5 ms·

> Ducts are dead. Ducted heatpumps are a thing here in NZ and make sense to me, not that I have used one. The heatpump sits in the roof and air is pushed into

> Ducts are dead. Ducted heatpumps are a thing here in NZ and make sense to me, not that I have used one. The heatpump sits in the roof and air is pushed into three or so rooms through ducts. If building a new house I think ducts would be the way to go.

fifteenforty 4y ago
You have to think carefully about where you run the ducts. They can be a huge source of energy loss. 40% is the number quoted by the EPA. Most roofs in Australia still aren’t sealed. The air barrier and insulation barrier is the ceiling. The roof space itself is not insulated, so the ducts are exposed to extreme temperatures, thus destroying the efficiency. Here is just one article on it: https://newenergythinking.com/2018/10/20/dont-use-ducts/ https://newenergythinking.com/2018/10/20/dont-use-ducts/
- teruakohatu 4y ago
  I hadn't considered that. My argument with split systems, at least how they are installed in NZ, is that they are usually installed in the main living area and if there is a second unit, in a corridor. So corridors are heated or cooled far hotter or colder than they need to be in order to heat/cool bedrooms.
  - deleted 4y ago
    [deleted]
  - thehappypm 4y ago
    I have two units that are heated by heat pumps in Massachusetts. One has mini splits. You definitely don’t generally put mini splits in every single room (like bathrooms or interior hallways) because each mini split requires tubing, is large, and expensive. No, I think it’s way more likely that you would have them in the bedrooms rather than the hallway
    - teruakohatu 4y ago
      In New Zealand I have seen small heatpumps in bedrooms, but I would have to say it is extremely rare. But we have many very toasty hallways leading to cold single glazed bedrooms!
      - thehappypm 4y ago
        That might be a climate difference — it gets below 0 Fahrenheit here every winter, as I understand it, NZ is quite a bit warmer, so maybe the strategy of “heat the core of the house and let it radiate out” works.
        teruakohatu 4y ago
        There are historical and cultural reasons for our poorly insulated and heated homes, but "heating the core" is not one of them. In the last few years the central govt has brought in legislation requiring landlords to heat and insulate homes to a certain standard.
    - fifteenforty 4y ago
      Exactly. In this example, which is pretty common here, I installed 1 in the living area and then 1 in each of the bedrooms.
- Gordonjcp 4y ago
  Why wouldn't you just lay insulation on the ducts, same as you do with water pipes?
  - fifteenforty 4y ago
    US and Australian units are different for insulation, but in my terms the insulation around the best ducts is R1.5, but good ceiling insulation is R6. 4x difference Edit: not to mention the huge difference in surface area. Ducts can expose your conditioned air to a huge, poorly insulated surface. Bad for efficiency.
    - briHass 4y ago
      Interesting. The code for duct insulation in unconditioned spaces in the US is R8, and they're pushing for higher currently. They also recently undid a long held myth about ducts buried in insulation leading to condensation issues. Most areas now allow ducts to be buried as long as you have R19 above and below, or R30 above. When I just installed a ducted mini for 3 upstairs bedrooms, I surrounded my R8 flex duct with R30 insulation.
      - EricE 4y ago
        lol - it's not a myth. It's physics: https://www.youtube.com/watch?v=Vufih-WN5R4 https://www.youtube.com/watch?v=Vufih-WN5R4
        mrexroad 4y ago
        Fwiw, context of this video is metal duct work. You’re not going to see R-8 flex duct buried in R-30 begin to sweat when the AC is running. In terms of controlling the dew point, the duct is no different than the conditioned space at that point. Like you said, it’s physics.
  - EricE 4y ago
    Over insulation introduces new problems like condensation (which causes mold and other nastiness) https://www.youtube.com/watch?v=Vufih-WN5R4 https://www.youtube.com/watch?v=Vufih-WN5R4
AOsborn 4y ago
I thought this was absolutely the solution but backtracking a little now based on experience so far. We have a two-level, five bedroom new build in Auckland which came with a single-zone ducted system. So outputs are the bedrooms plus upstairs and downstairs lounges. The vents are tidy and unobtrusive - much less space than a wall unit in each location. We're having major issues balancing the temperature across the different rooms as there is one thermostat. Think setting the temperature overnight for one room with a couple plus a cat vs another room with one of the kids. Basically the wife and I are always far too hot because otherwise we're freezing all the other rooms. Or setting a reasonable temperature in the lounge makes all the rooms icy in short time. I'm now thinking about forking out the couple of thousand to get a small heat pump installed directly into our room so we can run it separately from the rest of the house. So if building from scratch, either look into a multi-zone system or separate heatpumps. If you can get separate systems but hidden in the walls/roof that would be the best.
- dahfizz 4y ago
  I had a similar problem, but I decided that simply running the fan to mix up the air was a fine solution. The fan doesn't use much electricity, and it's good not to let rooms get too stale anyway. I have the fan programmed to run 10 or 15 minutes an hour regardless of if the heat pump needs to run. It keeps things pretty even.
- throwawaylinux 4y ago
  Can't you choke down the airflow from your bedroom duct?
- TedDoesntTalk 4y ago
  What about in-line duct fans or even register fans in the rooms that are not heated/cooled appropriately: https://www.amazon.com/AC-Infinity-Register-Thermostat-Control/dp/B0792QR5YT/ref=asc_df_B0792QR5YT/ https://www.amazon.com/AC-Infinity-Register-Thermostat-Contr... Appropriately placed In-line duct fans and register fans will pull the heated/cooled air where you want.
- thedougd 4y ago
  Have checked the ducts for dampers? They're often installed where the duct branches. It's not unusual to find they're not balanced well or the locking screws have loosened allowing the dampers to move on their own.

