# Corbett Lunsford Discusses New Innovations at the 2024 HVAC Show

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This Youtube video has a lot of information on cool products and innovations that are coming to market.

I was particularly interested in the new Sharp Airest mini-split air conditioner and heater (minute 9:33), the iFlo air conditioner drain line and pan cleaner (which breaks down the biofilm that can clog up and jam your air conditioner’s drainage system, causing overflows and floods – minute 17:03), and the Trueloads load calculator for designing HVAC systems (minute 19:55).

There’s also a great discussion at minute 22:13 with HVAC designer Alex Meaney about HVAC systems and equipment that probably only DcContrarian and a few others will understand ðŸ™‚

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1. Expert Member
| | #1

"Thereâ€™s also a great discussion at minute 22:13 with HVAC designer Alex Meaney about HVAC design that probably only DcContrarian and a few others will understand."

Well, I couldn't resist.

He lost me with "thermal mass is a thing."

2. | | #2

Open your mind, DC............LOL. Actually, I think he means that the amount of thermal mass in the building affects the need for heat and cooling, which then affects the size and layout of the system you should buy and install.

1. Expert Member
| | #3

For, oh probably four years I've been asking here how you measure the amount of thermal mass in a building. No one has ever answered me.

1. | | #4

I think this would be a fairly simple measurement. You could do it off the blueprints by taking into account the heat capacity, density and volume of materials. Alternatively, you could measure it experimentally after the building is constructed.
https://energyeducation.ca/encyclopedia/Thermal_mass

The primary challenge from my perspective in applying this concept in a building is account for where the thermal mass is with respect to the envelope.

For example, let's assume we have two buildings that are made entirely of concrete (concrete floor, ceiling, and walls.) One building has 10" of external insulation and the other building has 10" of internal insulation. They both have identical thermal mass but would they both feel the same to occupants?

1. Expert Member
| | #5

At the risk of being pedantic and going over ground that long-time readers of this forum have heard from me before...

The thing about "thermal mass" is that it's not a real scientific term. And when people talk about it, they don't agree about what they're talking about. Usually, what most people mean is what's actually called "heat capacity," which is the property of matter that governs how the temperature of it changes when heat is added or subtracted. Heat capacity can be calculated by multiplying the mass of something by its specific heat.

But people want "thermal mass" to be mysterious and magical, and "heat capacity" just sounds kind of boring. So they throw in factors like conductivity and density into some definitions of thermal mass. One formulation I've seen it to take several laps around the barn by starting with specific heat, multiplying by density, multiplying by volume. But density times volume is just mass and mass time specific heat just gives ... heat capacity. Some people want to make conductivity a factor, and say that two objects with the same heat capacity don't necessarily have the same thermal mass, although I'm still waiting for the explanation.

If we're just saying "thermal mass" is an alias for heat capacity, yes, heat capacity is real, it exists, and it does affect the performance of buildings. If buildings didn't have heat capacity it would be very hard to keep the temperature stable. And counter to what the guy in the video says, the Manual J process does account for -- albeit implicitly -- the heat capacity of a building. The implicit assumption is that by designing for the 99th percentile temperature, the building has enough heat capacity to keep the interior reasonable during brief excursions beyond the design temperature.

The reason this is a hot-button issue with me is that from time to time -- although less recently -- we get people here advocating for adding more "thermal mass" to buildings, usually in the form of poured concrete. And poured concrete, while a miracle substance in some applications, has no business on the interior of residences except in countertops, and is an environmental disaster. I've never read anyone who is an advocate of "thermal mass" try to quantify it, they just feel more is better. Which is why I ask the question, how do you measure your thermal mass?

Because if you're not measuring, you're just guessing.

1. | | #6

Thanks for the explanation. Lots of interesting topics down this wormhole.
For example:
- In regions where electricity is billed differently at different times of day, adding thermal mass can be used to allow the occupants to use energy when it is cheapest. In the extreme, they even have systems where large vats of water are frozen at night to then provide AC during the day. For all intents and purposes, that is just an example of adding thermal mass to a building.
- In some regions, the addition of thermal mass may eliminate or reduce the need for cooling during the day and heating during the night.
- In buildings or spaces that are infrequently used, an increase in thermal mass may increase overall energy consumption.

I think that an interesting thought experiment is to assume the walls, floor and ceiling are identical and to instead ask if it is advantageous to have a large thermal mass inside the building. For example, would it help or hurt the comfort and energy consumption if there was a 10,000 liter aquarium or a massive boulder in the building that was allowed to reach room temperature. If the goal is for the temperature in the building to remain stable, then the answer is yes. If the goal is to be able to quickly make adjustments, then the answer is no.

2. | | #9

One of my favorites, one of the larger ICF companies sells a form with less EPS and it uses a thicker concrete core as the alternative. They advertise it as having "more thermal mass for even better performance." Ouch.

I think many have this assumption that by adding thermal mass you are holding in heat that would otherwise be lost.

3. | | #7

I'm excited for Midea's PWHP (packaged window heat pump), a window-mounted, cold-climate capable AC/heat pump with "a top CEER of 16.0. It stands out for its energy efficiency, achieving a 2.35 COP at 17Â°F, SEER2 of up to 21.8, and HSPF2 of 11.6, all while functioning effectively down to -13Â°F without auxiliary heat."

No word yet on a release date for the general consumer market though.

