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Natural Gas vs Heat pumps for heating

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This is an interesting thread as I'm in the process of building my retirement home in Houston area where houses tend to be bigger than most.
As we build a high performance home, we have the luxury of considering several quality of life items on our list.
  • House will have solar panels and 4 PWs to feed up to 3 EVs in the long term.
  • Heat pump AC system: considering Lennox XP25 heat pump for our central air system with zoning. probably will use 3 as we have 2 stories and a conditioned attic.
  • Water heater: we want to use tankless water heaters but it seems the gas version is the most cost effective and efficient. I have looked into electric tankless but I don't think they compare to the gas version. Am I correct?
  • I want to put a ductless mini split in the theater and the garage, maybe Mitshubishi ones. Definitely the garage but not sure it's better to have the theater using the central air and have it on a separate zoning.

I'd advise the following:

  • Install as much solar is you can fit/afford.
  • That Lennox unit looks very nice. Another option would be to install two or three smaller systems rather than one large, zoned system. This might offer simpler ducting, more flexibility, some redundancy and better efficiency.
  • Electric tankless systems have demand huge amounts of power and also don't offer the efficiency of alternatives like heat pump water heaters. My ideal setup would be a heat pump water heater (or two if your house requires large volumes of hot water) with a recirculating loop that is activated by motion sensors in the areas where you want instant hot water (bathrooms, laundry, maybe kitchen). This can be easily accomplished with a Lutron smart switch, hub and Philips Hue motion sensors.
  • For mini-splits, both Mitsubishi and Daikin are top of the line. That said, many of the off-brand units (many made by Midea Ductless Cooling and Heating Systems | Midea ) available are of very high quality and offer similar efficiency and features.
 
Although I have HVAC central ducting, I stopped using the fan only for filtering years ago. I have a positive pressure system that brings in air from outside going through a 3 stage hepa filter. I got it because when I got a CO2 monitor, I watched it build up 800+ PPM with just 3 people in a 4000 sf house by the end of a weekend if we all stayed home. The positive pressure system filters air from outside and brings it in. This also prevents dust and other air from coming in from any imperfect sealing in the house. Smoke gets in easily through microscopic cracks and holes. The positive pressure prevents that and also drastically reduces stuff coming in from outside when we open doors to go in and out.

My air quality stays at a level that is equivalent to 0 on Purple Air.
I am curious about the details of your system. Can you share the details?

All the best,

BG
 
I'd advise the following:

  • Install as much solar is you can fit/afford.
  • That Lennox unit looks very nice. Another option would be to install two or three smaller systems rather than one large, zoned system. This might offer simpler ducting, more flexibility, some redundancy and better efficiency.
  • Electric tankless systems have demand huge amounts of power and also don't offer the efficiency of alternatives like heat pump water heaters. My ideal setup would be a heat pump water heater (or two if your house requires large volumes of hot water) with a recirculating loop that is activated by motion sensors in the areas where you want instant hot water (bathrooms, laundry, maybe kitchen). This can be easily accomplished with a Lutron smart switch, hub and Philips Hue motion sensors.
  • For mini-splits, both Mitsubishi and Daikin are top of the line. That said, many of the off-brand units (many made by Midea Ductless Cooling and Heating Systems | Midea ) available are of very high quality and offer similar efficiency and features.
Yes, Yes, install as much solar as you can fit, get approved.
 
I'd advise the following:

  • Install as much solar is you can fit/afford.
  • That Lennox unit looks very nice. Another option would be to install two or three smaller systems rather than one large, zoned system. This might offer simpler ducting, more flexibility, some redundancy and better efficiency.
  • Electric tankless systems have demand huge amounts of power and also don't offer the efficiency of alternatives like heat pump water heaters. My ideal setup would be a heat pump water heater (or two if your house requires large volumes of hot water) with a recirculating loop that is activated by motion sensors in the areas where you want instant hot water (bathrooms, laundry, maybe kitchen). This can be easily accomplished with a Lutron smart switch, hub and Philips Hue motion sensors.
  • For mini-splits, both Mitsubishi and Daikin are top of the line. That said, many of the off-brand units (many made by Midea Ductless Cooling and Heating Systems | Midea ) available are of very high quality and offer similar efficiency and features.
I would have considered a heat pump water heater if they had one that used gas instead resistance heating as secondary heating. When I was looking I couldn't find one.

Also, if one is planning on a central heat pump system and has gas (or some other fuel source), consider getting a quote for a hybrid heat pump/gas system. Depending on gas costs and how cold it gets in your area it may pay for itself over it's life. And the furnace can be run on a small generator or battery power (if planned for during installation) if the power goes out.
 
