5 ms·
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 Austral
by 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 agoI 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 agoI 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 agoIn 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 agoThat 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 agoThere 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 agoExactly. 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 agoWhy wouldn't you just lay insulation on the ducts, same as you do with water pipes?
- fifteenforty 4y agoUS 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 agoInteresting. 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 agolol - 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 agoFwiw, 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 agoOver 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