m not totally clear on what curate means in this context but am definitely amenable to editing for clarity!
Those are very valid criticisms. Before posting I felt there were two major shortcomings. 1) It’s argumentative (vs scout mindset), and 2) the claims aren’t well verified. Taking a different approach with 1) felt disingenuous, but 2) remains problematic.
I’m not aware of any quality empirical work directly focusing on the shortcomings of this workforce. I think this is partly due to a significant disconnect between people working in public health and people working in the industry. So when public health people encounter this argument they say something like “yes we’ll need more training for technicians” which isn’t really the claim I’m making (an important person from a PH thinktank actually just did this in response to this post lol). I’ll try to better corroborate the claims or come up with more readily documented ones. Ultimately I think we’ll still be left with something tantamount to a firehouse of anecdotes, which readers will have to decide whether or not to take at face value.
I can definitely better explain Manual J. I’ll also give some thought to illustrating the school building manager point more effectively.
Feel free to edit the headings however you see fit. I’ll look for that feature if I make any future posts.
Is it OK if I share the original draft with you? Thanks!
Thanks Rachel!
Exactly! I’m not making observations that people in the industry aren’t aware of. On the other hand, I’ve yet to see any sort of acknowledgement that this might feature in disease reduction decision-making. It’s made the last 3 years a bit surreal, tbh.
Thanks! I just signed up. Very curious to see if this is a feature of other technical areas.
Thanks! Glad you like it!
Fan energy is a mixed bag depending on motor type. Constant airflow fans have a fairly flat pressure:CFM curve and will increase energy but PSC motors will see much lower airflow and reduced energy as a consequence.
In heat/AC systems airflow reductions outside a fairly narrow range will cause shutdown/failure due to high heat/freezing coils. In filter only systems you’d probably see low airflow and premature motor burnout. In standard motor assemblies going beyond .2 iwc increase would widely be considered quite aggressive (I have a fairly high risk tolerance for crazy stuff in buildings and probably wouldn’t do this)