1. | | #10

I'm also very excited to hear more about it -- especially pricing. Looks very similar to the Gradient Comfort unit, which costs an eye-popping \$5,000 for performance that gets absolutely trounced by even low-efficiency mini splits.

I have trouble understanding why one of these units should cost 10x as much as Midea's inverter-based u-shaped window A/C. Turning it from an A/C to a heat pump should not increase the price by 10x... should it?

I'd like for Midea's PWHP to be \$2k or less. But given that they will almost certainly view Gradient as their main competitor, I'm not hopeful that we will see a price of less than \$4k.

Edit: BTW the stats for that Midea unit look amazing. A COP of 2.35 at 17 F is outstanding!

1. | | #11

Agreed! The Gradient Comfort pricing is nuts. I imagine they're pricing themselves as a luxury brand. Plus, they seem like more of a start-up. Being the first to market means they had to front the R&D costs (presumably).

Midea already has the logistics in place producing heat pumps, inverters, etc. at scale. I'm hopeful it will be a lot cheaper.

4. Expert Member
| | #8

If I'd have been asked to give that talk, I'd have said that HVAC is all about comfort, and there's more to comfort than temperature. Obviously humidity is a big factor, and so is solar gain -- when half of the room is in sunlight, one side can be much more comfortable than the other even though the thermometer reads the same air temperature on both sides. And radiation is a big factor, if the air in a room is at 70F there's a big difference in comfort when the walls are at 70F rather than 50F, or 90F rather than 70F. I feel that a lot of what gets attributed to "thermal mass" is really the impact of radiation. That big masonry fireplace doesn't make the room feel toasty because it's heavy, it's because it's warm and has a lot of surface area.

5. | | #12

Someone requested I weigh in here as the guy in the video. For context, I bumped into a friend at a trade show and answered a question off the cuff. And I stand by that answer. BUT I don't consider it to be a complete answer. I'm actually not capable of a complete answer. For what it's worth, I did mention the root cause of the problem- it's just that this conversation just doesn't happen to be focused on it.

The root cause of oversized heating loads is that we throw out all heat GAINS when we calculate heat loss with our current conventional methods. There are some newer methods like radiant time series/heat balance that do this less and some energy models try not to do it at all, but it's a problem every "peak" calculation has at some level.

We try to calculate the heat loads at night (no radiant gain) with no internal load. And if heat were instant, that would be appropriate. But it's not, heat takes TIME to move and has dynamic effects on the system itself while it's moving. It's why when someone says "well actually..." they're almost always right in these instances. The hole can always be dug deeper.

But no matter how much you dig, it's still a hole. So the real reason heat loads are oversized isn't thermal mass, it's that we throw away heat gains. And we throw away heat gains because they go away from time to time. Which is dumb. Why? Because thermal mass, or heat capacity, or just TIME is a thing. That heat doesn't instantly disappear, but we pretend it does.

And we do TRY to incorporate this into our cooling models. Using Manual J, a heavy wall in a climate with a high daily range (with temperatures that tend to swing a lot from daytime high to nighttime low) gets calculated at almost HALF the TD the weather data indicates.

The original sin of the whole thing is taking a dynamic system that is downright impossible to calculate perfectly and boil it down to fixed point(s) (even 24 hourly points is still an incredible oversimplification) but practical methods.

And if you ever want to point out that something is technically wrong in these situations, just focus on things that involve time and radiance. All of the engineering math is collapsed down from raw physics into simpler methods, but the impact of radiance and time are the places we take the greatest liberties.

Ever heard the one about the Physicist and the Engineer? A beautiful man/woman/whatever meets a Physicist and an Engineer in a bar and says to each "If you can close the distance between us, you can kiss me. The catch is you may only move half the distance between us at a time." The Physicist explained how they would never get there and walked away. The Engineer took a step forward, then a smaller step, then another even smaller step, then said "This seems well within acceptable tolerance." and kissed them.

1. Expert Member
| | #13

Thanks for coming by. A couple thoughts.

It's customary in certain calculations to assume that 65F is the break-even point for heating, the point where internal gains balance losses. Most prominently, this is the basis of the degree-day 65 measure. This is an approximation, and at one time it was a reasonable approximation, but as houses get better insulated and heating loads get smaller it becomes a less and less valuable approximation. In this post from last year I reported how on one day on my winter, at design-day temperatures (21F) solar gain and occupant activity were completely warming my house and the the heat wasn't running: https://www.greenbuildingadvisor.com/question/hows-this-for-solar-gain

Second point is that if you look at the history of HVAC, heating in particularly and especially hydronic heating, there was essentially zero penalty for oversizing. Often with oil and gas burning boilers the only difference between different capacities in the same line would be the orifice size on the burner and the price difference would be nominal. And radiators work as well at 10% capacity as they do at 100%. There would be a severe penalty for undersizing -- the homeowner would be cold on the coldest days. The bias toward oversizing is pretty deeply rooted and is going to take a while to overcome.

6. | | #14

So for the average layman or homeowner trying to get a handle on the size and strength of the HVAC equipment they need to install, would that Trueloads software (mentioned in the video link at minute 19:55) be of any value, or should you just let the experts do the calculations and tell you what to buy?

7. | | #15

Modeling is just an approximation of the behavior. Layout the zones, then tune PID loop to balance the energy.

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