fifteenforty 4y ago

You have to think carefully about where you run the ducts. They can be a huge source of energy loss. 40% is the number quoted by the EPA. Most roofs in Australia still aren’t sealed. The air barrier and insulation barrier is the ceiling. The roof space itself is not insulated, so the ducts are exposed to extreme temperatures, thus destroying the efficiency. Here is just one article on it: https://newenergythinking.com/2018/10/20/dont-use-ducts/ https://newenergythinking.com/2018/10/20/dont-use-ducts/

teruakohatu 4y ago
I hadn't considered that. My argument with split systems, at least how they are installed in NZ, is that they are usually installed in the main living area and if there is a second unit, in a corridor. So corridors are heated or cooled far hotter or colder than they need to be in order to heat/cool bedrooms.
- deleted 4y ago
  [deleted]
- thehappypm 4y ago
  I have two units that are heated by heat pumps in Massachusetts. One has mini splits. You definitely don’t generally put mini splits in every single room (like bathrooms or interior hallways) because each mini split requires tubing, is large, and expensive. No, I think it’s way more likely that you would have them in the bedrooms rather than the hallway
  - teruakohatu 4y ago
    In New Zealand I have seen small heatpumps in bedrooms, but I would have to say it is extremely rare. But we have many very toasty hallways leading to cold single glazed bedrooms!
    - thehappypm 4y ago
      That might be a climate difference — it gets below 0 Fahrenheit here every winter, as I understand it, NZ is quite a bit warmer, so maybe the strategy of “heat the core of the house and let it radiate out” works.
      - teruakohatu 4y ago
        There are historical and cultural reasons for our poorly insulated and heated homes, but "heating the core" is not one of them. In the last few years the central govt has brought in legislation requiring landlords to heat and insulate homes to a certain standard.
  - fifteenforty 4y ago
    Exactly. In this example, which is pretty common here, I installed 1 in the living area and then 1 in each of the bedrooms.
Gordonjcp 4y ago
Why wouldn't you just lay insulation on the ducts, same as you do with water pipes?
- fifteenforty 4y ago
  US and Australian units are different for insulation, but in my terms the insulation around the best ducts is R1.5, but good ceiling insulation is R6. 4x difference Edit: not to mention the huge difference in surface area. Ducts can expose your conditioned air to a huge, poorly insulated surface. Bad for efficiency.
  - briHass 4y ago
    Interesting. The code for duct insulation in unconditioned spaces in the US is R8, and they're pushing for higher currently. They also recently undid a long held myth about ducts buried in insulation leading to condensation issues. Most areas now allow ducts to be buried as long as you have R19 above and below, or R30 above. When I just installed a ducted mini for 3 upstairs bedrooms, I surrounded my R8 flex duct with R30 insulation.
    - EricE 4y ago
      lol - it's not a myth. It's physics: https://www.youtube.com/watch?v=Vufih-WN5R4 https://www.youtube.com/watch?v=Vufih-WN5R4
      - mrexroad 4y ago
        Fwiw, context of this video is metal duct work. You’re not going to see R-8 flex duct buried in R-30 begin to sweat when the AC is running. In terms of controlling the dew point, the duct is no different than the conditioned space at that point. Like you said, it’s physics.
- EricE 4y ago
  Over insulation introduces new problems like condensation (which causes mold and other nastiness) https://www.youtube.com/watch?v=Vufih-WN5R4 https://www.youtube.com/watch?v=Vufih-WN5R4

AOsborn 4y ago

I thought this was absolutely the solution but backtracking a little now based on experience so far. We have a two-level, five bedroom new build in Auckland which came with a single-zone ducted system. So outputs are the bedrooms plus upstairs and downstairs lounges. The vents are tidy and unobtrusive - much less space than a wall unit in each location. We're having major issues balancing the temperature across the different rooms as there is one thermostat. Think setting the temperature overnight for one room with a couple plus a cat vs another room with one of the kids. Basically the wife and I are always far too hot because otherwise we're freezing all the other rooms. Or setting a reasonable temperature in the lounge makes all the rooms icy in short time. I'm now thinking about forking out the couple of thousand to get a small heat pump installed directly into our room so we can run it separately from the rest of the house. So if building from scratch, either look into a multi-zone system or separate heatpumps. If you can get separate systems but hidden in the walls/roof that would be the best.

dahfizz 4y ago
I had a similar problem, but I decided that simply running the fan to mix up the air was a fine solution. The fan doesn't use much electricity, and it's good not to let rooms get too stale anyway. I have the fan programmed to run 10 or 15 minutes an hour regardless of if the heat pump needs to run. It keeps things pretty even.
throwawaylinux 4y ago
Can't you choke down the airflow from your bedroom duct?
TedDoesntTalk 4y ago
What about in-line duct fans or even register fans in the rooms that are not heated/cooled appropriately: https://www.amazon.com/AC-Infinity-Register-Thermostat-Control/dp/B0792QR5YT/ref=asc_df_B0792QR5YT/ https://www.amazon.com/AC-Infinity-Register-Thermostat-Contr... Appropriately placed In-line duct fans and register fans will pull the heated/cooled air where you want.
thedougd 4y ago
Have checked the ducts for dampers? They're often installed where the duct branches. It's not unusual to find they're not balanced well or the locking screws have loosened allowing the dampers to move on their own.