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I would have considered a heat pump water heater if they had one that used gas instead resistance heating as secondary heating. When I was looking I couldn't find one...
If an 80G heat pump does not have enough reserve and/or seasonally too low ambient air conditions for such a situation, one option might be (if enough room) to consider a serial setup.

In that case a HPWH could be primary and feed through a NG water heater. For most of the year the HPWH could supply all hot water needs, but if ambient temps become too low and/or demands exceed HPWH capabilities, could have the NG water heater on a temp set point to pick up any slack. Also in that case could go with a small HPWH since effectively total storage capacity is HPWH + NG water heater capacity.
 
If an 80G heat pump does not have enough reserve and/or seasonally too low ambient air conditions for such a situation, one option might be (if enough room) to consider a serial setup.

In that case a HPWH could be primary and feed through a NG water heater. For most of the year the HPWH could supply all hot water needs, but if ambient temps become too low and/or demands exceed HPWH capabilities, could have the NG water heater on temp set point pick up any slack.
Yea, I found DIY solutions but not an off the shelf integrated unit. My concern was mainly for power outages in the winter.
 
I would have considered a heat pump water heater if they had one that used gas instead resistance heating as secondary heating. When I was looking I couldn't find one.

Also, if one is planning on a central heat pump system and has gas (or some other fuel source), consider getting a quote for a hybrid heat pump/gas system. Depending on gas costs and how cold it gets in your area it may pay for itself over it's life. And the furnace can be run on a small generator or battery power (if planned for during installation) if the power goes out.

One of my personal goals is to eliminate natural gas. In addition to being a major GHG contributor (methane leaks), I view the infrastructure as being fragile (Texas deep freeze) due to our heavy reliance on it for both heat and electricity. Propane and diesel are both good emergency back-up options because they can be stored on-site, although I tend to lean toward a small diesel generator (I own a 6 kW Kubota two cylinder) for emergency backup needs since they're simpler than a propane generator in that there are no electronic ignition controls. The benefit of having a generator combined with battery storage is that you can recharge your batteries over time. The batteries will carry the big, intermittent loads rather than having to size the generator for your big loads.

What fuel mix one ultimately decides on should be driven by local conditions. Solar obviously won't cut it if you're in a cold region with poor sun conditions in the winter, so a fossil fuel backup option might make sense for those long, cold spells. My recommendations above were for the gentleman from Texas, who presumably has very good sun conditions. Surplus daytime solar can be soaked up by the electric hot water backup elements rather than sending power back to the grid, depending on which is more financially advantageous.

Sorry, that was a lot of information that nobody asked about... just figured I'd give some more color to my approach.
 
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The benefit of having a generator combined with battery storage is that you can recharge your batteries over time. The batteries will carry the big, intermittent loads rather than having to size the generator for your big loads.
While that sounds good in theory, so far it doesn't work in practice. There are few battery systems that are approved for recharging with a generator. I've heard Generac has a system and Enphase is working on one. Powerwalls can only be recharged from a generator in off-grid installations.

While you could do your own you are now outside of standard installations and possibly voiding warranties.

I wish I could recharge my Powerwalls using a generator.
 
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While that sounds good in theory, so far it doesn't work in practice. There are few battery systems that are approved for recharging with a generator. I've heard Generac has a system and Enphase is working on one. Powerwalls can only be recharged from a generator in off-grid installations.

While you could do your own you are now outside of standard installations and possibly voiding warranties.

I wish I could recharge my Powerwalls using a generator.

I guess I forgot to mention that another goal of mine is going off-grid with the exception of the occasional high energy density fuel delivery for emergency storage. That may or may not be possible depending on where we end up moving in the near future, but hey, everyone should have goals, right? :)

I've seen where generator integration into the Tesla Energy ecosystem might be coming soon, although I'm sure there will be limitations on how you're able to use it and under what conditions.
 
I guess I forgot to mention that another goal of mine is going off-grid with the exception of the occasional high energy density fuel delivery for emergency storage. That may or may not be possible depending on where we end up moving in the near future, but hey, everyone should have goals, right? :)

I've seen where generator integration into the Tesla Energy ecosystem might be coming soon, although I'm sure there will be limitations on how you're able to use it and under what conditions.


Lol sounds like you need to start a tree/brush clearing business and then take all the scrap to fuel a biomass incinerator on your property to get energy when the sun is less reliable :p
 
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Check out this more conventional air handler packaging (random links - they're available from other manufacturers and vendors):


Thanks for the further suggestion, yes, I've especially eyed the Daikin Fit (inverter-based) or Signature (conventional heat pump), as they have a cased coil that could just sit on my existing furnace blower. The "mini-split style" side-discharge outdoor units definitely fit better with the side of the house they would be mounted to. Bummer there are tons of Daikin dealers in SoCal or Central Valley, not a single darn one in the entire NorCal SF Bay area...

