An update video with a couple of video topics I'm floating

Perhaps one of the reasons oversized heat pumps are suggested is for their heating capacity during winter. It's possible a 3-ton unit may be required to keep the house warm in the winter, but may be oversized for cooling during summer. Some winter performance data would be helpful. I also suspect installers don't know how to size ventilation ducting. The house I'm in has long tiny ducts that are further split into long tiny ducts that do a poor job of heating/cooling all the rooms upstairs, yet the master bed/bath (upstairs) got a short monstrous duct that is clearly overkill for the task. The installers did a better job downstairs.

I'm late to the convo, but better late than never. After watching your video, I have two thoughts. One, you're right about central heating/cooling and that modern homes (x<30yrs) should be using this approach. Second thought, your concern over HVAC efficiency really takes root in passive environment control; insulation. Myself and many engineers who deal with facility management always need to take into account the "building envelope" and "fenestrations". I would suggest diving into ASHRAE materials on insulation and making a presentation on envelope materials, build orientation, and heat transfer. This is stuff some PEs literally think about for their entire career. An AC system will always be more efficient if you know how to first build an effective building envelope...and not put the duct work in the attic.

Grant Somerville

An HVAC installer friend of mine told me that the price they paid for the hardware would go down as the volume they sold went up. (The price difference was substantial.) I don't know if it was split by product category, but I could see this resulting in heat pumps being inexplicably more expensive because the sales volume was low. Location - Central Texas

Huh, I lived in Houston and (in my experience at least) it was hardly uncommon to blast a foot of insulation up into the attic without any rafter insulation.

I’m glad I live in the south, specially central Texas. Most of the HVAC companies in Texas would rather undersized than oversized a unit.

Massively undersized ducts are another common issue I have seen, especially in upgrades. Installers often ignore the increased airflow requirements of newer, more efficient systems. A recent example I saw was a 1960s furnace in a 1000 sq ft mild climate home that was replaced with a 2-ton heat pump without changing the ductwork. The entire home was served with four 4-inch ducts (plus an always-closed bathroom register). That's only good for 4x20 = 80 CFM. The unit, per spec, ideally required 800 CFM, and at least 700 CFM. Unsurprisingly, the system was unable to cool or heat well. Two separate techs were unable to figure out anything wrong with it after checking pressures and air temperatures. After researching the airflows, I was confident enough to have a contractor replace the ductwork to my exact specs. Even then, the contractor was complaining that I am oversizing the ducts, even though I spaced the ductwork to a total of 875 CFM, which is not too high. Needless to say, the unit is now working fine after the ductwork upgrade.

Ahmad Rahmati

When I moved into my home in southern CT in 2015, I had three companies come to give me a quote on replacing my furnace and installing central A/C. The first two companies suggested "Jurassic Park"-like tonnage for the A/C unit. When the rep from the third company came in, I showed him the other quotes, and he just laughed. "You install units this big," he told me, "you'll never get rid of the moisture. That's just malpractice." We had a longer discussion about it (standing in my basement), and he explained that Connecticut requires that an A/C system is enough to cool down the home to x degrees when it's y degrees outside. Even acknowledging that climate change is having a tremendous impact on the number of hot days we're having, he said that a lot of his competitors were trying to push more expensive, too-big units "just to be safe." But if your A/C isn't cycling long enough to get rid of the moisture in your home, that creates its own (significant!) issues. I told him that the "just to be safe" comment (which I'd heard from both of the previous salespeople) made me so angry because 1) that's not how HVAC systems work, and 2) preying on a homeowner's fear of doing it "wrong" so that you can sell a more expensive system is unconscionable. How many elderly people do we know who would hear "just to be safe" and say "Oh, well then, let's go with the 'safer' system (that just happens to cost $3,000 more)!"? Needless to say, I've used this company ever since and have recommended them to a half dozen friends who have needed new systems installed. They have never disappointed. (And I get a $175 credit each time, which is nice!)

I bet government incentives are playing a big role too. If the government will give you $3000 toward a heat pump, raise those prices $3000.

Wolfin.me

When we replaced the system in a rental house in Idaho several years ago, the installers happened to suggest a 2-zone system, which we went with. It was FANTASTIC being able to keep different floors at roughly the same temp. In 2020, almost no companies here in Eastern Washington even understood the concept. They kept pitching mini-splits rather than a 2 or 3 zone ducted central system. So we ended up using the only company that would do it. We love our 2-zone system, which didn't require any duct reworking. Doing a 3-zone would have been a lot of work, so we settled for having the main floor and basement on a shared zone. It would be great if you could include zoning somehow, since it improves efficiency but especially also comfort, if you have more than one story. Maybe that should be a whole video on it's own. Unfortunately, this company never suggested a heat pump. I wish I had better understood them, because I totally would have pushed for one. It would have saved us a ton of money (and cut our use of fossil fuels). When we replaced the AC in a Florida condo years ago, I think they were pushing for a 2.5 ton unit. I think I wanted a 1.5 ton, and I think we ended up compromising at 2. Which was still a bit oversized in practice. Yes, please help get the word out about proper system sizing.

Kevin Smith

Do you have any connection/have you reached out to Matt Ferrell? He did a combo water heater with HVAC (thermal battery) in his new home. https://youtu.be/SSN-np71d0Q?si=1shuqe9L4S0eiOFJ

Dre

Trane has some great resources on HVAC. For example, they have this one for residential sizing: https://www.trane.com/residential/en/resources/blog/size-hvac-unit-need/

Steven Nicklas

I feel that these video ideas would be greatly enriched with background regarding engineering practice for system design and capacity requirements, cost estimates, and relevant data. I don’t doubt that HVAC installers sometimes take advantage of the ignorance of their clients and I feel that education may be a better antidote than a rant.

Jeff Brown