this post was submitted on 24 Jun 2024
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Building HVAC engineering (equipment sizing, ducting design, etc.) has been largely handwavy bullshit for a very long time and only recently has moved towards any sort of precision. Not uncommon to find boiler plants that are 3-4 times the maximum heating load in the winter, or fans running at 100% 24/7 when code only requires half of that.
Costs just get passed on to tenants so there was never much motivation to do better, the only reason building owners are moving now is because of government regulation and incentive programs.
I used to work in HVAC. I remember we had a small cold room that was struggling to maintain temperature, as in, design was supposed to be 0ยฐF but it couldn't get below 36ยฐF. There was a large hole in the box that was undoubtedly the cause of the problem, so I asked the installer how they accounted for that. "Oh, I doubled the infiltration value." When I tried calculating the actual losses it was way, way higher than the infiltration value. Like, the room needed someting like 3-4 times its total refrigeration capacity to reach target with a giant fucking hole in the box.
No idea who thought putting a giant hole in the box was a good idea.
"Sealed" is also a vague suggestion with HVAC. Every ducting join, every piece of equipment, all of it leaks. I shudder to think how much heating/cooling is wasted that way.
I work in building science. It's obscene how little actual design and quality control goes into residential homes.
The typical design is just one step above being illegal, and people are often scared off of doing anything more than that by the threat of increased cost. However, they don't realize that they pay for it either way; either on their mortgage, or on utilities. Only one of those you can actually own in the end.
So how does a homeowner fix it? The duct work is already in, so is it just about choosing more wisely when replacing the furnace/ac/heat pump?
It starts early in the design process. But at that stage, it would be best to pause installation, have a mechanical engineer do the mechanical design (including equipment selection) based on an energy model and install the recommended equipment.
I loved that Technology Connections video.
Technology connections did a video on this, it's actually insane how much wastage there is
nice TC plug. One of my favorite channels and one of few reasons I use YouTube via new pipe and download the video. Let me also recommend Asianometery and Plainy Difficult.
Talking about energy wastage, next time you're walking around commercial buildings, pay attention to how many lights are on during the middle of the day.
Drove by a closed car lot the other day. The place has been abandoned for months. Weeds growing up everywhere. The entire lot is fenced off getting ready for demolition.
The only building on the lot is small and completely surrounded by glass walls, so you can see right through it. The red neon around the outside of the building is still on 24 hours.
condo had a fire and later I could see lights on every evening. I called it in but nothing happened. Seemed dangerous to me that power was not shutdown from going to it.
Ugh. Yup.
I learned that after buying my house. My furnace is 3x what my house needs and is expected to be an expensive repair someday.
DARN THOSE EVIL REGULATIONS!
Ironically in this case doing the job properly reduces costs significantly.
Everything in the chain from the outlets, ductwork, damper, valves, condensers, pipes, tray, fans, component ratings & switchboards can be reduced to a reasonable size.
Which then has peripheral benefits like reduced transport costs, crane lifts, space in service zones between floors/risers, materials & running costs of the completed building
they're filthy communists i tell ya