I'm recognizing the proper thing to do is just to rip out the furnace, and go all electric heat-pump with the air handlers you suggest, but just can't bear to toss out a 10-year young top-of-the-line Carrier furnace. But maybe retrofit one of these heat pumps with matching coil on the furnace now, and when the furnace gives out in another 10-years, drop in the air handler and rip out the coil/furnace....
 
Thanks for the further suggestion, yes, I've especially eyed the Daikin Fit (inverter-based) or Signature (conventional heat pump), as they have a cased coil that could just sit on my existing furnace blower. The "mini-split style" side-discharge outdoor units definitely fit better with the side of the house they would be mounted to. Bummer there are tons of Daikin dealers in SoCal or Central Valley, not a single darn one in the entire NorCal SF Bay area...

I'm recognizing the proper thing to do is just to rip out the furnace, and go all electric heat-pump with the air handlers you suggest, but just can't bear to toss out a 10-year young top-of-the-line Carrier furnace. But maybe retrofit one of these heat pumps with matching coil on the furnace now, and when the furnace gives out in another 10-years, drop in the air handler and rip out the coil/furnace....

You might be able to sell that furnace locally and recoup some cost. There is demand for used, good condition equipment, especially for people adding HVAC to garages and ADUs.
 
2) Zoned systems with Lennox to my knowledge rely on a combination of the iComfort S30 communicating thermostat and a somewhat poorly thought out zoning hardware/system. One thing that seemed to be a big miss is that the remote temperature sensors for the zoning aren't very useful. For example, I have an upstairs where the thermostat sits directly under a skylight. So what happens is the thermostat detects a lot of heat, while the rooms with registers controlled by this thermostat are more normal with sun exposure. You would naturally want remote temperature sensors so the S30 could treat the remote parts of the house instead of relying on the spot temperature where the thermostat is mounted. Nope. Not with Lennox. Fail.

The communicating systems, coupled with variable speed blowers, seem particularly smart for balancing A/C and humidity in summer, but my Carrier Infinity one seemed to be far less advantageous when I had it coupled just with furnace heating. I also had some ducting and temperature issues that I considered zoning, and even bought a Carrier Infinity zoning board off eBay, but also required very particular types of zone dampers too.

But finally in the end, last winter I installed a third-party DIY Smartzone zoning control board, coupled with Ecobee smart thermostats. Something to consider in place of your Lennox zoning, if you can lose the other benefits of the communicating thermostat - and it should be compatible with your existing zone dampers. My primary zone's Ecobee is behind a large aquarium, so I ignore it's own readings and instead use four remote sensors in different to balance temps and occupancy. The second zone's Ecobee also is mounted where the temps can be misleading, so I use a single remote sensor that better reflects the temps and occupancy for that zone. The primary Ecobee can still control two-stage heating and two-stage cooling algorithms through the Smartzone.

The Smartzone was <$200 and is great for tinkering, and an unused zone can also be configured for fresh air, as others are talking elsewhere in this thread, so I'm considering adding fresh air exchange next year as well.
 
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If you have a separate zone for the theater and is on while watching you may be able to hear it. If it on with the other zone, you could shut the opening so you would not hear it.
Consider a hot water recirculating pump and well insulated hot water pipes. With that tankless, it would run when water is not running to have hot water at faucets.

A high performance home should have staggered stud exterior walls for added insulation and less outside noise entering.
Of course double pane windows. Check out air tight drywall approach/method.
High R value in ceiling and under floor if not on a slab on grade. And, even on slab, consider foam insulation under the slab, again a good R value.

Theater: make sure you have ethernet to equipment cabinet; HDMI run to projector if one is used. Don't use ceiling speakers for your 3 front speakers and surrounds, only for Atmos setup; Two locations for possible subwoofers with power and RCA cable.; 12/14ga speaker wire, not expensive audiophile cables ;) .
If a projector is a possibility, a way to darken the room totally.
Vent equipment space to cool amps.
Don't have seating against back wall.

Ethernet cable in other areas besides a study. Sure wi-fi is good but ....

Theater should also have at least one dedicated 120V 20 amp power circuit for the audio amplifiers.
 
stay away from the super high efferent AC systems with variable speed motors because ANY repair will cost you $3K, cheapest repair would probably be the evaporator coil!!! No joke! go with single speed system, fans and compressor, with the highest SEER. Your better off with more Powerwalls to start a single speed system, becides you know you want more powerwalls!